Please show me your math grob... Based on Johns cad drawing posted on the other thread, which everyone seem to like for the most part… the 12'-0" F12 you would need 4 Pieces 12-1/2"X 8'-0" for the decks 8 Pieces 14” X 8’-0” for the hull sides 8 Pieces 7-1/2” X 8’-0” for the bottom panels. 2 Pieces 12-1/2” X 8’-0” for two bulkheads per hull and the transoms.
Now lets just forget about the fact that all these pieces have to be cut in one piece from a 4’ wide piece of plywood for now…which is a huge issue…lets just add all the pieces together 4 X 12-1/2” =50 inches 8 X 14” =112 inches 8 X 7-1/2” =60 inches 2 X 12-1/2” = 25 inches 247 inches Divided by 48” = 5.14sheets 49-7/32” =5.02 sheets Even giving you the fact that you will save material by nesting the parts, you will need most of that just to get the boat cut out of five sheets.
Some are saying we will keep it 12’ so there is only one joint between the 8’ panel and the four foot panel…did you forget about the 7X the thickness for the scarf joint? Lost another 13/16, and another 1/8” for the saw cut when you cut the panel in half to get the 4’ long pieces…and then there is the curve in the bottom and the sides, both of which will shorten the overall length, the most drastic curve will dictate the length of the boat…so now we are a couple of inches shy of 12’…oh but we can go thru the trouble to scarf the plywood again to add that couple of inches back on, but it was too much trouble to scarf 10” ….
I will say if you are using metric plywood the length will not be an issue, since it is slightly longer at 49-7/32” X 8’-2”. For those of us in the US, going to Home Depot for common exterior plywood (not recomended), you will definitely run into this problem.
If one would step back and look at the benefits objectively, they would be hard pressed to come to any conclusion other than to go for the increased length.
