GEL COAT CRAZINGS & SCRATCHES - Most cracks found on fiberglass boats are gel coat cracks commonly known
as crazing. They can appear as a single line, a series of parallel lines, or a spider web originating at
the center of an impact. It is caused by an impact or stress with enough force to crack the surface, but
not the glass beneath. The gel coat forming the finish surface is pigmented resin about 15 thousands thick.
Since there is no glass reinforcement in this surface, it is more susceptible to crazing than the fiberglass
under it. It is not necessary to repair crazing, except for appearance. To make a repair, the cracked gel
coat is ground away down to the fiberglass and filled with gel coat which is then sanded flush and polished.
In the case of multiple crazing it may be easier to grind off the gel coat in the entire crazed area and
re-spray a new layer of gel coat. The area is then sanded flush and polished. Scratches and gouges can
also be repaired with gel coat by filling the area, sanding flush, and polishing.
FIBERGLASS CRACKS ~W If the fiberglass under the gel coat is cracked, the gel coat will have a wide separation as opposed to a hairline crack. The gel coat should be ground off with sandpaper to expose the fiberglass. If the fiberglass appears dark, it is sound. Any glass that appears white is damaged and must be removed. The depression or hole is filled with new fiberglass and gel coated. This should be done by an experienced repair shop.
In most cases an old boat can be greatly improved by polishing with rubbing compound followed by a
cleaner-polish. Resurfacing an old boat with gel coat or paint is not recommended. Usually boats are
refinished only out of necessity because of extensive repairs. To spray gel coat, the entire boat
must be sanded to provide a rough surface which is necessary for good adhesion. Since gel coat is a
very thick material and will not spray as smooth as paint, it must be sanded after it cures, starting
with a medium grade paper and progressing to a very fine paper and then polished. The thickness is
critical, since it must be thick enough not to sand through yet not so thick that cracking will develop.
Refinishing an entire boat with gel coat would have to be done by the owner as a labor of love with no
value assigned to his time. Otherwise the labor costs could exceed the cost of building a new hull.
Painting with epoxy or urethane marine finishes is more desirable since the finish will not require sanding or polishing after being sprayed. The entire boat will still require sanding and masking before painting. The main disadvantage is the shabby appearance when the boat is scratched, exposing the original gel coat color underneath.