Plywood Thickness for Cold Molded Bottom

[chuckt]

I am replacing my bottom (well, the boat bottom--my personal bottom needs some work too but that's another issue). I have settled on a cold molded method using Okoume plywood. Oh, the boat is a 30' Chris Craft Express 1950. The orginal thickness of the double planked bottom is 7/8 inch. I was thinking two 3/8 inch layers or maybe three 1/4 inch layers. I am wondering if the 3/8 is too thick to bend to the curves--particularly near the bow. I Know Don Danenburg says in his book to use 1/4 inch plywood as his inner layer on boats greater that 20 ft. Yes, I know he doesn't cold mold but his first layer is plywood. Obviously, less layers means less work and less cost but that's not determinitive--I just dont want to waste effort or $$ for no reason.


.http://i571.photobucket.com/albums/ss151/cmeke0870/Transport/IMG00006-20091107-0757.jpg

[P.L.Lenihan]

Three laminates will be stronger than two. 3/8" ply will take the bend up forward. If things feel a bit stiff, go with narrower panels or lay the panels differently.That is;more parallel to the keel instead of 45 degrees to the centerline. Test with small sample of ply to determine max radius it will take.

Peter

[rbgarr]

IIRC this 26' boat had two layers of 3/8" plywood put on the bottom. The sections were designed, or 'developed' for it, which means that the plywood only has to bend in one direction to fit. The panels don't have to cup or bulge as well as bend. Plywood really doesn't do that well (if it can be made to at all) and strains the structure, fastenings and glue joints when forced to.


http://i48.tinypic.com/2qu4qxe.jpg
http://www.dhylanboats.com/