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Bertram31.com General Bulletin Board
Re: Gelcoat Repair
Posted By: Capt Patrick McCrary In Response To: Gelcoat Repair (BillC)
Date: Tuesday, 15 February 2005, at 2:36 p.m.
Bill,
MEKP, (methylethelketone in peroxide), is the catalyst for all polyester resins including polyester gelcoat. There is no need to thin the gelcoat.
Sand the repair area with 80 grit paper, feather edging into the immediate area surrounding the repair. Clean the surface well with acetone.
Mix a small amount of the gelcoat, about 3 - 4 oz. The mixing ratio for the MEKP when doing spot repairs is 6%MEKP:volume of gelcoat. 4 oz of gelcoat would be .24 oz of MEKP. That's about 110 drops, or a medium quick squirt.
Mix only enough gelcoat that can be worked into place within 10 minutes. More than this will only fire off in the cup and be wasted.
Use a 1 1/2" brush for the application.
On horizontal surfaces, apply the gelcoat to be well above the surface of the repair. After it cures over night, sand it down to just above grade with 180 grit paper, bring it to grade with 320 paper, then progress with wet sanding from 400 - 600 - 1,000. Coumpound with 3M heavy duty rubbing compound, then 3M FineseIt.
On vertical surfaces it may take more than one application to build above grade. A new application can be made as soon as the previous application is hardened, but still tacky.
If the application you are making is the final application for that spot, add a few drops per oz of Surfacing Wax to the gelcoat before mixing the MEKP. Be sure the wax is well mixed into the gelcoat. This will seal out air from the cure and allow you to sand when cured. Without the wax, gelcoat will remain tacky for days & plug up your sand paper...
Best regards,
Patrick
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