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Old 07-07-2009, 14:35   #1
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Gel Coat

I have a crack in my gel coat. I do not want to talk about what made the crack. Should I fix this crack by covering it with other gel coat? How does one do this? It is a very thin crack.
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Old 07-07-2009, 14:54   #2
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Unfortunately, in order to fix the crack one must have at least some idea of what caused it. I would repair a crack caused by me dropping something a lot differently than one that was a stress crack.

Anyway, a small cosmetic crack can be repaired with gelcoat but you'll need to match the color. I can give you long drawn out instructions on this but if it is just one small repair you are probably better off finding a repairman. It will be cheaper, if only in terms of material to hire it done. After all, do you need a quart of gelcoat, and the coloring agents?

A flat out stress crack will need to be ground down to the glass and any cracked glass also repaired otherwise the crack will come back. Once the glass is repaired, usually by a filling agent such as long fiber glass in epoxy, the gelcoat is then repaired as in the small ding.

For now, without knowing more, I'll opt for having someone else fix it. A simple fix does not take long.

Rich
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Old 07-07-2009, 18:14   #3
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I already have the gel coat and I think it is close enough in pigment that I think it will match. I caused the crack by driving into a dock okay? You got it out of me. Do I have to grind it all the way down or can I somehow inject it into the crack?
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Old 07-07-2009, 20:24   #4
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I used to work with gelcoat. Borrow/buy a dremel tool with a small steel grinder bit. Grind out the crack to the depth of the gelcoat, but no further. Sand lightly around the area. Tape. Mix the gelcoat with whatever thickener you use to make vaseline consistency. Add kicker. Mix thoroughly. Mix some more. Apply, leaving a little bit of a bulge. Let cure for longer than you think necessary, like maybe a day. Sand. Polish. If necessary, repeat. Goodluck.

Mainebristol SV Eider, B32
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Old 08-07-2009, 07:39   #5
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Mainebristol has the core of it.

A couple of points though. With gelcoat close enough isn't very when it comes to color match. Light colored gel will dry darker and dark colored gels will dry lighter. Plus the color will shift a bit after exposure to sunlight. So unless you want to go through the color matching routine, settle for the fact that the repair will sooner or later be visible.

He also left out a step. Most gelcoat will not cure, ever, if exposed to air. You will need to coat the repair with a liquid wax solution that, if memory serves, is known as PVA mold release. This blocks air and lets the gelcoat cure properly.

Finally, the sanding process is done using wet sanding and progressing down from 320 grit, 400,500 and 600 grit before buffing.

By the by, Bennet Marine Video have a 3 DVD set on cosmetic gelcoat repair that I used to learn how to do my own repairs. You only really need the first two of the set because the third just rehashes what's in them.

Hope this helps,

Rich
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Old 08-07-2009, 08:29   #6
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if you can't find pva or it is to expensive you can put a piece of cellophane/food rap over the patch. if you do this right it will leave a gloss finish to the patch, which if you leave at about the height of the tape off area you may not have to sand and buff/polish to get to same level as orig. gelcoat. i've done this on my own boat with with good results
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Old 08-07-2009, 10:23   #7
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Actually, there are air-cure glecoats now available which do not require coating in plastic. Furthermore, since it is only a small area, there are white color-match kits that come with a small amount of air-dry gelcoat, pigment and a color chart with precise instructions for getting the shade of white that matches your boat. Make sure that you properly buff and wax the area that you are using for your colour match.

I concur with the recommendation for use of a dremel tool to make a 'V' shape in the crack before applying the gelcoat. I wouldn't worry about sanding the surrounding area (so long as it is wax free) before applying the gelcoat - you will end up sanding the surrounding area in order to finish it and you will likely only want the new gelcoat to remain in the repaired and not the surrounding area.

Brad
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