dancam wrote:... Glued with tb2 or tb3 thinned down a little for more work time...
Unless you are in an especially hot and arid location and your glue application ends up as tacky as it would in a more standard environment before joining the components, for a wood to foam joint I would strongly advise against dilution. Any extra glue or moisture you add will have to be absorbed by the wood in order for the glue to set. For panels, in my experience this worked best with straight TB2 and a very thin rolled on application.
IIRC I shut off the fan (area fan that I use to keep myself cool) and just worked quickly to roll out the glue.
I did a built up floor using 5mm (3/16 inch) top and bottom plies and 1-1/2 XPS. Probably had too many xmbrs, but they were cedar, so a bit lighter than other species. I figured that it ended up about the same weight as 3/4 ply, but was insulated and much more rigid. At about 9'-8" x 64" when I picked up one corner it only lifted about 1/4 inch before only the far diagonal corner was the only thing touching. That's pretty rigid compared to 3/4 ply, even cabinet grade birch ply.
Re: the idea of using multiple types of insulation with garden mats filled with GS, etc. the best advice I can offer is don't bother. Building a camper is a big enough project as it is. Whatever your plans, whether the simplest of simple, or the most challenging build ever, it will be more work in the end than you expected it to be in the beginning. Every time complication is added it takes more effort (time) and material (cost and weight) than if a simpler method or material is chosen. There is more wasted material, more errors to correct and, when dealing with the unknown, more experimentation needed (more time and materials). This is not always a bad thing. The journey can be the destination, but there is plenty of room for creativity as it is and it is a long enough journey that the "onion" only needs so many layers. How much better insulated/lighter/dryer could it possibly be, and is it worth it? Spend the time and money on better quality materials, design/planning, accessory upgrades, artistic creativity, and fit and finish.
Don't get me wrong, I love TPCE and the journey that it has taken me on; but sometimes when you are doing something that started out as "cutting edge" you get to a point where you are wondering if other options would have been less tedious and you just wish you were done already. Of course, YMMV.