Tonto wrote:My reason for canvas is that I am not sure the 1/8" PVC and 2" thick foam will bond securely. Without a strong bond similar to PMF, the structural strength of the side and top is reduced. (Note: I am not an engineer, however.) I was even planning to frame the 4' x 8' foam panels in 1" x 2" wood to add to rigidity and create attachment points for the PVC to the wood (with screws?). If anyone knows of adhesive or glue that will create a strong bond between foam and PVC without damaging either, I am all ears.
If you are not sure that you can achieve a good bond between the PVC and XPS, make some test panels. The strength in a composite panel depends on the glue joint between the skins and the core, otherwise you are just flexing two thin membranes and a weak core independently. Adding canvas won't do much if the PVC is not bonded to the core. Furthermore, if you have issues bonding PVC to XPS, you will likely have similar issues bonding PVC to canvas.
I have used HH-66 cement to glue vinyl to vinyl with great success, but have no clue whether it would work with foam. Aside from bonding issues with PVC it has a poor strength-to-weight ratio. I think it is about 2x heavier than hardwood plywood for the same thickness with a 2-3 times lower modulus in the in-plane directions. Neither can compete with fiber glass for strength-to-weight ratio.
Noseoil built his floor out of 3mm Baltic birch with wood framing and foam (
https://www.tnttt.com/viewtopic.php?f=50&t=60248&start=15#p1093220. I've read through other build journals where 3mm BB was used for the bottom, and thicker plywood on top.