filling surface cracks

T

thebeingwithin

New Member
I just purchased a '73 Dolphin (much like a sunfish). It's in really good condition save some surface cracks in the fiberglass. If there were just one or two, I’d scrape them out and gel coat them. However there are quite a few. When I say surface cracks I mean very shallow hairline cracks. Some of them are so thin and shallow you can barely feel them as you run your finger across.

My question is thus; would a good paint seal, cover and keep the cracks from spreading? Or is there a better way to fill them than doing them one at a time?

Thanks
 
I think what you are describing is the spider web cracking classic with aging gelcoat. The thing to look out for is cracks forming concentric rings. That pattern is a symptomatic of an impact and could indicate underlying glass fiber damage. Random crazing occurs with years of exposure as the plasticizers leech away and the gelcoat layer contracts. Prevention of further spreading is accomplished with rejuvenating compounds sealed by UV resistant coatings, the sorts of chemicals and treatments gelcoat restoration kits are made up of.

To repair one of two approaches are followed depending on severity. For shallow surface cracking rubout or wet sand as best possible then UV protect and call it good – the restoration kit approach. Deeper cracks extending down to the fiberglass layer require sanding to base level and either painting or re-gelcoating. Reading the gelcoat guides and from my own experience, consensus is simply painting over cracks doesn’t last long. Paint won’t flow down into the gaps it only bridges them so they reappear in a couple of years. To get a long lasting paint job the gelcoat needs to first be sanded down enough to reach the base of the cracking. Then a good fairing primer topped by a quality paint has the best chance to last many years.
 
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