Sandblasting peeling gelcoat?

[SFT2]

I'm working on an '84 Baja 200SS with clear gelcoat flaking everywhere. Anyone know of a good way to strip it down to sound gelcoat to get ready for paint? I tried a palm sander earlier and it really didn't do much good. Maybe sandblasting? I'm doing everything from the rub rail up so hand sanding would take forever.

 

[drewpster]

Re: Sandblasting peeling gelcoat?

Are you sure it is clear gelcoat? Of course I could be wrong but I do not think gelcoat is typically used as a clear coating. Gelcoat is basically pigmented resin. And resin is normally not completely clear. Also gelcoat is normally applied fairly thick and it bonds really well. I have seen it crack without "flaking".
Is it possible is is clearcoat paint? If it is thin, I am guessing its paint. It would make sense, given paint would flake off gelcoat if it is not applied correctly.
I have removed paint from fiberglass by sanding and by using stripper made to be used on fiberglass. I lean toward using stripper when I have a large area to strip. A good way to verify it is paint is get a small amount of paint stripper (marine, for fiberglass) and try it on the surface. If the coating bubbles, its paint. If the stripper does nothing, its not paint.
Follow the stripper's instructions closely, how it is used makes a difference in how well it works.

 

[TheWoodCrafter]

Re: Sandblasting peeling gelcoat?

Sand blasting on fiberglass can tare right through the gel coat down to the glass.
Try soda, media or walnut shell blasting.
Or grinding. I am restoring a 1966 hull. Been painted at some time. I have been grinding on it for about a week with 40 grit on a 6" DA and RO sander. Slow but it can grind through the gel coat.
Are you sure it is gel coat flaking off? That sounds bad. Is the glass showing under the peeled off gel?

 

[SFT2]

Re: Sandblasting peeling gelcoat?

Good point. I haven't used gelcoat myself since I typically make parts out of epoxy, but this is a very thin layer. I suppose it could be clearcoat, but Baja would have been the ones to spray it since it's over the entire boat, inside and out. I'll pick up some paint stripper tomorrow and see what it does. If that does work I'll have to figure out a way to patch metalflake gelcoat on a few repairs I need to make. If it turns out I do need to sandblast I'll go with either glass beads or crushed walnut/corncob.

Here's a pic that kinda halfway shows what I'm dealing with, and gives an idea of how much surface I'm talking about. I'd really like to restore the existing paint scheme as much as possible, maybe even to the point of repainting with all 4 colors of metalflake reproduced in epoxy.

 

[TheWoodCrafter]

Re: Sandblasting peeling gelcoat?

I would think it is clear coat. The metal flake is most likely in the clear coat. Remove that and you don't have metal flake any more.
Is any flaking off over the metal flake?

 

[SFT2]

Re: Sandblasting peeling gelcoat?

There's no metalflake in the clearcoat. In the spots where the clear is gone completely it's still sparkly and fairly smooth. The entire hull is metalflake, too.

 

[oops!]

Re: Sandblasting peeling gelcoat?

metal flake is a pita !!!!......

but i wouldnt think it is in the gell.

one of the things told me about boats is the finish is paid far more attention than on cars.....its a macho thing.

but you might wanna read drewp's post twice

 

[drewpster]

Re: Sandblasting peeling gelcoat?

Keep in mind that if the metalflake is also paint, the stripper will remove it too!
I have heard of metalflake being used in gelcoat but it is possible the whole finish, metalflake and clear, is paint. Try the stripper in an inconspicuous place first like under a seat or behind a panel to be sure!
If the stripper takes the whole finish off, your back to square one.

 

[Bondo]

Re: Sandblasting peeling gelcoat?

I have been grinding on it for about a week with 40 grit on a 6" DA and RO sander. Slow but it can grind through the gel coat.

Ayuh,.....

I Agree,... That's the way to Do It.....

 

[wca_tim]

Re: Sandblasting peeling gelcoat?

I'm not an expert (on much of anything), but I'd be shocked if it was factory gelcoat... and on flake boats, the flake is usually burried in thick clear gel...

echoing some of the others and your thoughts as well, I'd treat it like automotive clearcoat (which surely would not have been put on at the factory...), and try a couple of paint strippers made for fiberglass. Once you get the paint off then see where you're at on the gelcoat and flake. You may wind up having to clear over it again, BUT if you do an anal retentive overly thoroug hjob prepping - especially to ensure removal of ALL oils and waxes... you should be fine.

