Fixing Chips and Cracks - SailNet Community
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Fixing Chips and Cracks

I bought an old Bristol 24 and the topsides are in need of some fiberglass and paintwork. I have asked people around the marina regarding the process and the best products and I've gotten even more confused. Everybody offers different advice. The topside has some minor spider cracks and nicks that need to be repaired. Can you give me some step-by-step advice on how to resolve this situation?

Sue & Larry respond:
The process for fixing spider cracks (sometimes called crazing) in gelcoat is simple, particularly since you plan to paint the surface. It sounds awful, but small cracks have to be opened and made into large cracks before they can be properly repaired. Use a v-shaped scraper, or a punch-style can opener to accomplish this. We also like to drill a small beveled hole at the ends of each crack to discourage it from traveling further in the future. 

Next, using a plastic spreader, apply a catalyzed epoxy resin that has been thickened to a peanut-butter consistency. Use a low-density filler like micro-balloons as your thickener because it will be easy to sand to a smooth finish. The first coat will shrink when cured so it will be necessary to come back, sand, and reapply a second coat to get a truly smooth result. After you've sanded your second coat smooth, you may be ready for painting if your technique has been good.

Nicks are treated in a similar manner to spider cracks. They also need to be enlarged and have the edges beveled for the repair material to properly adhere. We like using a Dremel tool with a cone shaped bit for this purpose. At least two passes, maybe more will be needed to smoothly fill deeper nicks.

Once both spider cracks and nicks have been filled, you'll want to get on with sanding the entire hull before applying paint. We use a long fairing board to get consistent sanding results over a large area. The best paint for do-it-yourselfer's is a one-part polyurethane paint. This type of finish can be easily applied using the roll and tip method (roll it on and immediately tip it out with a fine brush).
A great technical booklet called "Fiberglass Boat Repair & Maintenance" is available from Gougeon Brothers Inc., makers of West System Epoxy (, or have a look at some of the articles that Don Casey has written on the subject here at SailNet. You can start with Repairing Gelcoat Cracks and Chips.

Just a note about your spider cracks. In gelcoat, they are a result of either flexing or an impact.  If the cracks are a result of flexing, they may reappear in the future. Good luck with your project.

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