Need to do a temporary fix, does anyone know if epoxy will adhere to gelcoat? will of course rough up area and clean before applying epoxy, but will the epoxy stay, at least for a week while I sail

Turbo

yes

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Philip
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Yes. Epoxy will adhere to existing gelcoat. So your temporary fix should be fine. The problem comes from the reverse, gelcoat will not adhere to epoxy.

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Dave Wilson
Hobie 16, Hobie 14
Tampa, FL
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Is that true!? I just finished filling a pile of old rivet holes in my boat using marine tex (I know I know, but they were small holes on the deck). And I planned on just sanding and doing a gelcoat repair on them? Of course marine tex is a bit of a different animal.

Regards,
Dave

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Dave Bonin
1981 Nacra 5.2 "Lucile"
1986 Nacra 5.7 "Belle"
Winnipeg, Manitoba, Canada
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My previous post should have said "gelcoat does not adhere well to epoxy".

Marine Tex is epoxy and it is very handy for a variety of repairs. However, the only time I would use epoxy is when the repair is structural such as hull delamination and in situations like that, epoxy will give a superb mechanical bond. For largely cosmetic repairs on polyester resin laminates which includes most boat hulls, I would typically use a polyester resin based product. Its cheaper, easier to work with and the same stuff the boat was made with.

Repairs made with polyester resins are a lot easier to fair in since the patch material is the same density and hardness as the surrounding area. Marine Tex or any epoxy for that matter will be much harder than the surrounding surface.

Gelcoat is basically tinted polyester resin and will bond much better to existing polyester laminates than epoxy laminates. Generally, polyester bonds well only to polyester whereas epoxies bond well to lots of other materials. The gelcoats that I am familiar with typically recommend against using them on epoxy due to the bonding issues. The one exception I know of is West Systems. Their literature claims that gelcoat will adhere just fine to properly prepared West Systems epoxies. Although I've never tried it. Surface prep is critical so be sure to completely remove the amine blush. If you do try and apply gelcoat over epoxy you might want to see what West Systems has to say about surface prep, etc.

Good luck.



Edited by DaveW70 on Jun 15, 2011 - 02:01 PM.

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Dave Wilson
Hobie 16, Hobie 14
Tampa, FL
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Fairing epoxy is as hard or easy as you make it. MarineTex is as soft as the gelcoat.

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Rob
OKC
Pile of Nacra parts..
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Gel coat will adhere to properly cured epoxy. I tested it on my boat and it works fine.
I did some quite extensive repairs with epoxy (measured accurately by weight) and glass, let it cure a couple of days ( 48 hrs) sanded the repairs thoroughly then applied two coats of thinned gel coat with a roller and brush. I got the expected orange peel effect but that was no surprise. A week later I applied Ikea anti-slip tape which ate through my harness like a school of piranha's through a crippled horse. A week later I removed the tape and no gel coat came off with it. I mean none at all, which was a big relief because I knew about the theoretical adhesion problems of gel coat over epoxy. Maybe I just got lucky, I don't know, but I do know I'm happily "sticking" with epoxy for my repairs.
Dennis

(edited to say I sanded the repairs, which is crucial!)



Edited by dennisMe on Jun 16, 2011 - 01:27 AM.