Some folks have had good lick with small area repairs using fingernail polish to match flake and candy colors...

my two cents.. for what it's worth

 

[SFT2]

Re: Sandblasting peeling gelcoat?

Haven't tried any stripper yet, but I did look closely at the boat today. The flake, whether it's in the color gel or clear, is definately factory and is in fairly decent shape. The peeling layer has no flake in it at all and looks like polyester resin, but then old clearcoat doesn't look any different. It's very thin, so I doubt it's gel or resin. The plan for now is to get the flaking crap off, hopefully with stripper, and buff what's there. I'll fix the various chips that need fixing now with Marinetex and live with white spots until the fall when I can disassemble everything and paint.

 

[Coors]

Re: Sandblasting peeling gelcoat?

It sounds like it got dull, and got clear-coated.
I have heard bad things about soda blasting.
sounds like a bigger sander, with not too much pressure.

 

[Grits]

Re: Sandblasting peeling gelcoat?

SFT2

Have you contacted the manufacturer and ask what the boat is coated with. It sounds like someone shot it with a urethane clear coat. It is my understanding metal flake in/on fiberglass is actually in a clear layer of gelcoat. As mentioned above, it is a PITA.

If has been shot with clear the person that did it may have been trying to give the surface better UV protection.

Blasting with walnut shells would get expensive unless you could recover the media. It would be a slow process. TP Tools sells many different types of blasting media. Their website is www.tptools.com . They also offer a lot of information about what should and should not be used on different materials. They also compare the aggressiveness of different types of media relative to each other. I think the comparison will convince you baking soda or walnut shells would take forever and a dump truck load of media. I vote for trying paint remover.

Good luck and let us know how it comes out.

Grits

I have no interest in tp tools other than as a customer.

 

[TilliamWe]

Re: Sandblasting peeling gelcoat?

I agree it sounds like a clear coat added. Or isn't this what that VertGlas stuff does if you apply it, but don't maintain it???

 

[Coors]

Re: Sandblasting peeling gelcoat?

http://forums.iboats.com/showthread.php?t=239351

 

[tony112174]

Re: Sandblasting peeling gelcoat?

Good point. I haven't used gelcoat myself since I typically make parts out of epoxy, but this is a very thin layer. I suppose it could be clearcoat, but Baja would have been the ones to spray it since it's over the entire boat, inside and out. I'll pick up some paint stripper tomorrow and see what it does. If that does work I'll have to figure out a way to patch metalflake gelcoat on a few repairs I need to make. If it turns out I do need to sandblast I'll go with either glass beads or crushed walnut/corncob.

Here's a pic that kinda halfway shows what I'm dealing with, and gives an idea of how much surface I'm talking about. I'd really like to restore the existing paint scheme as much as possible, maybe even to the point of repainting with all 4 colors of metalflake reproduced in epoxy.

I also have same problem on the top portion of deck. Only where people have stepped over the years, and was wondering if it was possible just to do that part and put a new gelcoat finish over the whole thing. I have a 76 20 foot Ranger bass boat that i am slowly having to redo. (work on one area at tme during spring of every year so i can afford it). This is one awsome boat!!Very fast the trihull design makes it turn extra sharp at higher speeds. I have had it for about three years and this year, I'm rewiring the whole thing, new impeller, new fuel sending units and hoses, new gauges and hopefully this gel coat. If anybody has any advice for me feel free to send it. it will be greatly apreciated. Thanks

 

[Bondo]

Re: Sandblasting peeling gelcoat?

I also have same problem on the top portion of deck. Only where people have stepped over the years, and was wondering if it was possible just to do that part and put a new gelcoat finish over the whole thing. I have a 76 20 foot Ranger bass boat that i am slowly having to redo. (work on one area at tme during spring of every year so i can afford it). This is one awsome boat!!Very fast the trihull design makes it turn extra sharp at higher speeds. I have had it for about three years and this year, I'm rewiring the whole thing, new impeller, new fuel sending units and hoses, new gauges and hopefully this gel coat. If anybody has any advice for me feel free to send it. it will be greatly apreciated. Thanks

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