Compounded (tortured) ply construction.

The reply from Mr Watson misses the point in that the shoe size limitation does not arise from the deck shape which is just curved in one direction, but rather from the limitations imposed by using only two sheets of ply for building the kayak. It is also slightly tongue in cheek since only one builder has ever mentioned this to me & many have been built.
The point raised with regard to Uffa Fox, Mosquito aircraft & cold moulded construction are all different to compounded (tortured) ply construction which critically depends upon a curved keel line being forced to conform to a straight line on the keelson, or a fibre reinforced seam.
Uffa designs, notably the Firefly & Albacore, were originally built by Fairy Marine using hot moulded construction cured in an autoclave. They also built several larger sailing cruisers/motor cruisers using the same method. The Mosquito was certainly moulded, I believe by the hot process possibly utilising an autoclave to cure the glue, but don't post to tell me I'm wrong - I may well be.
Hope this clarifies the situation a little. Best wishes to all my readers!

 

Compounding is bending on the 2 directions of the plane (in the geometric meaning) a flat sheet to obtain a spheric surface. The amount of compounding depends on the material and its thickness. You can also "cheat" by working the material if ductile, or heating it like with foams or plywoods by example.
You can have a "partial" compounded surface when a succession of small compounded pieces are joined, and you can combine it with layering and gluing to obtain the desired thickness. That has also the advantage to "fix" the solutions of continuity so the compounded final panel is a monocoque.
The monohull Kriter V has been built in that way; complete sheets of plywood when possible instead of strips have been compounded on the mold, joined, and layered. It's a combination of cold moulding and compounding. The advantage is to suppress a lot of joints and also to cut radically down the amount of work of sanding. The surfaces are fair. Classic moulded wood is a pain as you have to sand each layer.
I'm pretty sure that Uffa Fox, like a lot of people during the fifties, tinkered with "true" compounding I mean joining the 2 flat halves of the hull by the keel and bending it in the 2 directions of the plane. It's a very tricky exercise when you want good surfaces, enough displacement for the boat, rounded shapes while not breaking the plywood...
Classic cold moulded wood uses narrow strips to minimize the problems of compounding veneers, you obtain a faceted surface you have to fair.
The Mosquito was moulded, but a lot of plywood panels were compounded. Look at the pics. Scantling inside plywood 1/16 (1.5 mm) Balsa 7/16 (9.3 mm) outside plywood 5/64 (2mm) and that works...(A link about the details;
http://users.skynet.be/BAMRS/dh103/fuselage-construction.htm
I have joined a pic of Attitude a 2005 8.5 m 950 kg catamaran made in 4mm and glass compounded plywood, a very good design and work, costing 1/3 of the composites catas, and the PDF of the article about this boat. I counsel to open it and to have a look at the pics...

 

The Mirror dinghy was tensioned ply and that was an early 1950s design.
Interesting in your post, Ilan Voyager, that you've shown the John Tetzlaff 2005 built 8.5 catamaran Attitude; he used the same construction technique on the slightly larger This Way Up, which was a few years earlier.
Aside from the stressed plyTornados in this country, the earliest in this technique would be Malcolm Tennants Bamboo Bombers; two were built in Auckland back in the late 1970s. And of course even earlier, in larger multihull sizes, like over 25 odd feet, the early 1970s Gougeons' Adagio has to be either the first, or close to it.
Hot and cold moulded boats were also done here in Auckland at a very early stage and Jim Young's 1957 swinging keel boat was cold moulded with glues and fastenings, the first in this country to use this technique.
Here is tensioned ply 32 foot Bamboo Bomber Supplejack being launched from Little Shoal Bay in 1977.

 

After studying Chris Kulczycki's book "The Kayak Shop" which shows two compounded plywood kayak designs (the Yare and the Pocomoke) I designed my own version of a kayak using this technique .




At that time I did not know of Dennis Davis' kayaks which are very similar but were created about three decades earlier than the ones by Kulczycki.

I also tried to design a rowboat using this fascinating technique.




But because the shape of the hull resulting by the use of this method is not exactly predictable I stopped bothering.

I think this quote from another book by Kulczycki (Stitch-and-Glue Boatbuilding) sums it up to the point:

Right now I keep myself busy with another method which also contains compounded plywood and allows a little more control of the hull shape but there are still some issues to deal with. It is an adaptation of the way birch bark canoes were made but replacing birch bark with plywood (for more information see: http://forum.woodenboat.com/showthread.php?165793-Plywood-Canoe-Concept-Birchbark-Style&highlight=).

Here are some designs:

 

Thanks for the replies - seems to have hit a nail with this topic. Chris Kulczycki actually pinched the design of my DK13, published in WoodenBoat, if you compare his book with my 1969 The Book of Canoeing you will find the essential keel line the same & & some of the photos virtually identical. Hey Ho, water under the bridge.
I like the canoes in the last post, very good shape.

 

The Mirror (70000 made!!!) was designed on 1962, I checked it. But there were ancestors in the 50ties. The beginning of the 60 was very active. Sail was popular.

