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Gellcoat (I think) flaking off
On Sun, 11 Apr 2010 11:13:54 -0700 (PDT), wheewhoo
wrote: Hi guys, thanks for the replies. So what I need to do is sand off the gelcoat (and whatever other layers are there), as I can definitely see the fiberglass where flakes have come away. Do I just need to prepare the bare (fiberglass) surface, and apply a new gelcoat? Or do I need layers of other stuff also? Lets say I have a large area of hull/keel that I have sanded back to the fiberglass. What are the steps I should take? Phantman mentioned bottom paint, and Bruce mentioned epoxy. Would it be epoxy, then gelcoat, then bottom paint? Thanks for the help! The basic task if to protect the underlying fiberglass from UV damage (a real threat in tropical climates) and water ingress which may take place over a longer period of time. There are two basic methods, to apply a gel coat or to paint, usually with an epoxy based paint. The gelcoat is much harder to apply and have a nice smooth shiny surface. The paint is much easier to apply but perhaps not as long lasting. Gelcoat Method. Grind/sand, the damaged areas back to a good solid surface. This surface can be either fiberglass or gelcoat but it MUST be a good solid surface. If gelcoat you must be certain that it is attached firmly to the underlying fiberglass. Once you have reached your base surface you must then "fair" the surface as smooth as possible as any craters, dips humps, etc. on the surface will be mirrored in the final finish. You can do this by grinding/sanding the surface until it is flat or you can build up the low spots with an epoxy filler using any of the harder, stronger fillers. Once things are fair you then sand with varying grades of sandpaper to about a 500 grip sandpaper. Gelcoat is nothing more then polyester resin with a coloring agent in it and comes in many colors. The mix also has a "wax" incorporated in it that when it is applied floats to the surface and causes the polyester to harden with a non-sticky surface. The gelcoat can be applied with a brush or by spraying but no matter how it is applied will probably not be the smooth, shiny, beautiful coating that you have envisioned. It needs work. Sand the gelcoat with progressive grades of sandpaper down to at least 1,000 grit and preferably finer. Once you have the surface as smooth as possibly then buff the surface to the required finish using a buffing wheel and polishing/buffing compounds as used for paint. If you did a good job it will be beautiful. Painting - Basically you do all the preparatory steps to get the hull smooth and fair and then apply two coats of epoxy resin to seal the hull. One method to avoid the "epoxy blush" problem is to apply the second coat of resin before the first coat is completely hardened. When it is no longer sticky but not hardened completely so that you can press your finger print into the epoxy apply the next coat. Finally after the last coat of epoxy (before it completely hardens) apply at least one coat of epoxy high build primer. Sand the hardened primer with about 400 grit sandpaper and do any touching up, sand again if necessary, and spray two coats of two part polyurethane paint. It will be beautiful if you did a good job. But don't kid yourself , either method is a substantial amount of work. The gelcoat considerably more work, but neither is a Sunday afternoon project. Cheers, Bruce (bruceinbangkokatgmaildotcom) |
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