Pocket cruisers [Archive] - Boat Design Forums

Guillermo

05-13-2006, 06:07 AM

Having opened a thread at the Sailboats forum about small seaworthy cruisers, I've considered the oportunity of also studying this concept for the motoring side of it.

So I propose now a discussion about 'pocket motor cruisers' understanding the term as motor boats under 30' able to do extended coastal crusing for a family (Up to 4 people), so not runabouts or dayboats, in a safe and efficient way.

The idea is to gather here what has and is been done around this concept and discuss their pros and cons, as well as the concept itself.

To begin with, I propose to have a look at WHIO, a very nice design from New Zealand, winning the Jens Hansen Cup for overall winner at the 2006 Seresin Estate NZ Antique and Classic. In this case WHIO was conceived for a couple cruising in style in warm climates, probably being rather a day boat with cruising capabilities, which would be in the 'lower' end of this thread's purposes. Design is from Peter Sewell and Bill Simpson.

http://www.steamlaunch.co.nz/Whio.html

MEASUREMENTS
LOA 9.1 m
LWL 8.9 m
BOA 2.24 m
Fuel 120 lt
Displacement 1350 Kg

DIESEL ENGINE
Make Toyota
Type 2C 1800cc
Hp 52

PROPELLER:
S/steel 21.5 x 21.5 in

AMENITIES:

Built in fridge and freezer
Berths for 2/3
Economical LED lamps
Depth sounder
Portable gas stove.
At present a Portaloo is provided, but is intended to install a drying type head.
Awnings are provided to enclose the after part of the boat.

PERFORMANCE:

Fuel consumption : aproximately 2 litres per hour at 10 knots. Accurate measurements have not been made for higher speeds but is estimated that it should not be greater that 6 to 7 litres per hour at 17 knots.

In easy sea conditions she cruises comfortably at 15 knots and 12 in heavier conditions, Whio rides smoothly with very little pounding. She steers very well running before the sea with no tendency to broach.

The following parameters were considered imperative in the design of 'Whio':

- The overall dimensions have to be below those which would incur the necessity of an oversize permit for trailering.
- In the interest of fuel economy and trailering 'Whio' has to be light and wherever practible the lightest materials possible must be used used.
- 'Whio' has to be capable of making coastal passages safely and at speed and be able to cope comfortably with adverse sea conditions.
- ...'Whio' has to have the appearance and elegance of a classic Edwardian launch.

tom28571

05-13-2006, 08:53 AM

Guillermo,

Are you proposing a discussion of Peter's boat or boats for coastal cruising in general?

Guillermo

05-13-2006, 10:06 AM

Are you proposing a discussion of Peter's boat or boats for coastal cruising in general?
Boats for coastal cruising in general.

tom28571

05-13-2006, 03:45 PM

On the home page of the forum, look down near the bottom at the Option One thread. Several people discussed just this kind of boat over a long period of time.

WHIO is a beautiful boat with exceptional performance. It is, however, a boat occupying a narrow niche that will not appeal to a lot of people. The accomodations are more spartan than most will accept. Peter had a well defined goal and stuck to it throughout the design and construction of the boat. The construction is pretty advanced for a novice and will not be inexpensive for a commercially built boat of this displacement. Peter is planing to build some for sale though. Since New Zealand is a more boat consious nation than we in the USA, perhaps they can find appreciative buyers there. The boat deserves an audience and I wish them luck.

Guillermo

05-14-2006, 12:43 AM

Thanks, Tom.
As far as I understand, in Option One the Specs were:

Size 29 - 32 feet.

1 Coastal hopping
2 Trailerable
3 Range 300 miles
4 Crew, 2 minimum
5 Price range, under 50K US, for home built.
6 Must be able to carry on a normal conversation at 3/4 throttle.

1. Max speed 25 - 28 knots
2.Max Cruise 20 - 22
3. able to maintain planing down to 12 knots and economical to operate throughout its speed range

Some preliminary scketches were posted.

But what I'm looking for is to show up what boats are in the market already (or in designer's boards), under 30', be them trailerable or not, not price limit.
So, this is not a thread for designers only, but for everybody just wanting to share boats they know within the scope of the thread, and discuss about them.

Cheers.

Guillermo

05-14-2006, 03:10 AM

Some very nice pocket motor cruisers from Paul Gartside. 22' (3) and 24' (2) designs.
http://www.gartsideboats.com/catpow.php

Specifications for 22 Ft Motor Cruiser "Jennifer"
Length overall 22 ft 0 in
Beam 8 ft 0 in
Length waterline 21 ft 0 in
Draft 2 ft 3 in
Displacement 4700 lbs
Fresh water 100 liters
Engine Perkins M30 29 BHP @ 3600RPM
Fuel consumption 2.47 liters/hour
Fuel capacity 260 Liters

From Paul's:
"She is comfortable, quiet, warm, and secure. Two steering stations allow for al fresco cruising when the weather is fine and cozy comfort when it is raining, as it often is on the BC coast. She has room to stow enough stores to be self sufficient in isolated areas for quite a while. Her accommodations, while compact, have all the necessities - heating stove, galley stove with oven,sink, head, good comfortable berth, comfortable seats. Special attention was given her soundproofing, so that even though the three cylinder diesel is forward under the double berth, she is quiet enough that conversation can be carried on at normal level. Fuel consumption is 2½ liters per hour at 6 knots and cruising range is 800 nautical miles."

tom28571

05-14-2006, 09:22 AM

To make any headway, you need to do like Peter Sewell and set some goals that define the boat. Gartsides boat is very nice but it is 6 knots. Your original post implies that you want to move much faster than that.

In the powerboat world there are displacement boats, semi displacement or semi planing boats and full planing boats. They are completely different concepts and call for different design directions, and consequent compromises, from the outset. I know of no boat in the size range you want that meets your other desires. If you can accept displacement speed or even semi-displacement speed, there are many, many boats to consider. If you want planing speed from just above displacement to above 20 knots with easy trailering, crew comfort and economical operaton, the list of commercially available boats that meets your other requirements gets very small - like zero. My boat, which is described in the Option One thread is an example, like WHIO, that sticks to a rigid set of goals. I'm currently working on a 28' version with the (nearly) same goals.

Willallison

05-14-2006, 11:17 PM

I too think you need to narrow your parameters somewhat guillermo. (Though it's worth noting that neither of the craft you've posted meet your initial requirements - neither will sleep 4 people, let alone accomodate them for an extended cruise...)
For instance, I had a Searay 270 Sundancer for a few years ( http://www.boatdesign.net/gallery/showphoto.php/photo/114/cat/500/perpage/24/ppuser/124 ) A young family of four could cruise on her extensively for a week or more - I did on a number of occaisions. However, I'm not sure it meets what I think you're lookinig for. With a range of under 200nm and only 90 litres of water, you'd probably be a bit hard pressed to be completely autonomous for a week.

You would also have to define what you mean by seaworthy too....

In the displacement world you could look at the Willard 30
http://www.trawlerworld.com/w30_bermuda.htm
As Tom suggests, there are any number of boats that might fit within your parameters...

ps. Tom - when do we get to see drawings / pics / progress re "Big Liz" (no disrespect to your wife intended...)

Guillermo

05-15-2006, 01:49 AM

Thanks a lot, Will and Tom.
Willard 30 is a very nice displacement long range small cruiser, much in the line I think this kind of boats should be for load carrying abbility (so allowing for long periods without re-provisioning) and fuel efficient motoring. I love the type, and adding some sail assisting-roll damping rig (not as much as to be called motorsailers), makes them an excellent option, in my opinion. I would appreciate very much all possible info on this kind of displacement boats.

But I do not want to learn only about those boats, that's why I didn't narrow the search. Fast cruising motor boats are also an interesting possibility for extended cruising, if you are in areas where provisions can be easily made, so you do not need to overload the boat. Something like a marinas-hopping-mixed-with-some-overnight-stays-at-anchor cruising scheme. I'm really interested in knowing more about this last type of boats. More interested than in the displacement ones, to be clear.

As to the crew, I said "up to four", so this meaning 4 being a top limit, but no a minimum. Sorry if I didn't explain myself. To clarify, let's say from 2 to 4, but the higher the number, the better.

May be seaworthy was not the right word. What I meant was sea going ability, so EU Design Category C, or higher.

Cheers.

Willallison

05-15-2006, 02:40 AM

on that basis, there are any number of boats to choose from - thousands in fact.
I'm not sure what CE certification the Searays carry - probably C

One of my favourites are the Nimbus range of boats www.nimbus.se

But it really depends on what style of thing you want to look at. As I see boats fall into one of two camps.
1. The less is more camp
2. The cram more into less camp.

My Searay was most definitely in the 2nd group.
Toms lovely Liz in the first group

Guillermo

05-15-2006, 07:17 AM

on that basis, there are any number of boats to choose from - thousands in fact...
Yes. A problem....
To refine search for fast cruisers, maybe we should limit things to the following:
- Pilothoused
- Full load considering fuel, 4 people (top), their personal equipment and provisions.
- Full load top speed something like 18-20 kn (+/-), so no 'sporty' boats. Boats have to be designed with fuel consumption efectiveness (reasonability?) in mind, as they have to be intended primarily as extended cruising boats, even if it is in short trips from harbour to harbour.
- The best or more interesting, in poster's opinion :)

By the way, I like quite a lot the Nimbus 28 Familia (And not only because it has an spanish name!)
http://www.nimbus.se/modelPageCoupe.aspx?pageid=438

tom28571

05-15-2006, 09:25 AM

The following is excerpted from some of my other stuff but I think it fits here.

Displacement boats are restricted to speeds below the "hull speed" of the boat determined primarily by the waterline length. For most smaller boats this will be about 6 to 7 mph. Planing boats can run at very high speed but tend to behave very poorly between their hull speed and up to about 16 to 20 knots. In this range they will assume a bow high - stern down attitude, make large wakes, steer poorly, absorb gobs of fuel and be generally unpleasant to be aboard. Unfortunately, this mid speed range is just where most cruisers would like to run if they had a choice.

This common characteristic is never relayed to a novice boat buyer by dealers or the sales brochures. These usually show the boat happily zipping across the water at high speed or sitting at the dock with the crew lounging about with a beverage in hand. Such poor behavior may appear for the first time when the proud owner takes the new boat out for a spin. Often there is great disappointment and the boat may spend far more time at the dock than the new owner intended. Perhaps one family member, usually the wife, does not like running at full bore all the time and the husband can't stand idling along at 6 mph. Of such circumstances are boat widows born.

Semi planing boats will run in the intermediate speed range but do require higher power and fuel relative to displacement boats. They will generally be heavier than planing boats and still make large wakes when pushed into their upper speed range.

---------------------

One thing to gather from the above is that your top speed range falls right where many (if not most) commercial boats that offer the amenities that you want are just getting onto plane. It's also the top end of the semi-displacement boat's capabilities. In both cases, the boat is not operating efficiently and is likely using gobs of expensive fuel. Neither is easily trailerable with anything like a family vehicle. Oops, I forgot about the monster SUV's now being found in driveways.

It's impossible to say anything about boats without personal wishes and prejudices getting into it.

Probably the quickest way to narrow the choices is to decide that the boat need not be trailerable. Next might be to lower your speed requirements so that displacement boats qualify. Then all your other wishes get a lot easier to satisfy.

Will, as you know this is at the opposite end of the spectrum from my boats. The 28 is an attempt to satisfy the wish for more room and amenities and still hold on to the requirements for trailering, economic operation and speed above 20kts. While "Liz" has proven to be capable of handling some rough conditions, I refuse to call either of them sea boats.

Guillermo

05-15-2006, 12:35 PM

Tom,

A 28' boat (24 Lwl) with 8.2' knuckle width at the stern, with proper forms, should go into full plane at something like 18 knots, as per the formula: Planning S= 4*LCG/(Bs^1/2), estimating LCG at 0.55 Lwl. And a similar estimative for a 30' comes to 20 kn. So my asking for 18-20 kn in full load condition pursued to screen for well conceived and built boats. But I admit it is a bit tight. What should we work with, 22-25kn? More? What's your opinion?

I haven't stated that the boats needed to be trailerable. And displacement boats qualify, for sure. See my previous posts.

Cheers.

tom28571

05-15-2006, 02:28 PM

I expect that your numbers are pretty close.

The problem that I see is that there is no reasonable margin between minimum planing speed and top speed. This means that the boat is either full bore or idling at displacement speed since anything in between is not a useful speed to operate at. If you want to have a top speed in the high teens, I would suggest a semi-displacement hull which will operate at all speeds up to its maximum.

My boats have full planing hulls and will operate smoothly and economically at any speed up to about 23mph but I don't think they will satisfy your other desires for cruising amenities. It's all compromises. When I hear of a boat or vehicle with no compromises, I shudder, since I know that there is one giant compromise - money.

Look at Sam Devlin's boats for an idea of how boats that suit your wishes might look. http://www.devlinboat.com/

Guillermo

05-15-2006, 04:24 PM

Tom,
Sam Devlin's Black Crown 29 with the 200Hp engine should reach 23 kn. She's a nice boat, although I do not like very much sterndrives. This boat having a pretty big interior, has a somewhat small cockpit, and even part of it is taken by the engine box, if I understand well her drawings (http://www.devlinboat.com/dcbc29.htm)
Maybe a solution allowing to have a free cockpit could be the use of a JetPac engine (www.swordmarine.com) hanging out the stern. Have to think about this.

By the way, Devlin has some nice looking Motorsailers designs I didn't know. Good for my Motorsailers & Motorsailing pages, thanks!
Some of those MS can be arranged as extended cruising motorboats, in this thread's line.

Raggi_Thor

05-15-2006, 06:09 PM

I think a cruising speed around 20 knots is more than enough.
Then you burn half as much fuel per mile as you do at 28 or 30 knots.
You can have 25 or 30 HP per ton instead of 60.

Willallison

05-15-2006, 08:48 PM

As always:D Tom's bang on the money with all his comments. My Searay, for instance had a minimum sensible planing speed of around 17 knots. I could keep it on the plane at slower speeds than this by trimming in the leg and applying plenty of angle to the trim tabs - I could get it down to around 12 or 13 knots in fact. But the fuel consumption would have been horrendous.
It's really a matter of determining what kind of boating you want to do. I bought the Searay in Sydney, where we operated it for a couple of years before bringing it home to Tasmania, where we used it for a further couple. We often spent up to a fortnight on board, but almost all of the cruising was in sheltered waterways where the biggest seas we were likely to encounter were the wakes from passing boats. It was an ideal boat for for that. I cruised at 20 - 24 knots.
However, it was definitely not a boat for doing extended open-water passages, where it might be necessary to slow to low planing speeds.
For this (if you set aside true displacement boats) then you really want a boat that will be both efficient and comfortable at anything from 10 to 20 knots. To achieve this isn't rocket science, but it does require a commitment to the "Less is More" principle.
Primarily, the boat MUST be kept light.
It should have a relativley high length/beam ratio
And, unless you prepared to accept high levels of trim, it must have low transom deadrise.

Guillermo

05-16-2006, 01:44 PM

Well,
Here you have the lines for the before mentioned WHIO, designed by Bill Simpson & Peter Sewell. Big L/B, slender hull, planning surfaces aft, canoe stern and very light cold molded construction.
In the pursuit of lighteness, she even doesn't have a steering wheel, but a wooden staff mounted to starboard of the steering position. She does 17 kn with just 50 HP and uses half a US gallon/hour at her cruising speed of 10 kn.
Peter also designed and built the propeller, claiming an 80% efficiency.
The boat can go astern at 12 kn!
I find this boat quite a nice piece of design and engineering.

Guest-3-21-09-10-33

05-20-2006, 04:20 AM

[QUOTE=Guillermo]Having opened a thread at the Sailboats forum about small seaworthy cruisers, I've considered the oportunity of also studying this concept for the motoring side of it.

So I propose now a discussion about 'pocket motor cruisers' understanding the term as motor boats under 30' able to do extended coastal crusing for a family (Up to 4 people), so not runabouts or dayboats, in a safe and efficient way......

What about this design:

Van De Stadt: http://www.stadtdesign.com/products/vds608_6531.htm
in drawings the 9,50 concept
in picture on sea trial the built wood core 12 mt
in picture on yard the smaller 8,50 begin build by AB (picture of plug/mould)

Guillermo

05-20-2006, 04:47 AM

Thanks Luigi. Very interesting boat with a different and intelligent lay-out. From Van de Stadt's pages:

Design 653
Length over all 9.50 m
Length waterline 9.35 m
Beam 2.40 m
Draft 0.55 m
Displacement 2.00 t

A pity they do not state more info, as power, speed, range, etc.

Design 608 (out of the range of this thread)
Length over all 12.00 m
Length waterline 11.80 m
Beam 3.00 m
Draft 0.70 m
Displacement 4.00 t

Keep on waiting for your Lobster Boat's info.
Cheers.

Guest-3-21-09-10-33

05-20-2006, 05:00 AM

I will come back with full specs, we are setting up frame for the 9,50. Moulds of the 8,50 (but it is just a small launch) is already finish

Anyway basic parameters of these projects are:

- light construction with modern composites
-classic design
-sailing boat type hull with round bilge easy planning at low speed (very low power planning hull)
-fuel efficiency
-trailerable, even the 12 mt, as very light
-simple but nice and classic interiors build with modern composites (visible on http://www.yachtdimension.nl/, cobuilder promoter)
-capacity of coastal and offshore passages (the 12 meter make Holland - UK trips, 35 + knots with single 250 hp)

Guest-3-21-09-10-33

05-20-2006, 05:43 AM

some updates :
sorry for the mistake, top speed of 40 ft is 33 knots with 250 hp
max speed 33 knts

fuel consuption at cruising speed 25 knt 25 liters, at top speed 40 liters

total weight 3300 kg
I will come back with more specs for the 9,50 meters project.

yacht371

05-20-2006, 11:02 PM

Check out the MC29 Power catamaran at www.aviadesign.com. It has about the same fuel consumption as WHIO, a higher top speed and meets the 4 person accommodation requirement. It is a GRP production boat so available to many who might not want to build their own, or can't afford a custom boat.

Guillermo

05-21-2006, 01:31 AM

Thank's a lot yacht371
(Sorry, I'd love to have used your real name, but the nick is all I have)
Very interesting design. I think it would be great if you broad here design and test details related with load and speed, as those are not clear in your web pages. I'd also like to know load carrying ability, if possible.

LOA 8.88 M 29'-1”
Beam 2.60 M 8'-6”
Draft 0.47 M 1'-7”
Disp. 1800 kg. 3960 lb. (I asume this is in lightship condition :confused: )

From Avia Design's pages:
"...Planing hulls are usually very poor at this, frequently requiring 20 mph or more for good running, and "mushing" badly at lower speeds, with the bow high and attendant poor visibility. Yet I notice that most cruising power boats seem to run between 10 and 18 mph, the least efficient speed range for a planing or semi-displacement boat. The narrow displacement hulls of a Motorcat are at their most effective in this speed range."

"...actual figures for the Volvo D3-160 diesel version...efficiency in the 10 to 20 mph range is outstanding."
RPM MPH L/h Gal/h MPG
1000 6.9 1.2 0.32 21.6
1200 9.2 2.5 0.64 14.4
1600 11.5 3.8 0.98 11.7
1900 13.8 6.3 1.63 8.5
2150 16.1 7.0 1.81 8.9
2500 18.4 10.0 2.58 7.1
2750 20.7 12.0 3.10 6.7
3000 23.0 15.0 3.87 5.9
3400 25.3 23.0 5.94 4.3
3800 27.6 27.0 6.97 4.0

More at:http://www.aviadesign.com/MC29Perf.htm

yacht371

05-21-2006, 10:14 AM

The MC29 was tested at about 2000 Kg. weight(based on where she floated) with 4 persons on board. In about mid July we will have one(single diesel version) in Vancouver BC where more extensive sea trials will be conducted. We haven't tested her in large seas yet.

Once there are more details they will be posted on the Aviadesign web site. You probably already figured out who I am.

Grahame Shannon

Guillermo

05-21-2006, 02:13 PM

...In about mid July we will have one(single diesel version) in Vancouver BC where more extensive sea trials will be conducted.....
Thanks, Grahame. WE'll keep on waiting for those tests' results.
Cheers.

Zewe

05-23-2006, 10:38 PM

I'd be interested in feedback regarding Sea Bright Skiffs in the context of this thread. I understand that this type of hull is quite efficient in the speed range that is being discussed, and can be more seaworthy than other designs that are offer similar efficiencies. One example:

http://www.boat-links.com/Atkinco/Cruisers/Naiad.html

Comments?

Randy Foster

Willallison

05-23-2006, 11:02 PM

Gilbert

05-24-2006, 12:51 AM

What sort of dire consequences are you expecting?

Guillermo

05-24-2006, 01:33 AM

I have no experience with the sea-bright skiff, so I can't help you there - sorry
But something caught my eye in the drawings on the link to the Naiad that you posted, is that the shaft appears to be set at an angle.
This is something that I've never come across. I assume its been done to try to offset the torque of the propeller, but I'd be concerned, particularly at speed that it might have some rather dire consequences
Yes, I find that quite strange, too. Propeller doesn't seem to be that big and power is not so high....:confused: Coming from a reputed designer as William Atkin, I would like very much to know the reasons.

Guillermo

05-24-2006, 01:38 AM

Out of size for the thread, but a very nice boat also:
http://www.loganboats.co.nz/

Designer Arch Logan 1912
Builder Logan Classic Boats
Construction Female moulded GRP
Interior Polished kauri
LOA 10m, 33ft
BOA 2.5m, 8ft
Draft 0.6m, 2ft 2in
Displacement 3.2t
Cruising speed 8kts
Engine Lombardini 1404m 39hp
Fuel consumption 3L / hour
Range 600 nm
Fuel Tank 260L
Water Tank 260L
Holding Tank 100L

A pity she's not containerable only for a mere 4"....

Guest-3-21-09-10-33

05-24-2006, 01:45 AM

so even this:
http://www.gerrmarine.com/images/boat_images/power/gerr34seabright/gerr34seabrightA.GIF
34-foot Sea Bright skiff, motorcruiser. Beachable on Sea-Bright-skiff box keel and trailerable at 8 foot 6 inch beam

LOA: 34 ft. - 2 in. (10.4 m)
LWL: 31 ft. - 6 in. (9.6 m)
Beam: 8 ft. - 6 in. (2.6 m)
Draft: 2 ft. - 9 in. (83 cm)
Displacement: 7.5 tons
Diesel: 300 gal. (1135 l)
Water: 90 gal. (340 l)
Speed: 8 kts cruise
Power: Single 46 hp.
Westerbeke Speed: 8 kts cruise, 9 knots max

Raggi_Thor

05-24-2006, 04:03 AM

I don't know why the shaft is angled.
But the hull shape is a bit simmilar to the one featured in one of the last isuses of WoddenBoat, also discussed here I think. Quite interesting.

SAQuestor

05-24-2006, 07:12 AM

Yes, I find that quite strange, too. Propeller doesn't seem to be that big and power is not so high....:confused: Coming from a reputed designer as William Atkin, I would like very much to know the reasons.

From: "Of Yachts and Men" by William Atkin. Tiller Publications Copyright 1997 by John Atkin ISBN 1-888671-07-06

From the treatise on "Hell Diver", a 35' Seabright skiff type power boat. Designed in 1935. 35' LOA, 32.5' LWL 10' 10" beam 2' 9.5" draft.

Page 129:

"The engine is off the centerline of the boat, and thanks to the box deadwood has very little angle of shaft - less than 5 degrees. At the flywheel end of the motor, the center of the crankshaft is 7 inches to the port of centerline; but at the deadwood the center of the shaft is on the center of the boat. The result of this is a splay to starboard of the shaft from the deadwood to the motor, the propeller being on the centerline. All single screw powerboats having righthand turning propellers have a strong urge to turn to port, or to the left. Now by spraying the propeller shaft, as accomplished in Hell Diver, this port urge is counteracted by diverting the slip stream from the propeller flowing to starboard, and the boat will hold a true course without correction of the rudder. I have used this arrangement very successfully, and it is a wonder to me that all powerboats do not employ it."

He goes on to mention that for lefthand turning props that the engine needs to be splayed to starboard.

But a few pages later he describes another Seabright type boat, the 25' Princess Lena. Lena has the traditional straight centerline prop shaft from a motor in the fore/aft center of the boat.

Best I can do here is [shrug] and say that both the father and son are passed on and there is no one left to ask for a technical explanation. I doubt John's wife Pat - who still sells plans BTW - would know why one boat has it and one doesn't if splaying the shaft was such a great thing.

[edit] BTW - the power specified for Hell Diver is a six cylinder Kermath Sea Captain with a 4 3/8" bore by 5 1/2" stroke pulling 50 horsepower at 1000 RPM. The prop specified is 19" diameter by 18" pitch Michigan Wheel.

SAQuestor

05-24-2006, 10:19 AM

Here's some scans of Hell Diver from the book mentioned in the previous message.

Willallison

05-24-2006, 11:48 PM

I could imagine that for a displacement vessel an angled shaft might be of some benefit - particularly for slow speed manouvering. But the Naiad is shown as having a top speed of 17mph, and whilst this is hardly record breaking, you could still imagine some strange things occurring. If nothing else you would have to have the rudder at an angle to counteract the offset shaft.
Consider the anodes that are placed on larger outboards. They are placed at a slight angle to offset the effects of prop torque. But they are very small and the angles are not large either.
And if it was such a great idea, why haven't others picked it up over the years?
Nope - respected or not, I think My. Atkin had this one wrong.

Getting back to WHIO, when I first saw the lines that Gillermo posted I was struck by their similarity to a boat I saw some years back in Woodenboat. It was a boat called Wood Duck which was based on the old Draketail launches. On closer inspection, the boats are indeed similar, though at 34' 8" LOA and with a beam of 10', Wood Duck is a much larger craft - and forgive me, it's also outside the scope of this thread. She also requires a 250 hp Cummins diesel to drive her to her top speed of 28 knots.
Where WHIO appears to feature a fair amount of hook in her buttocks lines, Wood Duck shows a little rocker in hers. There is also no keel on the larger boat.

http://www.belkovyacht.com/building.html

The boat was featured in the June 1997 Issuse # 136 of Woodenboat

Guillermo

05-25-2006, 01:34 AM

Thanks a lot SAQuestor (May I know your name?) and Will. I'm going to try more info on disalignement of propulsion trains from other authors.

Gilbert

05-25-2006, 03:32 AM

Will,
Atkin, in his comments, says that the offset shaft frees the rudder from the need to compensate for the propellor torque. If we can't accept the word of a man who has designed over 40 different Seabright skiffs and probably used most of them on the water, whose word can we accept?

SAQuestor

05-25-2006, 01:39 PM

Let’s explore these thoughts a bit.

I could imagine that for a displacement vessel an angled shaft might be of some benefit - particularly for slow speed manouvering. But the Naiad is shown as having a top speed of 17mph, and whilst this is hardly record breaking, you could still imagine some strange things occurring. If nothing else you would have to have the rudder at an angle to counteract the offset shaft.
Consider the anodes that are placed on larger outboards. They are placed at a slight angle to offset the effects of prop torque. But they are very small and the angles are not large either.
And if it was such a great idea, why haven't others picked it up over the years?
Nope - respected or not, I think My. Atkin had this one wrong.

Will,
Atkin, in his comments, says that the offset shaft frees the rudder from the need to compensate for the propellor torque. If we can't accept the word of a man who has designed over 40 different Seabright skiffs and probably used most of them on the water, whose word can we accept?

Will, I’m interested in those “strange things occurring” you mention. Care to elaborate on the specifics you envision?

Will’s comment further suggests that we should toss out “old” ideas just because others that follow haven’t picked up the idea and used it again and again.

With that theory, then we should toss many ideas that don’t fit ‘modern’ conventional wisdom.

Gilbert poses the proper question – whose word can we accept?

Down another path here for a moment. I want a retirement boat that I can transport from sea to shining sea and with a great lake or two in between. A boat that is suited to a summer in Alaska and a winter in The Bahamas. Next summer in Nova Scotia and next winter in the Sea of Cortez.

This idea is doable as a home built and owner trailerable concept. Portager’s numerous postings suggest that a 40’ plus boat can be transported across the highways and byways of North America. Option One is another viable concept. Tom Lathrop has posted that he is developing a 28’ version of his Bluejacket and that may be the most practical solution of all. We’ll see when that is done.

But the exact design of the boat is open to debate and discussion.

I’ve communicated with several much more knowledgeable people – designers that post on this forum – about adapting Atkin’s Seabright Skiff concept into a transportable boat that will fulfill the above requirements.

To a man they have pooh-poohed the idea. Not efficient. Too difficult to build. Not modern. The reasons are numerous and I’m not going to fetch the emails to enumerate each reason.

Regardless of their rationalizations, I can’t understand why a design that was fished in apparent safety for decades off the New Jersey beaches isn’t still appropriate for today’s world. What makes ‘modern’ hull forms superior? I’d suggest nothing except the individual’s opinions and bias toward their own training and body of work. I’d suggest that not many people – boat designers/naval architects notwithstanding – are able to come to terms with ‘borrowing’ another person’s ideas and giving credit for that idea rather than claim it 100% as their own. And no, this is not a slight at anyone that has posted in this thread, but rather an observation of general human nature.

