You know , that cardboard (chipboard) is interesting stuff... It sticks to foam like a magnet with TB2, and actually dries inside fairly quick on large surfaces ... And after that is easily waterproofed ... We’ve seen this material used inside cars and trucks for as long as I can remember... Lots easier to work than wood ... certainly thriftier, and seems to be stronger than the wood , the random direction fibers giving more overall strength than the wood which splits and runs with the grain. Which would also tend to localize any “damage” should that happen ...
Curiously , it’s about the same weight as wood , not really a surprise , because it’s made out of wood eh ...
No weight savings there , other than the fact that being a bit stronger, you can use a thinner cardboard. Used in the RIGHT place, for the Right job , this can be a great trailer building material ...
I still imagine Foam , with a thin chipboard skin outside (inside too), then covered over with a light canvas would be Solid like a "Tank” and have a nice smooth finish too ... !!!
Ps. We’re still searching for a supplier of 4’X8’ chipboard... I’ve seen it in the past ... I know somebody makes it ... That would be really NICE !!!