minimum plywood thickness

Hello all,

I am a newby in boatbuilding and was looking at Atkins designs, a simple 26' straight sections boat, Tang. What would be the minimum required thickness of plywood sheets, provided one adds some more expoxy and glassfibre cloth over the wood ? With 4 mm plywood, would curves in 2 directions be possible ? (for Atkin Bam design)

Thanks, looking forward to any good replies !

 

Hi ASM and a very warm welcome to the forum!

I think, more important than epoxy and glass on the outside, is internal strength from bulkheads and/or frames and stringers. 4mm seems a little thin for a 26 footer. James Wharram’s Tiki 21 is stitch and glue and uses 6mm ply.
I’m no expert however, and will watch this thread with interest.

PAR, where are you lad!

 

4MM PLY/ PUT your toe right thru it, I just built two 12 footers, 8mm, 12 on bottom, 6 would have sufficed
Is she a sailing? or what?
with strong frames you can bend 1/2" ply in simple curves, that is no compound
With a longer boat you can bend one inch ply, biggest ply maxi ever built Buccaneer, 78 foot chines sailing yacht Won Syd/Hobart classic, so there ya go

 

Thanks guys, information I can use.... I am playing around with the idea of self building, but for 2 years now... its like a virus, it comes and goes but never stays away. These are the two boats I was talking about:
http://www.atkinboatplans.com/ and then search for Bam and Tang, preferred Tang but want a tumblehome stern and a top section like:
http://www.messingaboutinboats.com/archives/mbissuejuly00.html
so a mix...
Would Tang be good in stitch and glue ?
Plus I want to make it inboard electric..... !

 

ASM,

There are many sites that sell plans for you to study.

http://www.bateau.com/

http://www.duckworksmagazine.com/r/plansindex.htm

http://www.selway-fisher.com/index.htm

https://www.boatdesigns.com/departments.asp?dept=2

http://www.devlinboat.com/

Compound curves are achieved with a combination of slitting thin sheets of marine ply and cold moulding to achieve designed scantlings. The entire hull and superstructure are encapsulated in specified glass fabrics with marine epoxy, all of which is painted or varnished to protect the epoxy from UV light.

Do the work properly and you could create some thing like these. http://powerandmotoryacht.com/vicem/

Pericles

 

I would strongly try steer you away from stitch glue, to building over frames upon a jig

 

Lazeyjack,

Your aluminium boats boats are skin on frame I believe and judging from your gallery, they are very fine craft. Which is why I can see you would prefer ply skin on jig mounted frames for an epoxy/ply composite boat.

However, by incorporating a number of techniques from all shipbuilding disciplines, it is my contention that a fully epoxy and glass encapsulated monocoque wood hull can be produced that will match quality hulls manufacture in steel, plastic and aluminium. Jarrett Bay, Sculley Boats, Paul Mann and Vicem build in combinations of BS 1088 and mahogany veneers. Indeed, the strength and integrity of the hull of the Vicem 85 permits considerable distance between the laminated mahogany frames. http://powerandmotoryacht.com/boat-tests/vicem/2007-vicem-85-classic/gallery.aspx

I am in the process of setting up to build my first boat using a substantial strong back to support and align a series of permanent and temporary bulkheads and frames on which to drape and secure the routed shapes of bottom and side panels. Once the shape of the hull is developed and plumb in all directions thickened epoxy is used to join these panels and freeze the shape of the hull. Cold moulded panels and strips of BS 1088 are Raptor stapled and bonded to the hull shape to achieve the designed scantlings. Perhaps 3 or 4 skins of ply and glass cloth to both sides ready for fairing and painting. Correct me if I am wrong, but aluminium tips the scales at 155lbs per cubic foot? Okume BS 1088 composite is 52lbs per cubic foot.

On that basis, an epoxy composite hull weighing the same as an aluminium hull will have much more thickness in its hull. Besides, wood floats.

I have the benefit of three sons of 24, 19 and 16, who are incredibly keen to build this 45 footer as they like boating. We have rented a warehouse for the build, so this is a professional approach by amateurs, to the challenge of self build. A bit like the two houses we developed together.

Stitch and glue on a strong back works very well, especially with designs that have been configured for the method. Change always happens and reading ASM's request for a 26 footer straight sections boat, has reminded me that the FL 26 might just suit him very well. Page 3 previews the lines.

http://forums.bateau2.com/viewtopic.php?t=13918&highlight=fl26



You have a very good reputation on this forum Lazeyjack and I enjoy your posts. I just think Boat Plans on line have advanced the cause of good design and Jacques's version of S&G deserves a wider audience.

Yours sincerely,

Pericles

 

I strongly advise you plop down the 55 bucks for the plans to "Tang" and build as suggested. Tang is typical of many of the Atkins V hulls and designed around a target speed. This means the hull, particularly aft, is shaped to run comfortably at about 14 knots with moderate power (a common theme with his designs). Building with different scantlings or different techniques, possibly lighter, maybe stronger, will not change the shape of the hull, which will just plow a pile of water, if pushed much past 14 knots. This coupled with the re-engineering of the scantlings and structure wouldn't offer the rewards, I think your after. In other words a lighter version of this hull will be of no advantage, you'll just have to add more ballast (which the plans suggest should be about 2/3's of a ton) suggesting this is a light structure (as designed) already.

