Wooden boat plans conversion

Hi everyone, I need some help with some structural enginering. I have plans for a 20 ft boat with an inboard motor in it. The plans show a cold moulded ply design over wooden frames, but I want to use foam and glass sandwhich, as I have some 600 gram double bias e-glass. I was going to use 15 mm foam with one layer of glass on the inside and two layers of glass on the outside. I would use timber for the keelson, chine and gunwhale, plywood over a few frames for the deck, and I would also need some girders I suppose. Do you think that this would be strong enough. Any help with this would be appreciated. Also if you could tell me how many girders or stringers I would need.

[mmd]

You are basically asking for a re-design of the boat, which is not a small task. Purchase Dave Gerr's book "The Elements of Boat Strength" to discover both the answers you need and the amount of effort it takes to arrive at them.