A buddies board got dropped and chipped the tip of his fin. It’s a Rainbow fiberglass fin. The fin chipped and delamed a bit in the area of impact. I cut out the delamintated fibers and sanded smooth transitions with course grit sandpaper. I used some SunCure, let it cure and was going to sand it smooth to the fin profile, but the SunCure didn’t bond well to the fin - just peeled up while I was sanding.
Does anyone have a recommendation how to repair this fin?
Hard to say what the problem is, all I can say is I wouldn’t clean it with anything, just sand it again real good with a coarse grit like 80, then use a small patch or patches of fiberglass when you repair it, and use some new resin. Leave it oversize, and sand to shape.
Kinda sounds like you should have left the delaminated fibers so the resin had a little more to hang on to, then cleaned them up after the repair.
You probably need to sand the area where the sun cure will bond. Did you do that? Scuff it up a bit, apply resin, let it cure, sand it all up nice and smooth.
If you don’t want to lay cloth, an easy fix is to add thicksil thickening agent. This adds enough strength and thickens up the resin enough to where you could put it on a vertical surface and it won’t sag. Then all you have to do is blend it to the fin…easy.
An easy and full proof solution is to just re-foil the tip of the fin. You will lose a little surface area but it will be fixed no problem. Of course you’ll want to re-foil the other fins to match.