Why does the Seabright hull form as refined by Atkin appeal to me and my trailerable retirement concept?

In order to get the most boat into a box that is defined by the rules of the road – 13’6” (4114mm) high by 9’10” (~3000mm) wide without a pilot car in most states – requires some ‘out-of-the-box’ thinking.

Think of the cross-section of a large trailer. When a “normal” boat sits on a trailer what do you see? If the boat has any kind of a keel, there is usually a huge empty space between the keel and the insides of the wheels/tires/fenders. If the boat has a Vee bottom, then the empty space is much less, but there is still some wasted area.

Think about a displacement boat suitable for the types of waters I mentioned above. There is certainly a chance that some adverse weather/wind/waves would be encountered at some point. What type of boat would YOU like to have when that happens?

Personally I’d like to have one that has some weight down low in the hull – low ballast if you will. On a boat that will be towed behind a heavy-duty pick-up it seems impractical to tote along a few thousands pounds of lead just to ensure some low ballast.

What, to me at least, makes much more sense it to locate the heavy machinery, batteries and tanks as low as possible. How to do that in a conventional hull form? Doggone difficult best describes it.

But if one takes a box keel ala Bolger (and others) or a Seabright keel from Atkin it is possible to get that space between the wheels filled up with machinery, batteries and tanks. That means that the remaining height can more easily accommodate living space while making the whole boat as stable, safe and seaworthy as possible.

I know that this is only one approach to hull design – and certainly not the only appropriate one for this sort of use. But it does (at least to me) appear viable.

Back to the shaft offset in Atkin's designs.

To dismiss ideas that are 50 - 75 or even 100 years old as impractical or obsolete or not appropriate because one has no personal experience seems to be the height of folly. How much valuable experience or information has been thrown away because it has been forgotten or hasn’t been widely adopted? Probably lots.

PERHAPS, just perhaps, this slight shaft offset is one of those good ideas that – for whatever reason – got ignored by the main stream of that era and never carried forward to us.

And granted, it may NOT be a good idea and was rightly ignored. But as Gilbert suggests, should we dismiss out of hand an idea of a man of such stature as Atkin?

Worthy of a discussion me thinks.

And Guillermo, here’s my name.

Best,

Leo

Guillermo

05-25-2006, 05:35 PM

Thanks, Leo.
As told before, I'll try to find something about not aligned propulsion trains in older boatdesigning books...

SAQuestor

05-25-2006, 06:07 PM

Thanks, Leo.
As told before, I'll try to find something about not aligned propulsion trains in older boatdesigning books...

Gracias mi amigo

tom28571

05-25-2006, 08:41 PM

Zewe

05-25-2006, 08:52 PM

Tom,

Can you expand on your comment that you

'don't think this form lends itself to trailering in a cruising size too well since it will need be heavier to get adequate stability with that much volume underwater'?

I am sure I don't understand what you are actually trying to say.

Thanks,

Willallison

05-25-2006, 09:21 PM

1st up, I'm not completely dismissing the idea of an offset shaft - though I will grant that my previous post would suggest that I am. And it's certainly not the case that one should dismiss an idea simply because others have not picked it up.
But I still have my doubts about this particular application of the idea. If the shaft offset is clearly visible to me in a scanned reproduction of some old drawings, then the angle must be fairly substantial. Just looking at it, it looks like four or five degrees. The boat also has a fairly substantial rudder.
So, again, just from looking at it, this seems like massive overkill to me. I've driven any number of single engined, inboard boats - both displacement and planing, and whilst the 'prop walk' that is present at idle can be awkward for some, the effects of the propellors torque generally becomes less noticeable as speeds increase.
That is not to say that the effects diminish as speed increases - clearly they don't - but any required steering input is so slight that it is barely, if at all perceptable.
Now - as to your question of the strange effects I envisage... With the shaft set at say 4 degrees off centre, I picture the boat doing 17mph with the helmsman hanging onto the tiller for dear life simply trying to keep the thing in a straight line. I know that Atkin says that the angle offsets the prop torque, but I just think its been overdone in this case.
I may be wrong - certainly happened before!:D

I would also concur with Tom about the boats suitability as a trailerboat. Under normal circumstances, when it comes to trailering, the lighter the rig the better. If you take lightweight construction and the box keel idea to the extreme, then only the keel sections would be immersed, making for a very unstable craft.
Also with Naiad you have very rounded sections, so any reduction in weight will lift the boat to a much narrower waterline beam - once again making the craft quite unstable. If it were a hard chined boat with almost the full beam at the waterline, at least you would gain some form stability

SAQuestor

05-25-2006, 11:08 PM

Will, thanks for the thoughtful reply.

{snip}If the shaft offset is clearly visible to me in a scanned reproduction of some old drawings, then the angle must be fairly substantial. Just looking at it, it looks like four or five degrees. The boat also has a fairly substantial rudder.
Based solely on the quote I posted above and assuming 6’ – 72” (1828mm) from the front of the engine to the prop, and using the figure of 7” offset at the flywheel (if the flywheel if forward on the Kermath engine that Atkin specified) then the degree of offset is just shy of 4º. If the flywheel is at the aft end of the Kermath engine, then the degree would be even more – perhaps as much a double. And you’re correct, I too can’t see how more than a few degrees would work.

{With the shaft set at say 4 degrees off centre, I picture the boat doing 17mph with the helmsman hanging onto the tiller for dear life simply trying to keep the thing in a straight line. I know that Atkin says that the angle offsets the prop torque, but I just think its been overdone in this case. I may be wrong - certainly happened before!:D
While I do not doubt your experience and knowledge, I would like to hear from some of the other folks with their thoughts.

{I would also concur with Tom about the boats suitability as a trailerboat. Under normal circumstances, when it comes to trailering, the lighter the rig the better. If you take lightweight construction and the box keel idea to the extreme, then only the keel sections would be immersed, making for a very unstable craft.

One thing that I failed to note in my screed above is expected trailering weight of the ideal retirement cruiser. Many heavy-duty diesel pickups can have a towing capacity of 14,000 to 15,500 pounds – 6350-7030kg. Subtract a generous trailer weight of 3000 lbs and one arrives at a maximum empty boat weight when sitting on the trailer of 11,000 to 12,500 pounds. In reality I’d imagine something in the 10,000-pound (4500kg) area would be achievable. Add fuel, water and stores for 30 days and cruising weight may increase by two or so tons to (give or take) 14,000 pounds, (6350kg).

And yes, this is not a boat that one would trundle off to the local lake for a Sunday afternoon cruise. Rather it’s a boat that that one would take to a marina with a straddle lift, set it in the water and go cruising for weeks or months. Then come back and set it back on the trailer for a trip home or to the next cruising area.

So I hope that mostly satisfies your concerns about weight reduction and stability.

Also with Naiad you have very rounded sections, so any reduction in weight will lift the boat to a much narrower waterline beam - once again making the craft quite unstable. If it were a hard chined boat with almost the full beam at the waterline, at least you would gain some form stability
Back when I started exploring this idea of a transportable retirement cruiser I did some AutoCAD drawings to see if the concept would even work. Attached are two VERY PRELIMINARY concepts – a jpg and a dxf file for your perusal and comment if you see a need.

Best,

Leo

tom28571

05-25-2006, 11:11 PM

Will explained it very well. It's a bit like deep V hulls. It's not coincidence that they are heavy, they have to be heavy in order to get enough of the boat in the water to make them fairly stable. At that they are not very stable at rest or at slow speed. Just looking at the lines of the Seabright skiffs, you could estimate the displacement required to set it on its waterline.

SAQuestor

05-25-2006, 11:21 PM

Saquestor,
I may be in error but I think the original thinking behind the Seabright skiffs was to launch and retrieve these work boats off the beach. Thus the flat bottom and the hidden propeller.
Tom, that’s my understanding also.

Up to moderate speeds, it also looks good from an efficiency standpoint. Also would be more seaworthy than a low deadrise form. I like the form but think it is probably limited to a relatively narrow beam for best performance. The engine and other stuff down low is also good for stability. .

Since I don’t think that a planing or semi-displacement boat of this size and weight would be economical to run, a hull form like this would of necessity, be displacement.

Your Liz design is nearly the opposite in that it’s light and planes at a low speed and thus is pretty efficient in its fuel usage. But these two types are really apples and oranges.

I don't think Bolger's box keels are this good. This is getting close to Atkin's tunnel hull designs.

I don't think this form lends itself to trailering in a cruising size too well since it will need be heavier to get adequate stability with that much volume underwater.

My 40 second evaluation, your mileage may vary.

Please see my response to Will and the attached jpg and dxf files.

In my mind the whole idea of either a box keel or a Seabright hull form is to get the fixed machinery weights as low as possible and to utilize all the space between the wheels of the trailer.

Best,

Leo

Willallison

05-26-2006, 12:02 AM

Zewe

05-26-2006, 03:04 AM

Thanks for the responses, Will, Tom and all. Perhaps I understand the point about trailerability now.

In stepping away from the question of trailering facility, I come to another group of questions.

Although they offer somewhat similar accommodations, the design Whio offers much lighter displacement than my estimate of the displacement of another of Atkin’s seabrights, a design called Jersey Blue:

http://www.boat-links.com/Atkinco/Cruisers/JerseyBlue.html

What are the pro’s and con’s of a heavier boat, within the context of this thread? I am assuming for these questions that both boats are built to form and spec’s that meet their design goals successfully.

The lighter boat will be more fuel-efficient, but what is being given up by choosing the lighter boat?

With regard to seaworthiness, would the crew be taking a larger risk in the lighter boat or the heavier boat, say, if they decided to make a crossing that would keep them out longer than the latest reliable weather forecast?

Are the two boats actually so different that it’s apples to oranges? It seems like the design goals for each are not dissimilar, so these should be fair questions.

The idea of using modern, relatively lightweight components and construction techniques to build an older design that was intended to weigh more seems to offer some room in the weight calculations for extra tankage, stowage, ground tackle and/or the occasional extra passenger. I wouldn’t suggest building the older design without the appropriate scrutiny/redesign by a qualified source, but it’s attractive to imagine some slack in the weight calc’s for a change. Am I naïve in letting my mind run in this direction?

I hope I don’t come across as being flip or bombastic. I am learning a fair amount while musing about the content of this thread.

Will - I typed this offline and posted it, and then read your most recent post. Your comments as they apply to my questions are duly noted...

tom28571

05-26-2006, 10:12 AM

Several others and I have been intrigued with a similar keel structure to the one you show. While I will never build such a boat, it does open up some possibilities. For me, one of the most interesting attributes is that it may be possible to cruise at speeds up to 20 or a bit more with high efficiency, low power and low operating expenses. I blue sky the thought of a very long canoe body (very high length/beam ratio) that assumes about 70% of the displacement. The upper body is of wide beam and only slightly immersed for form stability. The underbody could operate at the desired speed beyond the normal “hull speed” like a catamaran hull. The upper hull’s waterplane would be so lightly loaded in pounds/sq ft that planing would be possible with low power. The prop would be either tucked behind the underbody as you show or two props to either side, which would allow an even longer underbody. None of Bolger’s box keels seem to pursue this line of thought but Atkin may have had it in mind with some of his designs.

One issue is how to fair the bow smoothly into both structures for good rough water performance. Your lines look unfair and suspect to me. I might expect a lot of noise along with some other negative characteristics.

Such a hull might be a good choice for cruising but might also be too heavy to fit my weight limits. The launching ramps we encountered in Canada on a trailer/cruise there would have defeated the bigger and heavier boat and made some areas off limits without much time, bother and big bucks.

In short, the compromises I made in designing the BJ 24 still make sense to us and I don’t envy the bigger boats at all.

SAQuestor

05-26-2006, 11:40 AM

Leo - All this gets back to a debate that's been had a number of times on these boards - indeed Tom & I have discussed it on more than a few occaisions!:D
It really depends on two things
1. Whether you are after a boat that is trailerable or a trailerboat
2. Whether you're confident in handling a very substantial boat trailer combination (and whether you want the hassle that comes with it).

Will, you are exactly right. And I thank you for recognizing the difference.

{snip} I can assure you that you don't just bolt the thing on the back of the car and take off. Tyres, bearings, brakes etc etc are under much greater strain than normal trailering loads and require fairly regular replacement / service. Not only that, you are somewhat restricted in where you can go with such a large rig.

Being exiled here in south Texas (Really, I like the 5 or 6 months of 95° to 105° (35° to 40°C) temps.) we see thousands and thousands of wintertime “snowbirds” – seasonal residents as one friend calls them – that drag their trailers behind their ¾ or 1 ton PU’s from their frigid homes in Indiana or Wisconsin or ??? These folks might have a trailer as small as ~25’ and go up to behemoths that are 40’ or a bit more long and nearly 13’6” tall. Like this one as an example. (http://www.holidayrambler.com/models/static/presidentialsuite_chart.html)

All of these largest trailers seem to have 5th wheel hitches and tow just fine thanks. I had to go to our corporate office a few days ago from the R&D facility where I work – on the way back I passed a convoy of 3 of these enormous PU/trailer rigs. Each combo had a ~35’-40’ 5th wheel trailer being towed by a turbo-diesel PU – two Dodges and one Ford – and the couples in each were at least in their 60’s and perhaps, if the amount of white hair and wrinkles are any indication, maybe in their 70’s. The “suggested” speed on this portion of the freeway is 65mph (105kph) and all three were tooling right along at that speed.

My point of this little story is that if they can navigate a 50’ long trailer/truck combo through city traffic what’s the difference if it’s my retirement boat on a trailer instead?

Certainly, in matters of detail there are differences, but not in the concept – at least as I can envision.

What I can see as differences are:

1. Movable load on a trailer versus a fixed trailer load.
a. Must be tied down securely and frequently checked.
2. Over-width up to 16” (400mm)
a. Need permits, signs and maybe flashing lights to legally travel.
3. Trailer needs to be engineered for induced stresses.
a. Tires, wheels, brakes and frame members of correct size with added safety factor for load.
4. Tow vehicle rated for GCVW.
a. Maintained in good condition to avoid breakdowns.

Can anyone else see any other significant differences that I’ve overlooked?

It also depends on what kind of boating you do. Tom's boat was designed to specifically meets his needs and objectives. It does that very well - so well in fact that others pestered him to the point where he now sells the plans to her. But her success depends to some extent on remaining light. I've no doubt the boat would still perform well in a heavier state, but with a comensurate loss in efficiency. That's not a criticism of the design, it's simply a fact of life with planing boats.

I know. And Tom’s Bluejacket is another possibility – so much so I bought a set of plans a few weeks ago. :)

Obviously Bluejacket – or even the 28’ version that Tom is working on – is a much different concept than my Starsinger. Apples and oranges once again. Having said that, Bluejacket is a viable alternative if my health goes further south, if my investments tank or if the wife ultimately doesn’t want to invest her time and money in a larger project. Bluejacket was designed for a specific set of circumstances and in those circumstances the boat performs superbly!

Now if you are happy to doddle along at 6 knots or so, then you are quite correct, weight becomes less of an issue (setting aside the trailering thing). And for a 30ft boat 6 - 7 knots is about as fast as you'll be able to go before you enter the realm of diminishing returns. {the rest snipped}

And that once again illustrates why minimal overhangs and long water lines are a good thing for getting the most speed at efficient fuel consumption rates in a displacement boat. A reasonably efficient speed is ~6 knots. The key – at least in my mind – is being able to do that 6 knots on less than a gallon of fuel, hopefully significantly less. It’s doable, but lots of details have to coincide for that to happen consistently.

Best,

Leo

SAQuestor

05-26-2006, 11:46 AM

{snip} One issue is how to fair the bow smoothly into both structures for good rough water performance. Your lines look unfair and suspect to me. I might expect a lot of noise along with some other negative characteristics. {more snippage}

I understand your point and I want to make sure everyone understands that these were proof of concept doodlings rather than any effort to actually design something viable.

And yes, that box keel idea has seen the light of day in an Italian boat with the added feature of some "wavy" hull forms that (supposedly) minimizes wave making resistance, improves efficiency and yada-yada. I forget the name but it has been discussed here on BD.N about a year or a bit more ago.

Best,

Leo

tom28571

05-26-2006, 02:08 PM

Ah yes Leo,

That was/is the "Slider" that was on the forum. I can see that my comment needed more clarification. I knew that your sketch was just that and there had to be some way to blend the structures. I have not figured out how to do that most effectively either. It's easy if you don't mind otherwise useless length but my mantra is always efficient use of space and material. The idea of what I call the "two phase hull" was also discussed here on the forum a couple years ago.

Liz and I have been traveling about North America in a Dodge campervan since I retired. It has all the necessary features but at 19' is tiny compared to the big rigs like the one you showed. The one big difference between the two kinds is in the way they are used most effectively. We mostly travel, and camp in order to make the traveling economically feasible. The big rig folk stay in one location extensively and travel much - much less than we do. We have traveled to all the lower 48, Alaska, all Canadian provinces except Newfoundland and also in Mexico. We did this and still have a pretty normal home life where I can work on boats and make a nuisance of myself here.

We wake up and the weather is bad. So we travel. Takes about 5 minutes to get underway or set up. The big rigs take hours to get away and are limited to "improved" campsites while we can stop in rough spots that appeal to us. This same sort of reasoning applies to easily trailerable versus transportable boats.

As was said, it's all about personal choices and decisions. The more stuff you have, the more effort and bother there is to keep it fed and happy. I don't want to disparage the other point of view, it's just not for me. Many of my boating friends have much larger vessels, sail and power. Most seem to enjoy themselves although their toys consume much more of their time, money and effort than ours. Now, some have enough money that they just let someone else do all the work. That works too.

Guillermo

05-27-2006, 03:28 AM

I've been searching for disaligned propulsion systems and found nothing till now. Just the usual stuff about offset shafts and the like.
Maybe this Atkin's idea didn't work because cruising boats really do quite a lot of maneouvering, so an angled shaft adding side force to the propwalk when in astern wasn't a desirable effect...? Or, at the end of the day, propwalk was not such an important issue when going forward...? Just aesthetics...? :confused:

SAQuestor

05-27-2006, 07:42 PM

Ah yes Leo,

Liz and I have been traveling about North America in a Dodge campervan since I retired. It has all the necessary features but at 19' is tiny compared to the big rigs like the one you showed. The one big difference between the two kinds is in the way they are used most effectively. We mostly travel, and camp in order to make the traveling economically feasible. The big rig folk stay in one location extensively and travel much - much less than we do. We have traveled to all the lower 48, Alaska, all Canadian provinces except Newfoundland and also in Mexico. We did this and still have a pretty normal home life where I can work on boats and make a nuisance of myself here.

Yes!:!: Exactly what I have in mind.

One of the first inspirations for doing this came from these folks (http://www.geocities.com/bill_fiero/).

The sort of traveling that they do is amazing. But if you read the entire site you'll soon see that they have been traveling all their lives.

Best,

Leo

Corpus Skipper

05-27-2006, 08:29 PM

Something like this, Leo?

SAQuestor

05-27-2006, 09:27 PM

Something like this, Leo?

Kinda-sorta, but not exactly.

More like this sort of styling with a bit more room.

Guest-3-21-09-10-33

05-28-2006, 12:29 AM

this is a Devlin?

Guillermo

05-28-2006, 04:48 AM

Nice boat Leo.
Talking about not trailerable boats, I'd like to further explore the cat concept, like the Grahame ones (http://www.aviadesign.com/) or these Motorcats (http://www.motorcat.com/tec.html) from Poland. I do not like their modern styling (I'm a conserrvative guy, more in the line of this Tomcat 255 http://www.c-dory.com/24%20description.htm . Not precisely this particular one but you know the idea...), but the concept is appealing to me. Provided with the minimum possible power to fully plane under load, just to go let's say up to a maximum of 23-25 knots. Any other interesting cats?

Guest-3-21-09-10-33

05-28-2006, 06:02 AM

Here our new day cruiser power Catamaran under design by Albert Nazarov. A cabin cruiser version will follow.
Lenght 9,5 mt
beam 5 mt
3500kg of displacement
The first will be a day cruiser more as a “Floating Sala” with a rigid roof. Will follow a cabin version similar to the Prowler 9000 (with similar specs) by Shionning design.
Max speed with 2x90h.p 24 knots. For 2 per 75 h.p. 20 knots.
To be build economically in plywood epoxy (ply core between two layer of epoxy with GRP).
.

Guillermo

05-28-2006, 01:41 PM

Too much beam, to my taste. Have you figured out already accelerations?

Willallison

05-28-2006, 07:23 PM

Leo -
Can anyone else see any other significant differences that I’ve overlooked

Yep - thie biggest one. Boat trailers are continually subjected to a a regular dumping into the water - often salt water. This occures, more often that not, at the worst possible time - when brakes and wheel bearings are still hot. There are now excellent systems designed to keep lubricant in and water out, but this will always be the weak point of the boat trailer.

Tom - I too have looked into incorporating the catamaran hullform generally known as a displaning hull, into a slightly beamier monohull. I think I may have posted some images somewhere about the place too. Definitely worthy of further exploration. I'll dig up mu images and open another thread on the subject....

Guillermo - I too have had a bit of a look for info about offset shaft angles. Turned up zip. I'll have a bit more of a look, but still suspect the idea was given up as a failure....

Guest-3-21-09-10-33

05-28-2006, 09:18 PM

Too much beam, to my taste. Have you figured out already accelerations?
You have to consider the purpose of the project, a Floating sala for cairibean and asian tropical sea, no beam=no space, no space=no fun for the customer. I will consider for the cabin version, our own proposal project with no customer requirements, a smaller beam.

tom28571

05-28-2006, 11:08 PM

Leo -
Tom - I too have looked into incorporating the catamaran hullform generally known as a displaning hull, into a slightly beamier monohull. I think I may have posted some images somewhere about the place too. Definitely worthy of further exploration. I'll dig up mu images and open another thread on the subject....

Guillermo - I too have had a bit of a look for info about offset shaft angles. Turned up zip. I'll have a bit more of a look, but still suspect the idea was given up as a failure....

Will, A very descriptivename even if it doesn't sound too great.

Guillermo, I handled a 36' sailboat with the prop angled to starboard. No issues going ahead although we hit a deadhead in the Champlain Canal and had to get the exposed shaft replaced and the prop repaired. Most difficult boat to back into a slip I've ever encountered. Go figure.

Guest-3-21-09-10-33

05-29-2006, 01:26 AM

to understand better our catamaran purpose..
and after the cabin version we intend to propose.

fcfc

05-29-2006, 05:40 AM

They are not too pocket, but they are on the ligth side:
http://www.tennantdesign.co.nz/boats.php?boat=39
http://www.stanyonmarine.com.au/pdfs/10M%20DART%20BROCHURE.pdf

Both are powered by "small" outboards.

One thing bother me. They are not trailerable due to their beam. And trucking would be very expensive. (too wide).

I have seen tri with folding outriggers for trailering, but do "half able" catamarans exist ?

Because "half" of above catamarans would be easily trailerable, beam and weigth. Even containerable if you remove roof top :P .

Guillermo

05-29-2006, 06:32 PM

There are several trailerable sailing catamarans (or, at least, advertised as such). Just google for 'tarilerable catamaran'.
The 'Motorcat 30' is also advertised as trailerable, although beam is 2,89 m :confused:
http://motorcat.com/index_mc30.html
Some interesting thoughts about power cats consumption:
http://www.pedigreecats.com/faq.htm#consumpt

From "Sail" magazine:
"Cats on trailers
Most cruising cats must be kept on a mooring or in a wide slip and require a boatyard to haul and store. There are exceptions in a new breed of trailerable cats. Unlike most cruising cats with rigid bridgedecks, these high-performance cats in the 30-foot range have limited cruising amenities in the hulls, trampolines in place of rigid bridgedecks, and removable support beams. Once the beams are removed, the hulls, beams, and rig can be placed on a road-legal trailer and hauled by an average-size SUV. These cats won't rig and unrig as quickly as folding tris, but they do provide trailerability--albeit requiring some effort and planning--that was once considered impossible. B.S."

Anybady has more info?

Vega

06-18-2006, 08:21 AM

Not that I find it beautiful, but certainly it is a lot of interior space for a 28ft:)
The design is from Roberto Barros.

http://www.yachtdesign.com.br/02_ingles/index_ingles.htm

Willallison

06-18-2006, 07:46 PM

Hmm - agree with you about the looks Vega.....
But this boat fails my pre-requisite eat & sleep test.
It's simple. Boat sleeps 4 - should be able to seat 4 around the dinette.

This boat sleeps 4, yest only seats 2.
What do you do - eat in shifts?

yacht371

06-18-2006, 10:48 PM

The Motorcat 29 (see www.aviadesign.com) is legally trailerable at an 8'-6" beam, and weighing under 2 tons. The first one has just been shipped (to Vancouver BC arriving July 20). It offers cruising speeds up to 20 knots with outstanding fuel economy, power can be twin outboards or single diesel. Two tiny 15 HP outboards are enough for 10 knot cruising. Maximum speed with 160 HP diesel is 24 knots, and to be honest, she feels like that is pushing the envelope. It seems like 100 to 130 HP is plenty.

Guillermo

06-19-2006, 12:18 AM

Grahame,
I would like to see more photos of the Motorcat 29 under way from several angles and sppeeds to better realize how she motors, as at your pages there are only a couple of them. Is that possible?
Also: I find impractical the rounded roof around the companionway as it doesn't allow to use that space in the bridge for purposes such as keeping paper charts when navigating, etc., or other items.

Paulo,
I don't like the styling of the Barros design, either. Neither the design itself. She seems to be a quite beamy displacement boat, so not motor efficient and probably quite uncomfortable when on a seaway.

Willallison

06-19-2006, 12:22 AM

Re motorcat 29....
Always difficult to tell from pics, but I'd be more concerned about blind spots created by what appear to be very thick A & B pillars

fcfc

06-19-2006, 05:07 AM

Not that I find it beautiful, but certainly it is a lot of interior space for a 28ft:)
The design is from Roberto Barros.

http://www.yachtdesign.com.br/02_ingles/index_ingles.htm

Here is a clone in kit / homebuilding :
But a 28 ft displacement only should be in the 6 - 7 kts range. Not that much.
But it is on the cheap side to build (40-50 k€) and to operate. (small engine). Should be less than 1 gal /h.

fcfc

06-19-2006, 08:32 AM

You can also find theses:

http://www.rangertugs.com/r/r-25.cfm
http://www.c-dory.com/
http://www.nimbleboat.net/images/kodiak-trawler.pdf
http://www.nimbleboat.net/images/nomad.pdf

NB : The Glen L Hercules is for homebuilding.

yacht371

06-19-2006, 10:08 AM

Unfortunately I don't have more photos of the MC29 underway, we only had a brief test in the Oder river in March before the Wroclaw Police shut us down for breaking the speed limit (not posted). When the boat gets to Vancouver we will test it thoroughly and get better photos and videos. It felt very smooth riding and stable, but we didn't have any serious waves.

The rounded dash is not intended as an area to be used for charts etc. We will install a large Chartplotter directly in front of the helm. We do carry paper charts, and will use them for backup and planning. The dinette table is large and makes a good chart table. This boat sleeps 4 max, and the dinette seats 4 in comfort.

A Force 10 propane stove with grill will be installed in the galley.

Visibility:
The B Pillars are thick (they hold up the roof) but no more so than in other small trawlers, see photos of the Ranger 25 and Gen-L boats. What they don't show you is a photo looking out. In practice, when driving the boat I never felt there was a problem with visibility. We do think we can make the windshield a little wider on future boats.

I have experience with boats that use only thin aluminum frames on the windows, which are also expected to hold up the roof. They always leak sooner or later, and have been known to collapse entirely.

Visibility in a relatively slow boat is not the same as for instance in a car where speeds are much higher and you have traffic and pedestrians to contend with. That said, in this boat you can see out behind you, and I plan to install a rear view mirror. Many boats with an enclosed pilothouse lack any rearward visibility.

Vega

06-19-2006, 01:00 PM

Here is a clone in kit / homebuilding :
But a 28 ft displacement only should be in the 6 - 7 kts range. Not that much.
But it is on the cheap side to build (40-50 k€) and to operate. (small engine). Should be less than 1 gal /h.

That one is a lot better.
Who is the designer?

keysdisease

06-19-2006, 01:28 PM

Anybady has more info?[/QUOTE]

Look at this blast from the past, :)

http://www.thebeachcats.com/modules/gallery/album264

Vega

06-19-2006, 03:53 PM

The rounded dash is not intended as an area to be used for charts etc. We will install a large Chartplotter directly in front of the helm. We do carry paper charts, and will use them for backup and planning. The dinette table is large and makes a good chart table. This boat sleeps 4 max, and the dinette seats 4 in comfort.

It seems to be a very interesting hull, but I have some doubts about the design.

The boat looks like a sports boat, but it seems directed also to cruisers. I think that cruisers have a more conservative approach to aesthetics in what regards boat shape.

Perhaps that hull could be suitable for two different boats:

One, a sports boat, with the existing design, more powerful engines, and capable of 25k.

Another, with less powerful engines, maximizing consumption economy and interior space, with a better quality interior. This one would gain in appeal with a less “modern” look. Cruisers, in what concerns aesthetics tend to be a more conservative group than Sportboaters.

