Repairing Crack In Fiberglass

Rob C.

Rob C.

Member
My Sunfish has a small vertical crack in the laminate running about 2" up from the chine on one side where it bumped something that knocked some gelcoat off. There is no hole through the hull, but there is some delamination right at that spot. I stuck a small digital camera into the inspection port just ahead of the cockpit, and reached around the foam block and snapped a picture and it is obvious that some water has been seeping in around that crack.

Is it possible to grind this down and repair it from the outside or do I need to saw a hole in the deck to get to the back side of it and put a patch on the inside of the hull? The damage is just forward of the drain plug at the chine. I really don't want to saw a hole in the boat and install an inspection plate there.
 
It's probably better to grind it out from the outside. The repair is time consuming, but easier than it sounds. The delamination is likely to be more extensive than the crack. I had a similar crack that I fixed last year. It turned out to have almost 4 inches of delaminated fiberglass beneath the one inch gelcoat crack. I'd recommend using fiberglass mat instead of MarineTex if the hole caused by grinding out the delaminated area is bigger than about an inch or so. It will make a stronger, more permanent repair.
 
Geophizz said:
It's probably better to grind it out from the outside. The repair is time consuming, but easier than it sounds. The delamination is likely to be more extensive than the crack. I had a similar crack that I fixed last year. It turned out to have almost 4 inches of delaminated fiberglass beneath the one inch gelcoat crack. I'd recommend using fiberglass mat instead of MarineTex if the hole caused by grinding out the delaminated area is bigger than about an inch or so. It will make a stronger, more permanent repair.
Click to expand...


I watched this video and this is how I patched it with the exception of the formica because I just had a crack not a huge hole like this. I used the West Systems fairing compound instead of bondo because it came in the kit I bought at West Marine.

 
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