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Old 05-02-2013, 13:19   #1
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Just baught a Gemini 30ft - the top decks are full of spider cracks in the gelcoat - is this a common problem on older (1989) hulls due to the thickness of the geelcoat?

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Old 05-02-2013, 13:22   #2
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Yes. Get used to it. Not a huge issue other than cosmetics. It will never go away

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Old 05-02-2013, 13:27   #3
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Gelcoat cracks result from stresses placed on the plastic. They can be caused by dropping a winch handle or anchor on the deck, from heat and cold causing expansion and contraction, or internal movement below the gelcoat (pretty rare). Over time, they get bigger and dirt settles inside, making them more visible. When it gets to the point that it really bugs you, you can always do some stuff to it, but it's a pain, so many folks just live with it. If it was impact or heat/cold, you can always do some gelcoat repairs which involves matching the color, as best you can, and a bunch of sanding, etc. If the cracks are pervasive, you can also opt to paint the hull/cabin with linear polyurethane paint, a two part product that is very time-consuming and costly to apply correctly.
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Old 05-02-2013, 14:06   #4
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Old 05-02-2013, 14:44   #5
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If there are many cracks, I would expect core decay. The issue may be cosmetic but the actual damage may be under the outer laminate skin and will require a pretty advanced repair.

Is it a cored deck/panel?

If the panel is not cored, then it may be not sufficiently supported by internal structures - the laminate bends under stress and the gelcoat cracks.

If the core is done then you will hear the deck making bad noises when you are down below and your crew are walking over the affected panel.

A spider crack may be opened with a dremmel tool and filled with gelcoat. There is also something called the creeping crack cure but I have not used this stuff yet.

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Old 05-02-2013, 15:32   #6
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This is a problem ALL Geminis have, don't worry about it, it isn't structural.

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