Guillermo

06-19-2006, 03:57 PM

before the Wroclaw Police shut us down for breaking the speed limit

Wow! Risky business that one of yours!

I think it's a pity the rounded dash not being able at least to be used as a 'temporary storing' surface. You always need places aboard where to leave temporarily small items such as binnacles, caps, papers, etc, etc.

I agree with you aluminium frames to support the roof is a 'guarantee' of leakings sooner or later. There's not such a thing on boats as a roof where nobody ever climbs to....

Please let us know results when you perform more extensive tests in Vancouver.

fcfc: Nice posts, thanks. I had forgotten about Nimble boats. They have motorsailing versions of their boats.

keysdisease: Thanks for the post. Interesting although not very paractical for a cruising boat. I had read someting about that system somewhere else but couldn't find where.

Vega

06-19-2006, 06:32 PM

What about about this cute 25ft?

fcfc

06-20-2006, 04:09 AM

What about about this cute 25ft?

Fine, but at 5 tonnes 4 and 2 * 200 hp, I would not call it a "pocket" cruiser. About the same weigth and power as a Beneteau Antares 980. ( And probably around the price of an Oceanis 393 :D )

The C Ranger 25 has less than half the displacement, and only 20 % of the power. But the superstructure are ugly, probably because the hull is not deep enough to provide some headroom with a sleeker design.

Vega

06-20-2006, 07:55 AM

Fine, but at 5 tonnes 4 and 2 * 200 hp, I would not call it a "pocket" cruiser. About the same weigth and power as a Beneteau Antares 980. ( And probably around the price of an Oceanis 393 :D )
.

I don't see what the power or price have to do with the qualification for "Pocket Cruiser". Pocket Cruiser means small cruiser.

About the weight, it is needed for stability and that weight is a full weight load, for light weight you would probably take a ton out. And don't forget that this is a Class B boat, like the Antares.
About the Power 2X147kw it is just the Max power. Most of the boats have smaller engines.

About the price, this is a high quality boat, nothing to do with Beneteau, but even so it is not as expensive as you imply.

Look at the price of this used boat. Nice price...boat already sold:D

http://www.eyb-boats.com/fr/recherche.cfm?NumLangue=2&S_idPanier=JaDz4RC8W2Ud6H4bkbS3&monnaie=0&unite=m

Guillermo

06-20-2006, 02:05 PM

What about about this cute 25ft?
Nice boat with nice interiors, Who's the builder?
Having a look at displaced water produced when under planing (as per photo), she seems to be quite heavy. fcfc talks about 5 tonnes, confirming this first thought. Going heavy for this kind of (planning) boats doesn't make a lot of sense to me.

Although I'm fond of displacement boats, for long range motor-cruising under 30' probably fast ones are a better choice, because most of the time will be spent at marinas, ports or anchorages. With such an small boat very few will seriously consider any kind of passagemaking except the one that can be done in daylight hours and good weather (10 hours, 20 kn, 200 miles at the most?).

Unless having a lot of spare time available (I wish I could!) displacement hulls will confine the (not retired) user to coastal pottering in his/her home waters, which is very nice, but it is what it is.

Relatively high speeds and a low displacement combination make possible to reach pretty long distances, and then, if needed, easily bring the boat back home by truck, container, trailer, or the like. Or transported where needed.

A plumbed bow boat, with 8.5 m (28') Lwl, 2.5 m beam, 2500 kg loaded displacement and 20º deadrise, needs a 134 HP continuous rated engine (+/-) for an 18 kn ride. New Yanmar 4BY18 engine burns 7.5 lt/h at 3600 rpm (137 HP), so with only 75 lt (10 hours) you may reach destinations 180 miles away (weather & sea permitting).

270 kg 'wet' engine weight and, let's say, 150 lt fuel, 50 lt water, 375 kg crew (3 heavy)+stores and 125 kg 'diverse' hardware (ground tackle, batteries, other engine room appliances, etc), leaves 1550 kg for hull and its fittings & appliances, including shaft and propeller. Sounds this reasonable?

Peter Sewell got 1350 kg for the whole thing for a 9.1 x 2.24 m boat, with a 120 lt fuel tank (WHIO), so it sounds like it should be possible. Most probably it already has been done.

Will, Leo, Tom, others...?

fcfc

06-20-2006, 02:46 PM

[QUOTE=Guillermo]A plumbed bow boat, with 8.5 m (28') Lwl, 2.5 m beam, 2500 kg loaded displacement and 20º deadrise, needs a 134 HP continuous rated engine (+/-) for an 18 kn ride. New Yanmar 4BY18 engine burns 7.5 lt/h at 3600 rpm (137 HP), so with only 75 lt (10 hours) you may reach destinations 180 miles away.

[QUOTE]

something wrong somewhere ???

My own prog show me 60 hp for 14 kts. and 135 hp for 18 kts. The last 4 knots are expensive.

And a 135 hp should burn at least 23 l/h. 7.5 l /h only give you around 35 hp. There is a hundred missing.

fcfc

06-20-2006, 02:51 PM

The boat is sciallino 25.
A well equiped used boat can be seen here : http://www.barcoocasion.com/?zona=fichaAnuncio&anuncio=barcos&ver=4093

The full loaded weigth is 5400 kg. The payload is 800kg. So I have deduced the empty weigth is around 4600 kg.

Vega

06-20-2006, 04:30 PM

Nice boat with nice interiors, Who's the builder?
Having a look at displaced water produced when under planing (as per photo), she seems to be quite heavy. fcfc talks about 5 tonnes, confirming this first thought. Going heavy for this kind of (planning) boats doesn't make a lot of sense to me.
...
A plumbed bow boat, with 8.5 m (28') Lwl, 2.5 m beam, 2500 kg loaded displacement and 20º deadrise, needs a 134 HP continuous rated engine (+/-) for an 18 kn ride. New Yanmar 4BY18 engine burns 7.5 lt/h at 3600 rpm (137 HP), so with only 75 lt (10 hours) you may reach destinations 180 miles away.
...
270 kg 'wet' engine weight and, let's say, 150 lt fuel, 50 lt water, 375 kg crew (3 heavy)+stores and 125 kg 'diverse' hardware (ground tackle, batteries, other engine room appliances, etc), leaves 1550 kg for hull and its fittings & appliances, including shaft and propeller. Sounds this reasonable?
....
Peter Sewell got 1350 kg for the whole thing for a 9.1 x 2.24 m boat, with a 120 lt fuel tank (WHIO), so it sounds like it should be possible. Most probably it already has been done.

Will, Leo, Tom, others...?

That boat is a Sciallino 25ft and it looks that you have not seen my post, replying to fcfc.
The weight is 5400 kg at maximum load with 2x200hp engines.

As you know it is not very usual to give the displacement of a boat at Max load.
This boat is a very strong boat with an unusual load capacity.
The boat carries 700L fuel, 8 passengers, luggage (800kg), and 150L water.

If you take all this weight, including the weight of the two 2X200hp Yanmar (800kg), you get 2950kg for the hull and the interior, including a lot of equipment that comes standard with the boat.

If you change those engines (that are only the max power that the boat can carry) for 2x100hp engines (a more cruising adapted motorization) and consider as displacement not the max load, but the light weight, you will have 3450kg.

This weight is not far from the weight of the Seaward 25 (posted in another thread), that is a boat with similar characteristics, a strong and seaworthy small class B boat, as this one.

What you say about the power of the engine needed to go at 18 kn in a 2500 kg loaded displacement does not seem right to me. You need 134 HP continuous rated engine (+/-) , but for having that speed as a cruising speed you need an engine that has that power at ¾ of the max power.

For that you need the 6BY260. This engine can produce 260hp at 4000rpm, but only about 130hp at 3000rpm, a rotation adequate to a cruising speed (this series looks to be made for sportboaters and not cruisers. It has a lot of hp, but only at high revs).

The load that you propose for the 18k 28ft :”270 kg 'wet' engine weight and, let's say, 150 lt fuel, 50 lt water, 375 kg crew (3 heavy)+stores and 125 kg 'diverse' hardware (ground tackle, batteries, other engine room appliances, etc)” seems completely inadequate to me.

Who wants a cruising motorboat with only 50L of water and 150L of fuel?

The Sciallino 25 has also a nice semi-displacement hull, have a look:

http://www.sciallino.it/video/s25c-hull.wmv
http://www.sciallino.it/italian/sciallino25.php?espandi=4

Willallison

06-20-2006, 11:41 PM

Nice boat with nice interiors, Who's the builder?
Having a look at displaced water produced when under planing (as per photo), she seems to be quite heavy. fcfc talks about 5 tonnes, confirming this first thought. Going heavy for this kind of (planning) boats doesn't make a lot of sense to me.

Although I'm fond of displacement boats, for long range motor-cruising under 30' probably fast ones are a better choice, because most of the time will be spent at marinas, ports or anchorages. With such an small boat very few will seriously consider any kind of passagemaking except the one that can be done in daylight hours and good weather (10 hours, 20 kn, 200 miles at the most?).

Unless having a lot of spare time available (I wish I could!) displacement hulls will confine the (not retired) user to coastal pottering in his/her home waters, which is very nice, but it is what it is.

Relatively high speeds and a low displacement combination make possible to reach pretty long distances, and then, if needed, easily bring the boat back home by truck, container, trailer, or the like. Or transported where needed.

A plumbed bow boat, with 8.5 m (28') Lwl, 2.5 m beam, 2500 kg loaded displacement and 20º deadrise, needs a 134 HP continuous rated engine (+/-) for an 18 kn ride. New Yanmar 4BY18 engine burns 7.5 lt/h at 3600 rpm (137 HP), so with only 75 lt (10 hours) you may reach destinations 180 miles away (weather & sea permitting).

270 kg 'wet' engine weight and, let's say, 150 lt fuel, 50 lt water, 375 kg crew (3 heavy)+stores and 125 kg 'diverse' hardware (ground tackle, batteries, other engine room appliances, etc), leaves 1550 kg for hull and its fittings & appliances, including shaft and propeller. Sounds this reasonable?

Peter Sewell got 1350 kg for the whole thing for a 9.1 x 2.24 m boat, with a 120 lt fuel tank (WHIO), so it sounds like it should be possible. Most probably it already has been done.

Will, Leo, Tom, others...?

1550 kg for a 28-odd foot boat is certainly doable, but it requires pretty careful attention to weight control. There are other things to consider too.
For instance you are talking about a 1500 kg boat that must be capable of carrying another 1000kg of weight. A heavier payload will require a stronger - and thus heavier - structure, which may bump the weight up to over 1500 kg:( It's a never ending spiral of compromises and design descisions;)
20 degrees of deadrise may not be the best either. Whilst it's not in the realms of a true 26 degree deep-vee, you will still have to think about whether the weight of the boat is sufficient to adequatley submerge the chines whilst at rest. If not you will have a very rocky-rolly, noisy boat. And of course you will encounter a higher trim angle. If you're prepared to slow down a little in bumpy water you'd probably be better off with something more in the region of 15 degrees in my opinion.

Guillermo

06-21-2006, 02:10 AM

something wrong somewhere ???
My own prog show me 60 hp for 14 kts. and 135 hp for 18 kts. The last 4 knots are expensive.
And a 135 hp should burn at least 23 l/h. 7.5 l /h only give you around 35 hp. There is a hundred missing.
Ooops! Something's very wrong, sorry. It was 7,5 gall/h not lt/h when and where I saw it. Having a second look at the engine curves in internet (quite difficult to see numbers) I realize that for 2700 rpm (135 HP?) comsumption is not even 15 lt/h, so for a 10 hours ride is enough with 150 lt. Allowing for a 10% margin we could go for a minimum tankage of 165 l to keep weight low.

14 kn is too low to my taste, bringing the boat into a compromised region.

Paulo:
50 lt of water is quite enough to me as ususally trips will be from marina to marina (water available at the pontoons) and 50 lt are enough for 3 persons 3 nights when at anchor. On the Category B thing, I think Category C will be good enough for this design (It's a 'little' fast motor cruiser, and little fast motor cruisers shouldn't go out when waves are more than 2 m significative :) )
4RY180 engine has 180 HP maximum rating at 4000 rpm and a workable 135 at 2700 rpm (aprox). Anyhow I'm using this engine for the time being only for weight and consumption purposes.

....may bump the weight up to over 1500 kg.....you'd probably be better off with something more in the region of 15 degrees in my opinion.

Thanks a lot Will. Structure will be calculated and weight estimated after claryfing first the main design goals. About deadrise I still have to do more thinking on it.

Guillermo

06-21-2006, 04:29 AM

Nice site and nice boat, Tom.
http://www.bluejacketboats.com/bluejacket_24.htm

Guillermo

06-21-2006, 11:36 AM

Well, it seems I have some trouble here:

As per a well known estimating method (Hydrocomp) this supposed boat will not go into full plane until reaching 16.5-18.5 kn (depending on LCG position). Let's asume 20 kn, to be neatly into the planning zone.

Estimating the BHP needed for those 20 kn using several methods, I get:
- Barnaby: 107.7
- Crouch-Werback: 108.4
- Philips Birt: 108
- Skene: 85
- Peter du Cane: 83
- Keith (Japanese series correction): 108

Eliminating the two lower values, we can say 108 BHP seem to be a 'consensus' number. Allowing for 10% loses in shaft, appendages and gear, we arrive to a power of 120 BHP at its most, not the 134 I estimated before for 18 knots having used an spread sheet divulged in these forums (Bailey), that estimates wave making and friction resistances.

fcfc, what do you think? You said 135 Hp were good for 18 kn. What computer program are you using? (My NA one uses Mercier Savitsky's method, but I'm still not using it at this stage, as I do not have forms yet)

Other opinions, please?

Note
I'm working with the following:
Displacement = 2500 kg (5500 pounds)
Lwl = 8.5 m (27.89')
B (knuckle) = 2.4 m (7.87')
D/L ratio = 113,54

Vega

06-21-2006, 01:48 PM

If you want an economical boat, then what you want is not a planing hull, but a semi-planing hull, but a boat like the Andreyale 10m, designed by Joubert-Nivelt. This boat weighs only 2500kg and can make 15 Knots with a 60 hp engine, but the hull does not plane. Kind of cuts through the water. They should use a more powerful engine, because that speed is at 3000rpm and that is the max rpm of the Nanni engine they use, but not much, I guess that the optional 75hp would be fine.

But this boat, even bigger than the one you are talking about, does not gain in having a bigger engine than that. It is not a planing hull and the power would be wasted.

I Guess that with a 8.5M boat you can get around 13 knots (cruising speed) with a 60hp engine, wasting only about 7L/hour.

Nigel Irens, that has designed several boats (the Range series) with a hull that works the same way, explains what I am saying:

“As the performance of these semi-displacement hulls is very much linked to their waterline length, it follows that the bigger boats are more efficient for a given speed. That said, it is important to understand that this hull form should not be used if cruising speeds in excess of a speed/length ratio of about 2.5. are required - in this case 18.4 knots.(i.e.2.5 x the square root of the waterline length in feet). It would not be practical to install more power than is necessary to achieve a speed/length ratio of about 3.5.”

This means, that for being efficient, regarding fuel consumption, an 8.5 M boat designed with the kind of hull you are talking about, should not have a max cruising speed superior to 13k and it would be useless to try to go faster than 17.5K (even with a lot more powerful engine), at least according to Nigel Irens, and it seems to me that he knows what he is talking about:D

I would go for it. A speed of 13K, wasting only 0.6L/mile seems a good deal to me;)

Guillermo

06-21-2006, 03:24 PM

...with the kind of hull you are talking about...
What kind of hull am I talking about? :confused:

Vega

06-21-2006, 06:06 PM

What kind of hull am I talking about? :confused:

Humm, have you forgotten?:D

Relatively high speeds and a low displacement combination make possible to reach pretty long distances, …
A plumbed bow boat, with 8.5 m (28') Lwl, 2.5 m beam, 2500 kg loaded displacement and 20º deadrise, needs a 134 HP continuous rated engine (+/-) for an 18 kn ride. … so it sounds like it should be possible. Most probably it already has been done.

Will, Leo, Tom, others...?

Will has answered:

1550 kg for a 28-odd foot boat is certainly doable, but it requires pretty careful attention to weight control. …

20 degrees of deadrise may not be the best either. Whilst it's not in the realms of a true 26 degree deep-vee, you will still have to think about whether the weight of the boat is sufficient to adequatley submerge the chines whilst at rest. If not you will have a very rocky-rolly, noisy boat. And of course you will encounter a higher trim angle. If you're prepared to slow down a little in bumpy water you'd probably be better off with something more in the region of 15 degrees in my opinion.

We are talking about the boat you have suggested, a “A plumbed bow boat, with 8.5 m (28') Lwl, 2.5 m beam, 2500 kg loaded displacement …for an 18 kn ride.” A boat with“Relatively high speeds and a low displacement combination make possible to reach pretty long distances”, obviously a relatively fast boat with a low consumption.

Willallison has suggested a smaller deadrise. It looks that to be really effective it should have even a smaller one, at least if we are considering the successful experiences of Nigel Irens and Joubert-Nivelt in creating relatively fast boats with very low consumption (they are the ones that have managed to better comply with that objective, if we exclude cats, at least to my knowledge).

Now it is my turn to be confused…. What do you mean, isn’t your objective speed with very low consumption?:confused:

Guillermo

06-21-2006, 06:12 PM

isn’t your objective speed with very low consumption?:confused:
Desired speed with lowest possible consumption, yes. I've never said I wanted to go into the semiplanning mode. That's your assumption, not mine.

Vega

06-21-2006, 07:24 PM

Desired speed with lowest possible consumption, yes. I've never said I wanted to go into the semiplanning mode. That's your assumption, not mine.

You were talking about a boat with 8.5m with a beam of only 2.5m. I thought you were talking about a slender and light boat. I thought you were considering what Nigel Irens had said about it, regarding speed and fuel consumption in a slender and light hull.

The link to this paper has been posted by fcfc long ago and it is very interesting:
http://www.nigelirens.demon.co.uk/images/NigelIrens.pdf

‘THE APPLICATION OF SLENDER HULL TECHNOLOGY IN POWERED YACHTS AND SMALL COMMERCIAL CRAFT’.

Nigel Irens Design

This paper sets out to examine the role of slender-hull forms in the current powerboat market (both leisure and commercial), and suggests how that role might change in the future.

Although fuel prices are currently on the increase fuel is still a relatively cheap and available commodity but that the availability of suitable berthing facilities (mainly marina berths) is not. This has encouraged the development of short planing-hulled vessels.

Whilst these are usually fuelefficient at high speed in reality they may often be operating at low to medium speed - often because of adverse sea conditions. At these lower speeds their performance is often unsatisfactory
and inefficient.

SLENDER HULL’ DEFINITION:

In the context of single-hulled vessels the term ‘slender-hulled’ is used here in the absence of a more accurate generic term to describe any vessel that reaches its design speed with little or no dependence on dynamic lift. The following parameters describe the nature of these hulls:

Design speed would normally be in the region of up to 2.0 x _dwl(ft) although 2.5 x _dwl(ft) would still be realistic as a maximum cruise speed – at which point there would a degree of dynamic lift would be present.

There is, therefore, no pretence that slender single-hulled vessels
can be as suitable for high speed operation as dynamically lifted hulls.

Favorable displacement/length ratios are at the heart of a successful non-dynamically lifted vessel. Typically they will need be less than 100. [where DL = Displ. (long tons) /(0.01 x dwl )³ ].

.....
…it is only during the 20th century that the search for higher speeds has lead to the inevitable use of some kind of dynamic lifting technology to break free from the clutches of excess wave-making drag and, ultimately, skin friction – the Achilles heal of the slender hull.

As operating speed/length ratio increases it is well established that there comes a point where at least some degree of dynamic lift is necessary to avoid the need to apply exponential amounts of power.

The point at which this dynamic lift becomes essential depends very much on the configuration of the vessel in question; if it has a favourable displacement/length ratio, for example, then a nonplaning or semi-planing hull form can be driven faster without incurring excessive drag penalties but with only modest amounts of dynamic lift being generated.

To some extent favourable (low) displacement/length ratios may be achieved simply by using lightweight building technology but it is more likely to be the result of a fundamental design decision to cut down on both the living volume and complexity of its on-board systems ..

There are several areas in which slender- hulled vessels excel:

a) The dilemma with any planing-hulled vessel is to choose a dead-rise angle that is low enough to allow planing to occur at relatively low speeds (and reasonable power) and high enough to limit the hull’ s propensity to slam when powering to windward.

The sections of a slender-hulled vessel can be as deep as necessary to promote a more gentle upwind ride as the hull is not being asked to provide dynamic lift.

The most sea-kindly planing hulls usually have high dead-rise angles but, in consequence, high installed power requirements.

If they are designed to be able to make way fast upwind in almost any conditions (e.g.lifeboats) then they will also be heavy – which will again call for more power.

b) A relatively slender-hulled vessel can provide a good quality of ride upwind as a result of being long enough to span wave crests, ...

c) Planing-hulled vessels can be difficult to manage in following seas; by their nature the half-angle of entry of their waterlines is often very high – especially above the chine. If powering downwind in strong conditions there is a danger that such a vessel will plane into the back of a wave where it will decelerate very rapidly. As the mass of the engines is often
well aft on a planing-hulled vessel there can be a tendency for the stern to try to overtakethe bow. This is aggravated by the fact that the rudders - which are usually designed tooperate in the back-wash of the propellers – will lack area when the power is suddenlytaken off .

The result is that directional stability is difficult to achieve and progress can beslow and laborious at best - and dangerous at worst.

Slender hull drawbacks:

.. many marinas charging an increased tariff per metre for vessels over certain threshold lengths.

There are also other financial burdens to be born by the owner of the longer vessel: In the following comparison between a standard planing-hulled and a slender-hulled a common nominal displacement of 5.5 tonnes results in the planing-hulled vessel having a length of 10.20 metres against 12.00 metres for slender-hulled model – an increase of 18%.
…
In general terms the planing powerboat has a shape that is ideal from an accommodation point of view, the .. compared to the slender-hulled equivalent model ..

……………………………………………………………………………………………….
CONCLUSIONS

The first and most obvious conclusion that can be drawn ...is that high speed is an expensive option – no matter what hull-form is chosen.

Non-planing or semi-planing RANGEBOAT-type hulls are very dependent on waterline length if they are to produce really convincing performance figures. ..

The reality of the experience with operating the RANGEBOAT is that the vessel settles to a comfortable and sustainable speed of between 13 and 15 knots. The chart shows that fuel economy at those speeds is satisfactory. ..

Every effort has been made to reduce noise levels and the objective is to make it possible to use the vessel in much the same way as a sailing yacht is used, so that passages of 100-200 miles could be realistically undertaken .
.....
Future trends in fuel cost are unpredictable but likely to be more volatile than they have been in the past.
…….
The real question ..is : what proportion of the time spent underway in the average planing-hulled leisure powerboat is spent at the high speeds for which the hull was really designed ?

Figures may not exist to answer that question, but realistically it appears that high speed operation is very often limited by sea state.

The strongest argument to support the use of slender-hulled power vessels must surely be that they offer a pragmatic solution to this problem. Like their planing counterparts reality will dictate that even their lower cruising speed will often be further reduced as a result of adverse sea conditions, but they are fundamentally well adapted to performing in a seaworthy and safe way at any chosen speed.

Willallison

06-21-2006, 07:31 PM

It's all pretty simple really. If you want to do 18 knots with a 28' LWL boat then you are better off with a planing hull - though having said that, I've been aboard boats that are most certainly of semi-planing hullform that are still quite economical at up to about 20 knots.
The secret to sensible planing characterisitics - and by that I mean the ability to remain comfortably on the plane at lower teen speeds, is to keep the bottom loading as low as possible (Tom where are you!?!:D ). Off the top of my head bottom loading should be kept to about 250 kg/m^2 (of the waterplane area) and the power to weight ratio is ideally no more than about 25 kg/hp

Vega

06-21-2006, 07:54 PM

It's all pretty simple really. If you want to do 18 knots with a 28' LWL boat then you are better off with a planing hull

Of course. What I am saying is that in a semi-displacement 28ft hull, the kind Nigel Irens is talking about, you can go at 13 knots wasting half the fuel that you will need to go at 18k in a same size planing hull. And has Nigel has pointed out, you can only do 18knots in a planing 28ft hull with almost flat sea. If you have waves, probably the semi-planing hull is going to manage to go faster than the planning hull.

Willallison

06-21-2006, 07:54 PM

Vega - your post appeared whilst I was in the midst of typing mine, but it furthers the point:

Design speed would normally be in the region of up to 2.0 x _dwl(ft) although 2.5 x _dwl(ft) would still be realistic as a maximum cruise speed – at which point there would a degree of dynamic lift would be present.

There is, therefore, no pretence that slender single-hulled vessels
can be as suitable for high speed operation as dynamically lifted hulls.

With a LWL of about 28ft, Irens semi-planing form (and that's really all it is) is good to about 13 knots. If Guillermo wants 18, then he's better off with a planing hull. But of course there are the compromises that go along with this...

Willallison

06-21-2006, 08:00 PM

Ha - we are cross posts again!
You are quite correct Vega - and that was the compromise I was talking about. In general, planing hulls become less useful once you enter the realm of semi-planing and particularly faster displacement speeds.
But by keep weight low, trim correspondingly low (as for instance Tom has done with the Blue Jacket) a planing hull can be almost as good at lower speed as a semi-planing form, with the advantage of being able to travel faster when conditions permit

fcfc

06-22-2006, 05:34 AM

For Guillermo:

The power prediction I used is simply formula taken from a book. (Crouch I think).
For 18 kts,as the others said, the hull would probably be planning. So the requirement of the maximum possible waterline is not strong. So you will have a bunch of small planning boats, like the seaward, the sciallino, and even small antares like the 760. Note the antares 760 is category B4 too. But one problem is all theses boats need some planning surface, and all are wide, above trailerable limit.And weigth are also a bit above euro trailerable. Not by much, but above.

So that why I though of a non planning boat. Say lwl= 9m, Bmax 2.5m, cruise weigth 2.8 tonnes, empty weigth 2 - 2.2 t , cruise around 12 kts.

But I hit the following problems:

I computed Fn= 0,65 and Fnv=1,66 Clearly characteristics where you do not want to operate a hull. You need to be very narrow and ligth to go there. If I want to follow N Irens indications, I must have D/L better than 100 and lwl/bwl better than 4.5.

So reworked to lwl = 9.3m, bwl=2.06m, D=2.8t, L/B = 4.5, D/L = 100.

Now, the funny things start:

Cp should be around 0.65 - 0.7. Cm can be estimed to 0.6 - 0.65 (round chine) . This give a maximum canoe draft of 35 cm. This in cruise conditions. Waterplane area around 13 m². In light condition, should be 5 cm higher (wild guess) . So light canoe draft 30 cm.

Bare minimum engine heigth = 60 cm.
Bottom hull thickness + some space + engine + some space + soundproofing thickness + floor heigth = 80 cm at very minimum.

That means if you want to have the engine under a floor, that floor must be 45 cm above WL. ANd the cabin roof 2,25m above WL if you accept 1,75m headroom + 5 cm roof thickness , all this for a 2,06 m Beam at water line.

I do not think it is possible to have the engine under a floor like the planning hulls seaward, sciallino or antares. Theses hulls can do this because they are a bit heavier (I guess 3.2t, 3.5 t in cruise condition) , much shorter at LWL (guess around 6.5m) and lower Cm(V bottom with chines just under WL Cm +- 0,55). This give them a 25 cm deeper hull although wider at wl. (guess 2.5m)

The same for the head position. If the max draft is 35 cm, you will have hard time to put a floor more than 20 cm uder the WL.You will need to have a roof top 160 cm above WL. If you have 1m freeboard at that position, you would need a 60 cm hight roof. No. But you cannot add too much freeboard, since at one third of the length, the beam at waterline will be around 1.2, 1.5 m.

So you will have to go to layouts like the commuter27, but with an engine box somewhere, the engine box size is likely to be 80 cm len, 65 cm width, and height above floor 65 cm (Extra minimum dimensions), if floor 20 cm under wl. Or like the motorlaunch 40, without the aft cabin, with a two level roof (but, no standing room in the front roof) , and narrower. It is likely to have no more than a 30-40 cm passage each side of the engine box. 40 + 40 +65 is 155 cm wide. I remind you are 20 cm under WL, And Bwl is 206 cm. And then on the side of this passage, you can only have a shelves, seats, or narrow galley. No berths or head, unless you block one side passage. Remainder width to max beam is 45 cm each side.

Guillermo

06-22-2006, 05:52 PM

Excellent post, fcfc (By the way; May I have your name, please?)
Too tired today to work on the boat, I'll be back to it on weekend.

