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Old 07-11-2014, 09:02 PM   #1

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Default Polyester Gelcoat Repair Question

Hey guys,
So I pulled 3 molds off today and found that 2 of them had small holes a little larger than a pinhole in them. I used up all my polyester tooling gelcoat and rather not buy more since they only sell it by the pint,quart,and gallon down here to fix small holes. Since its polyester tooling gelcoat, could I use polyester resin to fill the holes and sand it? Have an extra quart of of marine polyester laminating resin.

Thanks in advance
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Old 07-11-2014, 10:42 PM   #2

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You can, it just won't be as durable as the rest of the surface. And polyester doesn't bond well, even to itself, so there's a possibility the repair delaminates when you pull a part. But I've done it a couple of times and never had an issue.

I normally put in a bit of calcium carbonate to toughen it up some.
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Old 07-12-2014, 08:33 AM   #3

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Make sure you put some styrene wax in the resin you use to repair so it cures well/properly.
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Old 07-17-2014, 08:49 AM   #4
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this stuff is great for mold repair. it spreads like butter and sands nice. wet sand and polish

use with cream (bondo) hardener sets up a little slower than body filler but makes for faster repairs. (good shelf life)
I have used it on epoxy & polyester molds

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Old 07-26-2014, 03:49 PM   #5

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Regular fiberglass resin will work also.
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Old 03-18-2016, 01:16 PM   #6

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Default Polyester Gelcoat Repair Question

Thread revival! Didn't want to make a new thread since it was already asked.

I recently made a mold for fender flares and brushed on the gelcoat because I don't have a sprayer for gelcoat. Luckily the gelcoat I got was brushable. The issue I ran into was that the gelcoat is uneven and the mold it self took a beating after pulling one part. My question is can I repair the mold with body filer and brush on the gelcoat again? With that, will it even out to a smooth surface and would I have to spray it with pva for it to fully cure?

Thank you!
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gelcoat, polyester, question, repair

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