Your understanding of the material comparisons is limited (the aluminum to okoume for example) these two, quite different materials have very different physical properties and are not easily interchangeable. Typical aluminum structures have a great deal more internal bracing and framing then say if compared to a well engineered taped seam build. This is because plywood panels are self supporting, able to span large areas without additional support, which isn't the case with aluminum hull shells.

Pick up a copy of Dave Geer's book "Elements of Boat Strength" and run down the proposed scantling differences on the method(s) you're interested in. This will help considerably in the conversion process, which I still wouldn't recommend without a reasonable structure engineering understanding, let alone the dynamics of yacht design in general.

I'm not trying to offend you, but am interested in your success. Tang (and Bam) is a great boat if built as designed and used as intended. It can easily turn into a ******* only a mother could love if much is altered in her structure or shapes. You are quite correct that using several wooden building techniques can produce strong, light weight boats that rival other materials, but there are many qualifiers and limitations, which I feel you need a better understanding of before tackling projects, that can take you and you loved ones, farther from shore then they, or you can swim back too.

 

i love wood boats too) In fact apart from the speed, of the build which is snaillike, I love the feel and the smell, and I do agree, they can be very very strong, Having said this, I steer away from sttch and glue because it seems a messy unpro way of doing things I agrree that if the skin is heavy you dont always need fromes, but when the boat gets some size, you have to stop it wracking, , with either decks, or soles, or both
On a 12 footer I build I glued the aft thwart in, it was a deep thwart degned to lay back in, abt 700mm deep, and the width of the boat in the stern, I dropped the boat onto my lawn and the bloody glueline cracked, So it seems to me, that unless youy have a frame, then you would need to glass tape all the joints I will admit I tend to see glue as runny weld, and timber constr. is not my forte' Besides I know nothing of many of the MODELS you North Americans talk of,
Cheers

 

Hello PAR,

I am assuming your post is for me, ,although it was ASM who brought up the subject of the Atkins "Tang". I've been experimenting with epoxy and ply over the last two years and whilst I would not compare my abilities with the skills and knowledge of professional boat builders, what I do know is how to employ the skills and trades needed in certain aspects of house renovation and selling on at a profit. So it is with boat building.

I shall not build a fabulous aluminium boat such as Lazeyjack creates. Instead, I have taken the knowledge freely given in forums such as this to design a vessel that can be built using the very latest developments in composite construction, in much the way that Sam Devlin started out. Whilst I shall not equal the craftsmanship of the internal fit outs from Devlin Design or Vicem, what I shall have is a vessel that will not let the family down. I come from a line of wood butchers and although my brother would beat his head against a wall at his thought that I can build such a boat, I love to point out to him that my first raft floated and his went down with all hands.

That was when we lived in NZ, '49 to '53.

What I would say is we are a family with a "can do" attitude. Unlike many others we do read the instructions first. For example, I will ask for directions in a town I do not know.

Thanks for your interest.

Pericles

 

LazeyJack,

As well as using decks, soles and athwartship bulkheads, longitudinal bulkheads such as bunk flats, storage cabinets and shelves are also bonded to the hull to prevent wracking. In some ways we are following the developments in Formula One, where the design of the monocoque chassis is so advanced, drivers walk away from crashes. Not that I use Kevlar and carbon fibre.

It's the concept that impact forces are distributed around the hull to minimise stress and damage and if the hull is damaged, a bit of ply and some epoxy will suffice.

Working single handed, epoxy and ply can be tiresome, but four of us achieve quicker results as a team, than as individuals. Building the hull is only 40% of the task. The rest is fitting out and for that I call in the experts.

Pericles

 

Tang/Bam vs Fast launch

Thanks for the input guys, it looks like this thread is running now. The fast launch 26 as pointed out by me in this forum by Pericles is just what I was looking for, I need to add another 4' .... to make it comparable with the superstructure I want to use as found on the bolger design day launch diesel inboard. I will talk to the designer see what he makes of he +4' ....

Do you guys think a electric version wil do fine in such a boat ? I am not for speed, I am for clever green boating with a good design.. design sells, green (electric) does not yet in boating industry.

 

ASM,

A 20 hp diesel engine running on vegetable oil is about as green as it gets at present. It should push an FL26 at displacement speed in still water without effort. However, a battery powered boat, recharged daily by mains electricity or a wind turbine is feasible, but depends on the use of your boat. http://www.thameselectric.com/

Ocean Navigator published the article below

http://209.196.57.126/ME2/dirmod.as...5F&tier=4&id=8D2597482B564E39B7575D95B1AAB289

Here is another site; http://www.electric-boat-association.org.uk/product-guide.htm


Pericles

 

Electric and FL26

Pericles, thanks... I like the cleanness of the electric version, with vegi oil, you still have internal combustion engine with all appendices attached and greasy environment. Electric is simple, brushless motor, batteries and controller. Furthermore, I would like to install some solar panels (neatly curved with the top side of the cabin) to get some charging forthe batteries (a day boat would be used mainly in weekends, which means 5 days for charging at a low speed, but will get some juice in the batteries besides just the shore power.

One could think of a veggi oil gen. set as backup power for long trips into nowhere...

 

Dear ASM,

I curious to wether you ended up building Tang. I'm thinking of building this design and would be very interested in pictures and more info.

Regards, Marcel