Pocket cruisers

[Willallison]

You'd think your logic would be spot on.... but - again bearing in mind that you'd need to 'do the numbers' (and by this I mean a detailed weight study) - it sadly doesn't work quite like that.
I don't know if Tom designed the 28 to take a bit more punishment, but that may not necessarily be the reason for the heavier scantlings. Quite simply, the bigger the boat, the heavier it will usually have to be built.
Further, with more volume, there's more temptation to fill it. And whilst you might adhere to the LIMP (ha! I just invented my own acronym!!... less is more principle:D :D ) cruising for extended periods requires more stuff. If you're in a position to restock a bit more regularly then this can be overcome of course.
And it may well be that a scaled up (and out) version of the BJ24 could be done, it's just my gut feeling that it's a big ask....

[Willallison]

Oh - and if you think you've got it hard, I've been trying to come up with a 40'er that operates along the same principals for several YEARS!:p

[SAQuestor]

Perhaps I am confused Will.

But it is my understanding that bottom loading is primarily a product of boat weight and area of the bottom when the boat is on plane. As I recall, deadrise angle also comes into play – something about how the water is vectored away from the hull - but I can't remember how much of a part it plays. At low deadrise angles it’s a rather small percentage if I recall correctly.

Again, IIRC, Tom based at least some of his initial work on his 24'er on material published by Lindsay Lord in "Naval Architecture of Planing Hulls". In that book Lord (at least what I got from its reading) says that long and lean on a planing hull isn't the best way to go.

In chapter 2, Lord describes an ideal "aspect ratio" for planing. On page 13 Lord says, "for accurate standardization, the aspect ratio is always considered as of the waterplane shape while the hull is at rest." He provides an illustration that I have duplicated on the attached Excel file. This Excel file allows one to vary the beam and length of the waterplane to get the resulting aspect ratio.

Lord goes on to describe the effects that varying the aspect ratio has on resistance (drag), load carrying capacity and planing angle. Lots of details in this chapter that I won’t attempt to go into. Suffice to say that through Lord’s towing tests he found that the “ideal” aspect ratio is .35. One can play with the numbers in the green boxes to see the effect that beam and length play on the aspect ratio.

In chapter 4, Lord seems to attract the most criticism with his unfortunate choice of words to describe (what I interpret and understand as) lower positive pressure that occurs towards the aft end of a planing surface. He uses the term “suction” and it is my understanding that other NA’s of some consequence and reputation have disputed this term and the way Lord describes the phenomenon. Because of this criticism I believe that much of Lord’s work has been unfairly discarded. If someone reading this thread can provide specific examples of where Lord’s work has been proven to be obsolete, I’d love to see the citations, arguments and counter arguments.

Regardless of the exact terminology, I can easily see that the maximum energy transfer between the water and the moving boat takes place at the intersection of hull and water when the boat is going sufficiently fast to achieve a planing condition.

Lord uses boats larger than what we are discussing here as examples and therefore we can’t easily go by the tables and illustrations in this chapter to extrapolate appropriate loadings for the small boats that pique our current interest. That said, Lord talks about boats with bottom loadings of 60 lbs per sq. ft. and up. He also talks about minimum bottom loading and the dangers that accompany too light of a craft in seas and winds that may cause behavior that could lead to capsizing. Essentially, lightweight planing boats SHOULD NOT be subjected to extreme conditions, offshore or otherwise.

My understanding is that Bluejacket performs as it does because the bottom loading is in the 30-40 psf range. But let’s take Lord’s suggestion and say we’re gonna keep the new design in the 40-45 psf range. The Excel spreadsheet provides an input variable for that and one can see what the resultant boat weights are estimated at.

With an aspect ratio of .35 and a bottom loading of 42.5 pounds per square foot, the resulting estimated gross displacement when on plane is about 6100 pounds. One can play with the input values (green boxes) and see how these results are affected.

Said another way – If I am going to maintain a bottom loading of 42.5 psf I can’t allow the boat weight – hull, motor, fuel, water, doodads, stores and stuff to exceed ~6100 pounds. If I go to 7000 pounds the bottom loading increases to close to 49 psf. This will increase the horsepower requirements needed to get the boat on plane and to maintain it therefore increasing fuel consumption and reducing fuel efficiency.

Conversely, if the total boat weight is about 5500 pounds, then the bottom loading decreases to about 38.4 psf and the horsepower required goes down and the fuel efficiency should go up.

I believe the key here is to balance hull weight, fuel and water capacity, required amenities and doodads to keep the initial weight as low as practical so that one has more room for stores, toys and ‘stuff’.

In the example in the Excel spreadsheet - If the hull weighs 2400 pounds (with tanks and batteries), motors 500 and fuel and water 1500 – totals to 4400. Leaving about 1700 pounds for people, clothes, food, toys and ‘stuff’ while maintaining a planing condition bottom loading of 42.5 psf.

Even if I bring another 500 pounds of LIMP reducing ‘stuff’ aboard, the bottom loading only goes up to about 46 psf. Still low according to my interpretation of Lord, but quite a bit more than the BJ24 or 28. So whether direct comparisons on performance can be speculated on or not is something for discussion.

Caveats. I’m sure that I’ve got the aspect ratio calculations correct according to Lord. The static waterplane area is correct, again according to Lord. The planing condition bottom loading numbers may not be correct as I can find no definitive numbers for how much of the forefoot comes out of the water when on plane. For this spreadsheet I have assumed that 2/3 of A is out of the water and not contributing to any planing lift. Further, I have assumed that the entire area of L is contributing to planing lift. This may need to be reduced by some small percentage but I have not run across any calculations or data that suggest what an appropriate reduction factor might be. So my point is to take the planing area and bottom loading numbers with a grain of salt. They are as accurate as I have information to make them, but that doesn’t mean 100% accuracy.

You'd think your logic would be spot on.... but - again bearing in mind that you'd need to 'do the numbers' (and by this I mean a detailed weight study) - it sadly doesn't work quite like that.

I agree that to get details on a specific design one would need to run a set of calculations. But would you concur that regardless of the specifics, that the principle remains the same?

I don't know if Tom designed the 28 to take a bit more punishment, but that may not necessarily be the reason for the heavier scantlings. Quite simply, the bigger the boat, the heavier it will usually have to be built.
Further, with more volume, there's more temptation to fill it. And whilst you might adhere to the LIMP (ha! I just invented my own acronym!!... less is more principle:D :D ) cruising for extended periods requires more stuff. If you're in a position to restock a bit more regularly then this can be overcome of course.
And it may well be that a scaled up (and out) version of the BJ24 could be done, it's just my gut feeling that it's a big ask....

And I don’t know the answer to your question either. I suspect your reasoning is why the increased scantling and plywood thickness. As for a scaled up BJ24 – it’s a done deal and I’ve got plan set #2 in my possession to prove it! ;)

And again, you may be correct that provisioning more frequently is the best way to go with a transportable coastal pocket cruiser.

Best,

Leo

[Willallison]

Tom sent me an email with the drawings for the 28. Unfortunatley I don't have them with me at the moment.
But you misunderstand my comments regarding an upsize BJ24 (easy to see why when I reread my post...). I'm not saying it can't be done, just that getting the kind of efficiency that the BJ24 enjoys might be difficult with the considerably beamier boat that you are describing.

