Quote:
Originally Posted by Brian B-P
Some manufacturers do use cored composites for floors, as well as for wall and ceilings. Most don't, because it is more expensive (in materials and labour) than using plywood.
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The foam is cheaper. However, in order to obtain equal strength you would need specific engineering to determine the exact layup requirements for a foam core floor.
Foam coring also creates it's own issues. Foam is actually more susceptible to water intrusion than marine grade plywood. When penetrating foam cored fiberglass you need to drill over sized holes through at least on side and the foam. Fill the void with epoxy and then drill your actual sized hole through the epoxy core to ensure the edges of the foam are sealed.
So, IMO the extra cost of a foam cored floor would not be in the floor itself, but, in the extra labor required every time you need to penetrate it.
I've owned a foam cored Corsair F24 Mk II for many many years. Prior to his death in 2017 the designer Ian Farrier sold plans to self-build his designs. He had online courses in fiberglass foam core construction which I completed.