Gelcoat issues

Questions about boat repairs with our resins and fiberglass: hull patches, transoms and stringers, foam, rot etc.
Mheltun
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Re: Gelcoat issues

Post by Mheltun » Mon Apr 16, 2018 10:22 am

silentneko wrote:
Mon Apr 16, 2018 9:44 am
Just curious, but did you try adjusting the catalyst/MEKP? Just as a test I think I would first clean an area well, first water or alcohol then maybe acetone and let it dry, then I would add another 0.5% MEKP. You will know if it works within a few hours. I had issues with gelcoat curing correctly as the weather shifted before.

I have not adjusted the catalyst at all. I’m mixing at what is recommended for 60deg. I’m going to try a few experiments this week on some small areas (filled screws) and see what happens. I will also try and warm the areas first to see if that helps. I can try to increase the catalyst as well. Thx for the tips. I’ll get it at some point.



tcason
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Re: Gelcoat issues

Post by tcason » Mon Apr 16, 2018 10:26 am

have you lightly sanded area before putting down gelcoat?

This may remove any "contamination" that maybe impacting gelcoat??

Mheltun
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Re: Gelcoat issues

Post by Mheltun » Mon Apr 16, 2018 11:39 am

tcason wrote:
Mon Apr 16, 2018 10:26 am
have you lightly sanded area before putting down gelcoat?

This may remove any "contamination" that maybe impacting gelcoat??
Yes, the areas were all lightly sanded and wiped with a ammonia/water solution. I’ve been told not to clean the surface with acetone before applying gelcoat. Apparently acetone can “wake up” the epoxy and cause further off gassing that can cause adhesion issues. Again this is not my theory just information I’ve read.

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Re: Gelcoat issues

Post by DAYTRIP » Mon Apr 16, 2018 5:21 pm

I will often double the catalyst with gelcoat. Mainly for similar reasons. It is testy and sometimes will be slow to kick. Try jumping it up a bit. Good suggestion

Mheltun
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Re: Gelcoat issues

Post by Mheltun » Mon Apr 16, 2018 5:30 pm

DAYTRIP wrote:
Mon Apr 16, 2018 5:21 pm
I will often double the catalyst with gelcoat. Mainly for similar reasons. It is testy and sometimes will be slow to kick. Try jumping it up a bit. Good suggestion

On some of the smaller repairs I’ll give it a try. Thanks!

Fuzz
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Re: Gelcoat issues

Post by Fuzz » Mon Apr 16, 2018 8:18 pm

Rather than trying different things on the boat how about making up a trail board from some scrap? This would let you try more than one thing at the same time. Also have you looked at the West System site? I think they might have some info on gelcoating over epoxy.

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Re: Gelcoat issues

Post by Fuzz » Mon Apr 16, 2018 8:19 pm

Rather than trying different things on the boat how about making up a trail board from some scrap? This would let you try more than one thing at the same time. Also have you looked at the West System site? I think they might have some info on gelcoating over epoxy.

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Re: Gelcoat issues

Post by pee wee » Tue Apr 17, 2018 8:12 am

Don't have any advice on gelcoat, but from what you describe it sounds like there is some amine blush remaining despite all your efforts. It's either still there or still coming to the surface, and it sounds like you let it cure long enough to take care of scenario two. The first step should be washing the epoxy surface, followed by sanding. If you sand first you will make it harder to get it clean, some say you're sanding it into the surface. Here's what West System has to say on it:

"To remove the blush, wash the surface with clean water (not solvent) and an abrasive pad, such as Scotch-brite(TM) 7447 General Purpose Hand Pads. Dry the surface with paper towels to remove the dissolved blush before it dries on the surface. Sand any remaining glossy areas with 80-grit sandpaper."

What epoxy are you using?
Hank

Mheltun
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Re: Gelcoat issues

Post by Mheltun » Tue Apr 17, 2018 12:00 pm

This is the epoxy I used :https://boatbuildercentral.com/products ... MarinEpoxy. I did do the sand and wet wipe with water but did neglect to blot up the water after, instead wiped off with a dry rag.It is a possibility that I smeared the blush around causing some of my issues.

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Re: Gelcoat issues

Post by Fuzz » Tue Apr 17, 2018 1:40 pm

Ok I guess I will admit it. I have put some gelcoat over the Marine Epoxy sold here. I did not have any problem with it kicking off and so far it has stuck. Maybe that was because the epoxy had cured for several months first or maybe I just got lucky. For the repairs you are doing I understand why you are using it but other than that it is a pain in the butt :help:

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