Just a moment more to tell all of you about a most interesting 100 knots concept yacht that is being developed by Donald L. Blunt and Associates (http://www.dlba-inc.com/) (Somewhat bigger and faster than my humble 28 odd boat!). Her main data (lightship condition) and parameters are:

LOA: 46.00 m
Lp: 39.10 m (Chine length)
BOA: 8.10 m
Bpx: 7.10 m (Maximum chine beam)
Bpt: 6.04 m (at transom)
CAP: 19.71 m
Ap: 242.63 m2 (Planning area enclosed by the chines)
Beta Transom: 8.00º
Beta Amidships: 20.38º
Design Speed: 100 kn
LCG: 16.51 m
Displ: 200 MT

CAP/Lp : 50.4%
(CAP-LCG)/Lp : 8.2%
LCG/LOA: 35.9%
LCG/Lp : 42.2%
Bpt/Bpx : 0.85
Lp/Bpx : 5.507
Ap/VOL^2/3 : 7.212
Lp/VOL^1/3: 6.741
Fnv : 6.825

Propulsion power: 36,077 kW (!)

Good night, everybody!

Willallison

06-22-2006, 09:07 PM

Far be it from me to level criticism at one of the current greats of marine design - but if I'm going to do 100 knots, I'd like windows big enough to see where I'm going!:eek:

tom28571

06-22-2006, 11:21 PM

I think the post of Nigel Irens is full of good reasoning.

I have not followed this thread for a few days and you guys have gone far and wide. Frankly, I am not convinced that a reasonable cruising boat of 28' LOA can be made to get 18kts with good fuel mileage and not be planing. That is a monohull, of course. To get that speed, a non planing hull will need a high L/B ratio. A sufficiently high L/B ratio to achieve that speed in non planing mode will likely be so narrow in beam that stability will be serious concern.

I believe Weston Farmer achieved this speed in his Coyote, but this was a lightly built open launch which he admitted was pretty tender. He had modified an even narrower hull to a bit more beam in which he said that the operators should have their hair parted in the middle for proper ballance.

Will, it was after studying this option that I decided to try the light weight planing route. Since I am willing to forgo much of the stuff aboard that many might consider necessities, I was able to get a boat with roomy accomodations in 24' LOA and still get a bit less than 2 gal/hr on cruises running at various speeds from 6 mph to 23mph and probably mostly at about 13mph. The aspect ratio is about 4.5 although less than that at higher speeds when the forefoot is out of the water.

Of course, I also cannot bash to windward in a high chop at high speed. I was just not willing to compromise all the other economic and trailerability attributes to get that ability. It has not been a serious problem.

My bottom loading is always less than your 250KG/M^2 though.

WHIO comes close to some of the performance discussed here but is a planing hull and has far less cruising comforts than even my boats.

Guillermo

06-23-2006, 01:56 AM

[B]....So you will have to go to layouts like the commuter27, but with an engine box somewhere...
Also very quickly in the morning, before going to work:

To keep interiors uncluttered there is the possibility of going outboard. To avoid using petrol, I was thinking about the JetPac thing. They have 150 HP and 200 HP diesel units, being both based on the same International Engines HS 2.8 lt, 4 cil. engine. The 150 HP version runs at 3600 rpm. (http://www.swordmarine.com/) I have to check out consumption.

8.5 m LOA (so plumb bows) plus 1.5 m JetPac length brings us to 10 m, which should not be exceeded, just to 'accomodate' the boat in a 10 m place at marinas. I think also 8.5 m and 2.5 MT is an absolute maximum for the JetPac.

JetPac weights a dry 428 kg 'on air' but it floats around 150+ kg out of it, depending on stern deadrise (Maximum 20º), so net weight would be in the 250-285 kg region with the proper deadrise.

What do you think about this possibility?

...A sufficiently high L/B ratio to achieve that speed in non planing mode will likely be so narrow in beam that stability will be serious concern....
Precisely.

Far be it from me to level criticism at one of the current greats of marine design - but if I'm going to do 100 knots, I'd like windows big enough to see where I'm going!:eek:
Well, I find the concept interesting from an NA point of view, but from the point of view of a boater I would ban those things out of the water! (I'm not even so sure about the 20 kn thing...! ;) )

fcfc

06-23-2006, 05:05 AM

Also very quickly in the morning, before going to work:

To keep interiors uncluttered there is the possibility of going outboard.To avoid using petrol, I was thinking about the JetPac thing.
....
What do you think about this possibility?

This is my own evaluation:

Inboard diesel, straight shaft: engine likely in the cabin.
Pros: weigth centering, rather ligth, electricity generation (no problem to have 100A), hot water generation, reliable.
Cons: space used if cannot be put under a floor, heat and noise in the cabin. prop draft if big prop for efficiency.

Inboard diesel, V shaft (ZF15 gearbox): engine in the cockpit, rigth after the cabin. (see rangeboat)
Pros: weigth centering, rather ligth, electricity generation, hot water generation, still reliable.
Cons: price, mechanical acces to shaft & stuffing box. Not too many angle available. Still some layout problem. Need a side access to the cabin. prop draft if big prop for efficiency.

Inboard diesel, Sail drive: (same as V drive)
Pros: weigth centering, rather ligth, electricity generation, hot water generation.
Cons: Propeller placement,efficiency unknow .Still some layout problem. Need a side access to the cabin.
I think it need more evaluation.

Inboard diesel, stern drive: (engine full aft)
Pros: electricity generation, hot water generation, still reliable. No layout problem.
Cons: heavy aft weight, efficiency unknow (small prop, loss in transmission), complexity, price (nothing specifically made for "small" power).

Outboard gasoline:
Pros: No layout problem, simplicity, price.
Cons: some aft weight, No electricity (or very few: hard to have above 20A), no hot water. Some problems with safety reliability and efficiency.

This is hard to objectively evaluate. My instinct would say straigth shaft, offset gearbox, kind of homocinetic coupling (aquadrive, python ..) for some angle. This would be the less trouble system, good efficiency from a mechanical point of view and decent price (although much more than an outboard) . But there is the space/layout problem.
The other option would be a single 60 hp outboard, 4 stroke, kind of high thrust/big foot for heavy boats. No space/layout problem and cheap, but I think the biggest problem for a cruise boat, before safety and seaworthiness, would be battery charging. At anchoring, you can run half an hour an inboard diesel at 1500 rpm with an additionnal alternator to give 100A. Running an outboard at 2000-3000 rpm some hours because you get only 10-15A would be less acceptable by the neighborhood.

For the jet pack, I fear it remove any trailerability. You have more than 400 kg at the rear end of your boat on you trailer (For comparison, a yamaha T60hp high thrust is 113 kg), so I guess it is not possible. So you have to remove your pack before trailering. The only way to remove it is with a crane. And where do you put it in your trailer or car ?.

Guillermo

06-24-2006, 04:40 AM

For the jet pack, I fear it remove any trailerability. You have more than 400 kg at the rear end of your boat on you trailer (For comparison, a yamaha T60hp high thrust is 113 kg), so I guess it is not possible. So you have to remove your pack before trailering. The only way to remove it is with a crane. And where do you put it in your trailer or car ?.
Maybe not. See attached photo. As a matter of fact a client of mine mounted the thing in a 6.4 m boat and he trailers it without problems. I think it's a matter of having the adequate trailer.

I do not like having petrol on board, so outboards are out of the question here. The 'standard' inboard engine and straight shaft installation is a cheap and sturdy solution (KISS principle), but clearly space is a concern here.

JetPac will not allow for hot water generation, but this is not important to me, as water consumption should be kept to a minimum, because of weight reasons (Showers: Ashore).

Sterndrives are cheap, but less efficient and prone to problems. I do not see a sail drive here either.

I'll keep on working on the thing. Maybe it's time for some drawings....

fcfc

06-26-2006, 05:40 AM

For the jetpac, I am still dubious. I speak of a boat about 9m or 9.5m length, weigthing 2 tons on the trailer. But 400 kg are overhang at the rear. And that leave only 1.6 ton for the boat. If that means a special custom made trailer, it reduces the interest of trailerable boats.

I also see clear advantages for the jetpac on boats where it is very complex to put an inboard, such as RIB or inflatables, or when you already have an outboard powered boat, and you want to change.
But when at the design stage, why would I prefer a jetpac over a classical inboard with a jet propulsion , when the boat can allow a classical stern inboard ?

Back to the layout with a straigth shaft. The logan 33 solved the layout problem by using an extremely long shaft allowing to put the engine under the fore V berth. What I do not understand clearly is how they solved the headroom problem. Seems that the cabin floor is at the same level in the firt or second cabin. There is the prop shaft under that floor. In the pilothouse, the headroom is correct, but in the front cabin, it should be short. But they probaly have headroom in the head. So I guess that the floor of the head is lower than the floor of the passageway, and the hull is deep enough to have headroom with the lower roof. So they may have a Cp in the 0.5 0.55 range, more of a sailboat than a semi displacement boat. (fine entries, deep hull). This would be consistent with the slow speed they have. It is a pure displacement / very low power hull, not a semi planning one.

And for planning hulls, there are photos of Dorado 30, planning hull, 9m length, 2.5m beam and 2.5 t. But the cruise speed may be higher than the 18 kts Guillermo is seeking for. And the accomodation a bit less. The headroom would be difficult to solve.

Vega

06-26-2006, 06:49 AM

QUOTE=fcfc]
Back to the layout with a straigth shaft. The logan 33 solved the layout problem by using an extremely long shaft allowing to put the engine under the fore V berth. What I do not understand clearly is how they solved the headroom problem.[/QUOTE]

This is the way to go, and it doesn't seem difficult to solve the problem.

If you look at the Andreyale 10, you are going to see that they have gone in the same direction.

This is just theoretical or you are thinking in making a boat along these lines?

fcfc

06-26-2006, 08:26 AM

This is the way to go, and it doesn't seem difficult to solve the problem.

If you look at the Andreyale 10, you are going to see that they have gone in the same direction.

Barely. The andreyale 10 does not have headroom in the head. And going from saloon to head means going outside. They have a bigger engine (60 -75 hp) than the lombardini 40 hp from the logan 33, and they did not put it under a berth, although they put it forward. They need their front cockpit.

This is just theoretical or you are thinking in making a boat along these lines?

Theorical and learning. I may play with FREE!ship, draw some lines, and eventually in the best case, end up with a R/C scale model. But no further. It is not my job.

I am not Naval Architect, but I know enougth to know there are in boat design some gory details I do not want to / cannot dig inside. Say weight and balance, building schedule/sequence for minimum time/machinery or corrosion/rot problems.

Nailed ? Bolted ? Screwed ? Bronze ? Inox ? galvanized ? Glued ? what glue ? Iroko ? Oak ? Mahogany ? Red Cedar etc ....

That s not for me.

Vega

06-26-2006, 10:34 AM

Barely. The andreyale 10 does not have headroom in the head. And going from saloon to head means going outside. They have a bigger engine (60 -75 hp) than the lombardini 40 hp from the logan 33, and they did not put it under a berth, although they put it forward. They need their front cockpit.

I am not Naval Architect, but I know enougth to know there are in boat design some gory details I do not want to / cannot dig inside. Say weight and balance, That s not for me.

Yes, but at least you have good sense:p

Seriously, the boat you want can be made. With headroom in the forward cabin, it will be probably ugly (at least for my taste), but perhaps you can have a big forward cabin without headroom (1.6M or so), and the rest is easy. You just have to have a long forward cabin, and a storage space at the bow to permit the engine to stay under the bed and even so, not to much in the front of the boat.

Of course, the interior and exterior design of such a boat is not difficult, but the calculations for the weight and balance of the boat are another story. You need for that not only a naval architect but one that have experience with this type of problems in this kind of very particular boat.

Joubert-Nivelt would be perfect....so, you can manage it if you pay the work.... and it would not be necessarily a complete project, but only hull and weight distribution, over some drawings provided by you. About building the boat there are plenty of small shipyards that have enough knowledge to give you a quote and sufficiently experienced to take care of all the details, even if the plan is only complete about the hull and weight distribution.

The only catch is that it will cost you a lot more than what you want to spend;)

yacht371

06-26-2006, 12:27 PM

For every speed/length ratio there is an optimum prismatic, LCB and volume distribution (curve of areas). Thus the optimum cruising speed should be chosen before anything else. Narrow displacement hulls can be more efficient than planing hulls up to a s/l ratio of around 3 (16 knots on a 28' WL). This is because the planing hull is not really "up on top" until beyond that speed.

Discounting catamarans, there are several ways to make narrow displacement hulls that have adequate stability. One is a power trimaran, with a narrow efficient main hull and a pair of "training hulls" which just kiss the surface. They need not be nearly as wide apart as a sailing tri, just about the same overall beam as an average monohull (3:1) should work fine. Unlike the catamaran this lends itself to very low CG since the narrow, fairly deep main hull will allow engine and tanks to be low down. I would stick to a semi-circular section to keep wetted surface to a minimum but use a higher prismatic and less rocker than a sailing hull.

A "planing" hull which does not have a "hump" in the speed curve and runs very well at s/l ratios from 2 to 5 is the patented "FlowMocean" design, there is an example on my web site www.aviadesign.com, the originator is Peter van Diepen at www.naviform.com

Another hull form which allows good performance in the speed range just above full displacement speed is the "displacement glider" (google the term). This is an Austrian design. Utilizing the same principle but a different shape is my own "powerkeel hull".

Propulsion: You can't beat a diesel with duo-prop for pure weight/fuel use/thrust.

Jet drives: I have owned a jet boat with a planing hull. Although great fun when viewed as an amusement park toy, the jet drive exaggerated the worst characteristics of the planing hull. At 1000 rpm the boat did 5 knots, at 2000 7 knots, at 2500 RPM, 8 knots, then bang a slight increase in throttle to 3000 RPM and you were doing nearly 30 knots. It was impossible to go 15-20 which would have been a nice cruising speed. This is because the jet is very inefficient until it reaches a fairly high critical RPM, then watch out. The planing hull also behaves like that, bad combination unless you want to go 40 knots all the time...

Outboards: modern 4 stroke outboards are quiet smooth and fairly fuel efficient. I like the Yamaha Hi-thrust 60, we tried two of these on our MC 29 "test mule" and got 16 knots on just one engine, we don't know the top speed with 2 as the engines hit the rev limiters before we got there. We will have to try again with more pitch. Still, fuel consumption will be 50% more than a single diesel, weight about the same.

For a true planing hull the one I have had the most success with (smooth ride, good handling and fuel efficiency) has a 24 degree deadrise at the transom, wide, deep chines so they stay in the water, and a center flat from midships aft (delta pad) which adds a lot of lift. This 25 foot boat runs great, is stable at rest, and does 33 knots with 230 HP (2 X 115 Yamahas). Video at http://www.c-kingmarine.com/video/cking-mr-video.htm

One trick used on this boat, and others I have done, is to angle the spray chines upward 5 to 10 degrees at the bow and then gradually flatten them out aft. This throws spray aft rather than sideways, and also stops the chines from making slapping sounds at anchor.

Sorry to be so long winded--they used to call me "the professor") when I was 6.

-Grahame Shannon

Guillermo

06-26-2006, 05:45 PM

Nice post, Grahame.
Interesting the FlowMocean hull, but I think I've seen this kind of hull before. I have to find out where....:confused:
Nice boat, the Marauder 250, Do you have a layout we can have a look at?

About your jets commentary, I've personally tried the JetPac 150 diesel in two different boats, and speed increase up to 28-30 knots was quite smooth passing through all the intermediate range. This equipment is quite effctive at slow speeds due to its relatively big impeller diameter (250 mm). What kind of jet drive did you own?

fcfc,
I love the Logan 33, but I'm trying to tighten here to boats less than 30' and these last posts specifically to no very fast planning boats.
On your question... "why would I prefer a jetpac over a classical inboard with a jet propulsion?", simplicity is the answer, as well as lower price and free space aboard. Which is not little....

Vega

06-26-2006, 07:35 PM

Narrow displacement hulls can be more efficient than planing hulls up to a s/l ratio of around 3 (16 knots on a 28' WL). This is because the planing hull is not really "up on top" until beyond that speed.

A "planing" hull which does not have a "hump" in the speed curve and runs very well at s/l ratios from 2 to 5 is the patented "FlowMocean" design, there is an example on my web site www.aviadesign.com, the originator is Peter van Diepen at www.naviform.com

Another hull form which allows good performance in the speed range just above full displacement speed is the "displacement glider" (google the term). This is an Austrian design. Utilizing the same principle but a different shape is my own "powerkeel hull".

"the professor"
Grahame Shannon

Well, you can continue to teach. It is a very interesting post.

!6 knots on a 28 ft boat and low consumption would be great.

Can you look at the drawing at post 91 on this thread and comment on the engine localization? I know that the boat works fine and makes 15k with a 60hp engine (it is designed by one of the best French Architects).

That boat has the engine in a very forward position. Do you think it is possible to put that engine even more forward? What are the implications of having the engine in that place?

I have googled for "displacement glider” as you said and its all very impressive:

“As the diagram illustrates, DG achieves in the transition speed range significantly higher speeds than both the displacement and planing boat given the same power input.

The DG-effect is valid throughout a wide speed range: for a boat of 14.6 m it is 9 to 19 knots.

The DG prototype achieves a maximum advantage over other hulls of approximately 30 per cent of power at 16 knots.”

http://www.alsphere.at/dg/performance.shtml

I don’t see why a DG (displacement glider) would not perform well in a 28ft, what do you think guys?

(Thanks for the suggestion Shannon, it seems very interesting. I have seen that you have done some tank testing with a dg model with impressive results, it would work with a 28ft?, or do you think the "FlowMocean" is better for this size? Can you compare both systems on a 28ft?)

some pictures of a DG hull:

yacht371

06-26-2006, 08:13 PM

The Displacement Glider and Flowmocean hulls are both suitable for smaller boats below 30'. Based on my tanks test I would say the displacement glider type of hull is better in the below 15 knot range than the FlowMocean. However at about that speed the FlowMocean crosses over and is better up to about 30 knots beyond which a deep vee takes less power. Both FlowMocean and Displacement Glider boats are quite superior to full planing boats in the below 20 knot range.

Here is a picture of a Flowmocean hull with an inboard diesel jet drive, 23 feet long.
http://www.aviadesign.com/images/cqac23.gif

This boat suffers from the jet drive problem I alluded to in my earlier post, in that it doesn't want to go slow. I would prefer a stern drive. Another problem with jets is they lose steerage when you cut the throttle suddenly, the natural reaction when faced with an obstruction. I never hit anything because of this but I scared myself a few times! They will crash stop fast though, just throw it in reverse.

My own jetboat was this one:http://www.aviadesign.com/jetboat/JUN3-1.jpg

That isn't me driving, I have more hair! This was powered by a 175 HP Mercury jet drive, a lot of power for an 1100 lb. boat, top speed 50+ knots. But nothing happens til 3000 RPM then HANG ON! I decided I'm too old for this type of boat. It was a 6.5" impellor. There is no doubt a larger and slower turning impellor would be better in the lower speed ranges, but I can't imagine it ever having the kind of "grip" you get with the Volvo Duo-Prop stern drive.

Marauder 250 layout, a typical West Coast boat...
http://www.aviadesign.com/images/24interior.wmf
This was the preliminary layout but the final is essentially the same. 30' with a 10' beam would allow a nice cruisng layout in this hull.

Grahame Shannon

Zewe

06-26-2006, 09:35 PM

Hi Grahame,

Do you have any experience with the Atkin seabrite style of hull form? Any comments that might compare them to the Flowmocean or Glider concepts?

Thanks

yacht371

06-26-2006, 10:03 PM

I don't have any experience with that hull form, but it seems to be the Grand Daddy of the displacement glider hull form, so it could be expected to have some of the same characteristics.

Many older powerboat designs are quite efficient as they didn't have today's light and powerful engines to work with. One yacht designer I sometimes do hulls for laughs at my efforts to produce efficent hull designs. He says many naval architects are idealistic about this but the clients don't care, they just order bigger engines if they want more speed.

Weight is the big enemy of speed. Unfortunately bigger engines weigh more and use more fuel so bigger tanks (always kept full) are in order. One of the fears we have with the MC29, which due to very carefull management of weights, is very light, is that owners will fill up all the available storage space, which is considerable, with heavy stuff, and then complain that she doesn't go! It was designed for 2 x 50 HP inboards or a single diesel but we have already had people ask if we can put 150 HP outboards on. The answer is NO!

fcfc

06-27-2006, 04:55 AM

!6 knots on a 28 ft boat and low consumption would be great.

This 28 ft hull should reach 16 kts with about 45 - 50 hp.
http://www.admiralstender.nl/default.aspx?template%5Ffile=default%2Ehtml&wgl=page%3Acore%3Apage%3A12%3AWebpagina%3A&sitelang=dutch
It is lighter than a Andreyale 10.

BTW, I am not sure Andreyale are not planning boats optimized for slow speed. The image below is Andreyale 15. You will see here Andreyale 12 with twin 175 hp for 24 kts and cruise 18 kts. http://www.castlemain.net/brokerage_caterina.htm
Definitely above rangeboat 12m which is optimized for 13 -15 kts with smaller engines.

SAQuestor

06-27-2006, 11:51 AM

As Tom stated in his recent post – this thread has been all over the place since I checked in last.

The following is just my personal opinion – FWIW – YMMV and all other applicable disclaimers.

Each person contemplating buying or building a boat has a different idea of what constitutes a suitable boat for their personal use. This is true no matter whether it’s a one-off design ala Whio, or a mass production boat that they espy at the local boat merchant.

The designs available at the local boat merchant reflect (at least here in the states) the (seemingly) inherent human nature desire that equates bigger, faster and with more “stuff” as being superior to other alternatives.

Tom Lathrop and his Bluejacket designs are the antithesis of this sort of logic. Tom’s design appears to meet some specific design goals extremely well. But it is what it is – and Tom has shunned trying to design a boat to be something for all people. If you can embrace Tom’s design criteria, (http://www.bluejacketboats.com/designing_liz.htm) then (IMO) Bluejacket is a “perfect” pocket cruiser boat. But if your wants/desires/needs are different, then… we move on to something else.

That brings me to four essential (in my mind) questions one must ask before buying or designing/building a boat.

1) Where do you want to go?
2) How fast do you want to get there?
3) How much “stuff” do you want/need to tote along?
3a)What is your amenity comfort level?
4) How independent of support services do you want to be?

One question at a time.

1) Where do you want to go?

If I want to go Tuna fishing 150 miles off the coast, that desire requires a far different design than if I want to cruise coastal bays and estuaries and the ICW.

Personally, I’m infatuated with Alaska and The Inside Passage. Lots of different boat designs/types/sizes make that cruise every year. The last boat I was on in those waters I had to dress for dinner and the cabin was 3 times as spacious as any trailerable boat will ever be!

But I want – almost have a primal need – to go back and explore the NW coast of British Columbia and SE coast of Alaska. Not once, but numerous times. And a 800’ cruise ship is not the way I want to go – there is no way to get up-close and personal with the islands, bays, fjords and waterfalls on one of those behemoths, regardless of how good the food and service is.

These folks - (http://www.geocities.com/bill_fiero/index.htm) and (http://www.georgeberotti.com/2Wander/) are doing it in 22’ boats. Please do “invest” the time to thoroughly peruse their sites, as their adventures and the documentation thereof are worthy of much wider recognition and praise.

So BC/TIP/Alaska is doable in a 22’er. 2) How fast then?

In this case, the C-Dory is reasonably capable of 15 knots – give or take. And that’s OK by me. But I also think that slower (reasonable) displacement speeds for a 28’er – 6 knots or so might be OK if the answer to question 3 and 3a is “lots”.

3) In the links mentioned above, it seems that these folks are pretty minimalist in their required “stuff” and comfort needs. Is the choice of a small-ish planing boat and the need for lightness right for me? Not enough data is currently available for me to make that decision right now. But I do recognize that it is a vital question that has wide-ranging repercussions across the entire range of design choices.

4) Finally, me thinks that if I’m so attracted to BC/TIP/Alaska that I must be prepared for most any eventuality short of replacing a motor in a remote fjord. That feeds back into question 3) – how much repair/distress “stuff” do I need to tote? As with all things boaty – one choice drives other choices and on and on.

So where does this leave us in this Pocket Cruiser discussion? Given the questions above, and the immutable fact that one design can’t be suitable for all conditions, it seems to me that instead of going all over the place with ideas, it would be much more productive to clearly state the design criteria and go from there.

Initially, Guillermo stated; “So I propose now a discussion about 'pocket motor cruisers' understanding the term as motor boats under 30' able to do extended coastal cruising for a family (Up to 4 people), so not runabouts or dayboats, in a safe and efficient way.” And further, “Boats for coastal cruising in general.”

Then Tom Lathrop and Williamson said, in effect, “Narrow the design parameters so we can have a reasonable discussion.” And then the thread went to wrack and ruin from there. :D {edit - for those that are irony challenged}

While certainly a wide-ranging and interesting discussion, I wonder if it’s useful in any way other than people posting pictures and providing links to (in their opinion) suitable candidate boats and designs?

So do we continue here? Revisit option one? Start a new thread with tight usage/design criteria?

I don’t know. I have no answer so I’m just going to drop this little doggie poop message here and run away from computers, the Internet and discussion forums for a couple weeks of badly needed R&R.

Best to all,

Leo

yacht371

06-27-2006, 07:48 PM

The thread has not, in my opinion, gone to wrack and ruin. Quite the contrary we have discovered the range of what constitutes a "pocket" cruiser. It is evident that some have bigger pockets than others. I used to consider a 30' boat quite a substantial yacht!

Anyway, I would like to introduce what may be the finest example I have seen of a pocket cruiser. It is written up in the June 2006 issue of WoodenBoat. WHIO is nearly 30' long and burns only 1/2 gal. and hour at 10 knots!!! She does 17 knots with only 50 HP. And she is very good looking to boot. http://www.steamlaunch.co.nz/Whio.html

How is this remarkable efficiency achieved? Light weight is the first thing. She weighs only about 1/3 as much as some other boats this size. The hull is a very fine example of a semi-planing or semi-displacement shape.

Disadvantage: you have to leave most of your "stuff" at home. My own feeling is the more stuff you have, the less value any of it has. Having just one source of propulsion will encourage good maintenance. A small capacity for foodstuffs encourages us to lose a little weight. No shower? Go for a swim.

It seems to me the under 30' "Pocket Cruiser" could be either a tubby "mini-trawler" capable of carrying lots of gear and fuel at 7 knots, or a faster lighter boat like WHIO or the MC29 which gets you there quicker, so you can spend more time relaxing, swimming and hiking.

My vote goes for the latter. If I'm going to go 7 knots anyway, I would rather sail.

SAQuestor

06-27-2006, 09:23 PM

The thread has not, in my opinion, gone to wrack and ruin.

Irony:

1. The use of words to express something different from and often opposite to their literal meaning.
2. An expression or utterance marked by a deliberate contrast between apparent and intended meaning.
3. A literary style employing such contrasts for humorous or rhetorical effect. See Synonyms at wit.

SAQuestor

06-27-2006, 09:56 PM

Anyway, I would like to introduce what may be the finest example I have seen of a pocket cruiser. It is written up in the June 2006 issue of WoodenBoat. WHIO is nearly 30' long and burns only 1/2 gal. and hour at 10 knots!!! She does 17 knots with only 50 HP. And she is very good looking to boot. http://www.steamlaunch.co.nz/Whio.html

How is this remarkable efficiency achieved? Light weight is the first thing. She weighs only about 1/3 as much as some other boats this size. The hull is a very fine example of a semi-planing or semi-displacement shape.

On a more serious note...

If I read this attached fuel chart from Whio's web site correctly, at 2500 PRM the boat is doing about 12-13 knots and using about 5.5 liters/hr for a NMPG of about 9.5 per imperial gallon.

Now, if I've done my conversion correctly that equates to just shy of 1.5 gallons US per hour for (let's say) 13 knots. That equates to ~ 8.6667 NMPG (US) or 10 statute miles per gallon (US).

Now, if I read Tom Lanthrop's numbers correctly he gets about 6.5 to 8.5 MPG (US) on his Bluejacket 24, Liz. Tom's web site. (http://www.bluejacketboats.com/)

Now, we can argue all we want, but it is readily apparent to me that Tom's boat has better overall accommodations than Whio. And that ties back into 3 of my questions above - where do you want to go, how fast do you want to get there, and how much 'stuff' do you need to be comfortable?

And no, I have not personally seen either boat - just the same pictures that most have seen.

Even the article in Woodenboat acknowledges that Whio isn't for everyone and that the amenities are lacking for lots of folks. But Whio works for the folks that use her, just the same as the 22' C-Dory works for Bill and El, (referenced in my post above) and Tom's 'Liz'. And more power to them all.

My vote goes for the latter. If I'm going to go 7 knots anyway, I would rather sail.

But 6 knots under reliable power may be much more attractive to those folks that want to take along 'stuff' or want to go to those areas that are not suitable for sailing.

As I said above:

Each person contemplating buying or building a boat has a different idea of what constitutes a suitable boat for their personal use. This is true no matter whether it’s a one-off design ala Whio, or a mass production boat that they espy at the local boat merchant.

OK - Supper is over and I'm back to packing for the road trip.

Best to all,

Leo

SAQuestor

06-28-2006, 12:06 AM

Packing is finished – ready to load the car in the morning.

So in keeping with the original thought of this thread, So I propose now a discussion about 'pocket motor cruisers' understanding the term as motor boats under 30' able to do extended coastal crusing for a family (Up to 4 people), so not runabouts or dayboats, in a safe and efficient way.
I present for your edification and viewing pleasure a series of affordable used boats that (in my opinion) fit the criteria first laid out.