Gary, Attitude is a good boat with an excellent ratio price/performance. And it won races...Your own posts on another 2009 thread about compounding.
http://www.boatdesign.net/forums/multihulls/where-catamaran-innovations-25898-10.html
Another 2011 thread
http://www.boatdesign.net/forums/multihulls/tortured-ply-theory-37934-2.html
with a pic of your foiler

A link http://www.gust.ax/gallery/blade/
A beautiful illustrative gallery of a nice 16 feet beach cata, very tortured plywood http://www.thebeachcats.com/pictures/?g2_itemId=11955

Attitude has a flavor of 1970 cat type like the Tennant ones, I do not know the actual underwater shapes and volumes repartition, I guess there are some differences with 1970 ones.
The formula light simple catamaran/alu beams/minimal amenities extended with a tent is a logical winner for small day sailers/costal cruising. Already in the seventies good small catas have been designed very soon like the Tornado (1968) and several others, it's on big multis that a lot had to be done as it's far more complicated.
For those afraid by a 4mm ply with glass and minimal framing, this system is very similar to the Lord one for fast boats. If you use an epoxy resin with 4 to 6 % elongation so it uses the glass fibre properties to the max the system can take a lot before breaking, as it's able to dissipate a lot of energy along the parabolic/pressure curves of the hull.
The mistake is to be afraid and to add reinforcements/stiffeners that create hard points, like deep stringers and very rigid bulkheads. In fact stiffeners have to be not too stiff...
Unhappily compounded plywood on multis needs a zen state of mind, a good eye and some self confidence of your capacity. It's not a everybody's method. And plywood does not sound high tech, so not good for marketing.
Some little tricks about the plywood;
0- To be cheap is a sin. Take the best quality marine plywood: no voids, excellent gluing, good faces, regular bends.
1- Weight each sheet. The heavier ones are the more rigid, keep them for the bow zone.
2- Make a test of flexibility on each sheet. There are different simple methods.
3- Eliminate the too light or too flexible, or the too rigid sheets of the compounding of the hull, keep them for other works like bulkheads, pads, stern etc...
4- Pair them, so the bending will be identical on each side.
5- A steam generator for cleaning carpets or a simple steamer for taking out the wall paper make miracles if well used. Some use towels and boiling water.

 

Flo-mo your canoes are sweet, the last one on the grass is a beauty. I have a lot of questions about the plywood you have used; birch plywood? or what other? Finlandese? Russian?
I have read the thread on Wooden Boat. Very interesting, the maximal use of the plywood is astounding.
Canoes are very hard to fold as you have 2 bows, that create a lot of difficulties...A little suggestion about the rowing boat. Try some models with "open" sterns, not canoe sterns, you'll be surprised by the nice shapes you can get, which can be used with a sliding seat. Canoes do not like rowing, as the movements of the body of the rower make them balance on the longitudinal axis.

And yes DD it's a fascinating topic! About people taking designs without giving credit I prefer not to comment...my words would be too strong for the forum.

 

For the prove of concept build of my Gorewood 14 Canoe I used 3 mm Poplar plywood because that is the only 3 mm plywood I could get in my area.

Luckily the build was successful but the only plywood I recommend for this endeavor is 3 mm marine grade Okoume plywood.

Here is a lengthy documentation of the build for those who want to know more: https://plus.google.com/u/0/photos/110113600099233990156/albums/6028954635110595585

At least I am quite pleased with the result:

 

belle, beau, merci, thanks
I admire so much people who have patience to wait glue setting
well done indeed

 

Flo-mo, very nice indeed. Thanks for effort of taking all the pics of the link https://plus.google.com/u/0/photos/110113600099233990156/albums/6028954635110595585
A must to see for all interested in wooden construction and compounded plywood.
As you are in Vienna, I guess you employed a plywood coming from Italy where there are several manufacturers. What do you reproach to the poplar compared to okoumé ? Thanks in advance for your answer.

 

Interesting - it seems that the curved ply technique is mostly trying to save on materials then ?

I suppose a size nine shoe size seems insignificant to a size eight builder, but then designers who dont cater for realistic client sizes have plenty of competition out there who can supply a realistic design.

"only one builder has ever mentioned this to me" means that 20 other people have just bypassed the design because of its advertised limitation, based on marketing statistics.

 

There is nothing wrong with poplar compared to okoume as their characteristics are very similar. It is all about the quality of the plywood.

In Austria the plywood made from poplar is only used for interior application. So it is nearly impossible to purchase high quality exterior grade poplar plywood. Then again in Austria boat building is not popular at all so it is even more difficult to get marine grade okoume plywood in small quantities for an acceptable price.

So my only chance to get my prove of concept build done was to use the readily available 3 mm interior grade poplar plywood (thin face veneer, poor quality of face and core veneer, no waterproof glue) and hope for the best. It also means that it was mandatory to completely sheath the hull with glass no matter what.

In the end, with the exception of some minor problems, everything worked out fine (maybe it was just luck) but I think with top quality marine grade okoume plywood the build would have been easier.