I’ve made at least a dozen XPS surfboards, heat is a problem, and adhesion to the foam is a problem. I’ve had several delam in the last 2 years, causing large bubbles. If you leave tiny pin holes in the glassing, it shouldn’t get air bubbles. As far as how the board feels in the water, XPS is somewhere between EPS and PU. XPS foam shapes easily and you can get a very nice finish, but leave it course.
I added this image of an older XPS I made then stripped to make another board. Even with the foam roughed up using a 60 grit sanding block, the glass peeled off so easily and clean. I used the stripped off glass for templates.
Wow, that’s impressive! Hard to imagine that it would come off so cleanly. Almost makes me think you would need to run a spiked roller over it all to make lots of holes before glassing!
I could only get 3" thick XPS and I shaped about 4 from a single sheet of 8’ x 24" x 3" XPS. On one of the boards I added a bit of nose rocker with this brick after I laminated the bottom. I really liked that board, but I don’t use it much now. A friend shot me riding it in 2015
The more small diameter holes the roller makes per square inch, the better.
The 7-row Wartenberg rollers (22 pins/wheel) I have make 44 perforations per square inch. Pinwheel diameter, pin-tip to pin-tip, is 1.125" (28.6 mm). Roller width is 1" (25.4 mm), pin-tip to pin-tip. Pin length is approx. 5-6 mm. Perforation hole diameter at the foam surface is approx. 1 mm. Space between perforation holes is approx. 4-5 mm.
This thread shows a XPS repair. The original glass peeled pretty easily. For the repair I manually stabbed a lot of holes. No delam yet, but no sun or hot cars.
Bufo (hydroflex) théorie was same, anchoring resin in blank like tree roots so lam stay stabilized by foam while it bend so it’s not buckle so easily. That’s how board break. They used stringerless blanks, came from windsurf world, initially they work with xps then move to pu and finally to eps. Worked well but not drastically better than other’s.
Everything that reduce skin buckling improve durability…