Thread: what is the right way to fix stress cracks in fiberglass

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I certainly wouldn't throw it away! :-) I have saved bodies that were totally covered with stress cracks. You need to not only repair the cracks, but add more stiffness.

I would do both things you have described. First I would see if I could do anything in that area to reduce the flexing, by addind a brace or something.

To repair the outer body, grind it back to glass and use a heavy grit, like 36 or 40. Rough the surface well, and make sure you have gone through any gel coat, and be sure to exposed the fibers in the glass. Work resin into the cracks, then lay up two layers of fiberglass "matting" over the damaged area. After it cures, put a few thin layers of plastic filler over the glass. This will make it cure completely, then block sand it flat, and primer heavily with catalyzed urethane.

On the inside,...to stiffen the area... I would repeat the process, but use two layers of fiberglass "cloth", and don't worry about the filler. It will cure with time.