Smoothing GRP panels for painting with damaged clear coat

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PostPosted: Sat Oct 19, 2019 12:06 pm
Hey folks,

I’ve inherited a 1999 C5 Corvette. It’s been lying out for years in direct sunlight in the South of Spain. I’m in the UK and have had it shipped back here. The clear coat on 5 or 6 panels is badly damaged, flaking and burnt looking from the sun.

It needs a fair bit of work as you can imagine. When I’m ready though, (and I’ve done this before with a steel bodied car) I want to prepare it for paint myself. I’m not 100% sure what the panels are made of. Anyone..? Not fibreglass I don’t think so that’s why I said GRP..?

What would be the best way to sand all this damage back, and any input on working with the material? I don’t like the idea of chasing edges of clear coat so I’m guessing fairly heavy sanding might be required.

Input and ideas very welcome please. I’m happy to invest in a DIY compressor and any body working air tools that might help me. Thanks
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PostPosted: Sat Oct 19, 2019 1:17 pm
just a shot in the dark, but I would check to see if you have any media blasting places near you that use plastic or walnut shells or some other non damaging abrasive.
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PostPosted: Sat Oct 19, 2019 1:48 pm
badsix wrote:just a shot in the dark, but I would check to see if you have any media blasting places near you that use plastic or walnut shells or some other non damaging abrasive.
Jay D.

I never thought about that as a possible option. Remove the panels and have them blasted. Interesting idea. I meant to check earlier which panels are like this. When I think about it maybe it’s just the rear bumper, the trunk/hatch and the passenger side rear quarter panel. Not at all sure about trying to dismantle the hatch/glass!

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PostPosted: Sat Oct 19, 2019 10:14 pm
Keep in mind that's not just regular fiberglass on that car. It is SMC fiberglass (sheet molded compound) which means ANY types of repair materials must say "SMC compatible" on the can or product sheet. SMC has it's mold release agent right in the plastic compound. Use standard fiberglass products for your repair and things will start peeling off very soon.
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PostPosted: Sun Oct 20, 2019 5:59 am
Thanks

As I suspected it sounds as though I need to understand how much the material should be sanded or blasted. or how safe any other method of stripping is. I could post a few pictures but I suspect that's not necessarily much of a help.

If I'm allowed to as a newish user I will post a few pictures soon.

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PostPosted: Sun Oct 20, 2019 8:39 am
If you do go that route make sure the company you go with can show either examples of late model fiberglass panels (preferably of the same vintage car) they have done or refer you to a past customer that had it done with them. Media blasting is knowledge and skill. Deficits in either can not only give you a poor job but ruin panels.
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PostPosted: Sun Oct 20, 2019 8:47 am
DarrelK wrote:If you do go that route make sure the company you go with can show either examples of late model fiberglass panels (preferably of the same vintage car) they have done or refer you to a past customer that had it done with them. Media blasting is knowledge and skill. Deficits in either can not only give you a poor job but ruin panels.


Yes I think I'd be very nervous about that. I've had a close look at the sun damaged areas today and am thinking it would first be wise to try to sand back the damaged clear to hopefully end up not chasing edges. My hope being non peeling areas still gripping the base coat ok. That way only some isolated areas will need taken back further rather than looking at vast areas needing paint/clear removed.

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PostPosted: Sun Oct 20, 2019 5:21 pm
In the areas of clear coat failure just remember..... ALL of the base and clear have to come off. If you try and bond new clear to the old base that is a recipe for failure.
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PostPosted: Sun Oct 20, 2019 10:38 pm
I've always found that the basecoat underneath failed clearcoat
comes off very easily. Try wetsanding with a bucket of water with
dishwashing soap added. I'll bet the paint will almost wash off...

Nice Vette.
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