UncleG,
I shape the XPS with a surform and 60 grit. I final sand to 100 grit. I then vacuum foam dust off surface. Then I use a modified TopFlite Woodpecker Tool (doubled the number of tynes). I perforate the shaped foam with the WP tool. I pre-seal with a thin layer of epoxy. Then sand to 150 grit. I laminate using epoxy with opaque white pigment (to reflect solar heat). I don’t use less than 1.55 pcf XPS. Saving my higher density XPS for when I have my new designs well dialed in.
The perforations the WP tool makes are linear. So I have started playing with the orientation of the slits relative to the long axis of the board.
Next board, I will pre-seal using epoxy with opaque white pigment and vac bag the pre-seal into the perforations. Tried 45 degree orientation last. Will try 90 degree next (should help minimize parallel surface movements of the glass skins). Will also laminate using epoxy with opaque white pigment.
Pretty sure I have it mostly dialed in now. But XPS does get soft in high heat.
I still have a few tweaks I can try to further imrove bonding/prevent heat delams (one would be using white EVA foam on the deck).
But the number one of advantage of XPS is it does not soak up water – 100% closed cell (does not breath).
Top tool in picture below has 8 rows of tynes (modified). Bottom tool only has 4 rows of tynes (stock).
Bill
