Hair Line Cracks in Gelcoat

[mobydick]

I have a Catamaran built in South Africa, only two years old, which has developed a few hair line cracks in the gelcoat.
The cracks are not in areas of stress and are only on the deck.
Do you think there is any danger of these getting worse? and what if anything needs to be done to repair them?
Any advice would be greatly appreciated.

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[ccscott49]

A watching brief for now I would say. If they get any worse, it would be a good idea to rout them out with a dremel tool, then re-fill with gelcoat and smooth and polish off.

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[Avocet]

I have the same problem but all over the upper areas of my topsides (again not stress-related). OK, my boat's 30 years old but I'm beginning to think it's an ultraviolet light attack problem. As I go round the turn of the bilge and get out of the light, my topsides look fine. I think it would be worth you monitoring the situation. If it is UV attack, maybe some sort of car polish with UV protection would be useful. Again, if it is UV damage, it should steadily get worse with time.

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[Close hauled]

My mate Dennis, who knows a thing or two about fibreglass, says that thet should be opened up with a dremel tool and filled. There was a good article in PBO about it a few months ago. I've got the same problem on a bit of the cockpit molding.

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[nicho]

A couple of years ago, my marina neighbour had a fair bit of this hairline cracking in a new Beneteau. They told him it was quite normal and not to worry about it. It did not seem to get worse, so he lived with it until the boat was sold. Presumably the purchasers surveyor did not seem to be concerned about it either, because it passed his inspection OK.

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[quaelgeist2]

According to GRP / Gelcoat experts, there are three different issues to distinguish: Cracks from
1) One-off load on the construction where the gelcoat could not stand the bending, compression, etc. forced on -> open and fill with gelcoat repair DONE
2) Constructive movements of the hull, e.g. rigg or wave induced -> whatever you do to the gelcoat, the cacks will return -> A good solution involves strengtheneing the whole construction. An indication for this case are "growing cracks"
3) Poor workmanship in the yard can lead to effects of 1) and occasionally even 2) (I believe to have a boat with THAT!). Not much you can do, but opening and then repairing with gelcoat is likely to cure it once and for all (if you have waited long enough...

good luck

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