So I like some – some I think are ugly. But they fit the original criteria.

My search criteria were:

Selected Search Criteria:
Boat Type : [(Power)] (69537)
Length: Between 24 ft and 30 ft (22213)
Price: Less than 65000 USD (33697)
Hull Material : Fiberglass (85028)
Fuel Type : Diesel (56864)
Number Of Engines : 1 (44753)

This certainly is not an all inclusive list, but rather a selection of what's available on Yachtworld.

As always, YMMV.

Leo

30’ Willard (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1436837&slim=quick&)
30' Hyundai Sedan Trawler (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1553096&slim=quick&)

28' Bayliner 2855 Ciera Sunbridge (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1530821&slim=quick&)

28' Cape Dory Flybridge Cruiser (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1344327&slim=quick&)
28' Northwind (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1456774&slim=quick&)
Albin 27 Aft Cabin (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1538001&slim=quick&)
27' Albin FAMILY CRUISER (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1525925&slim=quick&)
27' Marben Marine Fly Bridge Sedan (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1555052&slim=quick&)
27' Riviera Sedan (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1325069&slim=quick&)
26' Crownline 268 CR (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1379104&slim=quick&)
26' Four Winns 265 Sunbridge (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1547997&slim=quick&)
26' Honeymoon Flybridge Cruiser (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1425017&slim=quick&)
26' YAR SCARBOROUGH (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1515798&slim=quick&)

Guillermo

06-28-2006, 01:31 AM

Leo,
Thanks for all your nice posts. Enjoy your R&R !

Grahame,
I'm impressed with the displacement glider hull! Didn't know it, thanks a lot!

About this thread's opening of criteria, I'd rather prefer to keep it as wide as possible. I think we are getting lots of useful information on all available possibilities by keeping a creative discussion. This is not a 'collaborative design' thread, otherwise it should have been posted at the correspondent forum.

Cheers

yacht371

06-28-2006, 03:16 PM

As Leo says, the Bluejacket has better accommodation than WHIO primarily due to wider beam. Bluejacket's performance is excellent, 23 knots with 50 HP! The lines are not shown but from the description I gather it has downturned chine flats, rather like a milder version of the Flowmocean hull, and sounds like it behaves similarly in the way it goes on and off plane. What both boats have in common is lighter than average weight.

Both of these are nice looking although I prefer WHIO. It seems to me there are infinite variations possible in the area of performance and bottom shape, but weight is really the key, because that is the amount of water you have to push out of the way. The trouble with planing is the greater the lift, the harder the landing! For that reason at this size range I prefer boats that stay in the water, such as the displacement glider and displacement power catamarans.

Guillermo

06-28-2006, 05:21 PM

This 28 ft hull should reach 16 kts with about 45 - 50 hp.
http://www.admiralstender.nl/default.aspx?template%5Ffile=default%2Ehtml&wgl=page%3Acore%3Apage%3A12%3AWebpagina%3A&sitelang=dutch
It is lighter than a Andreyale 10.
That's Luigi's (*******) boat!

....Anyway, I would like to introduce what may be the finest example I have seen of a pocket cruiser. It is written up in the June 2006 issue of WoodenBoat. WHIO is nearly 30' long and burns only 1/2 gal. and hour at 10 knots!!! She does 17 knots with only 50 HP. And she is very good looking to boot. http://www.steamlaunch.co.nz/Whio.html

....you have to leave most of your "stuff" at home. My own feeling is the more stuff you have, the less value any of it has. Having just one source of propulsion will encourage good maintenance. A small capacity for foodstuffs encourages us to lose a little weight. No shower? Go for a swim.

It seems to me the under 30' "Pocket Cruiser" could be either a tubby "mini-trawler" capable of carrying lots of gear and fuel at 7 knots, or a faster lighter boat like WHIO or the MC29 which gets you there quicker, so you can spend more time relaxing, swimming and hiking.

My vote goes for the latter. If I'm going to go 7 knots anyway, I would rather sail.
Grahame,
I opened this thread with a post on WHIO. I find it a most interesting design and a very nice piece of engineering.
I agree with you about fast cruisers, instead of heavy ones, to cruise areas where refueling/reprovisioning/maintenance within the range are easy. Heavy is the proper option otherwise. On your KISS paragraph: I couldn't more agree.

Another question for you: What's your opinion on the 'Displacement Glider' forms being applied to commercial fishing boats? Alsphere claims that as one of the concept's target markets. I like the idea of using it for small coastal 'fast' fishing boats. In Galicia are very common 6.5 m - 10 m day boats, inboard diesels, with speeds in the 15-20 kn range. They are usually very, very fuel inefficient, specially when loaded. Maybe a 12 kn speed burning less than half of the fuel, may arise some interest nowadays.

yacht371

06-28-2006, 06:41 PM

Sorry, I didn't realize it was the same design. Still a good one!

The "displacement glider" or my PowerKeel shape would be excellent for those boats, maybe they could be powered to do 17-20 knots on the way out light, and 12-14 on the way home loaded with fish. Probably the existing boats are planing hulls, too heavy to plane properly when loaded.

This brings up the thought that a hull which works well heavy or light is ideal for long distance cruisers, which start out with a full load of fuel and stores then use them up as the trip progresses.

WHIO and ******* bring up the subject of wood as a construction material. I have owned two wooden boats, one bright finished, and they were not a lot of trouble to maintain, but had poor resale value. These days WoodenBoat is helping that aspect. Unfortunately here (West Coast of Canada) there are only a couple of good wooden boat yards, and costs are high.

Turkey seems to be a source of reasonably priced well made wooden boats, although I don't care for the designs in most cases. Indonesia and the Philippines should be excellent, having both the wood supply and reasonably priced labor however it seems the lack of stable government and a good justice system hold them back. China is the dark horse here. They are well organized, have unlimited cheap labor and seemingly money to invest. I wonder if anyone in China has considered building high quality wooden boats?

I would (wood?) love to design some. I haven't done a woody in almost 20 years!

Grahame

tom28571

06-28-2006, 10:45 PM

371 (a name would be good),

Since my Bluejacket is being discussed, I should give a little information. As many have said, weight is the key when you are looking for performance and economy in the same package.

The chines on Bluejacket are (I think) original with this boat. I got the idea while studying Weston farmer's Trumpet design which was claimed to run level at all speeds. I recognized that this ability was crucial to making a boat perform respectable through what is, for most boats, the never-never range fo speeds between hull speed and planing speed.

I thought Farmer had Trumpet to set up dynamic lift that was distributed unlike most boats where the lift is highest at the forward area where the hull meets the water and falls off monotonically toward the stern. My solution was to make the chines have a positive angle of incidence relative to the rest of the monohedron planing surface. Being at a down angle relative to the aft bottom, the chines naturally increase in width linearly until they are about 11" wide at the stern. The intent was to have the chines operate like low-drag permanent trim tabs and generate more lift aft. Further, the extra lift being generated at the aft chines would add stability, particularly longitudinal stability.

The result is a boat that rises almost level and never-never sticks its nose in the air and never exceeds a trim angle of more than 2 degrees. Now I know that this is not optimum trim for max speed but that was not the objective. The objective was for a boat that would run comfortably and economically in what is normally transition nose up, big wake, uncomfortable, power hog range for most planing boats. Longitudinal stability is high so that varying outboard trim has almost negligible effect on boat trim. Passengers moving fore and aft also has much less effect on trim than in other boats I have been aboard. Some loss in top speed due to extra wetted surface due to a smaller than usual trim angle is a price that I was willing to pay. A side benefit is that with the fine sections of the bow down, the boat takes chop easier until the waves get larger when I must reduce speed.

I know that many builders or designers claim that their boats run level but no one who has ever been on Bluejacket has ever been of a boat that performs like this. Leo, among others, has a video showing the Bluejacket accelerating from low to top speed with the attitude changing very little and the stern remaining at almost the same level through the whole speed range. When slowing down, the attitude remains almost the same until the speed drops to about 6 to 7 mph where the bow suddenly drops to static level. The overall result is that the Bluejacket will operate well at all speeds from about 10 mph to top speedpf abput 23 or 24 mph. Greater loads raise the minimum planing speed as well as the top speed but easy planing still occurs with 7 adult men aboard while top speed drops to about 19 to 20 mph. There is more info on my website at www.bluejacketboats.com if you are so inclined to look there.

Bluejacket is not all things to all people. It was originally designed for my wife and I to trailer behind our family vehicles and cruise in inland waterways in places that would be difficult or impossible with a large boat. This weekend we will launch (it is kept on a trailer in a boathouse I built) and go down to Beaufort to see all the tall ships taking part in the Pepsi Sail America event.

On the thought that the old Option 1 thread went to wrack and ruin, maybe that is too harsh. However, I think that it kind of died when it became clear that the various contributers, including me, had divergent views on the specific direction the design should take. This seems normal to me. I do think we all learned quite a bit from each other in the process. Because it is specifically about design, I think this forum avoids much of the chaff on others and teaches better than any other I am aware of.

Oh yes, the first box keel boat that I ever saw was on Japanese fishing boats in about 1950 or '51.

yacht371

06-29-2006, 11:39 AM

Hi Tom,
I greatly appreciate the performance of the Bluejacket, and you are definitely on the right track with the chine design. However it is not perhaps as unusual as all that.

The FlowMocean hull patented by Peter van Diepen is a well documented version of this type, with extensive tank testing and several vessels in service. It behaves very much as you describe Bluejacket. I think the proper term might be "low speed planing hull" by which I mean a hull which planes early and stays level. A lines perspective is below, this is a 36' version which I designed recently for an Ontario client, and is now well under construction, all parts CNC cut in aluminum. This shape is fully developable, and suits plywood as well.

http://www.aviadesign.com/images/FLO36linesper.wmf

Walter Schulz of Shannon Yachts (no relation) has designed a hull with similar charcteristics, although the shape varies somewhat being designed for fiberglass, so using compound curves. He calls it the SRD hull. www.shannonyachts.com

There are probably other examples, but these are two well documented shapes.

Incidentally, I know Walter Schulz was aware of the FlowMocean shape as he cites it in his patent application as "prior art".

Grahame Shannon

tom28571

06-29-2006, 12:48 PM

Grahame,

I am aware of Walter Schultz's SRD since it was in a Magazine early last year. He calls it reverse deadrise chine. I do know that it is unlikely that the idea was completely new but did wonder what the extent of his patent is. I should say that the thing that might be different in my chine is the change in longitudinal angle of attack, but maybe not. Early in the last century there was a "wave collector" chine which may have been similar. My chine was designed in 1997 and launched in the spring of 2000. Experimentation with wedges under the transom of a skiff showed that very little wedge could be effective. I use a positive angle of attack of about 1 degree relative to the aft planing surface. Several are under construction.

Looking at the Shannon website, I see different configurations and one that seems to take something from the box keel or glider concept. We had a discussion about this shape on this forum a couple years ago. I think Stephen Ditmore posted some lines of one version. I think of this as a two phase design where the keel runs at high L/B ratio (not planing) and the upper hull is of more normal 3.5 aspect ratio and does plane. Some of Atkin's designs seem to be headed this way, like the Rescue Minor as well as teh Jersey Sea Skiffs.

I look at this as a possibility for a more highly fitted out cruising boat than mine that would run in the high teens efficiently. The keel would carry maybe 70% of displacement and the upper hull 30%. The planing surface would thus be lightly loaded and efficient at the projected speed while providing needed lateral stability. The engine could either be an outboard or, for more efficiency, be down in the keel with a fairly straight shaft and a large diameter prop under the stern much like WHIO.

You are quite correct in that my hull should be called "low speed planing". In fact, that was the main intent. Study of some of Lindsay Lord"s work convinced me that it was worth a try, although almost no one else thought a 24 foot cruising boat would even plane with 50HP. I got bored with running the ICW at sailboat speed of 6 kts and decided that double that was the best speed for it. Not too slow for bordom and not too fast to enjoy the scenery. The level running was also a goal and fortuitously resulted from the same idea as the low speed planing.

Sorry this is so long but I lack the time to make it shorter.

yacht371

06-29-2006, 02:29 PM

Another example of a cruising boat in this size range that planes with 50 HP is the ubiquitous MacGregor 26, but then that's a sailboat...

Grahame Shannon

yacht371

06-29-2006, 07:18 PM

I was just reviewing test results on a 28 foot twin gas(450 HP total) deep vee planing hull. It gets its best (above displacement speed) fuel mileage at 25.3 knots (1.2 NMPG) and the worst mileage at 9.4 (.92). Even at a max of 35 knots it uses less fuel than at 9.4. This 10 knot range is where a boat like WHIO or the MC29 excel.

Grahame Shannon

Tad

06-29-2006, 07:37 PM

I see you guys are getting into the good stuff without telling me!

Thanks for your explanation above Tom, sounds sensible.

The "Displacement Glider" thread is here, http://boatdesign.net/forums/showthread.php?t=2545

Guillermo

06-30-2006, 04:21 PM

Thanks for the info on the other thread, Tad.
There you say there's no room in the hull, so not very good for a 30' minus cruiser. But this is not important at all for small fishing boats, so maybe it worths while (to me) to explore the idea.

What I find quite high is the claim of 30% fuel savings. Having a look at Grahame's tank-tests numbers for his Powerkeel I find figures are more in the range of a 22% at its most, if I understand well the numbers in Grahame's pages.

Grahame: These forms seem to work well only for a short interval of speeds, being around 4 knots, (8 to 12) in your test's data :confused: Am I interpreting correctly the thing?

yacht371

06-30-2006, 06:06 PM

Guillermo, my design was optimized for that speed range, you are reading the numbers right. However, that one was draft limited (the client lives on a canal with minimum 3' depth and also must fit through a bridge with 8' clearance). I think with a deeper draft and higher percentage of volume in the keel we could do better. I don't have figures for the Austrian design, but they seem to have the deeper draft I was not able to use, so they may do better at higher speeds.

In principal, this type of hull has most of the displacement in a long narrow form (the keel) and the upper portion is a very light displacement planing hull. The pressure wave from the keel helps add lift to the upper hull. The difference in wave making is fairly dramatic as the pictures on my web site show.

My numbers are reliable in the sense that except for the keel, the hull was identical, and tested at the same displacement in the same tank, so the percentage improvement is real. There is no benefit above 15 knots.

Unfortunately there are few documanted examples of this hull form. I would love to explore variations in a series of tests, but tank testing is very expensive.

An alternative methos, which we used on another project, is to build a series of 10' dinghies to scale, and power them with an outboard. This gives a real world feel for ride and handling, and the speed is easily measured and scaled. I did this once before (except the final target was a 10' dinghy!). We discovered several shapes that didn't work. We had 2 motors, 1 5HP and the other 8HP, both Hondas. All the boats planed with the 8, with one person aboard. Only one planed with 2 people and 5 HP. That shape is below.http://www.aviadesign.com/X10body.wmf

Note shingled bottom, fairly shallow deadrise. This makes a good 10' dinghy, and would be OK in a cruiser for sheltered waters, but too hard riding offshore.

Anyway, the dinghies can be built cheaply in ply, stitch and glue. We managed to do them in 1-2 days, although the one above was computer cut and we made a mold, this obviously done as we closed in on the best shape.

Grahame Shannon

Guillermo

07-01-2006, 02:27 AM

Grahame, I have some questions for you:

What's the load carrying ability of your design as to keep the hull's efficiency? Have you tested the 36' model for different load conditions?

You tested a 36'. For a boat in the 22' to 33' range, would it be possible to reach efficient crusing speeds of 12-15 knots with this kind of hull? In what load condition?

This last question is related with this other one, If the upper planning portion of the hull submerges under load, until what depth (% of draught or whatever) is the hull still efficient?

Your Powerkeel forms seem to me to be a mixture of a boxed keel and a bulbous bow. The Displacement Glider, on the other hand, seems more like a boxed keel with a sharp bow.

You state in your web pages: "A standard bulbous bow hull where the bulb fairs into the hull gives best results at a S/L ratio of 1.1 (6.8 knots for this hull). This one gives the best results at S/L ratio 1.5 or 9 knots."

DG claims their hull is more efficient than a displacement on and a planning one for Fn between 0.4 and 1.0 (Metric) This is S/L between 1.36 and 3.35 (Imperial) if I didn't make a mistake. This is a very wide range. What do you think?

Tad? Tom?

tom28571

07-01-2006, 12:30 PM

Guillermo,

I will leave this to Tad to make an informed answer since it is a bit out of my experience. Off the cuff though, the bulbous bows that I have seen on small boats have not been very successful. Unable to show advantage in other than very low sea state and limited to narrow speed range, if at all. Just looking at the sketch, I might think that there would be some slamming in rough water with the nearly flat fore sections of the upper hull. In speculating about the box keel concept, fairing the fore sections into a form that will be reasonably comfortable in a large chop or waves seem to be critical in making the whole thing work well.

I think that in order for the concept to be a satisfactory cruising boat, it should run comfortablly and economically at all speeds from zero up to the high teens.

yacht371

07-01-2006, 05:52 PM

Tom has a good point, the more volume there is in the keel, the flatter the upper sections get. It must be so, or the chines would be well out of the water and the boat would flop over. However, my experience with other hull type leads me to believe the the central part of the hull takes the brunt of the impact when falling off a wave, and the boat is already substantially decelerated by the time the upper sections hit. Neverthe less, this type suits bigger boats bets. It is also harder to build than some other hulls.

I don't think I would recommend the powerkeel hull for the type of boat we are discussing here, since it as its best in speeds just above displacement range. The Flowmocean hull is probably the best fit. I have tank test data, which I have extrapolated to a 28' x 10' beam x 8000 lb. boat. The following assumes 65% prop efficiency.

Knots HP GPH NMPG
5.18 3 0.17 31.30
6.29 6 0.31 20.01
7.04 9 0.47 15.03
8.15 15 0.77 10.61
9.26 21 1.04 8.89
10.00 24 1.21 8.25
11.11 30 1.48 7.52
12.22 36 1.79 6.82
13.33 43 2.13 6.27
14.44 51 2.55 5.67
14.81 54 2.71 5.46

The model test was limited by the speed capabilities of the towing tank. The odd intervals are the result of the scaling formulae. Extrapolating beyond these figures suggests 120 HP would give about 22 knots.

Caveat: your mileage may vary. Tank testing and scaling have limitations. I have included factors for wind drag and hull roughness but these are very approximate. To be safe, I would add 25% or so to the required horsepower. Prop efficiency can vary a lot. Long thin blades like WHIOs are very effective, but rarely used because they take extra draft and you need a big reduction ratio or a slow turning engine.

Grahame Shannon

Guillermo

07-03-2006, 05:34 AM

Just an interesting info on powerboats sales in USA:
http://www.info-link.com/bellwetherreport.asp

brian eiland

07-06-2006, 04:10 PM

Just found this thread. It would be interesting to have "yacht371" the PowerKeel developer add his observations to this other thread.

I had posted over on this new thread ,"Displacement Glider, PowerKeel, etc?" http://www.boatdesign.net/forums/showthread.php?p=95771 (http://www.boatdesign.net/forums/showthread.php?p=95771)
Hello Mark,Stick to you guns lad, I like this concept of a marriage between the PowerKeel hull concept and Paine's Steadysailer design. It certainly offers the 'sailing alternative' to Dashew's FPB concept.

And I think we will see more of these long-range passagemaker ideas evolve as the new world order of fuel prices become reality.

And just to add more spice to the discussions I will reference this subject thread on a few other similar discussion threads

yacht371

07-13-2006, 06:21 PM

Zewe

07-13-2006, 06:51 PM

That is one sexy little trimaran!

Vega

07-14-2006, 08:49 AM

Very nice trimaran. The Design is very good. It is very dificult to design a tri or a cat to look like "in tradition" and at the same time looking modern too. This one looks just right;)

tom28571

07-14-2006, 03:26 PM

Once you decide that the disadvantages of a multihull powerboat are acceptable, such boats as this one can make a bit of sense. Trouble is, few have been willing to accept those negative aspects. If you just look at this handsome little launch, the problems related to making it into a viabler cruiser are apparent. Initial cost, slip cost, carrying capacity compared to monohulls of similar dimensions, trailerability, etc.

A local guy built a larger power tri (about 26', I think) about 10 years ago. The main hull was beamier than this one, but still slim, with a V planing bottom and the amas were designed to ride on the wave generated by the main hull. Top design speed was about 50mph. I saw the boat but was not able to find out what happened to it.

Guillermo

07-14-2006, 08:05 PM

A lovely looking power trimaran that somehow manges to look traditionally yachty and ultra modern at the same time. Smaller than our target, but looks like it might scale well.
http://www.kenau.nl/
Grahame Shannon

Very nice looking, indeed! (Although I wouldn't like to see this Keanu ferociously fighting the Spaniards....:D )

yacht371

07-31-2006, 11:38 AM

The Motorcat MC29 has arrived in Vancouver, and we have had it operating for a week. Performance figures and photos are at www.aviadesign.com/MC29

The finish and construction is excellent, being the first one there are a few stowage enhancements needed. Performance is good, but I have to learn to steer as it is very different from my sailboat with its 6 foot deep rudder. That said, I haven't really had any trouble getting it to go where I want it to.

Ride is excellent. We blasted through a big tide rip at 20 knots when bigger boats were slowing right down and smaller one becoming airborne. You could tell the water was rough mainly by the noise but G-forces were low and it was in no way a jarring ride.

Grahame Shannon

Guillermo

08-01-2006, 06:30 AM

Nice results, Grahame. Less than 1 Lt/NM at 20 kn in loaded condition is very atractive.
I find the wake to be somewhat 'dirty' as per the photos at your site. At what speed and load were they taken? Would it help to use chined hulls, instead of rounded, to avoid water going up the sides? Also, maybe rising the central hull at the stern out of the water would flatten the wake?

Congratulations for your new boat. I wish you the best of lucks in the commercializing.
Cheers.

yacht371

08-01-2006, 12:25 PM

Hi Guillermo,

The wake IS a bit dirty looking at maximum speed (the photos were at 23+ knots) cleaner as you slow. The boat had 5 people on board, full tanks, and all my tools for installing equipment, so she was heavy. Wave propogation is small and the wake doesn't seem to disturb sailboats. We have developed spray rails for the bows which are not yet installed on this boat, we are waiting for them to arrive. These raise the bow a bit and clean up the spray patterns. Even without them, she is the driest boat of this size I have ever been aboard.

Grahame Shannon

Guillermo

09-07-2006, 10:33 AM

Here a nice design from Tad Roberts:

DOWN EAST 26
LOA: 26' 0"
LWL: 23' 8"
Beam: 8' 6"
Draft: 12"
Displacement to DWL: 3600 lbs
Power: 90 HP 4-stroke outboard motor
Cruising Speed: 20 knots
Top Speed: 25 knots

http://www.tadroberts.ca/services/small-boats/down-east26.php

yacht371

09-11-2006, 08:37 PM

I have added video footage of the MC 29 in action at www.aviadesign.com/MC29

The Tad Roberts design is a great looking boat, and should be economical to build. Too bad there don't seem to be any reasonably priced prodiction boats of this type.

Grahame Shannon

Guillermo

09-12-2006, 03:10 PM

Nice video Grahame.
Riding seems soft, indeed.
How does she perform in tight turnings at high speed?
And in beam seas?
Cheers.

yacht371

09-12-2006, 04:17 PM

Thanks Guillermo.

The turning radius is fairly large compared with a vee bottom monohull, but you can crank the wheel all the way over at full speed without fear. The maximum outward lean we measured was 10 degrees, and that was achieved by twirling the wheel rapidly from lock to lock at full throttle, not something you would do in normal operation.

No boat really likes a beam sea, and she does try to profile the waves, so there is some lateral motion, but she never gets the deep rolling that many monohulls do. It is best in a big sea, to alter course slightly so you are crossing the waves at an angle. Downwind in big seas there is no tendency to broach, but a bit of steering is required.

On the weekend we took the boat to Seattle for the floating show, covering 150 miles in 8 hours running time, including a 6 mile slow section through the narrow Swinomish channel. We never hit any rough stuff, other than ferry wakes and Bayliner wash(bigger than ferry wakes). No other boat passed us, although there were quite a few that could have if they didn't mind burning the fuel. We used approximately 40 US gallons for this trip.

That all said, the boat is great, but I miss sailing. Powerboating is like running a DVD movie in fast forward. You get to the end quicker, but it isn't as satisfying.

Grahame

Guillermo

09-12-2006, 04:21 PM

....but I miss sailing. Powerboating is like running a DVD movie in fast forward. You get to the end quicker, but it isn't as satisfying.
:) :) :)

Guillermo

09-18-2006, 01:10 AM

I have been reading about Sea Skiffs, Sea Bright Skiffs, Rumrunners and the like, at the most enjoyable Gerr's "Nature of Boats". Well, it seems like very few things are really new in this old round world talking about hull forms. Displacement gliders and the like seem to have been inspired in Seabright skiffs (I've read that somewhere else in these forums, but didn't fully realize the thing till now. :( )

Gerr cites the King 28-Foot "Sea Speed Skiff", produced by King Boatworks in 1920's & 30's. This boat was capable of cruising at 22 knots with a single 150 HP inboard. Quoting him: "Sea Bright skiffs have all the attributes for the perfect family cruiser: comfort speed, seakindliness, shoal draft, and economy...." Any other opinions?

Have a look at this interesting hull: http://www.woodenboatrescue.org/carview.php?view=28

I attach the lines of several Atkin's seabright skiffs, "Everhope" (20' tunnel stern), "Ghost" (28' day cruiser) and "Jersey Blue" (25' cruiser) (http://atkinboatplans.com)

Seabright skiffs have been partially treated in these Boatdesign's threads:
http://boatdesign.net/forums/showthread.php?t=7891
http://boatdesign.net/forums/showthread.php?t=7713
http://boatdesign.net/forums/showthread.php?t=4480
(And a couple of them more)

And even here in this same thread! See the excellent post number 39 (http://boatdesign.net/forums/showpost.php?p=89943&postcount=39) and post # 45 (http://boatdesign.net/forums/showpost.php?p=90023&postcount=45) by SAQuestor. I'm getting old...:( :(

Related matters can be found at:
http://www.boatdesign.net/forums/showthread.php?t=12945
http://www.boatdesign.net/forums/showthread.php?t=12512

Searching these forums for 'box keel', a lot of other threads are available.

Willallison

09-18-2006, 01:24 AM

That all said, the boat is great, but I miss sailing. Powerboating is like running a DVD movie in fast forward. You get to the end quicker, but it isn't as satisfying.

...ahh - then you're not going quick enough!:D

and of couse, going quicker means you can travel further in the same time...

ahh, Will, so profound, so profound....:p

Guillermo

09-19-2006, 12:37 AM

...and of couse, going quicker means you can travel further in the same time...
Yeap. But we have an old Madrid's song (Chotís) from 1930 or so, which's words more or less say the following:
"The time it took you to come from La Bombi to Madrid's center in a horse cart, it brings you now to New York an airplane; but, what the hell are you doing so early in New York?"

Take it easy. ;)

Cheers.

P.S.: "La Bombi" is the park of "La Bombilla", only a few km away from Madrid's center.

Willallison

09-19-2006, 01:16 AM

:D ... LOL - I like it it.
Aren't the bars open all night in New York?

Guillermo

09-19-2006, 01:37 AM

Aren't the bars open all night in New York?
Not only bars....! ;) ;)

SAQuestor

09-20-2006, 06:42 PM

vac-il-late
intr.v. vac-il-lat-ed, vac-il-lat-ing, vac-il-lates
1. To sway from one side to the other; oscillate.
2. To swing indecisively from one course of action or opinion to another.

The ONLY positive thing I can say is that I have not made any wood commitments. Still looking at plans. Still trying to make a determination on what is the absolute best design for my perceived needs.

To recap. I want a transportable retirement cruiser. A boat that I can use to spend the summer in the Great Lakes and transport to Florida to cruise over to The Bahamas for 4 months in winter. Next summer up the Inside Passage to Alaska and back. A winter cruise to Baja. Etcetera and etcetera until I’m too old or too sick to continue.

Various threads on various boat message boards have questioned this concept and the pros and cons have been argued till the skin is worn off our finger tips from typing.

There are several critical limiting factors. In order to NOT require a trailering permit for travel on federal highways (interstates) within the USA, the trailer and load (boat) must be less than 13’6” high (4114mm) and less than 102” – 8’6” wide (2590mm). State and county roads may have other size requirements, but all federally funded roads must adhere to these size standards.

Length is another issue entirely. Generally, any combination of tow vehicle and trailer & load that is less than 50’ (~15m) is OK. Some states say 45’ (~13.7m) and some don’t care if the combined length is 65’ (~19.8m).

Any boat that is large enough to be able to cruise in the areas I want to go will weigh in excess of the trailer brake limit – so trailer brakes are not an issue, they’re required – and only common sense.

I can stand to be corrected here, but as far as I can find out, as long as the GCVW (Gross Combined Vehicle Weight) is less than ~18,000 pounds – depending on the state you claim residence in – you will not need a special chauffeur’s license. Generally this means that if your boat and trailer can be towed by a heavy-duty American pickup truck, you’re good-to-go.

Personal preferences will dictate what you are comfortable with as far as size goes. Some folks drive semi’s and do so with aplomb. Some folks are scared spitless to drive an SUV on a residential street, let alone on a freeway. YMMV will certainly apply here.

