Gel coat over epoxy primer

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peter-curacao
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Gel coat over epoxy primer

Post by peter-curacao » Fri Sep 22, 2017 4:03 pm

Hi Guys I'm ready to finish the bottom on the flyer, I was thinking gel coat but when I was in the shop reading the label it says do not apply over paint, does That mean I can't apply it over epoxy primer either? :doh:



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Re: Gel coat over epoxy primer

Post by Jaysen » Fri Sep 22, 2017 4:13 pm

For some reason I thought gel couldn't go over epoxy... or is it polyester can't go over epoxy? I'm to young to be this old.

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Re: Gel coat over epoxy primer

Post by Fuzz » Fri Sep 22, 2017 7:56 pm

Most folks say you can not gelcoat over epoxy. But I have read where a few folks claim they have done it and it worked just fine. Having never tried it I KNOW nothing :doh:

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Re: Gel coat over epoxy primer

Post by dbcrx » Sat Sep 23, 2017 3:42 am

Gel coat will bond to epoxy. I think the reason people may think it doesn't is that polyester is not as good for mechanical bonding as epoxy is. That doesn't mean it won't bond - just that it won't bond as well as epoxy. For small repairs in gel coat I would have no issue doing a fiber repair with epoxy and then applying polyester gel coat to match the original finish. Over an entire hull though I wouldn't do it. Gel coat is normally slightly porous and over a large area constantly under water you may end up with it delaminating. Probably not immediately, but maybe sooner than you'd like. Plus, gel coat is not easy to apply nicely - even by spraying - and will need flatting and polishing to achieve a nice finish. If it were me, I would go for a few coats of a decent highish build epoxy primer then either just paint with a good marine topcoat, tinted/graphite epoxy, or antifoul/coppercoat depending on how long it is likely to stay in the water for.
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Re: Gel coat over epoxy primer

Post by topwater » Sat Sep 23, 2017 9:15 am

I wouldn't put gelcoat any where near that boat :!: Ever see a production boat with osmosis blisters on the bottom :?:
Plus it really not that hard of a coating, if you put it on too thick it cracks, if there is any flex it cracks , if you hit somthing
or drop something it chips . Gelcoat sucks , the reason they use it it's cheap and looks pretty for awhile. IMHO.
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Re: Gel coat over epoxy primer

Post by peter-curacao » Sat Sep 23, 2017 9:33 am

Okay Gentleman thx for the answers this gave me a whole other inside on gel coat therefore I will omit the idea of gel coat.
I was thinking graphite also but I want a matt finish on the bottom so probably I will grab for anti fauling again

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Re: Gel coat over epoxy primer

Post by Eric1 » Sat Sep 23, 2017 3:45 pm

peter-curacao wrote:
Sat Sep 23, 2017 9:33 am
Okay Gentleman thx for the answers this gave me a whole other inside on gel coat therefore I will omit the idea of gel coat.
I was thinking graphite also but I want a matt finish on the bottom so probably I will grab for anti fauling again
Peter do a test with graphite. After it cures wet sand it and feel how slick it is!

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Re: Gel coat over epoxy primer

Post by peter-curacao » Sat Sep 23, 2017 3:52 pm

Eric1 wrote:
Sat Sep 23, 2017 3:45 pm
peter-curacao wrote:
Sat Sep 23, 2017 9:33 am
Okay Gentleman thx for the answers this gave me a whole other inside on gel coat therefore I will omit the idea of gel coat.
I was thinking graphite also but I want a matt finish on the bottom so probably I will grab for anti fauling again
Peter do a test with graphite. After it cures wet sand it and feel how slick it is!
Eric Thx but I just finished with the anti fauling

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Re: Gel coat over epoxy primer

Post by Eric1 » Sat Sep 23, 2017 4:24 pm

peter-curacao wrote:
Sat Sep 23, 2017 3:52 pm
Eric1 wrote:
Sat Sep 23, 2017 3:45 pm
peter-curacao wrote:
Sat Sep 23, 2017 9:33 am
Okay Gentleman thx for the answers this gave me a whole other inside on gel coat therefore I will omit the idea of gel coat.
I was thinking graphite also but I want a matt finish on the bottom so probably I will grab for anti fauling again
Peter do a test with graphite. After it cures wet sand it and feel how slick it is!
Eric Thx but I just finished with the anti fauling
I saw it! You don't play around! :D

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Evan_Gatehouse
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Re: Gel coat over epoxy primer

Post by Evan_Gatehouse » Sun Sep 24, 2017 1:09 am

It is possible to spray gelcoat in a mold and apply epoxy layers over it. But not always successfully! Barry Carroll, US builder of a bunch of production Mumm / Farr 30s, 36, CM1200 tried this with very poor results.

Much easier to just epoxy primer and paint. Gelcoat is really designed to spray into a female mold and have polyester layers added over it. Nobody working with epoxy high performance boats uses gelcoat; they all use paint.
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