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Old 11-04-2011, 14:50   #1
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Gelcoat Problems: What to Do ?

Hi,

We recently had our boat sandblasted and removed I don't know how many years of hard anti-fouling. After letting her sit for the the winter we are now ready to figure out what to do. There seems to be blistering between the gelcoat and the glass. As far as I can tell it doesn't go into the glass. What would you do? (photos below). We have though about sanding out each one with a dremel.. but that would take forever, or take all the Gelcoat off, or simply sand smooth and fill... Thoughts/ideas?

Geoff.


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Old 11-04-2011, 18:26   #2
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Re: Gelcoat problems - what to do?


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Old 11-04-2011, 18:54   #3
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Re: Gelcoat problems - what to do?

I wqould say that is a mfg contamination prob. if they are still in business put a fire under their feet and tell them you are going to post international this condition. the second pic shows blobs in the gel-coat by your right index finger of gel-coat/contamination or over catylized gel coat or other contamination.
to fix i would get a moisture meter to tell if the hulls are actually (dry), then mix an epoxy (i would use vinyl-ester resin if this what the hull is made of) bog and cover waterline down filling holes, then sand and barrier coat and paint
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Old 11-04-2011, 18:55   #4
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Re: Gelcoat problems - what to do?

I had a similar problem. I ended up peeling all the gelcoat (had it done) and the first layers of glass and then putting a couple layers of new cloth on it, refairing and sealing. This was overkill. I think that just removing the gelcoat would have been enough as there was really no delamination below it. The problem was between the laminate and gelcoat. If I was doing it again. I would strip the gelcoat and seal in all with epoxy and sealer and put on bottom paint. I did this 17 years ago and never had a hint of a problem since.
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Old 12-04-2011, 07:25   #5
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Re: Gelcoat problems - what to do?

I had a similar condition on my hull. I ended up grinding the entire gelcoat off the bottom. The hull is drying out now as I had many large blisters amongst the smaller ones.

Photos of my bottom project here: Project - Bottom Job | Facebook
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Old 13-04-2011, 20:25   #6
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Re: Gelcoat Problems: What to do?

All - Thanks for the feedback!

Beersmith - great photos of your refit!
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Old 13-04-2011, 20:45   #7
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Re: Gelcoat Problems: What to do?

All the old gelcoat has to be blasted off. It then has to be allowed to dry. Then a few layers of an epoxy barrier coat like Interlux 2000 has to be rolled on.
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Old 13-04-2011, 23:37   #8
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Re: Gelcoat Problems: What to do?

Dealing with similar issue, though yours do appear to be larger and deeper than the bubbles in mine. Spent hours and hours and hours researching. Read every article, report, study, test and opinion I could find on the internet. For every ten articles published there were at least 12 different opinions expressed. Everything from

A. your boat is ruined unless you strip 2-3 layers of glass off the hull and relay with resin X, Y or Z

to Z. hit with a sander and 60 grit, slap on some bottom paint and don't worry about it.

Some said sand or soda blasting is the only way as it gets into all the soft/weak spots to blasting will ruin the boat as it opens up lots of fibers an a quick path for new moisture to diffuse into the glass so use only a power planer type tool.

Every opinion on resin type you can imagine.

My final decision. Go with a planer not blasting. For me this was the right choice because the blisters were very shallow and it leaves a much smoother, cleaner surface making the restoration part a lot easier. Also a lot less messy. The blaster may work better in some cases. Not sure if the rougher surface and exposed, broken glass fibers will make a path for future water penetration or not.

Vinlyester resin in tests seems to show slightly better resistance to moisture penetration than epoxy but I chose Interlux 2000 epoxy for two reasons. One I am familiar with it and it seems to be tried and true. Second the guy I hired uses it and prefers it.

Ask me in ten years how it worked out.
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Old 13-04-2011, 23:59   #9
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Re: Gelcoat Problems: What to do?

That looks like craters blasted in the gel coat by the sand blasting medium. You should have had it soda blasted as the soda isn't hard enough to damage like that. You can either remove the gel coat and refair the hull or fill the pukas and grind smooth. The former is going to be very expensive and take a lot of time to refair the hull.
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Old 14-05-2011, 17:56   #10
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Re: Gelcoat Problems: What to do?

Thanks all - we have decided to sand off the bottom, fair and interprotect the bottom.
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Old 14-05-2011, 18:45   #11
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Re: Gelcoat Problems: What to Do ?

sanding off three layers of fiberglass is probably unneccesary. i dont know if sandblasting would work or not, its worth a shot. i wonder what a needle gun would do. i do think a dremel would be way to tedious, i would tear it up with a grinder before i stooped that low.


what make of boat was that? year?
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Old 14-05-2011, 18:59   #12
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Re: Gelcoat Problems: What to Do ?

unless i'v lost my vision, if you look closely at the surface by the hand an below you will see blobs in the gell coat. that is not caused by blasting. that is over catalyzed gell coat and or contaminant in it, causing those blobs , and voids. looks like a crappy gell coat lay up!!!!!!!!???????
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