Gator417 wrote: Plywood is anything but light though. Its probably the heaviest material one could possibly use in building a camper. Not to mention its not used, structurally, by any camper manufacturers.
Gator
Weight for weight it's as strong as steel and duralumin ... and it used to be used by RV manufacturers.... back when they could build a 24 foot 3000lb trailer, instead of 5000lb and have the cheek to call it a lightweight.
Was it said on this thread or another I was in recently "Think aircraft not tank" the saying went. Stressed skin, part of a composite, not huge slabs of 7/8ths (Edit: yah it was gunguy up there, derp, couldn't see it for the life of me when posting.)
There's some people building with foam, but unless you go real thick with the skin it is prone to dents and not many of them would let you jump on their roof, for larger than teardrop size you probably have to build with bulkheads and compartments, skin both sides.
But anyway, get an 8x4 sheet of your suggested alternative, put it in between two sawhorses longwise and stand in the middle of it, now what does it weight for same deflection doing same with 1/2" ply?
Edit: IF you're thinking that the frame is the strongest part and everything else just loads it down, you're misunderstanding your application of materials, if that were the case, then these houses should have stood up to 200mph winds without all that "baggage" because they were fully framed...
http://www.bramptonguardian.com/news-st ... struction/ but no, sheathing wasn't done. Frames just racked. Roof sheathing was there though and roofs landed fairly intact.