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Gelcoat repair DIY


whichwaysup

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Hey all - 

One of the benefits of the recent repair to my boat was that I ended up with a fair amount of leftover oyster white gelcoat.  It has about a 6 month shelf life, and I'd like to use what I ahve to address some scratches on the bottom of the boat.   This is the gelcoat itself, not the patch paste.   I'm pretty familiar with working with fiberglass, and I've done enough research on gelcoat repairs to have a basic understanding.   I do have one question - It seems like I need to use a PVA after the repair to get the gelcoat to completely cure.   Is this correct?

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  • 2 weeks later...

Hey WWU,

 My understanding of the PVA is that it is more of a releasing agent when using gelcoat in a mold "Boatworkstoday"  Andy is a glass master has many videos" .  If my memory serves me correctly, if you were to brush on the gelcoat on an area of the hull the only way you would be able to get that smooth out come if to press a peice of material that had PVA sprayed on it so that you can make it match the original.  Otherwise you would need to sand and buff till your elbows broke...

 

I hope I am saying this correctly...

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You can add waxing/sanding agent to the gel-coat. The waxing/sanding agent is wax suspended in styrene which floats to the surface of curing gel-coat, allowing it to cure to a sandable finish. It is available at most fiberglass supply stores. I've had mixed results with this stuff. The wax tends to separate from the styrene while sitting in the container. For best results, you need to let the agent warm to at least 80 degrees and then mix it thoroughly by shaking the container. Because I am generally mixing small batches of gel-coat, getting the proper ratios of sanding agent and MEKP can be a little tricky. I tend to go a bit higher on my MEKP ratio in order to get the gelcoat to cure to a harder, more sandable finish. If you can, work in direct sunlight, on warmer days, with as little humidity as your locale allows. Do not do any glass work in the last 3 hours of the day. Falling temperatures and dew will ruin your work. Also, do not do any glass work if there is any risk of rain. Even if your work is protected from the rainfall, the boosted humidity and falling temperatures associated with the rain will also ruin your work.

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Its been awhile....so memory not great but had similar situation with leftover gel and I stopped by Spectrum as they are local to me and bought 2 diff additives. One was a filler of sorts...maybe cabosil (sp) and the other something else. Anyhooo....what they gave me turned my gel into a paste that I applied, it dried I sanded and polished and made the repair and me look like I knew what I was doing lol

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Cabosil will thicken gelcoat but it will lighten the color slightly. If you're using it as a filler and plan to finish over it with gelcoat it won't be an issue. If you plan to just make it a one-step process, you're going to be able to see the slight color variation in the patch job.

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