So the girlfriend scraped her 7’0" single fin on some rocks at low tide. The “encounter” put a small pressure ding on the bottom, with cracks and scrapes surrounding the impact site. Board is glassed heavy, with gloss and polish. The interesting (and troublesome) thing that is now happening is that as she rides the board more, a small crack is spreading from the ding, across the bottom of her board to the stringer.
I scolded her, and the board is now out of the water, waiting for my caring hands to bring it back to health.
Any suggestions how to fix? I’ll sand it all down, and cover the original ding with a new piece of cloth, add gloss coat and polish, but what about this extending crack line? What causes it and how should I deal with it?
Gloss resin is more brittle than sanding resin (hotcoat resin) so it will give better results when fine sanding and polishing, but it does not flex as well. It tends to crack easier on impact or extreme flexing (before flexing far enough to begin buckling).
It should be fixed as well, and the best way to fix it is to sand it down to the cloth to get the crack all the way out, then re-gloss or patch it if you sanded into the cloth very much. (It’s usually best to patch it.)
I’m guessing it would probably stop it from spreading, but with some good sander control and a keen eye, you can remove the crack completely.
I probably didn’t explain it very well in my previous post, but the idea is to sand out the crack completely by sanding all the way down to the cloth where the crack is. Then patch (add cloth) over where the crack was to replace the cloth you ground out getting to the bottom of the crack. You also want to sand a narrow width path over the crack. You don’t want to sand a wide area when removing cracks like this, and be very careful. On thin glass such as what would be on the bottom of a board, it is very easy to sand to far into the cloth and build up enough heat from sanding to make the remaining glass blister up. Take your time and use your best eye, and let the area cool down ocassionally while sanding.