Gel Coat Patch-up

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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John B
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Gel Coat Patch-up

Postby John B » Fri Sep 14, 2018 1:57 pm

Hello. I ordered some "paint ready" desert tan gel coat to start on a few small repairs I want to make on my 1984 Montauk. I will be repairing holes placed under the outer lip of the gunwale from snaps that were screwed in for a boat cover. I will also fix a few nicks and scratches towards the bow but mainly on the "smirked" portion of the gel coat.

Q1: For the holes on the bottom of the outer lip of the gunwale, is it still preferred to use chopped fibers and resin to fill the holes since the holes are upside down? Can I use hull and deck putty instead or anything else that is preferred? Also, should I look at spraying these small areas or using a brush to paint the small holes?

Q2: For the scratches and nicks on the smirked area of the hull, how would I get the gel coat to not sag off the smirked area? Do I thicken the gel coat or just apply a lot then sand down to follow the contour of the smirk?

Thanks for a reply.
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1984 Montauk

jimh
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Re: Gel Coat Patch-up

Postby jimh » Fri Sep 14, 2018 2:32 pm

John B wrote:Q1: For the holes on the bottom of the outer lip of the gunwale, is it still preferred to use chopped fibers and resin to fill the holes since the holes are upside down?

A1: I have had good success filling small holes, such as left from now unused fasteners, with epoxy resin and low density filler. Then I put a piece of masking tape over them to retain the resin from oozing out.

John B wrote:Q2: For the scratches and nicks on the smirked area of the hull, how would I get the gel coat to not sag off the smirked area? Do I thicken the gel coat or just apply a lot then sand down to follow the contour of the smirk?


A2: gel coat resin usually is supplied in a rather thick consistency, almost like peanut butter. In order to apply gel coat resin with a sprayer the resin is diluted with a solvent that will flash off and evaporate. The paste-like consistency of gel coat resin ought to allow it to not sag too much if applied to a hole where gravity will make if flow out. Also, you can cover gel coat resin with something like a plastic, say a Saran-Wrap type material, to which it should not adhere. This will keep it from sagging and also help it to cure. Gel coat resin won't cure if exposed to air. Some "patch kit" resin has already had a wax mixed into the resin that will tend to lift out of the mixture and form a surface coat to let the gel coat resin cure.

But get more advice, as I am not much of a gel coat application expert. I accomplished it many years ago. I described my efforts in a brief article.

The Epoxy Cure
http://continuouswave.com/maintenance-logs/epoxy/

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John B
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Re: Gel Coat Patch-up

Postby John B » Fri Sep 14, 2018 2:49 pm

jimh wrote:But get more advice, as I am not much of a gel coat application expert. I accomplished it many years ago. I described my efforts in a brief article.


Thanks, Jim. I will try just one of the holes with that method and see how it goes. The gel coat does have wax in it already, so it should be good to go there. I also picked up some PVA to assist in the curing process.
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1984 Montauk

jimh
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Re: Gel Coat Patch-up

Postby jimh » Fri Sep 14, 2018 5:18 pm

I should have mentioned: if you use epoxy resin, be sure to post-cure it with some gentle heat, then wash it thoroughly in soap and water to remove any amine blush. If there is any amine blush residue, the amine will inhibit the cure of polyester resins like a gel coat polyester resin. But, as with any sort of painting, with proper preparation the top coat finish will look fine applied over an epoxy resin repair.

The reason I like epoxy resin for small repairs: you can get pre-measured small batches in foil packets (like a Catsup foil pack at a take-out restaurant). This allows you to make a small quantity of resin with precisely measured amounts of resin and hardener, which will guarantee good results. I have fixed many small fastener holes this way, and on some--the ones that are highly visible--I have top coated them with polyester gel coat resin with good results.

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John B
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Re: Gel Coat Patch-up

Postby John B » Sun Sep 16, 2018 2:38 am

jimh wrote:I should have mentioned: if you use epoxy resin, be sure to post-cure it with some gentle heat, then wash it thoroughly in soap and water to remove any amine blush. If there is any amine blush residue, the amine will inhibit the cure of polyester resins like a gel coat polyester resin. But, as with any sort of painting, with proper preparation the top coat finish will look fine applied over an epoxy resin repair.

The reason I like epoxy resin for small repairs: you can get pre-measured small batches in foil packets (like a Catsup foil pack at a take-out restaurant). This allows you to make a small quantity of resin with precisely measured amounts of resin and hardener, which will guarantee good results. I have fixed many small fastener holes this way, and on some--the ones that are highly visible--I have top coated them with polyester gel coat resin with good results.


Thanks for the additional information. I already have quite a bit of G/Flex 655 thickened epoxy but can add a filler to it to thicken it up a little more. By gentle heat, do you mean like a heat gun or a blow dryer? How long do you apply the heat to remove the residue? I was planning to do a light sanding to the epoxy once its hardened to get better adhesion to the gel coat.
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Sunny San Diego
1984 Montauk