Again - this is just my gut feeling. Tom would no doubt have examined this at length, so he'd know better than I. But by way of example, consider this simple comparison:

Lords aspect ratio = 0.35 ( or length/beam 2.9:1 ) (which I believe you've based your numbers on)
BJ24 AR = 0.26 ( L/B 3.9:1 ) my guestimate based on Tom's published specs

In regards to bottom loading, if my memory serves me correctly, Tom used 65% of the at rest AWP for his calculations. So if you assume that the 65% represents the AWP whilst on the plane and that we require a bottom loading of 50 #/sq.ft, then you require a bottom loading of 32.5 #/sq.ft based on the at rest AWP.
Plugging that into the top 1/2 of your spreadsheet, you now have a required loaded displacement of 5400#. In itself, this seems doable...:p

But the low bottom loading is only part of the story. Equally important in allowing the BJ24 to plane at such low speeds are the low deadrise, location of the LCB (Tom noted that somewhere recently, but I can't find it now...) and the design of the chines. It must all work as a whole.

Guesstimating again, I would venture to suggest that the beam of the BJ28 is closer 7'1" than the 9'10" that you are proposing.

Once again, I haven't done any real calculations, so this is all just conjecture on my part

[Pericles]

Renn Tolman has built around 100 of his skiffs and many others have been constructed from the plans in his book. The Jumbo has been stretched to 25 feet so far, with a beam of 8' 6".

At the Fishyfish site, you will find many pictures. It would seem that every builder modifies the basic idea to suit their needs. Even Renn! http://www.fishyfish.com/renn_tolman/index.html

Ray Brown published the build of his diesel powered Jumbo http://www.backporchboat.com/ and if it is not an inspiration then I do not know what is.

Beauty is in the eye of the beholder http://www.anchoryachts.com/sterlingyachts.php and the designer of this vessel owns one.

At 43 feet it is outside the remit of the thread, but it serves to illustrate the retro look allied to modern construction as posited on earlier pages. (15)

The raised foredeck is easier to construct than a cuddy and offers safer footing when mooring as well as somewhere to sit in the sun other than the aft cockpit. Sam Devlin rebuilt a Czarrina 30 to provide more internal space. http://www.devlinboat.com/constructioncz30rehab.htm

Guillermo, your Jet Jane 25 designs are very exciting and thought provoking. The evolution from traditional pilothouse to what looks to be a streamlined sport fisher with Carolina bow flare, (also flair and great looks) is intriguing. Which will you build?:confused:

Pericles

[Pericles]

Here is a Down Easter that will not break the bank.:cool:
http://boatplans-online.com/studyplans/DE25Cabin_study.htm

It would probably benefit from having flat chines added to hull, but that would increase the beam somewhat.

Pericles

[fcfc]

For SAquestor : I think Will is not fully wrong.

Running some numbers, you will find for scaling up a bluejacket 24 (empty 1850 lbs, full 2850 lbs, len 24 ft) to a 6100 lbs model,
you will need to scale it by 1.28:1. (6100/2850)^(1/3)

So that makes now a 31 ft boat, about 10 ft wide. It will weigth 6100 lbs full.
But when bluejacket goes to 15 kts, you will need to go to 17 kts to have the same hydrodynamic effect. And you will need 120 hp when bj 24 needed only 50. speed is (scale factor)^0.5 , but power is (scale factor) ^ 3.5.

An then you will have to build a 31 ft hull, 10 ft beam , with engine, batteries and cruising layout (galley, head etc ...) of about 2900 lbs.

A scaled up empty BJ 24 would weigth 3900 lbs. 1000 more.
Ligthening 25% a BJ hull is not realistic unless you go extreme building technology far beyond the intended price.

BTW, 2900 lbs is about the weigth of Whio. Seriously narrower and about empty inside. And certainly without the scantling necessary to go planning loaded at 6100 lbs without breaking at the first slam.

Without forgetting that the 120hp outboard will eat alone nearly 20 % of
your intended cost. And you will be surprised by the fuel burn.

[tom28571]

Just got back to this thread today,

There is so much in the last few posts that it is hard to know where to start or what to address. As always, everyone will read and draw their own conclusions. I also want to stress that I am not the guru here, just another amateur designer seeking the good stuff.

I think there is one area that may need some clarification. The aspect ratio relates only to the waterplane, the vertical projection of the boats bottom from its waterline, not the actual area or have anything to do with the overall beam or length of the boat. My initial projected aspect ratio was approximately 0.35. For initial calculation, I did use 65% of this area to get an estimate of the planing waterplane. Like most of the figures related to planing, this does not even remotely remain fixed. For example, look at the series of photos in: http://www.bluejacketboats.com/Bluejacket%2024%20photos.htm

I am sorry that I have to use one of my own boats for all of this but that is what I have and know most about.

Notice that the area contacting the water is progressively less for each increase in speed. Clearly, using one number for area in calculating bottom loading or aspect ratio is misleading. As speed increases, the area contacting the water decreases, the bottom loading increases, the aspect ratio increases and the trim angle increases.

From close inspection of these photos and knowing the weight of the boat, we can estimate all these numbers. We could perhaps also derive a coefficient of dynamic lift related to the trim angle. The weight of the boat in this condition is about 2400lbs, the LOA is 24', the max WL beam is 80" including flats and splash rails, the transom WL beam is 72" including flats and splashrail. Using the photos and these numbers, we can each come up with the useful characteristics that will be far more accurate than fixed estimates.

One thing of particular interest is the trim angle. (Not considering the percentage of boat weight supported by buoyancy) The trim angle will ALWAYS adjust itself to provide the dynamic lift to support the weight of the boat at the speed it is running. Dynamis lift is proportional to the sine of the trim angle. Speed, trim angle and weight are interdependent and can not be considered alone. Confusion can come from these photos in noting that the trim angle is slightly greater at the highest speed which may be counter intuitive. This undoubtedly results from the bottom loading going up faster than the speed so that more trim angle is required to support the weight.

This can quickly become a chicken and egg discussion and there are other considerations like the CG that play a part.

Ignoring luck, all good designs start with an exaustive list of goals that have been refined to weed out incompatibilities and impossibilities. Then these goals or requirements are weighted in order of their importance to the individual design. That the resulting boats are highly varied should be no surprise and our discussions often become tangled because we may be reading from a different list. The design goals of the boat in these photos were ordered to favor low speed planing and level trim over top speed and inshore performance over offshore capability. Another thing of note in the photos is that the transom never sinks below its at rest level. Well, maybe just a little.

Other items on the list were not ignored and impacted every other item. It is called the "design spiral" for a good reason. It usually feels like there is no ideal exit point from the spiral. That is because there is no "ideal" exit, only a result that is a compromised acceptable one.

Looking at the DE25, it might at first appear that the list of design requirements were the same as mine for the BJ24. They are actually quite far apart in many details that would be very important to individual owners. Different strokes.

Scaling up a boat is not so simple. Scaling up a powerboat, particularly a planing powerboat, is not like scaling up a displacement sailboat. I don't think the usual ratios apply very well. I would prefer, for other than small increases, to start with a clean sheet of paper. I'm a little uncertain about this though.

