Cuppa wrote:Certainly no advice from me.... just a question.
Given that you have the accuracy of the CNC router & the design advantages this offers ..... why are you choosing to build using timber(lumber) rather than a lighter waterproof material like polyurethane foam fibreglass sandwich? Design can mean that no fasteners at all are required, the whole thing is glued together...
Hi Cuppa, I'm glad you asked that question, because I can get up on the soapbox for a minute or two.
Well, a couple of reasons... First of all, the idea never occurred to me.

I honestly haven't done any research into Foamie construction. Second, I wanted to go with what I know, and stick to more or less traditional construction (kinda the same as reason 1). My goal was to have a wall that weighs less than plain old 3/4 ply, has insulation for the cabin, and that provides machined surfaces for attaching bulkheads, etc.
I'm using lumber for the framing because (no offense intended to those who've done it.) every time I see someone screwing into the edges of plywood, my inner woodworker cringes, because this is very likely to split the laminations. Screwing into the edge of a board is OK because there is no possibility of delaminating natural wood. Final assembly will be by glue-and-screw for strength. I wanted the strongest possible joints since I do some moderate offroading from time to time. Screws will be going through plywood faces into the lumber. The proper way to do it IMHO.
I took a quick look at your friend's build, and I will be going back to take a closer look. It is an interesting concept that might fit in with my next build. (There's always a next build, isn't there?)
Anyway, thanks for a good thought-provoking question.