i dont think you should use wood at all....

make the hull from insulation foam, then fiberglass over it...but when you fiberglass, use epoxy resin, not the polyester resin, that stuff eats foam...

foam is easier to work with as you make the hull from a solid block, its lighter, and it floats already, no need to worry about flotation....

maybe the only peice of wood you might want to use is where the motor mount will be, just to have a solid base to attach it to..