Has anyone considered building with no structural wood...not even in the floor? Items like windows and doors could easily be made to have a frame (possibly wood) that sandwiches the edges of the opening in the foam wall. (It would be like the way a drain is screwed into a hole in the bottom of a sink but it is really just screwed into it's other half and some putty is used to keep the water from leaking.) I think it could be done, but the only engineering question I have not figured out would be how to attach a hatch.
Could a floor be strong enough with just foam, cloth, and glue? Maybe additional strips of foam/cloth/glue (fcg?) reinforcement would be enough. I would probably want a layer of thin wood placed (not attached) on top just to spread the load of a knee (or a leg on a dutch oven) and make it easier to sweep clean. Would a drop floor in all foam actually be stronger due to the box shape? How much could it overhang the trailer frame? How would it attach to the frame? Would a sleeve over the bolt be enough to keep the bolt from compressing the foam? If so, would a huge washer on the top and bottom be enough to spread the load? How do people handle the bolt heads that hold the HF trailer together when they add a floor on top. Do they drill recesses when they use plywood so the board lays directly on the frame or do they let it sit on top of all the bolt heads leaving an air gap? I would guess with an all foam floor it would support better with recesses for the bolt heads.
Has anyone made a foamie and then covered it with aluminum? If you did, and you used no wood whatsoever, how would you attach the edge trim? If the windows were made as mentioned above, the aluminum could be floated and clamped under the window and door trim along with the wall, but that does not help with the outer edges.
I have been really slow with my build. I have finally finished the HF frame assembly and it has only been 16 months since I purchased it. (Although when I purchased it I had absolutely no room in the garage to assemble it. Thanks to Craigslist, I have enough room and cash to do the build. My trash is someone else's treasure..) It has an extended tongue, the frame is assembled as a 4x10, and it has shocks installed. It is way overkill if I change my mind and make a foamie on my 1700 lb HF frame. My TV was traded in last Summer so I need to get a hitch installed on another vehicle. Life gets in the way of life sometimes.