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post #1 of 6 Old 04-10-2013 Thread Starter
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Painting right over gelcoat, no sanding necessary

I recently took part in a work party on the (25 year old) boat I race on, and the owner decided to paint certain areas of the deck. All we did was basically scrub it down well, then rub in "wil-bond", then went directly to rolling on primer (I think 545 was the primer not sure though).

I did not realize you can simply paint over gel coat, I thought you had to remove it.

The gel coat on my deck (my own 30 year old boat) is pretty porous, though the gel coat on the hull is still shiny. There is some crazing but nothing major.

I have been contemplating re-painting my boat for years, but I thought it would require a ton of sanding and just wouldn't be worth the amount of time necessary. I am not seeking a top-notch professional job, but rather one good enough not to effect resale value negatively.

Has anyone else heard of not sanding, just using surface preparation/de-glosser on the gelcoat then painting right over that with epoxy based primer?

If so, should I try and fill the minor crazing that exists with epoxy and filler prior to painting? Maybe sand the crazing only? I feel like the cracks are so small that filler won't fit in...
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post #2 of 6 Old 04-10-2013
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Re: Painting right over gelcoat, no sanding necessary

Yes if you get it really clean the primer will stick

Just keep in mind the paint will never hold up like the gelcoat did and there is NO going back

FWIW on the Cal 29 I a very happy with tan interdeck as I can live with the life and the rubber particles in the paint make a very good non-skid

I have not had any adhesion issues with GOOD clean and paint NO primer

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post #3 of 6 Old 04-10-2013
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Re: Painting right over gelcoat, no sanding necessary

Some primers are good at filling small crazing (like Interlux Epoxy Primecoat). I would degrease and sand.

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post #4 of 6 Old 04-10-2013
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Re: Painting right over gelcoat, no sanding necessary

Absolutely.. there's never been a need to 'remove' gelcoat but it needs to be dewaxed and thoroughly cleaned - a scuff sanding will help but no need to grind it all off.

The crappy job is repainting over old paint - especially if you don't know what was used the first time. Then you've got to get the old paint and primer off without ruining the fairness of the original gelcoat underneath - difficult to do.

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post #5 of 6 Old 04-11-2013
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Re: Painting right over gelcoat, no sanding necessary

gel coat is just thickened and pigmented polyester/fiberglass resin.

Easy to paint. But the real issue is UV damage which has broken down the resin and make for a chalking - porous - not good bonding surface. The fix is a solvent thinned eopxy primer like esp 155 which will firm up the surface and provide a good, fresh bonding surface.
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post #6 of 6 Old 04-12-2013 Thread Starter
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Re: Painting right over gelcoat, no sanding necessary

Quote:
Originally Posted by pauloman View Post
gel coat is just thickened and pigmented polyester/fiberglass resin.
Interesting I did not know that


On another note, I think one of biggest problems with sanding the old gelcoat isn't so much doing the flat areas, which won't take long to scuff up with a power sander. The issue is the non-skid. If a "de-glosser" can roughen it up enough to hold paint, then you don't have to sand through the non-skid which would be a huge job, you could just paint over the existing stuff and add some grit to the paint.
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