Stress cracks are caused by movement or flex fiberglass will tolerate some flex but the gel is hard and brittle it will crack. Some boats have thin fiberglass on the upper deck there may not be anything you can do to prevent stress cracks. Here is what I did on my 89 Supra Sunsport.
Chamfer the holes so the stress is on the fiberglass not the gel cote. Reinforce as much as possible under the deck where the tower legs attach.
I used 3/4'' plywood covered with fiberglass and then epoxied them to the under deck. I also made larger aluminum backers out of 1/4'' thick material.
Its been 4 years and no cracks.
I chamfered thr holes using a countersink bit you can see the different colors of gel used on the top deck
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum You cannot attach files in this forum You cannot download files in this forum