[SAQuestor]

Will, fcfc and others, I would suggest that none of the statements you have made are incorrect. In fact, I agree with much of the content.

Perhaps I am not the “great communicator” that I fancy myself. Perhaps it is the limitations of this medium where nuances are difficult to convey. Regardless of the exact reasons, it appears that we are not on the same page when discussing a 9 meter-ish long by 2.8 meter-ish wide planing hull. If we could verbalize here, I think it would be like one person saying to-ma-to and the saying tom-at-o. Same vegetable – different pronunciation.

A couple of points. The BJ28 design looks similar to the BJ24. The construction techniques are similar. But it is a different boat, not a scaled up version of the BJ24. I hope we aren’t discussing and comparing the BJ24 design to a much larger boat. The BJ24 is a wonderful boat and attempting to increase its size by 25% would appear to be a foolish endeavor. That said, scaling an existing design up or down by ~10% seems to be within the realm of “standard practice” – at least as best as I can determine and as Pericles pointed out the Alaska Skiff of Renn Tolman has had that done to it by numerous people. And as Tom just pointed out, a fresh sheet of paper may be the best solution overall.

Next, it appears that my Excel file has been misinterpreted. I originally created the spreadsheet to attempt to determine what the maximum length of a hull could be while staying under the legal width for towing here in the US and also maintaining something close to the .35 aspect ratio.

The numbers in the file are not set in stone. They desired length or beam can be manipulated to produce an aspect ratio in the area of .35. The file is supposed to merely illustrate that one can change the beam and length of a boat and maintain something close to the .35 ratio.

The bottom area and bottom loading sections are new as of 11/17/06 and as I said in an earlier post, they are subject to change as better formulas are determined and applied. Anyone can change the formulas in the appropriate cells to reflect the .65 reduction factor that Tom used in his calculations. That should yield a closer approximation of the gross boat weight when in a planing condition. And having done that, it may not be practical to use a planing hull for those fortnights away. Willard 30 here we come! :D

Best,

Leo

[fcfc]

Or dreams...

My conditions (money and living place) only allow me a trailerable boat. I live nearly 1000 km away from sunny sea and I am not rich enough to remotely own a boat for a limited use during summer holidays only. The nearby sea may be OK for some week ends, but I will never spend summer holidays there.

Boats I could afford (homebuild or used, barely brand new if mass produced and certainly not one off built) would be like a scaled down andreyale 33. http://www.tofinou.com/en/andreyale10.php , shortened and lightened a bit to fit on a trailer, (around 31 ft, 4600 lbs). or like admiral tender http://www.admiralstender.nl/ , lengthened and weighted (and of course a cabin).

Now the problem:
Meanwhile dreams, I do sail. The only way for me is to rent sailboats on the sunny location . They are egg bathtubs like Bavaria 30, or so. They are among the cheapest holiday liveable thing on water to rent.

And I would like in my trailerable powerboat 8.6 ft beam, 4800 lbs displacement the same layout of a sailboat 11 ft beam and 8800 lbs displacement.
I wont spend any buck on a powerboat with only half of this accomodation. I would prefer rent a sailboat.

And for now, I can turn the problem any side, I have no found a way to cram such layout in a trailerable boat. (And owning a such a sailboat is no go since not easily trailerable)

So for me, its is still chimera for a long time.

[Guillermo]

Guillermo, your Jet Jane 25 designs are very exciting and thought provoking. The evolution from traditional pilothouse to what looks to be a streamlined sport fisher with Carolina bow flare, (also flair and great looks) is intriguing. Which will you build?:confused:
I'm working on the more agressive looking version. I hope to be able to post something else soon, but this will take its time as it is not an earning money project (for the time being) and I have only spare time for it.
Cheers.

[Willallison]

I think there is one area that may need some clarification. The aspect ratio relates only to the waterplane, the vertical projection of the boats bottom from its waterline, not the actual area or have anything to do with the overall beam or length of the boat. My initial projected aspect ratio was approximately 0.35. For initial calculation, I did use 65% of this area to get an estimate of the planing waterplane. Like most of the figures related to planing, this does not even remotely remain fixed.

Based on the specs on your website Tom (LOA 24'3", BWL 80"), I estimated your LWL to be about 23'6", or 282" - thus giving an aspect ratio of 0.28
So when you say you aimed for an aspect ratio of about 0.35, I can only assume that you did that based on some sort of shortened WL in an attempt to represent the WP whilst on the plane...?
All the info I have suggests that aspect ratio is calculated on the at rest LWL / BWL, as these figures are too difficult to accurately determine whilst on the plane.

In regards to the 65% of AWP, it would be interesting to go back now, with a series of photo's and see just how close to the mark you were. Given the level running of the BJ24, I wouldn't be surprised if the figure turned out to be somewhat higher. Though for many boats, it probably wouldn't be high enough!

fcfc - if you are a long way from the water and thus unlikely to use a boat very often, then I think there's a lot to be said for chartering. Afterall, a boat is costing you money whether you use it or not.....

[Guest-3-21-09-10-33]

Or dreams...

My conditions (money and living place) only allow me a trailerable boat. I live nearly 1000 km away from sunny sea and I am not rich enough to remotely own a boat for a limited use during summer holidays only. The nearby sea may be OK for some week ends, but I will never spend summer holidays there.

Boats I could afford (homebuild or used, barely brand new if mass produced and certainly not one off built) would be like a scaled down andreyale 33. http://www.tofinou.com/en/andreyale10.php , shortened and lightened a bit to fit on a trailer, (around 31 ft, 4600 lbs). or like admiral tender http://www.admiralstender.nl/ , lengthened and weighted (and of course a cabin).

.


Not really expensive, now we will build the new 31 ft and 40 ft from Van De Stadt design. The 8,50 (so called Admirals Tender) and the 9,50 (or 31 ft) will have different cabin solutions soon.
See http://www.classicsolution.nl/
and
http://www.stadtdesign.com/products/vds608_6531.htm
or
http://www.stadtdesign.com/products/vds608_653.htm
or
http://www.superioryachts.biz/
http://www.admiralstender.nl/

Than see also our gallery with this boats during construction: http://www.boatdesign.net/gallery/showgallery.php?cat=500&ppuser=7697

[Guillermo]

Nice boats, Luigi. Keep us informed on the 8,50 and 9,50 cabin solutions.

Pericles,
I borrow your post on the Tolman skiffs to highlight here their interesting hull lines derivation on Sea Bright skiffs' ones.

[SAQuestor]

Pericles,I borrow your post on the Tolman skiffs to highlight here their interesting hull lines derivation on Sea Bright skiffs' ones.

Global warming hasn't reached Alaska yet! Look at how they are bundled up. In the second picture notice the fellow holding the coffee cup by the top. His hand is near cooked lobster color from the cold. :eek:

[Pericles]

Guillermo,

My pleasure. I am guessing here but it looks like Renn is modifying his first design, the Standard 18 footer skiff that does not have chine flats on its 7'6" beam. The Widebody has 3" chine flats and the Jumbo has 4" chine flats and are absent on the model. As Tolman Skiffs are working boats, powered by outboards, could the reversed V serve to protect the propellor?