My research has also shown that a load (boat) that is less than 10’ wide (~3000mm) will have little trouble transiting the various states to get to the cruising grounds that I want to visit. Certainly one might need an OVERWIDTH sign across the transom, and in some few states a flashing light setup would need to accompany the sign. But in no state that I can find info on is there required an escort car. Just do not exceed the height restriction of that 13’6”. (And even that is a bit flexible.)

So… Our dream retirement boat can have an easy max beam of 9.5’ (~2900mm), be less than 13’6” tall when sitting on the trailer and be something in the neighborhood of 28’ (8.5m) to 34’ (10m) long without any major transportation issues.

I want to once again emphasize that this is not a boat that one would haul to the local lake or river for an afternoon’s frolic. It may be too much to tow for just an overnight excursion on the weekend. It is intended for extended expeditions of a week or more.

So let’s go back to vacillate.

On one hand I am very attracted to a simple, lightweight planing boat like Tom Lanthrop’s Bluejacket series. (http://www.bluejacketboats.com/)

This sort of boat holds lots of attraction for me, especially now that Tom has finished the plans for his BJ28. But unfortunately my personal situation says that the drawbacks MAY outweigh the positives.

So I vacillate back to either full or semi-displacement boats. And there are numerous designs to choose from, many have been talked about in this thread, particularly the Seabright designs from the boards of John and William Atkin that Guillermo Gefaell has recently discussed. But this is not to exclude other designs and designers that post here (and elsewhere) – Tad, mmd and other’s that escape my feeble memory right now.

So if you’ve read this far you may be wondering why the vacillation? Amenities, plain and simple. Momma (the Admiral) needs electric power to power a medical device. That means batteries and an inverter. I want some doodads – RADAR is on top of the list with a laptop and charts, GPS and stereo and etcetera. To carry this a step further, if I’m going to spend anywhere from a few days to several weeks aboard a boat I want to be able to find a nicely quiet, remote anchorage and be able to spend a few days there ‘communing with nature’, so to speak. In my mind that means having enough battery power to NOT have to run the engine or a generator daily. Somehow that’s the antithesis of my reason to seek out this quiet cove in the first place. So can a planing boat carry enough batteries to enable this? Sure. At the expense of poor performance and economy.

So, if we put the same battery load into a semi or full displacement hull form and the drawbacks are not as severe as long as we don’t try to move too fast. Push too hard and the economy goes to pot.

But there are pluses with a semi or full displacement hull too. Probably an inboard diesel instead of an outboard gas engine. That means one can easily have a large alternator to quickly charge a battery bank. It also means that one can tote along enough water to make hot showers practical. And a water maker to replenish the water and refrigeration for ice for the sundowners, etcetera and etcetera.

But the drawback is that the boat is no longer ‘simple’ and more gear and mechanical ‘stuff’ is required and therefore more expensive to build and maintain, etcetera and etcetera.

Can you say vac-il-late? Six weeks or six months from now I'll be convinced that I can't afford a complicated boat and go back to favoring a simple lightweight planing boat.

The ONLY positive that I can see from this vantage point in time, is that I am not ready to cut wood for this dream cruiser for at least 2 more vacillating years. H3ll, I could be dead by then and it won’t matter. Until then, just call me “Boing-bing-boing, Ricochet Rabbit!”

Best,

Leo

Guillermo

09-20-2006, 07:05 PM

...Can you say vac-il-late? Six weeks or six months from now I'll be convinced that I can't afford a complicated boat and go back to favoring a simple lightweight planing boat.....
I'm afraid that for pocket motor cruisers, options are only two:
Wanting long range, long stays at anchor?: Displacement boats
Shorter range, mostly marina staying and ocasional overnighting?: Semi or full planning boats.
There's a corolary:
No money?: Dream. It's for free. :)
Cheers.

Willallison

09-20-2006, 07:08 PM

SAQuestor

09-20-2006, 08:22 PM

I'm afraid that for pocket motor cruisers, options are only two:
Wanting long range, long stays at anchor?: Displacement boats
Shorter range, mostly marina staying and ocasional overnighting?: Semi or full planning boats.
There's a corolary:
No money?: Dream. It's for free. :)
Cheers.

Guillermo - you wound me to the depths of my soul. ;)

To dream, perchance to dream. What good man if there are no dreams that can be made reality?

Seriously, since the cruises I want to do can be considered coastal cruises (with perhaps a leg of the Inland Passage and the hop across the Gulf Stream) a range of 500-600+ miles should be quite sufficient. In Tom's BJ28 design that should only be something in the neighborhood of 100 US gallons (378l) and very doable with a couple of underfloor tanks.

I disagree that one has to frequent marina's and only have occassional overnighters on a planing boat of reasonable size. Please see Bill and El Fiero's (http://www.geocities.com/bill_fiero/) site and Penny and George Berotti's (http://www.georgeberotti.com/2Wander/) site. Then for the C-Dory manufacturer's (http://www.c-dory.com/) site.

Best,

Leo

Willallison

09-20-2006, 08:47 PM

I disagree that one has to frequent marina's and and only have occassional overnighters on a planing boat of reasonable size

Absolutely true.
I spent up to a fortnight away from docks on my 27ft Searay, with 2 adults, 1 baby and 2 dalmations! When I was but a chosper, our family of 5 regularly did the same

SAQuestor

09-20-2006, 08:53 PM

Well Leo - I'd go somewhere down the middle if I was you. A relatively simple, reasonably light weight displacement boat should do the trick (have you checked out the posts and website of Mike Schooley? Known as Portager around here... Speaking of which I keep meaning to drop him a line - we haven't seen him for some time...)
Anyway back to the boat. Personally, I'd still go for a planing hullform, such as Tom's. One designed to run happily anywhere up to about 18 - 20 knots. I'd flick the big battery bank in favour of a small genset myself (or engine running). An hour a day is a small price to pay for the flexibilty it can bring. Spectra make an excellent range of small watermakers which can reduce the weight of water you are required to carry, but cost and complexity would probably see me compromise and have the capacity to carry about 200L of water. That should last at least a week with 2 people who are used to being sensible about water use.

Will, Yep - Mike Schooley's idea got me started on this crazy idea/quest. But he had a much different idea than what I came to realize would best fit my circumstances. IIRC, Mike was going for something over 40' (12m) and much wider so that it would not be as easily transportable as what I envision.

You are not the first to mention and advocate a small generator as the solution to the power problem. And when I am all finished moaning and groaning, swaying this way and that, that could be where I end up.

But in the mean time I read posts, buy and peruse reasonably priced plans, go to the marinas and drool or shake my head at some of the monstrosities that the buying public has plopped down their hard-earned (or inherited) dollars for and now want to unload with less than a couple hundred hours on the clock for a 5 year old boat. Yuck!:eek:

I remember back to a grade school field trip where the class went to the Oregon Museum of Science and Industry - OMSI - when I was in 5th or 6th grade. I was facinated by the huge pendulum they had in their lobby. You know the type - a long cable holds a large heavy ball and as it swings back and forth the earth rotates under it and it therefore knocks down pegs every few minutes.

I see lots of life like that pendulum, swaying back and forth. This week, this month, this year it will be at the extreme right, next week, next month, next year it will have swung to the extreme left. All the while the mean is somewhere closer to the middle - at any one moment in time it's maybe a little right or maybe a little left, but usually in the vicinity of the center. On the grand scale of things, it seems to me that there is some pendulum-like rhythm to the way that thinking folks approach their outlook on life. I know that I see things vastly different now that I am in my late 50's than when I was in my 20's.

All of that to say that when it comes time to fish or cut bait, I'll fish. But until that time when a decision becomes mandatory, I'll continue like the pendulum, having my internal debate - this way or that, while also listening to folks that are willing to share their knowledge and experience with those of us that are less knowledgable or experienced. Hopefully, by the time it actually comes to cutting wood and spreading epoxy, an answer will be crystal clear and the decision made easy.

Best,

Leo

Guillermo

09-21-2006, 06:00 PM

Leo,
Let's revisit WHIO (http://www.steamlaunch.co.nz/Whio.html), at the post which opened this thread:

LOA.................. 9.1 m
LWL.................. 8.9 m
BOA.................. 2.24 m
Fuel ................. 120 lt
Displacement...... 1350 Kg
Engine............... Toyota 2C
Hp ................... 52
Propeller............ 21.5 x 21.5 in, 2 blades
Consumption....... 2 lt at 10 kn

Sh'e capable of 17 kn with just 50 HP, and has accomodation for 2-3. Trailerable.
Cruises comfortably at 15 knots and 12 in heavier conditions, has a smooth riding with very little pounding, and steers well running before the sea with no tendency to broach.
At 10 knots she will do 540 miles (allowing for a non-usable 10% in the tank).
What do you think about her?

Willallison

09-21-2006, 07:00 PM

Whio is an interesting and elegat little boat - but I don't think I'd like to spend more than an occaisional overnight on her....

SAQuestor

09-22-2006, 11:44 AM

Leo,
Let's revisit WHIO (http://www.steamlaunch.co.nz/Whio.html), at the post which opened this thread:
{snip}
At 10 knots she will do 540 miles (allowing for a non-usable 10% in the tank).
What do you think about her?

Whio is an interesting and elegat little boat - but I don't think I'd like to spend more than an occaisional overnight on her....

Whio is an elegant boat. She has a wonderful ‘classic’ look while using modern methods and materials. The engineering thought and execution is, in my opinion, impeccable.

Frankly, I’d be proud to have built a boat that was half that nice.

If I lived in the same area that Whio cruises, she might be the perfect boat. But I don’t – and the areas I want to cruise a boat are far apart with extremely divergent conditions that may be encountered. So Whio’s minimalist approach, while right for the area and owner, are not right for me. And like Will, I would not want to spend more than a couple consecutive nights on her.

Best,

Leo

SAQuestor

09-22-2006, 11:56 AM

After considering Guillermo’s question above, I’d like to take a bit of time to branch off and explore a similar but different path.

Disclaimer – I am not a math whiz. Never was. Never will be. But while that is true, it is also true that I can understand clues when whacked really hard with a cluex4. Hopefully someone will be gentle with the cluex4 about similitude that I’m asking for now.

Please see the attached drawing from Paul Gartside (http://www.gartsideboats.com/catsteam.php). I chose this particular one for an illustration because I like its lines, but there are many other examples available on the web that are in the same family.

19 ft Steam Pinnace, Design #132

Construction: Strip planked/cold molded. A fine, high transom stern as seen on this little launch is ideal for smaller power plants like steam engines. The extra waterline length will allow it to out-perform similar size boats of the fantail stern model. Add to this, simplicity of construction, and it is surprising that it is not seen more often.

This little boat was drawn especially for the home builder and the plans are very fully detailed. Construction is strip planking overlaid with two layers of cold molded planking for a stiff, light, frameless hull. Suitable for steam engines of 2 - 3 horespower or small electric plants.

Specification Table for 19 Ft Steam Pinnace

Length Overall 19 ft 6 in
Length Waterline 18 ft 11 in
Beam 5 ft - 7 in
Draft 1 ft 10 in
Displacement 1735 lbs

Looking at the lines drawing – it seems to my eye that this design has easy flow lines – water will easily flow around the boat and therefore requires little power – as Mr. Gartside says – 2-3 hp.

As you might remember from my earlier posts in this thread, I want a transportable boat that is suitable for various near-shore excursions of varying length – from a week to 3-4 months.

Let’s apply what I understand about the principle of similitude.

I’m going to work in millimeters, as that is so much simpler for my feeble math-challenged mind to comprehend.

I want a total beam of 2800mm (about 9’2”). So I do the simple math and it comes out that I need to multiply by 1.645 to achieve my desired beam.

Using the same 1.645 constant, that means the boat also lengthens to 9777mm (32’1”) and the draft goes to 919mm (~3’).

I seem to recall that displacement would change at a different rate - the square or cube or something… – so I’ll stay away from that for now.

So… I’ve applied the same constant to the design – in my mind that means that though the lines expand, the relationship between them remain the same. Correct?

Ass-u-ming that is so, then the horsepower requirement will go up based on increased skin friction and increased displacement. I doubt in a linear fashion, but I suspect not in a logarithmic manner either. Let’s get really extravagant and for arguments sake say, 8x or 24hp.

So for guesstimates sake, we spec out a diesel of about 32-35 horsepower for that extra bit of power for those times that unexpected adverse conditions force us to plow through wind and wave to get to a safe harbor.

N.B. – real numbers will be calculated by professionals that understand the math much more thoroughly that I do.

Regardless, we should now have a hull with sufficient volume to support the required tankage, assorted gear and amenities required for a couple to cruise for a few weeks to a few months while requiring very little power for ‘normal’ flat water conditions – rivers, canals and sheltered lakes.

By expanding all the dimensions by the same constant – 1.645 – the waterline length increases to 9484mm (31’1”) – leading to a hull speed of about 7.5 knots. But, from what little I understand about reading hull lines, it would be difficult to get too much more speed from this enlarged hull form because of the shape of the buttocks lines – the stern would drop into the ‘hole’ that the wave train generates at S/L of 1.34.

Reducing speed to a more reasonable S/L of 1.18 – ~6.5 knots, I would GUESS that the boat wouldn’t require much horsepower and would sip diesel at a very low rate.

Now… Here’s where the cluex4 comes into play. What the heck am I missing here? There has got to be some factor(s) that either I don’t understand or am missing completely, otherwise there would be more boats of similar lines – give or take a bit – being designed and built by either home builders or custom shops.

I can understand that this might not be a commercially viable idea – but why not for a transportable owner/builder one-off?

Please do not respond with simple comments like, “No, that’s a stupid idea.” Rather I’d like to see, “No, that’s a stupid idea because…”

Thanks in advance for helping with my education. Hopefully there are dozens (hundreds?) of other folks that will also gain some knowledge from those habitués that have the correct clues to dispense.

Best,

Leo

Guillermo

09-23-2006, 04:19 AM

Leo,
Your idea is not stupid at all.
Those lines are lovely, derived from rowing boat's ones, so pretty efficient to motor at low speed/length ratios.

Your Lwl would go up to 9,45 m (based on Gartside's 18' 11 "). Asuming a waterline beam of 2,52 m, and a body draught (amidships) of around 0,4 m (As from Gartside's drawing, roughly), and keeping the Block Coefficient the same as for the Steam Pinnace (0,36) we come to a displacement of around 3500 kg (7772 lbs).

We need around 700 lbs/SHP for an speed/length ratio of 1.18 (6,58 kn), this calling for an SHP power of around 11 HP. To drive the hull at 7,48 kn (hull speed) we should use a figure of around 500 lbs per HP, so we'll need around 15,4 HP for that. Allowing for gear loses (3%) we'll need a continuous BHP of 16,6 HP, which brings us to an engine rated around 18.5 HP (assuming continuous as a 90% of rated HP). Let's make it 20 HP for that extra muscle sometimes needed.

I'd appreciate if you and Will could tell me what would you change in WHIO's design to make her acceptable for you to sail her for extended periods of time. An slender hull like that is pretty efficient in semidisplacement mode, so allowing for higher speeds with modest power, and also with a better seakeeping abilities than a wider hull. The derivation proposed by Leo on the Steam Pinnace, although being a lovely hull, will never be able to reasonably motor over her hull speed.

Cheers.

(P.S.: Doubling dimensions, you go up to 4 times the surface area and 8 times the volume).

Tad

09-23-2006, 03:54 PM

So we have Whio at about 3000 pounds and the scaled Steamer at 8000 pounds, there's a great deal of territory in between. Whio is an elegant vessel but not too suitable as the family cruiser, more like a weekender at best.

As a half-way point I would suggest something like the sketch below. She's 28' LOA, 26'6" LWL, beam is 8'6", max draft is 2'0", max displacement is 5000 pounds. Engine is a Yanmar JH4 at 55 HP, maximum cruising speed is 13.5 knots at 2.7 gph. 9.5 knots is just over one gph. Four berths inside, a real galley, a separate head, she could in fact handle a small family cruise of 10 days or so.

Tad

9268

Guillermo

09-23-2006, 04:57 PM

Tad,
I liked the Down East 26 at your web pages. I've previously posted it at http://www.boatdesign.net/forums/showpost.php?p=104167&postcount=148

In this new nice design of yours, what's the stern like? Is it veed with a tunneled propeller, or (what it seems to me) is it a flatted tug-like one?

Berth at companionway seems short. Does it open sideways?

Could the design be streched to 30' to get bigger room and improve performance?

Going diesel-electric would allow to take the engine from the middle of accomodation, thus allowing for a different arrangement. What do you think?

Cheers,

Tad

09-23-2006, 08:54 PM

Guillermo,

The hull form is shown below, yes, the transom is veed and the propeller is in a pocket with full skeg to protect it.

The aft berths are two singles fore and aft, the feet extend under the cockpit seats. This berth can also be made up (with back cushions) as a huge double athwartships. Thus mom and dad have options to sleep together or alone, forward or aft. The boat would also be usable by two couples.

Can it be stretched? Sure, but this was an attempt at the minimum which could do what was originally requested.

Diesel-electric would certainly be possible, but it will add weight, complexity, and cost. A decent sound deadening box, flex mounts, soft coupling and thrust bearing are off the shelf items for this size. The ultimate would be a big Honda outboard way aft in a well.

Tad

9275

tom28571

09-23-2006, 09:29 PM

Very interesting interior Tad, don't think I've ever seen anything like it. Such quarterberths are common in sailboats but never thought of them like that in a powerboat. The helm arrangement looks like it might have been dictated by the engine placement. Helm vision aft looks pretty restricted.

A very nice looking boat although I have some personal issues with the unusual interior. Hey, you gotta give free rein to your pencil to ever get away from the usual. I think most of my qualms would be solved with an outboard which you probably have also considered.

SAQuestor

09-24-2006, 12:29 AM

Your idea is not stupid at all.
Those lines are lovely, derived from rowing boat's ones, so pretty efficient to motor at low speed/length ratios.

{snip}

although being a lovely hull, will never be able to reasonably motor over her hull speed.

Thanks for that Guillermo - but do you suppose that this speed limitation is the only reason that boats with this hull form haven't been designed and built of late?

Your calculations of the low HP required would seem to bring it in to the realm of practical as fuel prices rise - and rise some more.

Is there some other major (or minor) drawback that I'm unable to see?

Thanks,

Leo

Guillermo

09-24-2006, 02:24 AM

Tad,
I love the lines.
2.7 gall/hour at 13.5 kn is pretty attractive. My good old 'Marie' is only able of 7.6 kn at that consumption at its best (But she's moving 13 tonnes, with pure full displacement lines, of course!)
What about her initial stability? Wouldn't she be somewhat tender?
I coincide with Tom's concern about rear visibility from the helm position, precisely on the starboard side. COLREGS state you must give way to a vessel coming as abaft the beam as 22.5º on that side.
How much cost would a diesel electric system (such as the Ossa powerlite) compare in price against the usual stuff? (only order of magnitude)

Leo,
I do not know why that kind of hulls are not more usual among boaters, but I imagine it's mainly because till now fuel has been very cheap and time to enjoy boats very short. ;)

About drawbacks of the design for your intended use, I see a couple, at a very quick sight. One of them is some lack of rear space, due to the closing sidelines, and the other one is that probably her prismatic coefficient is around 0.5-0.53, which is low if efficiency is wanted at near hull speed. It is better to keep this prismatic coefficient high than low, as the loses due to it being high when going at lower speeds are lower than the contrary. Maybe lines should be altered somewhat to better cope with cruising needs. Probably some alterations to the freeboard should be also made to arrange for internal volume.

If those lines are suited to what you want, depends on your precise needings and would need a detailed study, I'm afraid.

Tad

09-24-2006, 12:20 PM

Helm vision aft looks pretty restricted.

Well....that's nothing a couple of big truck mirrors (P&S) wouldn't solve :D

Actually I was thinking to use a trick I recently noted on another boat. They had the enclosed head in a deckhouse like this, aft of the helm, but installed windows in the bulkheads so normally you could look right through. Just pull the shade when the head is in use. I my proposed boat the forward window could be very small as it's quite close to the helmsman's face. This actually works quite well.

Other visibility options would include a sliding hatch over the helm so I could sit on the roof and steer with my toes. I would also have full controls in the aft cockpit for fishing and for docking.

Guillermo,

She is a small boat and will move underfoot, she will be more tender than your average hard-chine box-boat, that is guaranteed! But there is always a tradeoff, a slim fine-lined form was the primary goal, and useful interior volume the secondary goal in this case. The reason for the deep vee hull is to move the heavy weights below waterline. I would pay a great deal of attention to reducing weight up high, foam or honeycomb cored cabin sides and top, engine, tanks, and batteries are down low, overall vertical height is minimized.

I would use this hull as a test bed for various (unending actually) stabilization systems. The first one I would like to try would be fixed foil-shaped bilge fins fairly far aft, angled outboard but not extending beyond the beam or draft of the hull, with very short cord length (perhaps 2-3' at the root and tapered).

I would also like to test a flume tank on the roof, a vertical dagger board on centerline in the cockpit, pivoting bilge boards above the waterline aft and extending horizontally into the quarter wave, and maybe even some bat wings. If I was cruising the West Coast in this boat I would fit a short pair of stabilizer poles and tiny paravanes.

Just guessing I would think that a straight diesel-electric system, engine, generator, motor, controller, and installation, will easily run double the cost of an engine and shaft.

All the best, Tad

tom28571

09-24-2006, 08:02 PM

Well....that's nothing a couple of big truck mirrors (P&S) wouldn't solve :D

I would use this hull as a test bed for various (unending actually) stabilization systems. The first one I would like to try would be fixed foil-shaped bilge fins fairly far aft, angled outboard but not extending beyond the beam or draft of the hull, with very short cord length (perhaps 2-3' at the root and tapered).

I would also like to test a flume tank on the roof, a vertical dagger board on centerline in the cockpit, pivoting bilge boards above the waterline aft and extending horizontally into the quarter wave, and maybe even some bat wings. If I was cruising the West Coast in this boat I would fit a short pair of stabilizer poles and tiny paravanes.

All the best, Tad

Good luck with the bilge fins. I know of one boat they were tried on and there was very little noticeable improvement. This was an old Navy whaleboat, a noted roller.

Why not a big gyro wheel:D :?:

Guillermo

09-25-2006, 08:53 AM

I've tested long bilge fins in my boat (around 2 m length 0,20 m wide), but dampening is very small. And they produce annoying 'bangs' when short beam or quarter waves hit the hull when heeled.

Tad

09-25-2006, 09:56 AM

Tom,

If the stabilizing gyro was also the generator in the diesel-electric propulsion system.....we might have something! ;)

Tad

Tad

09-25-2006, 10:47 AM

Bilge keels would look something like this....

9309

Vega

09-25-2006, 02:32 PM

This one has some kind of stabilizing keels. I don't know if they work, but it looks to be a nice Design. It's an Aluminium boat by Dutch Architect Firm: Ankersmit Marine .

http://www.ankersmitmarine.com/engels.html

tom28571

09-25-2006, 02:47 PM

Tom,

If the stabilizing gyro was also the generator in the diesel-electric propulsion system.....we might have something! ;)

Tad

Started to mention that since there were some municipal buses that had big honking wheels spinning at gosh awful rpms to power them between charges when they were off the grid. In some ways this is similar to the hybrid auto in that the wheel can be spun by a low power driving force over long term and can exert lots of torque for short periods.

Raggi_Thor

09-26-2006, 02:34 AM

tom28571

09-26-2006, 09:27 AM

They also help when drying out.
One builder of small fishing boats here, typically 10 meters long, alsways fit a anti roll tank on top of the wheeelhouse. They seem to know exactly how to shape this tank and how much water to hhave in it. The manager told me once it's not much water needed.

Of course, what they are doing is increasing the rolling moment of inertia to damp out rolls. I think they had better know just what they are doing since righting moment is adversely affected by extra weight up high. This is one of the factors given for the loss of the fishing boat in the "Perfect Storm". Not water, but more structure high above the designed center of gravity. Fishing booms serve the same purpose but they can be set nearly horizontal to the same effect without the higher CG.

Raggi_Thor

09-26-2006, 09:51 AM

Yes, but you need very little water up on the roof because of it's dynamics.

Guillermo

09-26-2006, 05:53 PM

Bilge keels would look something like this....
Those seem to me to extend beyond beam or draft. Are they?
Aren't they too exposed? They should be pretty strong to whitstand possible hits from floating debris.
I'm not sure if fixed bilge keels are of real use when cruising at 9,5 knots or over, with hull in semiplanning mode. I'm not sure if benefits will compensate the increased friction drag. And at rest, I think they are not very useful, indeed (Unless unacceptable big)

Guillermo

09-26-2006, 05:54 PM

One builder of small fishing boats here, typically 10 meters long, alsways fit a anti roll tank on top of the wheeelhouse. They seem to know exactly how to shape this tank and how much water to hhave in it. The manager told me once it's not much water needed.
I would love to have a deep look to that.

YankeeBoater

09-26-2006, 10:26 PM

So I am sticking with a mid-20's (feet) in size, and since you say cruiser, assuming we need a good deal of interior space along with a head, usable galley and sitdown eating space...

For a displacement boat, I like Michael Kasten's little aluminum Boojum 25, which has lead ballasted bilge keels, tapered/rounded stern, and a nice horizontal driveline due to the rocker of the bottom:
http://www.kastenmarine.com/boojum25.htm

For a semidisplacement boat, I like two "off the rack" boats from Canada, both with outboard power, soft chines, and a reasonable pricetag... the Rosborough RF-246 sedan cruiser:
http://www.rosboroughboats.com/rf246/sedan/246Sedan.htm

...and the Caledon 27 from Caledon Boatworks (beautifully finished inside):
http://www.caledonboatworks.com/Caledon%2027.htm

And for a planing boat, I like the off-the-rack, deep cockpit, deep vee Osprey 26 Long Cabin (unfortunately they just revised their website, and not much is available right now info/figures):
http://www.ospreyboats.com/OPHpgs/26LC.html

Guillermo

09-28-2006, 12:28 AM

Willallison

09-28-2006, 01:58 AM

I would also like to test a flume tank on the roof, a vertical dagger board on centerline in the cockpit, pivoting bilge boards above the waterline aft and extending horizontally into the quarter wave, and maybe even some bat wings. If I was cruising the West Coast in this boat I would fit a short pair of stabilizer poles and tiny paravanes.

Tad - Righto - I'm quite happy to be the fool who asks the obvious question.... what are bat wings?

I too regularly incorporate tunnel berths into my powerboat designs. I've often wondered why they aren't more common.
Your interior is indeed an interesting one. I've mucked about a few times with trying to eliminate the blind spot created by a sallon-level head. pop-up roof's, head set down into the vee of the boat etc, etc. Sadly, they are a necessary evil, and I'm yet to come across the ideal solution...

Raggi_Thor

09-28-2006, 05:40 AM

Water tunnels in planing motorboats work very well, when you stop the boat sinks down to it's chine and feels very stable.

Here's another little Swedish sailboat,
campus 650 and 630 from Fabola, design by Bernt Lindquist.

Tekniska specifikationer:

LOA: 6.60 m
Length of hull: 6.20 m
Bredd: 2.30 m
Draft: 0.25 - 1.20 m
Ballast in keel: 60 kg
Water ballast: ca 150 kg
Mastheight above water: 9 m
Main sail : 9.00 m2
Genua : 8.00 m2
Spinnaker: 22.00 m2Dry weight (on the trailer) : 455 Kg

www.fabav.se (only swedish?)

YankeeBoater

09-28-2006, 11:26 AM

Interesting boats, YankeeBoater. A pity that only Michael Kasten post info on performance, various displacements and the like. Probably it's because Boojum is the only displacement boat of them four. I would like to know how those said semidisplacement boats perform when loaded.
Cheers.
Yeps... there is not that much testing info on modest sized displacement and semidisplacement boats, because unfortunately there is not a strong market interest there, so not many made and not many written up or tested.

There is a Caledon 25 on boats.com right now - they give the dry weight, and capacities for water and fuel, so with the densities of those fluids and a typical engine weight, working out a displacement would be a couple minutes work. This particular one is wearing twin 60hp motors, for which they list top speed as 19 knots, and cruise at a respectable 15 knots. Fuel burn isn't given, but can't be too bad for 120hp 4-stroke at roughly 4000rpm. I think this sort of boat is quite attractive.

The Kasten boat is very handsome and impressive, and interesting for me in a fantasy kind of way. But it's a very specialized boat - don't think the market is very big for it (even if it could be offered at a competitive price). For any displacement boat of moderate size, running 6 knots not only lacks thrills, it severely limits how far you can get in a given time. Sailboats of course run this same speed range, but they are virtually silent running boats that are run from an open cockpit, where you can feel the wind, sun, listen to the surf and birds, and have a great view of all that is passing grandly around you, and so have a completely different appeal.

Tad

09-28-2006, 03:25 PM

The bilge fins do not extend beyond the hull draft or waterline beam. I make no claims for them, NA Pat Bray has made some claims (as has one of his clients) and I would like some real experience with them. As well I would love the opportunity to compare various systems on the same hull under conditions that I could document and control. Will it happen....who knows what next year will bring. Maybe a model?

Obviously the bilge fins would help a great deal when running off in a sea!

