Pocket cruisers

[SAQuestor]

Originally Posted by yacht371

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.

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.

Originally Posted by yacht371

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:

Originally Posted by SAQuestor

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]

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

So in keeping with the original thought of this thread,

Originally Posted by Guillermo

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
30' Hyundai Sedan Trawler

28' Bayliner 2855 Ciera Sunbridge

28' Cape Dory Flybridge Cruiser
28' Northwind
Albin 27 Aft Cabin
27' Albin FAMILY CRUISER
27' Marben Marine Fly Bridge Sedan
27' Riviera Sedan
26' Crownline 268 CR
26' Four Winns 265 Sunbridge
26' Honeymoon Flybridge Cruiser
26' YAR SCARBOROUGH

[Guillermo]

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]

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]

Originally Posted by fcfc

This 28 ft hull should reach 16 kts with about 45 - 50 hp.
http://www.admiralstender.nl/default...sitelang=dutch
It is lighter than a Andreyale 10.

That's Luigi's (A******) boat!

Originally Posted by yacht371

....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]

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 A****** 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]

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]

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.



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]

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]

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]

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]

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]

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 Am I interpreting correctly the thing?

[yacht371]

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.

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]

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?