Tom, you mention that the chine flats on "Liz" taper in width from zero at the bow to 12 inches at the transom. Does that mean 6 inches per side?

A 30 footer with a maximum beam of 8'6" would be pushing the envelope for trailering in the UK. However, the DownEaster 25 http://boatplans-online.com/studyplans/DE25Cabin_study.htm
has a maximum beam of 8'4", a hull weight of 1750lbs and a displacement of 2800lbs. The draft, inclusive of skeg, is 14" and PPI at DWL is 600lbs. Hull is 80 hours work, with 250 + hours to completion and the plans are $165. That would be fine for the UK. Being careful with bulkhead placement would enable the DE 25 become a DE 27 or DE 28 and that 10% in length would be invaluable to those who would welcome four real berths. A 90 hp outboard would deliver 22 mph with 3600lbs all up. Perhaps even more with chine flats!

I believe I have two boats in me and am house hunting for a somewhere with the space and access to build them. Here is one possibility, http://www.swalemarina.co.uk/ and here is another, http://www.ironwharf.co.uk/.

The first boat will be along the lines of Guillermo's original proposal on 13th May, but 10% longer, as trailering is not an option. LOA 33' BOA 12', Bow deadrise 24 degrees, midships to transom deadrise 12 degrees, chine flats zero at bow running back to 9" per side at transom, with 5 degree negative angle. Hull bottom 1" and hull sides 3/4". Superstructure is Paraglass 22, sandwiched between 1/4" Meranti. http://www.univar.co.uk/downloads/Parabeam_for_yachts.pdf

Construction in Epoxy/Meranti BS1088 using Sam Devlin's stitch & glue/cold moulding techniques. "West" 5-1 epoxy minimises print through compared with 2-1 epoxies. Power looks to be Volvo D3 190 hp with Aquamatic Duoprop. Fittings from Vetus. Awlgrip finish. Built to comply with RCD. NMEA 2000 with Octoplex cabling.
Four proper sized berths with decent facilities and the crew can sling their hammocks in the engine room.
(Ahaa Jim m'lad, it's a great life in Nelson's navy!)

Although I have been planning since early summer, sketches are still just scribblings on sheets of A4. When they are decent and I figure how to post them here, I'll do just that.

The second boat? A Viking longship, so I can travel to Valhalla. Cast adrift on the open sea and set on fire by a shower of flaming arrows. Pretty spectacular.:D :D :D :D :D :D :D


Pericles

[tom28571]

Based on the specs on your website Tom (LOA 24'3", BWL 80"), I estimated your LWL to be about 23'6", or 282" - thus giving an aspect ratio of 0.28
So when you say you aimed for an aspect ratio of about 0.35, I can only assume that you did that based on some sort of shortened WL in an attempt to represent the WP whilst on the plane...?
All the info I have suggests that aspect ratio is calculated on the at rest LWL / BWL, as these figures are too difficult to accurately determine whilst on the plane.

In regards to the 65% of AWP, it would be interesting to go back now, with a series of photo's and see just how close to the mark you were. Given the level running of the BJ24, I wouldn't be surprised if the figure turned out to be somewhat higher. Though for many boats, it probably wouldn't be high enough!
....

Will,

The waterline length is actually about 22' 10" but that is not the main difference between your figures and mine. The main difference is in the method of measurement. Your number applies to "beam/length ratio" and mine is based on Lord's method of calculating "aspect ratio". These are different concepts and the aspect ratio takes the geometric shape of the waterplane into account. I used a method similar to the one Leo posted in post #253 on page 17 of this thread. I think it is a more informative look at the actual bottom shape since it takes long skinny bows and narrow transoms into account and B/L does not. This method gives an aspect ratio of 0.35 for BJ which is not surprising since I forced it to be that way.

Trying to measure the aspect ratio from the photographs is not at all easy since the spray hides the actual waterline and the viewing angle is not perfect in all the photos. You are certainly correct that the aspect ratio will increase as the speed and trim angle increases but I cannot say accurately just what it is. In very high speed small planing boats when the hull is almost out of the water, the aspect ratio can become quite high, even 4.0 or more.

[Guillermo]

As Tolman Skiffs are working boats, powered by outboards, could the reversed V serve to protect the propellor?
I'm not sure about their intention when adopting those lines, but probably they are looking for better efficiency when planning (The inverted V sections look like an extreme version of Peter van Diepen's 'Flowmocean' lines) and maybe increased grip in the turnings, but we should ask them. I would like to know how this hull performs whith waves.

Hope to see your sketches soon.

Cheers

[tom28571]

Guillermo,

Tom, you mention that the chine flats on "Liz" taper in width from zero at the bow to 12 inches at the transom. Does that mean 6 inches per side?

Pericles

I missed this one earlier. The aft sections are monohedron. The chine flats are designed to be at a positive 1 degree angle of incidence relative to the aft buttock lines. Therefore the width of these flats increase going aft and they are 11 1/2" in width at the transom on each side. The transverse angle of these flats is about 2 1/2 degrees cathedral (down). The objective was to create extra lift to the aft bottom where the lift coefficient decreases on most boats. My thought was to make low drag trim tabs in the effort to get the boat onto plane early. The fact that the stern never sinks (as the photo series shows) and the longitudinal attitude is very stable indicates that these flats are at least partly responsible for this desirable behavior.

This was my one original contribution to the design of this boat. All the rest was following the guidance of other designers I studied in books. Of course, the idea may not be completely new since so many innovations have been tried in the past and never made it to the mainstream for all kinds of reasons.

[Guest-3-21-09-10-33]

Nice boats, Luigi. Keep us informed on the 8,50 and 9,50 cabin solutions.

.

Here the new Classic Solution 9,50 with sport cabin (under construction) and classic cabin (near future). In picture 850 Admiral Tender under assembly:

[fcfc]

Are you sure it is the 9.5m sport cabin and not the 12 m sport cabin ?

Seems that forepeak (1 m) + v berth (2m) + head (0.8m) + settle (2m) you are not at the half of the boat with 5.8 m.

[Pericles]

Guillermo,

Steveoh, the guy who runs the Fishyfish Tolman site, posted at around 5-30 California time 18th November about Renn's new design. " know it's not new news, but Renn sent me pictures of his new
design. You can see them:

http://www.fishyfish.com/renn_tolman/index.html

It's gonna be interesting to see how it turns out, and what sort of
mileage it gets. It's my understanding that he's aiming to design/
build a super efficient keel drive, diesel powered boat. Folks can
correct me if I'm not totally clear on this."

Steveoh has also placed Renn on Wikipedia. http://en.wikipedia.org/wiki/Tolman_Alaskan_Skiff

Tom,

Many thanks for explaining the width of the chine flats on "Liz". You have achieved in your design a craft than runs true and smooth in a manner that can only be accomplished on other designs by retro fitting hydraulically or electrically powered flaps.