Will....What are Bat Wings? Uh... the flapy things that bat's fly wit....err, oh ya you mean BAT WINGS? I posted a picture of some here a while ago, they are flat plates that extend horizontally from the keel, with braces on the outboard end to the topsides. Very ugly but popular with round bilged fishing boats in BC.

We saw Boojum again in Port Townsend a couple of weeks ago, she sits in a back corner of the yard and has never been far, AFAIK. My son's comment was , "wow, a tugboat on mushrooms!" Cute, but immensely complex and top heavy and slow. The boat is not used (IMO) because there's no place to be outside on it, and only one tiny access door to a pilothouse with only one seat in it! All passengers are relegated to sitting below decks while cruising, thus it's not too interesting.

Tad

Guillermo

09-28-2006, 04:12 PM

Obviously the bilge fins would help a great deal when running off in a sea!
Oooops! Yes, of course.

Willallison

09-28-2006, 06:43 PM

Tad - ah got you now - yes I remember the images you posted now - bit like Benny Lexcen's Oz2 keel on steroids!

Outside of the range of this discussion I know but here is an image of one of my own drawings that incorporates tunnel berths...

tom28571

09-28-2006, 07:32 PM

Wil;l,

You don't include section lines for these but, to my uneducated eye, they look a lot more wholesome with undoubtedly better handling than the early ones. Look good to me.

Willallison

09-28-2006, 08:31 PM

Thanks Tom - yes, she's somewhat different to others that I've posted in the past: still quite light for her size in order to allow slow planing speeds and economical use, but without the attempts to go terribly fast as well - top speed is around 25 knots. I don't have a copy of the lines here, but I'll post some before long.
She features 'soft chines' - quite round forward that harden as they move aft. This will increase the drag a smidgen, but is a tradeoff against the chine slap that hard chined boats exhibit whilst at anchor - one of my pet hates, as it keeps the wife awake: happy wife, happy life;)
Back to the tunnel berths, I actually had another version that features berths either side of the companionway, with a slpit head / shower forward, but in the end opted for the larger head and over / under berths

brian eiland

09-30-2006, 11:34 AM

Started to mention that since there were some municipal buses that had big honking wheels spinning at gosh awful rpms to power them between charges when they were off the grid. In some ways this is similar to the hybrid auto in that the wheel can be spun by a low power driving force over long term and can exert lots of torque for short periods.
Actually I believe what you are referring to were some buses that operated in Europe (Swiss I believe) that utilized the flywheels in a regenerative fashion....that is the flywheels absorped the braking energy, and then utilized that to help in accelerating away from the frequent stops.

They were of the 'old fashion type', that is big steel flywheels in contrast with the 'super flywheels' fashioned of carbon fibers.
http://boatdesign.net/forums/showpost.php?p=85848&postcount=163 (http://boatdesign.net/forums/showpost.php?p=85848&postcount=163)

Guillermo

09-30-2006, 12:40 PM

Yeap. The name of the game for our next future will be storing energy.

SAQuestor

09-30-2006, 10:32 PM

George and Penny Berotti have posted the final narrative and pictures of their 2006 Alaska cruise on their site - http://www.georgeberotti.com/2Wander/

In the summary they detailed the following:
2903 NM total
280 Engine Hours
10.4 Avg. MPH
958 gallons of gas
3.4 GPH
3.03 Avg. MPG
$4.08 US$/Gal.
$3,909.22 Total US$ fuel cost.

Those numbers total out to almost $1.35 US$ per nautical mile! And that on a 22’ C-Dory boat with what looks like a 90 hp 4 stroke Honda outboard. WOW! :eek: may be an understatement.

The other critical part that is not detailed in the summary is the very small range that the boat had/has. This short range on a full fuel load forced them to buy fuel at some very expensive places. They could not pick and choose their fuel stops. This is detailed in the narratives.

I doubt very many people would disagree with the following general arguments.
1. Worldwide demand for crude oil is growing.
2. Many major oil reserves lie in a very politically volatile part of the world.
3. Many existing oil fields are past their prime and their output is declining.
4. New discoveries of substantial oil fields are becoming rarer.
5. There is apparently much oil bearing strata, oil sands and oil shale, etc. that is undeveloped but is very expensive in both terms of dollar cost and environmental cost to develop.
6. Most easily exploitable oil has been found.
7. New discoveries will most likely be deep underwater and/or much deeper in the ground.

All of this suggests that all fuels derived from hydrocarbons will not, over the long term, go down in price, except as manipulated for short-term political reasons.

So we can look forward to fuel that is more and more expensive. Mr. Berotti’s experience this year strongly points toward the need for boat designs that;
1. Have sufficient economy to double, treble or even quadruple the average MPG they actualized.
2. Have sufficient tankage and thus the range to bypass the smaller fueling opportunities in favor of places where fuel is shipped in via barge instead of 55 gallon drums.

In my mind this problem immediately suggests that the desired speed of travel is critical to being able to get those 10+ MPG averages. Slow down would be the watchword. It seems to me that the boat design could be optimized to allow a higher average speed while keeping a ‘reasonable’ MPG average. Once again, compromise rears its head and may limit what is practical versus what is possible.

{snip}
Leo,
I do not know why that kind of hulls are not more usual among boaters, but I imagine it's mainly because till now fuel has been very cheap and time to enjoy boats very short. ;)
About drawbacks of the design for your intended use, I see a couple, at a very quick sight. One of them is some lack of rear space, due to the closing sidelines, and the other one is that probably her prismatic coefficient is around 0.5-0.53, which is low if efficiency is wanted at near hull speed. It is better to keep this prismatic coefficient high than low, as the loses due to it being high when going at lower speeds are lower than the contrary. Maybe lines should be altered somewhat to better cope with cruising needs. Probably some alterations to the freeboard should be also made to arrange for internal volume.
If those lines are suited to what you want, depends on your precise needings and would need a detailed study, I'm afraid.

Humans, being human, tend to get tunnel vision with what they are comfortable with – with what they are used to. I do a bit of graphic design work along with technical writing in my day job. Every time I attempt to introduce a ‘different’ look to the documentation, the almost universal reaction is “I don’t like that. It is not how we’ve done it before.” But unfortunately how “we’ve” done it before looks (IMO of course) like it was produced on a 1950’s manual typewriter and mimeographed in a back room somewhere. Well, maybe it is not quite that bad – but you get the idea I’m sure. And this sort of tunnel vision most likely carries over to boat designs too. Some individual's that post here seem to be able to easily transcend this problem and some are having a bit more difficulty leaving a well known comfort zone.

I am not suggesting that these particular lines (in post #167 of this thread) are in any way ideal. It was more the concept of a displacement hull form that requires a minimum of horsepower to move along at about S/L 1.2 that I wanted to explore.

In a planing hull form. Tom’s Bluejacket designs can achieve (IMO once again) remarkable economy at low planing speeds that leave many other designs plowing the water with bow high. Tom reports in his plan package and in numerous posts on various internet boat forums that his 24' Liz routinely achieves double the mileage that the Berotti's actualized - 6.5 to 8.5 MPG at about 13-15 knots on Liz.

In order to achieve this performance the entire boat must be kept lightweight. This is not meant as a critique – it is a fact that adding weight to planing designs is detrimental to economical operation. And I suppose that we can also extrapolate that hull design - the C-Dory and the BJ series - plays some major roll also. But in all fairness, we don't know the traveling displacement of Berotti's Wanderer - they might have been very heavy with supplies for their Alaska voyage.

Regardless, my understanding is that the same is true for displacement designs – but to a lesser degree. The performance and economy penalty for adding a ton of weight is not as severe as it is in a planing hull.

So let's look at some hypothetical numbers for a displacment hull on the same Alaska trip.

As a reminder - Wanderer's numbers for a planing boat.

2903 NM total
280 Engine Hours
10.4 Avg. MPH
958 gallons of gas
3.4 GPH
3.03 Avg. MPG
$4.08 US$/Gal.
$3,909.22 Total US$ fuel cost.

Displacement hull, Average 6k speed - doubling the fuel mileage.

2903 NM total
484 Engine Hours
6 knots Avg.
479 gallons of fuel
.99 GPH
6.06 Avg. MPG
$4.08 US$/Gal.
~$1,950 Total US$ fuel cost.
$.67 cents per NM

Displacement hull, Average 6k speed - tripling the fuel mileage.

2903 NM total
484 Engine Hours
6 knots Avg.
319 gallons of fuel
.66 GPH
9.09 Avg. MPG
$4.08 US$/Gal.
~$1,300 Total US$ fuel cost.
$.45 cents per NM

Displacement hull, Average 6k speed - quadrupling the fuel mileage.

2903 NM total
484 Engine Hours
6 knots Avg.
240 gallons of fuel
.5 GPH
12.12 Avg. MPG
$4.08 US$/Gal.
~$975 Total US$ fuel cost.
$.34 cents per NM

As usual, I suspect that reality lies somewhere between the two extremes. So if it is desirable to tote along more fuel, more water, more amenities and doodads, and regardless of the exact numbers, it appears that it is more economical to do so in a displacement hull.

But I face is the dilemma of doodads and ‘stuff’. If I can convince myself (and the Admiral) that I do not need lots of doodads and amenities, then Tom’s 28’ BJ design is a great boat design for my desired travels. And I suspect that the 28’er will actualize a fuel economy in the 5-7 MPG range at 12-14 knot cruise. The plus is that it is 2x to 2.5x faster than a displacement boat of similar length. The negative? Lightweight is watchword of the century and therefore many fewer doodads and much less ‘stuff’ can be toted.

If I come down on the side of ‘stuff’, then IMO it becomes a quest to find the hull form that will tote the ‘stuff’ most economically, thus my questions about a hull form that was specifically designed to be powered by low horsepower steam.

I recognize that the hull form that I posted from Paul Gartside is not ideal for a hull that requires some storage space for long term cruising needs – amenities, stores, fuel, water, etc. But somewhere between a big wide square transom with lots of storage and a elegant wine glass form, there has to be a compromise that would providing sufficient storage and support for increased speeds yet allow excellent economy at S/L ~1.1 – 1.2.

BTW, I did contact Paul Gartside about enlarging one of his hulls and his comment was that regardless of what else was done, the L/B ratio needed to stay at 4:1 or greater to achieve the economy and low HP requirements of the original hull. That meant that the LOA would go to near 11 meters with a 2800mm beam. I think that is too long for me.

Just some thoughts for rumination when the mind wanders from playing with the grandkids into more esoteric realms.

Best,

Leo

Guillermo

10-01-2006, 04:52 AM

tom28571

10-01-2006, 12:02 PM

With some trepidation, I will hope to add some light without adding too much confusion.

I am not too surprised at the low fuel mileage registered by the C Dory on the Alaska cruise. The C Dory is a pretty small boat and although about the same hull weight as the BJ24, it has a much smaller hull bottom. Loading this small boat down with all the stuff needed for a long cruise will make its bottom loading in lbs per sq ft very high. This, in turn, will make the power required to plane it high. Thus, the fuel use is high.

The C Dory 22 has a bottom area of approximately 65% of the BJ24.

At the same displacement, the at-rest bottom loading for the C Dory is over 1.5 times higher than the BJ24. Bottom loading for displacements of 2400#, 2850#, and 3400# are 35, 42 and 50 #/sq ft, at rest. For planing, these increase to 55#, 65# and 77#/sq ft. The planing numbers are probably higher but I assumed the same planing trim angle for both boats.

Under the same displacement conditions, the BJ24 numbers are: 23#, 27.4# and 32.7#, at rest, and 34.3#, 41# and 48.5# when planing.

At planing speed the C Dory loading is even more than 1.5 times the BJ24 because of a higher trim angle.

Dealers for the C Dory insist on installing at least a 75hp engine because they say the boat does not plane well when loaded with smaller motors. They also place a long anchor chain in the bow to hold the bow down and help get the boat up on plane.

Without considering any other factors, these data indicate that the BJ24 will deliver a much lower fuel use than the C Dory. There are many factors that determine the efficiency of a planing powerboat and these are only a couple. While I tried to design an efficient hull, I did not force the design so far as to maximize fuel use. Therefore it is possible to design a boat that will easily beat my numbers by making other compromises than the ones I chose. For example, Whio is a very attractive boat and delivers impressive performance and I congratulate Peter on an excellent design and build. He did make some pretty stiff compromises in cruising comfort and cost to get the boat he wanted.

There aint no free lunch. The C Dory draws admiring remarks from others when seen on the water. A close friend has one that I have driven and been aboard on many occasions. Part of its appeal is the fact that it is based on the dory, which many consider a very attractive hull form. I concur on the shippy appearance but do not agree that the dory hull form is a good one for all uses, especially a planing powerboat.

I hope this helps rather than hinders this discussion.

I also want to clear up the BJ24 fuel use a bit. The numbers given by Leo are a bit misleading. I do not know the specific fuel use for any given speed. My numbers are based on usage for complete cruises at varying speeds. Another example is a cruise of Ontario Canada of 350 miles. On this cruise, the average speed was between 10 and 11mph taken from the hour meter and log. In cuts, near locks and other low wake zones the speed was much lower than in open areas such as lakes and the North Channel. The fuel mileage was 6.9mpg. This cruise of about 3 1/2 weeks represented one with more than the normal amount of cruising load aboard.

Guillermo

10-01-2006, 12:41 PM

I hope this helps rather than hinders this discussion.
Yes, it does.

SAQuestor

10-01-2006, 12:52 PM

{Snip}

So we need to go bigger to get 6 - 6.5 kn speeds at 1.1 - 1.2 s/l ratios. Something like 30 ft Lwl.

I am sorry that I was not clear here – I was not suggesting that a displacement boat as short as the C-Dory would be suitable. A displacement boat in the 28’ to 32’ (8.5m to 9.75m) range with a LWL as long as possible is what I was thinking of.

For fuel efficient pocket cruisers (And we are talking here under 30' LOA), I think we can state the following:
Full displacement: Nice for very extended voyages in areas with little chance of fueling/provisioning. Prismatic coefficient around 0.63. Power and fuel tankage optimized for 1.1 s/l ratio. A cruising mode only apt to people able to enjoy long periods without working.
Planning: Cruising mode in short hops in areas where fueling/provisioning is easy. For a 26' Lwl you'd be planning at 15.5 kn and at 13.5 kn for 20', with a proper design. To not be very fuel hungry, cruising speed should be limited to a 4 s/l ratio. Due to higher speeds, extensive areas may be enjoyed in a short time. Lightweight essential. Crews should be limited to a couple.
Semiplanning: Something in between. L/B should be kept high, weight down and lines carefully studied. Probably the most compromised design. I think even 30' is somewhat low for this kind, if extensive cruising with occasional refuelings is a goal. Cruising speed should be around 12 kn for 28 Lwl.

With planning and semiplanning boats we may enjoy far away cruising grounds by going trailerable. An extra bonus over heavyweighters (Except the smallest ones).

Cheers.

Once again it seems to boil down to suitable answers to these questions:

1. Where do you want to go?
2. How fast do you want to get there?
3. How much ‘stuff’ do you want to tote along?

Each one of these questions has a numerous sub-questions. Finding answers to these questions requires a deep understanding of yourself and your goals. Each answer begets a set of design criteria and thus one might be able to narrow the search for the best design for your set of circumstances.

Two examples for me – I’m currently struggling with ‘stuff’ and economy.

If I want amenities on a boat, a real head & holding tank, a real shower with real hot water, then that points toward a displacement hull with an inboard diesel to tote along the tanks and necessary associated equipment to support the ‘stuff’. And that is not going to be the inexpensive way to go. ‘Stuff’ costs money to buy and maintain. But while this is the expensive way to go, the boat would seem to me to be more suitable for cruises of many months duration where one could find a nice quiet anchorage and soak up the natural beauty of the spot. To me it would be seemingly more comfortable because you’d, in essence, have a floating RV. Economy in a displacement hull can be had if one is not in a hurry as Guillermo suggests.

But if I can be satisfied with “sun-shower” on the aft deck and I can get away from the idea of electronic doodads galore, then a lightweight planing hull would be eminently suitable. Going this way accomplishes several things – two of which are less initial building expense and a less expensive tow vehicle would be required. There seem a myriad of other positive things that a lighter weight throughout would produce.

But the drawback as I see it is this seems more like tent camping rather than the comforts of an RV. Economy in a planing hull means that one has to a) initially have the right hull form and b) be a staunch adherent to the mantra of lightweight – both in boat structure and the amount of ‘stuff’ one totes along. So this brings up the question of exactly how independent from marina services can one be in this sort of boat? One would (probably) tote less water, food and fuel. So how often would a re-supply be required?

So there, in not so much of a nutshell, is the conceptual struggle that I am engaged in. Lots-O-‘stuff’ or less ‘stuff’ is the question that my poor pea brain is struggling with – and most likely will continue to struggle with for a while.

Best,

Leo

Willallison

10-01-2006, 06:29 PM

All this talk of economy bring's a wry smile to my face. Only this last weekend I was amused to hear the very proud owner of a new boat proclaiming the outstanding fuel economy of his new 4-stroke outboard. "It uses half as much as the old one", he said. I asked why he had decided to replace the boats original 2-stroke.... "it used to cost me $100 each time I went fishing", he replied.
So he's spent 20 grand to save 50 bucks each time he goes out....

The moral of this story isn't so much that you shouldn't stive to build an economical boat - simply that it isn't the be-all and end-all. It's just one of the compromises that must be considered in the overall design. As Tom suggested - he could have designed Liz to be even more economical, but it would have involved compromises he wasn't prepared to make.

Just as an aside, we own a heavy (almost 3 tons) 25ft deep-vee fishing boat. It runs a pair 225hp Dfi merc o/b's. At 5 knots we can get over 7 nmpg. Of course at 50 knots the consumption is considerably more!:D

So - my suggestion would be to make a list with 2 columns.
Must Have's
Would Like's

You can then set about deciding which of the latter's you must sacrifice and which you can include. Only then are you in a position of being able to decide what sort of boat you should have

SAQuestor

10-01-2006, 06:47 PM

tom28571

10-01-2006, 09:28 PM

Leo, as you sit on the cusp of your dilemma while trying to decide which way to move, think about this. Deciding to go for the "stuff" is an open ended pursuit with the desire always staying one step ahead of where you are at the time. Going is the other direction sets some real limits at both ends and makes you think hard about what you really need or really want.

In designing a couple of our houses, I found it far better to start small and enlarge to satisfy some real need or desire. Starting with no limits always ended with a cut down model to fit economic reality that just did not satisfy as well. Start off thinking like a backpacker and add stuff when you decide that you just cannot be happy without it. Will's lists fit somewhere in there.

As long as it remains a dilemma, it cannot be solved except by coin toss. Only when it becomes a problem can a solution be worked out.

My, that sounds profound:D

Especially on Sunday evening:p

Willallison

10-01-2006, 11:55 PM

Guillermo

10-02-2006, 12:00 AM

Only when it becomes a problem can a solution be worked out.
Wow! You should add that to your signature!

yacht371

10-02-2006, 11:15 AM

Fuel economy:
If you want a really economical powerboat, let me tell you about my 37' sailboat. It weighs about 16000 lb., and has a 29 HP engine. It uses 1.5 GPH at WOT which is 7.6 knots or 5 NMPG. But at a steady 6 knots, consumption is just 1/2 GPH or 12 NMPG. That is dragging a 55' mast through the air and a 6'-6" deep fin keel through the water. The mainsail can be hoisted to steady the roll in a beam sea. Wait a minute when I did that we gained a knot of speed...wonder what happens if we shut off the motor?

Just kidding about shutting off the motor. Seriously, buy a clapped out racing sailboat, throw away all the sails. Reduce the keel depth and ballast by half, and shorten the rudder.

Depending on the size of the craft, there are several ways to make it a better powerboat. An engine as small as mine won't push the boat well to windward in a gale, so a bigger (but not more than 50HP) engine would be good, not to increase speed but to maintain it in adverse conditions. Mine has a folding prop but use a 3-4 blade fixed prop on your power boat.

If you can find a center cockpit style boat, add a hardtop and fixed windscreen and presto you have a trawler that gets triple the mileage of a Grand Banks. If possible I would keep the rig, but cut it down by half and have the main recut as a flat steadying sail.

Aft cockpit boats can get the same treatment, or you can gut the interior, and build a nice raised saloon/wheelhouse, and raise the aft cockpit to have a cabin beneath it.

All this will vary with the boat. The faster the boat was as a racer, the better the fuel economy when it gets to be a power boat.

Clapped out racing boats are available quite cheaply, and as long as the hull is sound, you can make a great boat for little money. Hurricane aftermath is good time to look for boats with broken masts.

Grahame Shannon
"Please, don't give me any more STUFF. Ok, I'll except food, beer or good wine..."

tom28571

10-02-2006, 02:54 PM

Interesting point Grahame. This has been done many times but I have missed any glowing reports of its success. I can think of a number of issues that might be a cause for not doing it. Rolling, for instance. Most sailboat hulls would probably be very bad at this as a motorboat. Getting rid of the keel and rigging would make it necessary to add a lot of inside ballast to get the boat on its design lines. Speed for another, since being stuck at displacement speed is one driver for many here to go for a powerboat in the first place.

Efficiency under power and possible economy of purchase are the two real advantages I see. It is not hard to design a powerboat that will give equivalent efficiency at those speeds with better characteristics in other areas.

There are some sailboats that would be much better at this than others. I'm think of fat little centerboarders with flatish bottoms and hard bilges. Catalina 22 comes to mind.

SAQuestor

10-02-2006, 08:14 PM

A little Hi-Octane gas on the fire.

Check this one out! (http://www.wilburyachts.com/brokerage/details.asp?BrokerID=43&type=pleasure)

A bit too much varnish for my personal taste, but I could easily see building something of a similar style, with modern methods of course, and trailering the resulting boat all over North America and being able to find that remote anchorage for a few days.

Best,

Leo

Willallison

10-02-2006, 08:33 PM

Funny - don't recall seeing "store your gas (LPG) bottles in an old keg" in the ABYC reg's.....;)

Guillermo

10-04-2006, 06:01 PM

I've worked out an evolution on Tad's boat, using his idea of the prolonged bunks towards the cockpit and the overall look, but limiting hull length to 7.5 metres, as boats under this length doesn't pay the 13% registration tax in Spain. And instead of going only semiplanning, I went up to planning ability. Of course, this is a very preliminary idea.

To this, I first took out engine from the living area, bringing it to the stern by means of using a JetPac 150 HP diesel (A conventional outboard may be used too, with some advantages, but those kind are gas and that's more expensive in consume and less safe than diesel). I went for low planning speeds, with a cruising one of 18 kn and a top of 21-22 kn (with a 200 HP unit, top speed would go around 25 kn)

Second, I split kitchen area to both sides, making it very simple, and hide a pretty nice sized refrigerator-freezer under the pilot seat.

Third, I propose to solve the heads problem by making it compatible with navigator's (or co-pilot) place. Loo is under the co-pilot seat (just a matter of rising the seat when in sanitary use. It may be flushing or one of those 'drier' type). Sink is under the 'chart' table in the front and over the under forward port berth (I think there's enough room for this between berth and console without getting tight). There's even the real possibility of mounting a proper shower. This 'navigator-heads' space is privatized when in sanitary use, by means of folding screens and curtains.

Fuel, water and waste tanks are under the living area floor, to get those weights as centered as possible, to minimize trim changes (position not yet well defined)

Under the cockpit sole there's ample room for fenders, etc.

Hull would be round bilged (tight turn) with a stern deadrise of 12-15º, looking for efficiency in semiplanning mode and the low planning speeds considered.

Main aprox. characteristics are:

L hull: 7.49 m
Lwl: 7.00 m
B: 2.55 m
Bfl: 2.3 m
Power: JetPac 150 HP @ 3825 rpm
Fuel: 300 litres
Water: 200 lt.
Waste: 80 lt
Crew: Up to 4 cruising.
Loaded displacement: 3000 kg
Trailering weight (Lightship+engine in air): 2000 kg
(engine weights 428 kg dry, but floats off around 150 kg)
Maximum speed: 22 knots @ 150 HP
Maximum continuous speed: 20 kn @ 125 HP
Cruising speed: 18 kn @ 100 HP

Consumptions and range (assuming a non usable 10% fuel):

22 ltph (5.8 gph)at 20 kn, range 250 NM (3.45 mpg)
16.3 ltph (4.3 gph) at 18 kn, range 300 NM (4.19 mpg)
12 ltph (3.2 gph) at 15.5 kn, range 340 NM (4.75 mpg)
......
(Yet to get trustable enough numbers for semiplanning speeds)
......
2.65 ltph (0.7 gph) at 6.8 kn, range almost 700 NM (9.71 mpg)

What do you think? Is it feasible? Makes sense?

(Notice: I'll be out there sailing the Canary islands till the 16th, so I'll not be able to post till then. Cheers)

Willallison

10-04-2006, 08:19 PM

SAQuestor

10-04-2006, 09:42 PM

{lot's of snippage}

Aft cockpit boats can get the same treatment, or you can gut the interior, and build a nice raised saloon/wheelhouse, and raise the aft cockpit to have a cabin beneath it.

Grahame,

Is this one (http://www.yachtworld.com/core/listing/pl_boat_full_detail.jsp?slim=quick&boat_id=1597308&ybw=&units=Feet&currency=USD&access=Public&listing_id=17144&url=) sorta what you were talking about?

They are listing it as a "motorsailer" but it's not real easy to see the sail part of that term. :confused:

Regardless, it looks like an old sailboat hull to me. - Well, maybe not old - could be the sailboat part was just never finished and it was easier to put a full PH over the cockpit? Dunno.

fcfc

10-05-2006, 03:15 AM

Why not this one ?
http://www.rangertugs.com/r/r-25.cfm

The only real *BIG* problem for me is the Special Price from $109,937 plus freight, tax & options and a market price over 130 000 $ :(
http://www.trawlersmidwest.com/instock.htm#C-Ranger%20Tugs

Gilbert

10-07-2006, 12:18 PM

Gilbert

10-07-2006, 12:31 PM

Well I don't see the attachment. I'll try again.

Vega

10-07-2006, 12:42 PM

How about this one by Erik Dijkhuizen?

http://www.dijkhuizenyachtdesign.nl/Launchdichtset.htm

With an engine between 18-100hp it looks to be an economical one.

SAQuestor

10-07-2006, 03:22 PM

Hi Leo,
I'm attaching a quickie freeship file that may come close to matching your trailering parameters.
As to the Inland Passage part of your retirement plans, why not consider buying a salmon troller to satisfy your Alaska and B. C. curiousity and have a more manageable trailerable rig for less ambitious trips? Just a thought.
I like your retirement plans.

Thanks for that lines plan. I like it a lot!

Your idea has merit, but I am adverse to paying for a boat that would only have limited use and then having it in a slip for 8 months a year.

I figure if folks can do it safely in a 22' C-Dory - then a 30'-ish one-off would work too.

Best,

Leo

Guillermo

10-16-2006, 03:53 PM

Guillermo - your partitioned loo is exactly the sort of thing I was proposing in my earlier post - the trick is to make it practical to use. I'm not too sure about the idea of the wife cooking up a storm on one side of a flexible screen whilst I'm disposing of one on the other!:eek:

3000kg - it's pretty bloody heavy this boat!
The kitchen position can be side-swapped with the sink, wich also makes more sense from the point of view of plumbing. We may even eliminate the basin over the forward bed, making things even more simple. Screens may also be fixed, instead of folding, with transparent topsides and a sliding door or the like. But I'd rather prefer the folding ones.
I think some discipline should be needed aboard (as in any other small boat like this), to not go 'looing' when cooking or dining time.

Weight of the boat is certainly heavy, but I have not done a detailed weight estimative yet. As the smallest JetPac is 150 HP, I tried to figure out the performance for a heavy boat supposition with a fully (generously) loaded condition. If afterwards the lightship+engine weight (2 tonnes now) may be reduced, as well as cargo (1 tonne), the performance will improve.

Willallison

10-16-2006, 06:04 PM

I know you've discussed it elsewhere, but I'd be interested in your reasoning behind incorporating the jet-pac. I would have thought that an outboard would be lighter, simpler, smaller and more efficient at the sort of speeds anticipated.

and yes - you are right - discipline is always required when it comes to using the head on a small boat!
I think eliminating the small basin is a good idea. Whein I 1st saw it I thought it looked like a good thing to bang your head on whilst emerging from the front bunk. And with a sink so close by, why bother.

hardyha

10-16-2006, 10:36 PM

hi there, i have an 18 foot bayliner capri hull. It was powered by the woe-full force L drive. Can anyone give me any advice on re-powering this hull, either pod with out board or in board. any advice would be greatly appreciated. cheers mark

Guillermo

10-17-2006, 12:38 AM

I know you've discussed it elsewhere, but I'd be interested in your reasoning behind incorporating the jet-pac. I would have thought that an outboard would be lighter, simpler, smaller and more efficient at the sort of speeds anticipated....
Visit: http://www.swordmarine.com/Features/advantages.htm
They explain better than I could do the supposed advantages. Having tested some units, and having one client (professional) with a unit mounted for one year now, I quite agree with the general picture, although I have some doubts about a couple of comparisons there. I have to say they are not as silent as stated in the chart, i.e., although they comply with RCD noise levels exigencies (Certified).

