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Old 04-04-2009
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Repairing cracking gelcoat

Hi everyone. I'm new to this forum and it sure looks like this is the PLACE to get boat repair information.
I have recently purchased a 1963 GRP Silhouette sailboat. I am going to try and completely restore the boat. I have begun to sand off the old finish, so far I have got the hull sides from the deck down to the waterline and the transom sanded. I used a random orbital sander and 40 and 80 grit.
What I have found so far is that the surface is cracked and crazed fairly extensively.I would say that the
gelcoat is essentially gone. Would it be better to;
1. Use a fairing putty to fill and smooth the surface then use a high build
primer and paint? I have heard Pettit makes a good one.
2. Coat with epoxy? West system or other.
3. Put a layer of say 1.5 oz. fiberglass cloth and resin? Polyester or epoxy?
Thanks
John

Last edited by Jhoward60; 04-04-2009 at 09:17 AM.
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Old 04-04-2009
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john, if the gelcracks are deep try to use a dremal tool or simular tool to grind out the cracks .if you don't no matter what you do they will only return. once you have them ground out ,use a good marine filler then sand smooth.this is what i do for a job. but remember they are not structual it is just the gelcoat . unless hull has been damaged in some way. good luck charlie
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IF it is just cracked gelcoat, there's no reason to put a layer of fiberglass down. Just open the cracks up a bit and fill with MarineTex or other thickened epoxy. Either paint or gelcoat the epoxy once it is cured.
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Old 04-05-2009
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if the whole hull is crazed i would sand it with the 80 grit like you did. then mix up some epoxy and colloidal silica, and roll on a a few coats, then sand smooth. sanding will be tough using the silica but it will be a strong coating. you will have to paint the boat after wards or the epoxy will not hold up in the sun.
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IF you decide to go the route scottyt suggests, I highly recommend getting the epoxy as fair as possible before it cures.
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jhoward60, When following any of the good suggestions above, I would add the process of a shallow round drilled hole at the end of all or at least the larger cracks. This will likely distribute the stresses that might cause the crack to grow in the future. This is especially a prefered step it you are using the faring material as opposed to a new expoxy layer.
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as dog said you would want it as smooth as possible, the silica will make the epoxy hard as hell. you could also use a light weight fairing filler after the slica filler to make it easier to fair and sand.

the reason for the silica filler is it will make the epoxy structural instead of just a weak coating.

if you wanted to go crazy, there is some exotic fillers for epoxy that give it various properties. like ground up neoprene for extreme flexibility.

basicly you want a coating that has some strength, not just a coating. but you could also spray or roll on more gel coat, with the last layer a finishing gel coat, or sprayed will mold release to get it to cure completely.
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Thanks for all the good information. I'll probably go with the epoxy coating. I've got some pictures of the damage but I can't post them for some reason.
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Here are some pictures of the damage.
After sanding 1 pictures by jhoward60 - Photobucket
After sanding 1 :: HPIM0996.jpg picture by jhoward60 - Photobucket
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Originally Posted by Jhoward60 View Post
Thanks for all the good information. I'll probably go with the epoxy coating. I've got some pictures of the damage but I can't post them for some reason.
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