It has set me thinking that my 33 footer with 12 degree deadrise monohedron from transom and 24 degrees deadrise at the bow, would benefit by increasing the chine flats from 9" at the transom to 15", keeping the 5 degree negative angle. This would appear to increase stability at rest and achieve planing without the "transitional hump". You gave "Liz" a 25 degree bow deadrise, a difference of 15 degrees. On that basis, I suspect I should look at setting my convex shaped bow at 27 degree deadrise to minimise the wake at 4 mph in harbours and rivers.

All the best.

Pericles

[Willallison]

Tom - correct as usual... that's what comes from posting off the top of your head, without giving time to think 1st!
For those without access to the derivation of Lord's aspect ratio:

Aspect Ratio = mean beam / wetted length

where mean beam = width of dotted rectangle shown below
wetted length = distance from transom to a point midway between the entrance of the stem and chine.

[Guillermo]

Another interesting boat, Gerr's 28' Offshore Skiff:
http://www.gerrmarine.com/power_30.html

LOA: 28 ft. - 3 in. (8.6 m)
LWL: 24 ft. - 0 in. (7.3 m)
Beam: 8 ft. - 0 in. (2.4 m)
Draft Hull: 11 in. (28 cm)
Draft Propeller: 26 in.
Displacement: 5,200 lb. (66 cm)
Headroom: 6 ft. - 4 in. (1.93 m)
Gasoline: 120 gal. (454 l)
Water: 25 gal. (95 l)
Power: 75- to 150-hp outboard
Speed with 75 hp: 16 knots cruise, 19 knots max
Speed with 150 hp: 23 knots cruise, 26 knots max

[tom28571]

Guillermo,

Last year I had an oportunity to drive and observe an Offshore 28 owned by a friend. First, it is a dory form with the usual characteristicsof that type. It is a flat bottom hull with a narrow waterline beam on the bottom of only 5' on a max sheer beam of 8'. Because of this narrow bottom, it is pretty tender, especially at the dock. Stepping aboard is something of a surprise. It banks steeper in a turn than any other boat I have ever been aboard. Although 28' over all, it is not a very big boat in terms of interior room and most movement will naturally be restricted to inside the bottom beam as in most boats.

When running together with only the owner of the Offshore skiff aboard and 5 adults aboard the BJ24, we were about 3-4mph faster with our 50hp than he was with a 75hp. Gerr designed the boat for fishing offshore and it is undoubtedly better suited to that than cruising inshore and protected waters.

These are my impressions but your mileage might vary.

It has been suggest here and elsewhere that prospective boats shuld be subjected to a comprehensive list of attributes to see how they compare in a more objective manner than just a quick look affords. For instance, some people just like dories and tend to overlook their considerable limitations when used in ways completely counter to that which the dory form was developed for and was so successful at.

[Pericles]

Guillermo,

That Dave Gerr Skiff is very good looking and with the flat bottom even simpler to build than a Tolman. Alaskan seas might be a little unforgiving however, so a V hull would probably be my choice, were I living there.;)

As far as Renn's new design is concerned, Skiffkits posted the following.

"I've known about it for quite a while. Renn jokingly accused me of
being an "Industrial Spy" while I was taking pictures of the model
at the Homer show. But since he's let the cat out of the bag!

His new design is based on a Rescue Minor type bottom married to the
Jumbo sides/sheer. The RM design is an Atkins design from the '20-
40's, google Atkins boat designs. Most RM type hulls are small
diesel inboards (18-25 hp), some were larger, with a max hull speed
of 18-20 knots. The prop sets directly behind the "Dead Box", the
design is said to be super effiecent, it is also very shallow draft
and can be easily beached as it will sit level, the prop sets in the
tunnel and is protected by a metal bar running from the dead box
under it to the rudder protecting the prop. Renn was hoping to
start on the full size hull (22') about now, don't know if he has.
Tim Davis, now back in Homer, plans on building a similar hull, 28'
when he gets his shop completed.

I highly doubt kits will be produced as it is a much more
complicated bottom design, Renn plans on using a somewhat different
building techniques and materials that probably will not lend itself
to kit building.

There's a company in the UK that marinizes small Japanese Kubota
diesels and imports them to the US, they would be the power of
choice. At one time there was also someone marinizing VW diesels
from Rabbits in the US.

Renn's shooting for less than a gallon a cruising day for fuel
consumption.

Will be interesting to see how it progresses.

Neal
Skiffkits"

Should anyone wish to join a lively, friendly and informative group of boat builders, just apply at http://www.fishyfish.com/tolmanskiff.html

Regards,

Pericles

[Guest-3-21-09-10-33]

Are you sure it is the 9.5m sport cabin and not the 12 m sport cabin ?

Seems that forepeak (1 m) + v berth (2m) + head (0.8m) + settle (2m) you are not at the half of the boat with 5.8 m.

You right, we still wait drawings for the similar version of the 9,50 from Van Dee Stadt design. This is the 12 mt sport cabin and I attached it to show the cabin design style, but the 9,50 will be very similar even less roomy.

[Guillermo]

....The prop sets directly behind the "Dead Box", the design is said to be super effiecent, it is also very shallow draft
and can be easily beached as it will sit level, the prop sets in the
tunnel and is protected by a metal bar running from the dead box
under it to the rudder protecting the prop.
Pericles (I'd love to know your name, just not to call you by the nick),
What about the room for the propeller? It seems there's not enough for an effective one, unless the blades come down further than the hull bottom, thus avoiding beaching.
Cheers.

P.S. Please excuse me if Pericles is your name!

[Guillermo]

... Because of this narrow bottom, it is pretty tender, especially at the dock. Stepping aboard is something of a surprise. It banks steeper in a turn than any other boat I have ever been aboard. Although 28' over all, it is not a very big boat in terms of interior room and most movement will naturally be restricted to inside the bottom beam as in most boats.
I thought so, thanks for the info on the real thing.
Cheers

[yacht371]

Food for thought.

I have just spent the summer and fall in possesion of a boat which meets many of the criteria mentioned in this post. It is an MC29 Motorcat which is trailable, light, fairly quick and gets outstanding fuel economy with its single diesel. I'm putting it up for sale with just 66 hours on the engine.

Why? I'm going back to sailing. Fortunately my sailboat, though listed, did not sell.

In the MC29 the best cruising speed from a comfort and economy point of view is 18 knots. At that speed we covered long distances quite quickly. When cruising my preferred days run is 20 to 30 miles between anchorages, even less in some areas.

We are early risers, and the result is, we tend to be at our destination by 9 AM! What to do with the rest of the day? Of course we could make longer trips each day, and easily cover 100 miles or more. But I'd rather go slower and enjoy the scenery. We did go from Vancouver to Seattle in a day for the boat show, but that was a delivery trip, and quite tiring.

Another thing is that any time of year, is there is a sunny day, with a bit of wind, I love to take the sailboat out alone, and just sail back and forth in English Bay, enjoying the day. This seems completely pointless in the powerboat, just uselessly burning up fuel. On the sailboat I can engage the autopilot and eat lunch, whereas on the MC29 I heave to for that as you must keep an eagle eye out for debris in our waters.

Guillermo mentioned in one post that his kids get restless on trips longer that an hour or so. Mine are grown up now, so no longer an issue. But perhaps the Banjer 37 is more of a slow motor boat than a sailboat. My Hanse 371 Tangleberry is a high performance sailer, quite thrilling in a decent breeze, and when the kids were younger they enjoyed steering it. My son loved setting the spinnaker and made a great foredeck man.

