Hi Yorky,
yep, Cleg and Mick would be old-school on epoxy, for sure…that is, they might have tried it and canned it as too hard a long time ago.
If you are doing EPS as opposed to composite/vac bagged skins, you want to seal your shaped blank, or else it will wind up airy. There will be endless input on the various merits of spackle techniques in the archives.
Also, theres no need to squeeze your resin overly hard to get a light lam…Epoxy does’nt have the fume-off factor of styrene based polyester, so what you mix in the pot all goes on the board, rather than 30-40% wafting off into space. This means you literally use less resin, and epoxy itself weighs less.
SP is one of the older systems which turned loads of crew off epoxy 20 odd years ago. In short, it was evil.
Unless they have changed the formula, and I apologise to any Gurit industry lurkers if this is the case, the stuff does’nt rate for surfboards. The metho- (Aust. for denatured Alchohol) rubbing thing has been surpassed as a necessity in recent resins that don’t do whats called “Amine Blush”. This is a greasy film that rises, much like wax in styrene does in a filler coat of Polyester. It needed to be removed, or you next lam layer, filler coat or laps will fall off. In the past, this meant scrubbing off with metho, which meant dirty laps.
I can recommend two Aussie made epoxies you should be able to find…ATL’s surfboard formula and Botecote with UV additive in the hardener.
All thats required with these for your laps and filler coats to adhere properly is a light scuff of the lam weave with 240 on a soft pad, or scotchbrite on an orbital.
Crew will stock all sorts of imported resins…avoid Nuplex and West-system, they fall into the same category as SP. If unsure, sniff the hardener…If it is piss-yellow and stinks like a slaughterhouse, its wrong.
BTW - add a capfull of normal wax in styrene for your filler coats.
Josh