Guillermo

10-25-2006, 02:34 PM

What do you think abot this type of styling for the Jet Jane 25?
Internal lay out is kept as already posted before, but, as explained some posts ago, switching sides among kitchen and sink. Also the basin at the front is eliminated.
There will be also a pêche-promenade version, with only the two bunks forward and a 2+ m cockpit.
Still working on hull forms and weights distribution.
Hull lines have turned to chined ones.
Cheers

fcfc

10-26-2006, 08:24 AM

fcfc

10-26-2006, 08:30 AM

Another way to solve the engine space problem is two small engines under settles as devlin czarina 30 :
http://www.devlinboat.com/dccz30.htm

Guillermo

10-26-2006, 02:16 PM

How do you come for LH = 7.5 m.

My copy of 8666:2002 exclude from LH detachable items, and lists as examples outboards and outdrives, but specifically includes "detachable parts of the hull wich act as hydrostatic or hydrodynamic support".

The shape of the jetpack do provide significative hydrostatic and hydrodynamic support.

I am asking this, because LH is an important length for ISO, for the scantling. But is also sadly a basis for taxes. (french tax lower limit is 7m, and belgian is 7.50m)

Thanks for your interesting comment.
The Jetpac provides hydrostatic and hydrodynamic support, for sure, but in my understanding of ISO 8666:2002 we should not consider it a "detachable part of the hull", but an outboard engine. Anyhow as it is quite important to me to properly check this important matter (precisely because of taxes in Spain where 7,5m is also a limit), I think it's wiser to put the question to a Notified Body. I'll do that.
Cheers.

ron17571

10-27-2006, 08:03 PM

I read this whole thread,i guess it all comes down to money and how biga pain in the butt u want your boat to be,trailering some giant heavy thing around once in a while,still dosent sound good,are u married?and no im not interested.would make a big difference on how and what u do this with.A smaller easier to tow boat would be my answer.mabe the sailboat turned motorboat would b good,sure would use less gas.something like a McGregor 26?with a small outboard it would cruise preety good.from reading all of the posts i almost want to find one and do it myself.could tow it with any normal pickup truck instead of a high dollar diesel.curious what you decided.

Guillermo

10-28-2006, 04:56 PM

...are u married?
Happily. Six children ;)

ron17571

10-28-2006, 05:46 PM

Makes a difference in what kind of boat to have,if the wife isnt happy nobodys happy kinda thinking!with six kids u could save fuel with a buncha oars.Then they would be to tired at the end of the day to cause much trouble.

Guillermo

10-28-2006, 05:48 PM

...with six kids u could save fuel with a buncha oars.Then they would be to tired at the end of the day to cause much trouble.
Wonderful idea! I have to try that in my present boat, a 12 tonnes motorsailer! :D

Raggi_Thor

10-30-2006, 02:16 AM

Six kids should equal 2 or 3 hp :-)

Guillermo

11-07-2006, 07:30 AM

fcfc

11-09-2006, 04:55 AM

Another funny thing in LH "cheating", is in the beneteau powerboat range.
The Antares 760 is 744cm Lh. The bigger Antares 8.8 is 749 cm Lh.
Commercial length 1.2m bigger, Lh 0.05 m bigger.

Some day, you will have "removeable" stems. Just imagine a vertical watertigth bulkhead at FPP. Bolt on this a stem. This stem is not structural part of the boat, do not have hydrodynamic/static support (just barely touch water at rest), and is removeable. So all the front overhang do not count for Lh.

Crag Cay

11-09-2006, 05:28 AM

Some day, you will have "removeable" stems.
This has been done. I had an 1970's vintage S&S boat that had a removable stem part so it could rate under both IOR and MORC.

It was only a tiny fitting, but I took the idea further on a more recent design to allow a boat to enter short handed races, some of which have a 30ft max and others a 30ft min loa requirement.

Guillermo

11-09-2006, 04:29 PM

That's common practice with sterns. Many models around have 7,49 m LH (because of the 7,5 m limit in several countries) and named "Whatever 820" or the like, having huge bathing platforms being some of them real removable sterns. The removable stem you mention, fcfc, is an interesting loophole, indeed. I think it may open very interesting possibilities. Mmmmm....;)

Have a look at this interesting scandinavian boat: Yamarin 74 Cabin
http://www.yamarin.com/index.cfm?ChangeSetNow=5

LOA 7.40 m (24ft 3 in)
Beam 2.60 m (8 ft 6 in)
Weight 2100 kg (4630 lbs)
Berths 3 + 2
Max power 165 hp (Yamaha ME372)
CE Category C
Price (inc VAT) from 62,295 british pounds (Wow!)
It is said to cruise economically at 25 kn, having a top speed of 31 kn

SAQuestor

11-11-2006, 10:03 AM

Amalgamation: a mixture or combination. And so this posting will be. As always, this is just my not so humble opinion.

As I recall the thesis of this thread – a discussion of boats suitable for cruising in protected waters and coastal areas.

First off – let’s toss this one into the ring as an example (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1623454&lang=en&slim=quick&) from years past that was eminently suitable for coastal cruising. I AM NOT suggesting this is the perfect boat for today’s market. But why not something similar?

Let’s chat a bit about fuel. Some threads here and some on the Usenet (rec.boat.cruising) are alternatively suggesting that fuel in the near future (5-10 years) will be plentiful, just more expensive. Then someone comes along with the Peak Oil theory and argues that if you don’t have a blow boat you won’t be able to go anywhere in 5 to 10 years. Hopefully obvious to other folks besides myself is that the truth probably lies somewhere toward the middle of those two extremes.

I’d suggest that we will indeed pay more for gasoline and diesel and natural gas and kerosene etc. In fact, any product that has a petrochemical base – plastics of all sorts, including epoxy. But I do not believe that oil based fuels will dry up completely in (at least) my lifetime – which, God willing will be another 40+ years.

Some folks posit that sailboats are more suitable as they use less fuel. I’ve read arguments that 1000 miles of coastal cruising only used ~100 gallons of fuel on a sailboat, but used over 800 gallons on a similar sized powerboat. Of course the person posting this tidbit on rec.boat.cruising was the sailboat guy and overlooked replacement costs of sails and rigging as they figured total costs. Then he also overlooked the speed factor. The boat that burned 800+ gallons was a heavy semi-displacement boat (specifically mentioned was one of these) (http://www.yachtworld.com/core/listing/pl_boat_detail.jsp?currency=USD&units=Feet&checked_boats=1594520&lang=en&slim=quick&) that was pushed into the multiple gallons per hour speed range instead of the sailboat’s displacement speed. Apples and avocado’s both grow on trees, as both types of boats float, but that’s as far as this comparison can logically go.

<snark> Other folks are OK with driving a Hummer, Escalante or a F250 Supercab as their commute vehicle. And don’t forget that it is their “right” to use from the worlds resources at a disproportionate rate – just because they can afford to. These same sorts of folks are less concerned about the amount of fuel that their boat uses, ‘cause it’s just another status symbol of their success and wealth. A boat is something to be used and sold as whims come and go.

As an aside – I was on eBay a couple of nights ago looking at marine diesels. There’s a Yanmar 3gm there from a 2000 model sailboat – a 40’-ish Beneteau IIRC - that had “wind damage” and wasn’t worth repairing and was being parted out – engine, winches, etc. What does trashing a 5 year old boat say about our world-wide throwaway culture? Nothing good I'm afraid. </snark>

But there are some folks – many that inhabit these environs on a regular basis – that see some folly in the idea of $400k boat sitting vacant at a marina most of the year and when it does leave the dock it costs a couple of Boat-Bucks for fuel and other necessities of the weekend.

Some of us here see the need for an affordable boat to buy (or build!) that won’t eat us alive in fuel costs. A boat that perhaps can spend several months in a marina slip or on a mooring and the rest of the year on a trailer in our side yard covered against winter’s ravages, thus saving the costs of winter storage on the hard at a marina. Or if the preparation/launching/retrieving is free of too much hassle, then the boat can live in the side yard year-round, only visiting the water as time permits.

Speaking of marinas – it seems that the value/price of water-side land is rising so fast that marinas are being bought out for condo’s and other assorted high profit developments. So that is even more incentive for a boat that is less dependent on traditional marina services.

There are even a few of us here that have the vision to see that a suitable cruising power boat can be completely trailerable without being a burden to trailer, launch, retrieve and store at home.

Having read this thread since May 2006 I think that the “general consensus” is something between 7.4 and 9 meters in length and a maximum beam of (depending on the country) of about 2.4 to 2.7 meters.

Some folks are less comfortable with boats that are longer and weigh more. Some folks have no problem with the idea of a boat that is longer and heavier. So it all comes around once again to what’s suitable for an individual circumstance.

Recognizing that some folks have tax and regulation issues to deal with for the longer and wider boats, I believe that a distinction that needs to be made is the duration of the cruise and the amenities that one wishes to take along. If we recognize that a three day weekend outing four to six times per cruising season with a single ten day cruise thrown in, involves a different set of requirements than an extended cruise of two or three months duration. Once this distinction is recognized – that the heavier and longer boat will be launched and retrieved once or twice PER YEAR versus six or seven times (or more) for the shorter lighter boat, then we can more easily justify the time and expense of the preparation/launching/retrieving of the larger trailerable boat.

If one has a weekend to cruise and get back to a paying job on Monday, then ease of use – setup, launching, speed and range, retrieval and making road ready are of paramount importance.

Whereas, if one is going to trailer to a distant launch point for cruising grounds such as Puget Sound and Alaska, the coast of Maine, the Trent-Severn Canal and associated Great Lakes, etc. – for a summer long cruise, then the amount of time it takes to tow the boat there, set it up and launch it is of much less importance than to the weekend guy. And to our European, Australian and New Zealand friends, please forgive me as I know not where you would want to trailer a boat for extended cruising opportunities. So I only cite where I would like to go in North America.

I can certainly recognize the G-PITA (Giant Pain In The Ass) it would be to try to do the weekend cruise thing with a heavy, large boat. I would theorize that most folks can also easily see those drawbacks and with the rare exception, try to avoid that sort of hassle.

Additionally, I can also see where some folks might not want to hassle with the larger boat at all, regardless of the duration of the cruise and any additional comfort potential it would provide. And that is why ice cream stores offer 31 different flavors.

Back to fuel. One might suppose that the folks that are interested in the “weekend” pocket cruiser would be less concerned about fuel usage than the longer use folks. Perhaps so, but there is nothing to prevent designing and building a boat that sips, instead of gulps, fuel – as long as the end user fully understands that 35 knots ain’t gonna be economically possible – along with the resulting higher horsepower and stronger, heavier boat needed to carry the higher horsepower and tankage, ad infinitum. So the cost of playing around on the water for the weekend is gonna skyrocket to several hundred dollars for the ephemeral joy of going fast for a short time.

But as shown in several different threads over the past few months, there are designs that can cruise in the mid-teens and still burn only a few gallons per hour. Y’all know of my positive bias toward Tom Lathrop’s Bluejacket series. Using Tom’s reported fuel usage; it’s possible to do something like 130 miles (209 km) on about 20 gallons of gas. That’s far enough to get from the launch point to a quiet anchorage in two hours on a Friday afternoon. Another 50 miles (80 km) of messing-about on Saturday to a completely different anchorage and ~50 miles (80 km) back to the launch point on Sunday.

Personally, I am still not convinced that a semi-displacement boat can achieve these sorts of mid-teens speeds with the same sort of low fuel consumption rates, irrespective of Whio which Guillermo cited to start this thread. I’d love to be able to completely understand how a hull that is not performing in displacement mode or in full planing mode can NOT use fuel at a prodigious rate. Witness the anecdotal tale above of the sailboat versus the Nordic Tug style boat. Can anyone cogently make the semi-displacement case?

Then we have the gas versus diesel discussion. Inboard marine gas engines are (comparatively) cheap, easily found and installed. There are some drawbacks in that gasoline is more volatile and requires some special precautions to keep the boat from exploding! Inboard diesel engines more efficiently use fuel and don’t require the same precautions to keep the boat from exploding, but initially cost more.

Although not having personally run a spreadsheet on total gas vs. diesel costs, I would suspect that the equation would look somewhat similar to the sail versus power comparison when the costs of sails and rigging maintenance/replacement is factored in. Can anyone comment on the inboard gas/diesel installation and running costs?

Let’s close this treatise out with this thought. A boat similar in looks to the Elco Cruisette I first mentioned with a modern efficient underbody and built with modern methods – lightweight fiberglass foam sandwich construction for commercial production and/or lightweight strip/cold molded with epoxy/glass construction for the home built folks – could very well be a winner. Put some nice wood topside with a bit of varnish and I’d suggest that oohs and aahs would follow wherever the boat was floated.

Best,

Leo

FAST FRED

11-11-2006, 01:01 PM

A very comprehensive look at Gas vs Diesel is offered ,

http://www.yachtsurvey.com/GasDiesel.htm

For all but the longest range HEAVY vessels , the gas option would seem best.

INCLUDING engine life , and cost of ownership maint!

FAST FRED

Guillermo

11-11-2006, 02:10 PM

Nice post, Leo.
There are also some extra considerations to take into account when choosing a boat, either for weekend or long range (or long time) cruising.
One of them is if you have or not little children. One of the problems I had experimented with my beloved Banjer "Marie", being a really heavy weighter (and so slow, what I personally like) is that my children get bored if sailings are longer than, let's say, 1 hour long (You know that kind of questions: when will we arrive? how long it will take, etc?). So I can manage to get them awake and interested (except when we are trawl-fishing, which keeps them well awake) only for something like 7 miles, 10 at its most, when cruising. This keeps us very close to the home port, to my taste, and the one who gets bored, after doing this, weekend after weekend, it's me. And when we go cruising for longer periods, it would be nice to be able do 20-30 miles in a row in 1-1.5 hours time, this allowing switching from Ria to Ria in an easier mood, and reach more distant anchorages and marinas.

The boat I proposed some posts ago to fulfill this kind of demand, the JetJane 25, allows a couple with two children (or even 3) to do this kind of cruising scheme. They will be able to reach a 30 miles far away destination in 1.5 hours, which opens a lot of possibilities for weekends and the typical 10-15 days cruising in summer.
And if sometime they want to go for real long range cruising, they may do more than 700 nautical miles at 6 knots with the 300 lt (80 gall) tank.

About your question on the consume in the semiplanning zone, there is a difficult to predict zone between 1.4 and 1.8 S/L ratio, more or less, but from there up, power needed is quite predictable (always supposing an efficient design, of course). At an S/L ratio around 2.2, JetJane 25 should trot along at 10 knots, using an shp power of around 36 hp and a consume of 1.7 gph. Range would be in excess of 400 miles (All this with a total load of more or less 1000 kg, with full tanks. Of course fuel and water consume will lower this weight and will increase either speed or range)

Cheers.

P.S. Here the specific consumption table for the JetPac D150

150 HP
RPM --- GAL/HR -- LITER/HR
750 ---- 0.27 ---- 1.02
1000 --- 0.30 -----1.14
1500 --- 0.70 ---- 2.65
2000 --- 1.60 ---- 6.06
2500 --- 3.00 --- 11.36
2600 --- 3.30 --- 12.49
2800 --- 3.80 --- 14.38
3000 --- 4.50 --- 17.03
3200 --- 5.30 --- 20.06
3400 --- 6.30 --- 23.85
3500 --- 7.00 --- 26.50
3600 --- 8.30 --- 31.42

Willallison

11-13-2006, 11:02 PM

Leo - A boat that operates in the semi-displacement speed range can be made to operate efficiently, but the compromises that are necessary would generally preclude a cruising boat at the sort of lengths you are considering.
The boat must be -
1. Light (a displacement/length ratio of less than 100)
2. Narrow (a length/beam ratio od at least 4.5:1)

If these criteria can be met, the boat ought to be efficient at SL ratio's up to around 2.0, maybe 2.5

So if we work kind of backwards using the trailerboat requirements: assume a max beam of 2.4m and a waterline beam of 2.0m, you would require a waterline length of 9m - so an LOA of say 9.5, or 31ft. For a D/L of 100, it would have to weigh just under 3000kg (loaded).
Doable, for sure, but you'd have to be pretty rigid in sticking to the less-is-more principal.

Willallison

11-13-2006, 11:40 PM

SAQuestor

11-14-2006, 07:34 AM

Sorry - my calcs are a bit screwy there - I used the LOA, not the LWL. It makes things worse. With a LWL of 9m, you need to have a loaded displacement of no more than 2600kg in order to have a D/L of <100.
It's getting harder...

Per Will's calculations and looking strictly at semi-displacement boats, we're apparently back to where we started - Whio (http://www.amateurboatbuilding.com/articles/design/whio/whio.html).

Will, thanks for running the numbers.

Best,

Leo

Willallison

11-15-2006, 04:47 PM

fcfc

11-16-2006, 04:57 AM

Between the 1350 kg of whio and the 2500 kg of andreyale 33, (http://www.tofinou.com/en/fiches_tech/Andr10en.pdf), there should be some life ...

SAQuestor

11-16-2006, 01:36 PM

Ah yes - we are back to Whio, which reinforces my point to some extent... it's difficult to pack what I'd call a cruising boat into a design of this nature. For, as lovely as she may be, Whio definitely doesn't fit my definition!

Nor mine, as beautifully designed, engineered, built and used as Whio is.

Well, we’ve got nearly 250 posts in this thread – certainly not a record, but that’s still covering lots of water!

Seems to me that once again that all of this boils down to three questions.

1) Where do you want to go?
2) How much “stuff” do you want to take with you?
3) How fast do you want to get there?

It seems that there is a new or used commercial boat available in the under 10 meter class that will allow multiple variations on the above three questions and satisfy just about anyone’s needs for seaworthiness, accommodations and speed.

I’ve spent some time over the last few days reviewing some of the Option 1 thread. After reading in that thread it seems to me that a 4th question might be appropriate – How much do you want to spend?

Even though the spending question is intrinsic in all three questions, it may not be as obvious as it really should be.

And the reason for this 4th question is two fold. Initial purchase costs and then yearly operating costs. As we all know, more of anything costs more $$$. And in all things boaty, it’s a nasty spiral that can easily get out of control.

There have been just shy of 1.867 zillion words written about crossing oceans. Boats, equipment, life aboard in tropical paradise, how to cope with storms and failure and medical emergencies, ad infinitum. Every conceivable topic has been covered in umpteen different ways. Canals in Europe? Not a problem. Cruise the Med? Ditto. Wanna spend time in New Zealand? Great Barrier Reef? Chagos? San Blas? Some scores of people have been there, wore out the tee shirt and wrote about it. So if that’s where y’all wanna go, you’re not gonna have to be a pathfinder.

Same can be said for where I wanna go. And it’s fairly easy to find a couple million words in books, magazines, cruising guides and maps about what I want to do in my retirement years. Where pray tell is that? Check these four links out for a good idea.

A 14 day trip to Alaska. (http://www.fineedge.com/ARTICLES/alaska_by_wooden_boat/marks_log.html)

Same trip (I think) just a different perspective. (http://www.nwyachting.com/articles/ip2ak_1/ip2ak1_1.htm)

The Wanderers. (http://www.georgeberotti.com/2Wander)

And our perennial favorite, Halcyon Days. (http://www.geocities.com/bill_fiero/index.htm)

One minor issue I have is not just once in a life time. Rather, I want to go back again and again until my health won’t allow me to. With the right boat and good health, that could be 80±, with God willing of course. But my proposed odyssey isn’t limited to that part of the world. Oh no! Perchance I want to see the coast of Maine or the canals of SE Canada and the NE US. Maybe winter in the Florida Keys. Perhaps The Bahamas?

Will the same boat do all of these? Dunno. But I do know one thing – I’ve got no great desire to spent November through April north of 30°. And conversely, I’ve not great desire to spend May through October south of 45°.

Of late I’ve spent some considerable time reviewing the Option 1 section. Interesting ideas there.

The $50k limit in the O1 section is about right – at least for me. My problem – and I would assume others have the same or similar issues – is that I can’t afford $50k 2 or 3 times until I get the right boat for the cruising grounds I want to frequent. So that’s why I spend so much time and effort here and on other forums attempting to refine both what I want and what I really need versus what is practical and affordable. I want to do it right only one time.

Where I am struggling right now is with the issue of how much stuff do I want to tote along? Well, my desire is to be able to be independent of marina services for at least a fortnight at a time. Only going in for fuel and groceries. And if it’s done right, that fortnight could stretch to double. But to last even a fortnight will take some careful planning and execution on a 30’ boat.

So my dilemma – what is the right boat?

Looks like this design – the Willard 30 (http://www.yachtworld.com/core/listing/boatFullDetails.jsp?boat_id=1436837&ybw=&units=Feet&currency=USD&access=Public&listing_id=1021&url=) - is just about right. Seems to have enough room for a couple and occasional guests. Storage for ‘stuff’ and adequate capacities for fuel and water. Plenty of range as long as ~6 knots is OK.

Dimensions:
LOA: 30'
LWL: 27'6"
Beam: 10'6"
Displacement: 17,000
Draft: 3'6"
Ballast: 4300

Except. Isn’t there always an exception? The exception is that because of the dimensions noted, it would be prohibitively expensive to transport the boat across the continent several times to take advantage of the various cruising areas we’d like to explore.

The obvious answer is to concentrate cruising activities in one area – say Puget Sound to Alaska. But that leaves out spending winters on the boat south of 30° north. OK. Then stay on the east coast – North in summer and south in winter. Fine, but that leaves Alaska out. Either/or choices like this suck, don’t they?

For some folks, the Willard 30 (or similar) may be a great choice for a pocket cruiser. But going back to the diverse cruising areas that I desire to explore, is there a better choice? Perhaps.

On the Option 1 thread, Will and Michael Schooley (Portager) had a conversation here. (http://boatdesign.net/forums/showthread.php?t=754&page=6) BTW, has Mike (Portager) disappeared completely from this forum?

Both Will and Mike presented some design options – please see the attached pictures.

So where does these ideas land us?

Tom Lathrop is well known for his 24’ Bluejacket design, Liz. Tom contributed a great deal to the O1 threads. His knowledge and experience is evident throughout, and continues today. IMO, his 24’er – even stretched to 27’ is not a suitable platform to leap from.

But Tom has recently published a brand new design – based on the 24’ design – but now expanded to 28’. Essentially heavier duty and, well, heavier overall. A much bigger boat. Unfortunately it doesn’t appear that Tom has any information posted on his web site about this new design. But I’ve got a set of plans! Yeah!

As we all know, Tom’s 24’er planes at very low speeds and obtains excellent fuel efficiency – in the range of 6-8 MPG. Several design elements contribute, but one that I see repeated time and again is low bottom loading, i.e., plenty of bottom area and low overall weight – of the boat itself and ‘stuff’ being toted along.

Tom has limited the overall beam of his new 28’er to 102” (2590mm). As we know, here in the states we can tow loads wider than that with an appropriate permit in the various states we would be transiting. So it is possible to expand that overall beam to a full 3000mm – 118” or 9’ 10” and still be able to tow the boat as a private citizen.

Maintaining the same design ratios that Tom used could mean that the length could increase to ~30’ (9.1m) to ~31’ (9.4m) when the overall beam is increased to max as long as the waterline beam is also increased in proportion so the overall aspect ratio remains (nearly) the same. Bottom area and loading would obviously have to be recalculated, but I would take a SWAG that the increase in payload would be on the order of at least 700 lbs (317kg) and perhaps as much as 1200 lbs (544kg) while maintaining the same bottom loading figure. Please remember that’s just a SWAG.

Regardless of the exact number, it does mean some increase of toting ability, whether that is fuel, water, stores, crab traps or electronic toys. And yes, it also means an increase in trailering weight and the resultant increase in towing capacity of the tow vehicle and trailer capacity. That vicious circle once again.

And once again back to the four questions:

1) Where do you want to go?
2) How much “stuff” do you want to take with you?
3) How fast do you want to get there?
4) How much money do you want to spend?

So let’s answer ‘em.

1) You already know from the verbiage and links above.
2) Dunno fer sure just yet. More accommodations and ‘stuff’ than Whio and less than a Grand Banks 32. Please note in that same O1 thread that on pages 6 & 7 Will and Mike discuss amenities, toys, doodads and other ‘stuff’.
3) I think 12 to 14 knots as a cruise speed would be just about right. Easy to cover 125 miles in a day or get across an exposed patch of water in a narrow-ish weather window.
4) For everything? Under $100k. For the boat alone – under ~$50k building it myself over 3-4 years.

And to clarify and amplify #4 – A previously owned suitable tow vehicle - $8 to $12k in today’s dollars. Suitable trailer – new – under $10k. Preventative maintenance and spares for these two items - $2-$3K. A total of $20-$25k.

IIRC, Tom mentioned in the O1 thread that he built ‘Liz” for under $20k, motor and trailer included. Obviously that’s a few years ago and also obviously a smaller, lighter boat that what I am proposing. Regardless, we double Tom’s costs for the boat and motor, add 40% for inflation, toys, doodads and ‘stuff’ that we desire and he did not buy and we’re still under $45k. Add in some tools and other ‘stuff’ necessary for building the boat – generously add another $10k – and the grand total for boat, trailer, tow vehicle and spares is in the neighborhood of $80k. All paid for in cash over a 4 year period and without touching a dime of retirement funds.

Add in operating, insurance and maintenance expenses over a year – call it $15k/year and any sensible person can easily reach the conclusion that sitting in a rocking chair on the front porch will be lots cheaper and certainly less stressful. But then the view never changes.

So the conclusion I reach is that an outboard powered planing boat of ~9-9.5 meters LOA with a beam of ~2.8-3 meters towed behind a older heavy duty American pickup truck is the best compromise design for cruising the varied areas that me and The Admiral would like to visit. Just have to remember that excessive toys, doodads and ‘stuff’ are verboten!

As always, your mileage may vary.

Best,

Leo

Willallison

11-16-2006, 05:10 PM

Willallison

11-16-2006, 05:26 PM

oh, BTW, I tried to contact Mike (Portager) some time back, to see how his project was progressing. Sadly, he never got back to me and I note his old web address is now someone elses. I guess we can only hope that all is well...

Guillermo

11-16-2006, 06:35 PM

..pointed out ad-nauseum (how do you spell that?)
Ad nauseam

One possible solution would be to build a simpler craft for your regular jaunts and then charter for more serious offshore-type cruising...?
Sensible idea.

1) Where do you want to go?
2) How much “stuff” do you want to take with you?
3) How fast do you want to get there?
4) How much money do you want to spend?

And also (They should be interlined between your points):
- With how many?
- Of what ages?
- For how long?
:)

SAQuestor

11-16-2006, 07:08 PM

Leo - I only see one potential problem with your logic.
It wont work!:eek:
Well... ok... it might work. But, as Tom has pointed out ad-nauseum (how do you spell that?) and you mentioned yourself, part of the secret to the succes of "Liz" is her light bottom loading. That comes primarily from light weight, which in turn is a result of fairly narrow beam, and a strict adherance to the less-is-more principal.
Without having run the numbers, my 1st reaction would be that you can't simply make it longer and considerably wider and still maintain that low bottom loading.

Will, please take a look at your quote above. What you say goes contrary to what my logic says. That is that when you keep weight constant and increase the area of the bottom, bottom loading goes down. Conversely, when one keeps the area of the bottom constant and increases the weight, the bottom loading goes up. Logic tells me that one can increase the area of the bottom and also increase the weight of the boat and load and the bottom loading can remain constant. Perhaps my logic is flawed. If so, please explain how.

I am working on an Excel spread sheet that will illustrate my thinking. Hopefully that will be finished before I go to bed tonight and the sun sets in your part of the world.

Additionally, please see the last sentence of the last paragraph of my post concerning the less is more principle.

But the biggest concern I have is your desire to be self-reliant for at least a fortnight. This requires that you carry considerable fuel (assuming your not simply going to be at anchor the whole time...), water and stores. All these things are heavy.

Agreed. But as you imply, if one isn't running around all over hell-and-gone at top speed, then one requires less fuel capacity. Perhaps a fortnight is unrealistic. Actual numbers will have to tell the tale.

Add to that some of your desired cruising grounds - which are definitely off the beaten track, you are going to require a boat that is designed to operate offshore, which "Liz" really wasn't. This in turn requires a heavier build.

Again, agreed. In my post I did mention that Tom’s 28’er is a heavier built boat. Heavier scantlings, bottom and sides.

Another thing to consider is the fact that as your boat gets bigger and heavier, simply trailering it around and putting it in and out of the water, becomes more of a hassle. I regularly tow a 4 ton rig around and I can tell you that there's way more involve than simply bolting it to the back of the car and off you go. I'm not saying it can't be done (obviously, as I do!) just that the harder it is, the less often you'll do it.

You are correct. But as I have pointed out in other posts, this boat would not be used for short day or weekend trips for the very reason you cite. Once off the trailer the boat would be used for a week to a couple of months before being loaded and hauled someplace else. And yes, it is possible that the boat would sit on the trailer for weeks on end before going out for another excursion.

So hopefully I’ll have that spreadsheet done shortly along with a post that explains my thought process and understanding of how a planing hull works.

Hopefully in the meantime you’ll look at the first quoted section above and add a bit of your thought process to that.

Best,

Leo