So, here are my plans for the sailboat. Already it has a hardtop dodger and windshield, but I will add a full cockpit enclosure. I will add an electric winch handle (the Cranker adapter pluse a cordless right angle drill). This is because I do find raising the big mainsail a bit of a chore. Once it is up, the boat is very easy to handle with its self tacking jib. A new, high tech jib will improve performance further.

Part of the fun in sailing is planning to take advantage of the wind and tide, and timing it. In the MC29 we just go, as we have enough power top overcome the local tides.

I used to thing that power boat people were restless energetic people who just had to move fast, but having tried it, I realize that I'm the restless, energetic type and a sailboat suits me better!

By the way, my sailboat has excellent accommodation for 2 couples, and greater weight capacity, so it is better suited to my 2 month summer vacation (I'm semi-retired, 58 years old) than any power boat I could afford. If I get another power boat in future, I'm thinking Nordhavn or Diesel Duck type. Then I suppose the fun will be sitting in the engine room tinkering...

Grahame Shannon

[Guillermo]

Sensible thoughts Grahame. I agree with you 100%
By the way, very nice boat the Amazon 44. I'm going to list it at my Motorsailers & Motorsailing web pages.
Some questions about her:
30600 lb displacement in what condition?
May I know her body draught, sailing area (I,J,P,E) and heeling arm, please?
(And also wetted surface for the 30600 lb displacement?)
Cheers

[fcfc]

You right, we still wait drawings for the similar version of the 9,50 from Van Dee Stadt design. This is the 12 mt sport cabin and I attached it to show the cabin design style, but the 9,50 will be very similar even less roomy.

The problem on the 9.50 would be headroom (among other space problems). Seems that the 9.50 classic have nowhere standing headroom in the cabin. Perhaps the sport cabin can do better in the pilothouse.

[Guest-3-21-09-10-33]

The problem on the 9.50 would be headroom (among other space problems). Seems that the 9.50 classic have nowhere standing headroom in the cabin. Perhaps the sport cabin can do better in the pilothouse.

will ask to Chees about (Van De Stadt owner/designer)

[Pericles]

Guillermo,

In post 237 you mentioned removable sterns. There is such an item that also enables the repowering of craft with time served inboards.

http://armstrongnautical.com/brackets.htm

At the end of October I commented on their possibilities at the Tolman forum.

---"Ken's link to the Armstrong deckplates also has another heading. "Brackets". How about a positive flotation O/B bracket? It could be created in marine ply and bonded to the transom. It is certainly worth a look.

If you think of the "Bracket" only as a full width extension of the hull, say lengthening the 22 footer Jumbo to 25 feet at a lower sheerline, then the extra length is used as a step up over the transom. Built to match the underwater lines as a completely separate component with its own flotation chamber and bonded to the transom, if it did not function well, then a chain saw would part it from the vessel with ease. The inherent flotation would enhance fitting twin O/B engines.

The Armstrong "Bracket" is a fit all design, hence it does not extend down to the bottom of the hull. There are too many variations in transom deadrise. Tolman builders can match the hull shape and thus extend the effective length of any of the skiffs as well as being a mounting platform to climb aboard. As a separate component, it could be assembled inexpensively and bonded to the transom with epoxy. If it were sucessful, then it could be either fitted with Armstrong deckplates or buoyancy foam filled. The unit represents a method of testing the effects of increasing waterline length without great expenditure."--

I would also add that instead of filling the unit with buoyancy foam the interior could be fitted with petrol tanks thus keeping the fire risk out of the boat's interior.

This could lead to the concept of "cut & shut" boats. Slip in an extra compartment if you have guests.:D :D

The Chinese "treasure" ships of the Ming dynasty were built with separate water tight compartments

Size of the Chinese Fleet
“In its heyday, about + 1420, the Ming navy probably outclassed that of any other Asian nation at any time in history, and would have been more than a match for that of any contemporary European State or even a combination of them. Under the Yung-Lo Emperor [Zhu Di] it consisted of some 3,800 ships in all, 1,350 patrol vessels and 1,350 combat ships attached to guard stations (wei and so) or island bases (chai), A main fleet of 400 large warships stationed at Hsin-chiang-khou near Nanking and 400 grain-transport freighters. In addition there were more than 250 long-distance ‘Treasure ships’ or galleons (Pao chuan), the average complement of which from 450 men in +1403 to over 690 in 1431 and certainly overstepped 1,000 in the largest vessels. A further 3,000 merchantmen were always ready as auxiliaries, and a host of small craft did duty as despatch-boats and police launches. But the peak of the development which had started in 1130 came in 1433, and after the great reversal of policy the navy declined much more rapidly than it had grown, so that by the middle of the +16th century almost nothing was left of its former grandeur.” – Needham, Vol 3, p. 484 (Martin Tai evidence).

The Chinese Fleet arriving at Calicut
“More than eight hundred sail of large and small ships had come to India from the ports of Malacca and China and the Lequeos [Ryuku Islands], with people of many nations, and all laden with merchandise of great value which they brought for sale… they were so numerous that they filled the country and settled as dwellers in all of the towns of the sea coast.” (Chaudhuri, p. 154) (Evidence provided by Professor James Finlay of Arkansas University.)

Bases
In parallel with Zheng He’s development of his fleet went that of overseas bases. By 1421 the Chinese had bases around the Indian Ocean and down the East African coast to Sofala. They already had an extensive network across Indonesia, the South China Sea and in New Zealand.

Experience
Since 1405 there had been five voyages becoming progressively more adventurous as the years went by. During the fourth voyage the Chinese had separated their fleets and sailed far down the East African coast.

Where the Chinese fleet went
“Chinese . . . with Tartairs, Japanese and Koreans . . . crossed the Maritime Stretch . . . into the Kingdoms of Quivira populating Mexico, Peru and other eastern countries of the Indies [America]” – Carlos Prince (Annex XXVI).

SUMMARY
The whole world had been charted before Europeans set sail. Only the Chinese could have done so.

http://www.1421.tv/pages/evidence/content.asp?EvidenceID=168

Regards,


Pericles

[Guillermo]

...If you think of the "Bracket" only as a full width extension of the hull, say lengthening the 22 footer Jumbo to 25 feet at a lower sheerline...
That's a nice solution for some boats. But in the EU (from the laws point of view) one have to be careful when the 'bracket' adds hydrostatic or hydrodinamic lift, it's then considered as part of the regulamented LH (length of hull) so maybe affecting the fiscal categorizacion of the boat (So more taxes to be paid)


SUMMARY
The whole world had been charted before Europeans set sail. Only the Chinese could have done so.
The Arabs (probably Nabateans) were sailing the Indian Ocean at the same time, also charting the zone and even coming up the South China Sea. Chinese and Arabs traded those seas hundreds of years before the europeans even thought in going there (precisely to try to take from the arabs the exclusivity of the trading of spices and the like)

Cheers

[Pericles]

Guillermo,

Thanks for your remarks. I wonder when the EU will tax beam as well. Cat owners look out.:mad:

The Jetpac supports 150 kg of its 400kg weight hydrostatically, stern drives and outboards are trimmed in to provide hydrodynamic lift and hydraulic trim flats do the same. I believe you mentioned that the Jetpac is not considered to be an increase to the LH. On that basis, a flotation device that partially supports the weight of the outboard(s) and acts as a swim platform as well, should be exempt, especially if the device were bolted on rather than glassed in place.

