David Watkins of Parrish, Florida, asks:
“I have a 15-year-old fiberglass boat that I bought new. It has spent most of its life either in Florida or the Caribbean and has suffered severe exposure to the sun. There is surface crazing or cracking on the deck, coach roof, and upper topsides. These are not stress cracks, but they are widespread. Do you have some thoughts on what I might do to refinish these surfaces?”
Don Casey replies:
The crazing you see is normally caused by the expansion and contraction of the gelcoat, and the tropical sun can be a contributing factor. This takes place because the surface gelcoat is relatively brittle compared to the underlying laminate, which is strongly reinforced with glass fibers. While manufacturers try to hit a happy medium, the thickness of the gelcoat is the determining factor here and this is mainly determined by the skill of the worker spraying it into the mold.
A little preparation and paint can restore faded glory. As long as the condition is caused by crazing, not flexing, the standard cure is to apply two coats of a high-build epoxy primer and sand between coats. The epoxy paint is designed to be thin enough to penetrate the cracks but adhesive enough to serve as a filler. After the primer has been sanded to a smooth surface, apply a two-part polyurethane paint. When this paint is applied properly the results can be spectacular. In your part of the world the finish should remain glossy for at least five years.