Tortured plywood designs

My own design being built to 1/2 scale

My own design that is shown in first post.
Regards
Craig

 

This Time

Had wrong photo format.
Craig

 

Nice design, but it doesn't look like tortured plywood

 

No as mentioned it is flexi ply as that was being discussed when I chipped in, sorry will butt out now.
Craig

 

There is a bit of confusion in this thread...I have some experience in compounded (or tortured I do not like this word) plywood as I have made 5 "18 feet" catamarans with this method. The last one was a 18 sq.meter mono rig weighting only 89 kg (196 pounds), with a width of 3.20 meters and a mast of 10 meters...

Wood has a very special way to answer to compression stresses; the cellulose cells will deform but not collapse and with some precautions won't break in tension. And it's this is the quality that's used in compounded plywood.

You'll obtain shapes of double bends without wrinkles as the excess material in the compression side will gently "shrink". After you stabilise the wood with epoxy (epoxy is not specially dangerous, vinylester is far more dangerous because of the solvent styrene).
Steam, hot water and isopropyl alcohol can help to convince the plywood to bend...

Foam is useless for that as it has not the "good" behaviour in compression and it's too weak in traction.

Compounded plywood is when you "form" the WHOLE boat from 2 panels (example the Tornado catamaran). That makes very good cats and tris, and a few monohulls.

There are limitations; thin high prismatic coefficient hulls, light displacement and a major drawback for some relying on the computer magics: none software to help you. With 6 or 6.5 mm max practical thickness you'll be limited to about 35 feet boats. But the shapes obtained are amazingly varied.

In fact the lone way of design is to make 1/12 models with birch aircraft plywood of 0.8, 1 and 1.2 mm corresponding to 3, 5 and 6 mm okoume plywood. And experience.

It's eyeball boat building with just a few drawings to guide you.

There are 2 main variations at my knowledge making a complete hull from 2 side panels:

Stressform of the Gougeon Bros (the 6 mm plywood is coated with epoxy with a 120 to 200 grams/ sq. meter glass cloth OUTSIDE) so you can get more bending without breaking the plywood in tension.

Cylinder mold which uses pre-formed panel of 6 to 9 mm to get rounder hulls. Hughes has designs until 60 feet for a motor trimaran, and 40 feet in cats. The pics shown in the post #44 are a variation of cylinder mold. Very nice pics and boat.

After you have a variation with a bottom (grossly the water underside) made of glass, strip plank or whatever, and 2 plywood topsides that are bent to shape into a female jig. The possible weak points are the joints between the bottom and the topsides.

All these are a very good method as multihulls imply a lot of surfaces. And you get it fair and smooth, with very litle sanding. A true life saver.

Happy new year.