How about a clipper bow that opens up and back like a RoRo ferry and rests on the foredeck? Difficult to engineer, I grant you, but it would give the law makers a difficulty. The Sealine SEC system that extends the cockpit by nearly 500mm, how is that rated? http://www.sealine.com/aboutus_innovation.aspx

The Chinese ships of the Ming period were crewed by many nationalities including Arabs, but probably not Nabateans

"As allies of the Romans the Nabataeans continued to flourish throughout the first century. Their power extended far into Arabia along the Red Sea to Yemen, and Petra remained a cosmopolitan marketplace, though its commerce was diminished by the rise of the Eastern trade-route from Myoshormus to Coptos on the Nile. Under the Pax Romana they lost their warlike and nomadic habits, and were a sober, acquisitive, orderly people, wholly intent on trade and agriculture.

They might have long been a bulwark between Rome and the wild hordes of the desert but for Trajan, who reduced Petra and broke up the Nabataean nationality as the short-lived Roman province of Arabia Petraea.

By the third century the Nabateans had stopped writing in Aramaic and begun writing in Greek instead, and by the fourth century they had converted to Christianity[4]. The new Arab invaders who soon pressed forward into their seats found the remnants of the Nabataeans transformed into peasants."

http://en.wikipedia.org/wiki/Nabateans

Best regards,

Pericles

[fcfc]

For changing LH, the tax issue is a minor one, mainly psychological. In most cases, the amount of tax is rather small compared to the boat price.

More important is certification and insurance.

What would happen to a 5.90m boat (certified with the the simplified process), extended to 6.10m without recertification. And that boat capsizes with casualties. At 6.10m, you would need the complete certification process. The boat may not pass since it has not be designed for it.

6.0 m is an obvious limit not to cross, but there are a bunch of other limits where under a certain LH, one kind of (safety) equipment or certification process is considered satisfactory, but above, you need a beefier one.

[Guillermo]

fcfc
I agree with you: equipment is also something to take into consideration. About taxes: here in Spain if you go over 7,5 m you pay a 12% tax on the price of the boat, but not so under that. So quite a difference.

Perry,
I'm not able to find out the info on the Sealine SEC system at their web pages. Where is it?
On the Nabateans, have a look at:
http://nabataea.net/who1.html

[Willallison]

The Sealine SEC system extends the cockpit by a metre or two. It was primarily introduced as a way of lowering marina fees. Personally, I wonder about the additional weight and complexity that such a system introduces. Then again, here in Oz, we don't pay 3000 euro's a month to park our boats!

Pericles - trimming in a sterndrive our outboard doesn't provide additional hydrodynamic lift - at least not directly, and not in the same way as trim tabs do. Instead it vectors the thrust. In the case of trimming in, it lifts the stern to some extent by vectoring that thrust downwards. Shaft drive boats, with angled shafts, do the same.

[Pericles]

Will,

Vectored thrust. Yes, just like the F22A Raptor. Now that would be a really useful power plant for a motor cruiser.;) ;)

Guillermo,

Is that 12% extra VAT or a special purchase tax on which you also have to pay VAT as well?

For Sealine SECS see here. http://images.google.co.uk/images?hl=en&q=sealine%20secs&btnG=Google+Search&ie=UTF-8&oe=UTF-8&sa=N&tab=wi

Regards,

Pericles

[Willallison]

:D ... yes - something I'd definitely like to see - with someone else at the wheel!

[Pericles]

The Alsphere site has a photo of on of their hulls. http://www.alsphere.at/dg/index.shtml

If the deepest part of the keel was fitted with lifting surfaces, hydrofoils or similar?? This could be a possible result. http://www.airchair.com/:p :p :D

Here is a video. http://www.videovat.com/videos/2103/hydrofoil-surfboard.aspx

On the subject of extending boat length in harbour, how about designing the aft cockpit like a drawbridge so that whilst at sea it is pulled vertically up against the aft cabin to prevent swamping in following seas and lowered on cables to the horizontal, like an eight feet long, full width bathing platform with bulwarks? Un Passerelle par excellence!

Guillermo,

Off topic, but thanks for the Nabatean link. Very interesting. I enjoy archeology and geography very much. Here are 3 of my favourite sites on science and living. http://johnhawks.net/weblog/topics/meta/neandertal_or_neanderthal.html

http://www.scienceblogs.com/loom/

http://www.second-opinions.co.uk/ Especially see http://www.second-opinions.co.uk/cholesterol_myth_2.html

Regards,

Pericles

[fcfc]

On the subject of extending boat length in harbour, how about designing the aft cockpit like a drawbridge so that whilst at sea it is pulled vertically up against the aft cabin to prevent swamping in following seas and lowered on cables to the horizontal, like an eight feet long, full width bathing platform with bulwarks? Un Passerelle par excellence!


There is the beneteau Antares 980 with a "sliding" transom. Rear position, you have a big cockpit, but no swim platform. Front position : moderate cockpit + significant swim platform.

I have also seen on the web an "opening" transom. like ferry ramp. At sea, the transom is vertical and closes the cockpit. At mooring, it can be rotated aft, up to the level of the cockpit sole. Make a giant swim platform the full cockpit length + transom height.

[Guillermo]

Is that 12% extra VAT or a special purchase tax on which you also have to pay VAT as well?
For Sealine SECS see here. http://images.google.co.uk/images?hl=en&q=sealine%20secs&btnG=Google+Search&ie=UTF-8&oe=UTF-8&sa=N&tab=wi

You pay both, this tax and VAT.
Thanks for the link. Definitely I don't like how the thing looks.
Cheers.

[Guillermo]

Thttp://www.second-opinions.co.uk/cholesterol_myth_2.html

Wow...!

[Raggi_Thor]

Still off topic, Guillermo and Pericles, but I think we have to drink more red wine and olive oil :-)

[Pericles]

In the same glass?:D :D

Pericles

[FAST FRED]

I have also seen on the web an "opening" transom. like ferry ramp. At sea, the transom is vertical and closes the cockpit. At mooring, it can be rotated aft, up to the level of the cockpit sole. Make a giant swim platform the full cockpit length + transom height.


AS designed by the pick up truck folks, circa 1920.

FAST FRED

[Guillermo]

Raggi,
I'm not displeased with the size of my portions of red wine and olive oil....;)

[Pericles]

On the Bray Yacht site http://www.brayyachtdesign.bc.ca/ there is a photo of a hoist for a RIB on Slideshow 1. It is similar to the hoist on skip trucks. If both the cockpit with the RIB sitting on or in it, were to be carried on the roof of the aft superstructure, arrival in port would be followed by lowering the cockpit and RIB into the water, floating off the RIB and mooring alongside and then lifting the cockpit into its location aft. Granted this is only possible with large craft.

