> What i had planed was a outter hull then take off mold and blow in
> fiberglas ribs and then a inter hull and put liquid sirofoam in between. i
> do understand that this boat will be very heavy estmaite around 16 tons
> would be avrage

Robert the way to produce the hull you are talking about would be to cover the mold in some sort of foam sheets these would then become part of your hull structure you could then blow your glass on the inside of the hull you cold also make foam or ply bulkheads and again blow your glass to them you will also need a strond keel and stringers.The outside of your hull will still be better layed by hand with matt and cloth as a chopper gun would leave a surface that would need a lot of fill to fair it. Concrete boats work well a number of boats have been commercially built here in NZ in the past and lasted the test of time . What about Steel ?