Innovation, thy name is Complexity. :D :D

Pericles

[Geoh]

How about this Allweather 26' http://www.allweatherboats.com/
I KNOW SLOW BOAT TO CHINA but seaworthy

[Raggi_Thor]

Nice, good and sturdy looking, but it should have a small rig :-)

[Raggi_Thor]

Viksund 27, a motor-motorsailor...
this is for sale,
http://www.maritimnord.no/ProViksund27Col.htm

[Geoh]

I found the Viksund 27 Columbi on the net but it is in New York and I am on the west coast...I agree it is the only boat i liked better than the Allweather i bought.

Regards
George Hood

[Raggi_Thor]

You have probaly read the story about Ragnar Thorsets trip to New yourk in a Viksund 33 :-)
http://www.silverdonaldcameron.ca/viksund.html

[Guillermo]

Has it appeared any new kid (pocket cruiser) on the block in these last months, deserving to be brought here?

Cheers.

[Mark Van]

I've designed a pocket cruiser that fits.

Mark V 28

LOA 28' 0 "
Beam 7' 6"
Draft 14"
Disp 4,000 lb


http://markvdesigns.tripod.com/sitebuildercontent/sitebuilderpictures/mv28studyplan.jpg

http://markvdesigns.tripod.com/sitebuildercontent/sitebuilderpictures/.pond/mv28view1.jpg.w560h336.jpg

http://markvdesigns.tripod.com/boatbuilding/id16.html

[Guillermo]

Nice boat, Mark!
(Also the 20' and the 39')

Cheers.

[Corpus Skipper]

Hi all, very interesting thread. I've been intrigued by the seabright hull for a long time, and I'm just wondering: would this hull form make for a good fishing skiff, as in a shallow water boat for redfishing in south Texas? The efficiency of tunnel hulls with outboards is atrocious, and with gasoline in line to reach $4 a gallon this summer, I'm thinking a seabright hull with a small diesel inboard might just be the ticket. I ran across a website of a fella with a 20 foot seabright type boat with a (I believe) 20 hp Kubota that would do 20 kt. for 20 nmpg. Of course it was a trim hull, which no one seems to like any more. Beam is king, gotta stuff in all the latest widgets and whatnot. I know that even a modest diesel/ gearbox costs quite a bit more than an outboard, but going from 2 mpg to 20 is quite an improvement. I've seen that even Renn Tolman has incorperated the seabright concept into his latest skiff. ability to run in 6" of water is necessary, and according to the afore mentioned website, this is quite feasible. I'm just wondering if the increased cost would be well recieved in lieu of the much improved efficiency. I'm figuring a real world fuel economy improvement of 300% would make the initial expense worth while for the average use of 100 hours per year (and more is usual here with our extended boating season). I think even with a wider beam, a 300% increase is not out of the realm of possibility. I prefer the trimmer hull myself, but "creature comforts" are what sells today. Any thoughts?

[carlos bairo]

hi
guillermo;;
i am new in the forum i building a tug boat in aluminium 21ft design by
kent atkinson fron GLEN L MARINE DESIGN (TITAN).,the shrink wrap way.
i will like to have your advice and help could by posible tu contact you in espanol beacouse my ingles is very limited on writting no to reading.
my knowledge on engines ,exhaust sistem it is limited but i will prefer dry exhaust sistem i am open for your profecional sugestions,

gracias :: juan carlos bairo

[Guillermo]

Juan Carlos,
Please write me to: g.gefaell@gestenaval.com
Saludos.

[carlos bairo]

grasias guillermo por to deferencia,
naci en uruguay decendientes de espanoles ,i llevo en sydney 34 anos .
constructor naval calderero, soldador de alta precion ,supervisor 40 anos en el oficio y me retiro el proximo ano.
escrvir el ingles se me da muy mal y no me gusta escrivir en el forum con faltas de ortografia ,e leido mucho de tus articulos muy asertados juan carlos

[Boston]

would this one be outside of the design parameters :D

http://pal2pal.com/BLOGEE/images/uploads/yacht3SOLENT2103_468x350.jpg


great thread guys
thanks

[Knut Sand]

would this one be outside of the design parameters :D

Bonzai trees?

[tom28571]

would this one be outside of the design parameters
thanks

Shouldn't that swimming pool have baffles:confused: The miniature golf course looks nice:p

[rasorinc]

where is the hellipad?

[Willallison]

Oh c'mon guys - this is a shining example of how the superyacht crowd are going green....

[Boston]

if you made it big enough, you could harvest algae and process it into alcohol for fuel

[Guillermo]

Here a clever small waterballasted sailing boat, performing several features I really like. Among them what they call Asymmetric Capsize Buoyancy (ACB) and a boarding permanent step in the trailing edge of the rudder.

http://www.swallowboats.co.uk/content/view/115/110/

From the site:

"Once fully inverted another big safety feature automatically kicks in. Her Asymmetric Capsize Buoyancy (ACB) is a real life saver. Boats that will self right from 90 degrees are usually also very stable upside down. Two or more crew have enough weight to right her from a full inversion, but ACB makes this possible even for one relatively small crew member. It works by flooding one side buoyancy tank when inverted, which destablizes the boat and in about 60 seconds, gives her a noticeable upside down heel angle. The skipper should wait on top of the up turned hull and right the boat by leaning on the centreboard, helping the boat heel to the same side as that induced by the ACB. Once righted, the water in the buoyancy tank floods out though the outboard well via the self draining cockpit floor.

........

We have talked a lot about capsizing, and righting, but getting back in can be a real problem for all but the young and fit. BayRaider has plenty of positive buoyancy so floats quite high even when swamped. Our solution has been to fit the rudder blade with a permanent step in the trailing edge, rather like a winglet at the end of an airplane wing, it sits about 12 inches below the surface and acts as a step for re boarding. The mizzen mast is within easy reach to grab hold of as is the stocky mizzen mast partners."


Cheers.

[Boston]

thats pretty dam cool G

[Guillermo]

Pericles brought my attention to this contest:

PBB's DESIGN CHALLENGE II

Design Parameters:
Must be trailerable for affordable launching, over the road transportation, and storage.
Max beam 8 ; max length 40 (legal trailerable dimensions in many states)
Minimum length 24 , stem to transom
Trailerable weight (with engine) should not exceed 3,500 pounds
Must burn less than 2 gallons per hour (7.6 l/hr), maintaining a 10 knot cruising speed in a 2′ (0.6m) chop and 15-knot breeze while carrying 800 lbs/362 kg (family of four). Favorable consideration will be given for continued efficient fuel consumption and good seakeeping abilities at speeds in excess of 10 knots
Must include at least Spartan overnight accommodations (berths, head, galley) for two adults and two children
Must be a new design
Submissions should be the designer’s original, previously unpublished work, and include lines, profiles, sections, table of offsets, accurate weight study, cost calculations, and performance predictions. (All designs will remain the property of their designers.)


More at: http://proboat.com/design-challenge2

Thanks, Perry.

Cheers.

[Willallison]

Now that's starting to look interesting! Designing a 40' x 8' boat that can sleep 4 and weighs less than 3500lbs should result in some interesting boats....

[duluthboats]

Lol!!!