To Paint a Fiberglass Car

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chimpvalet
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To Paint a Fiberglass Car

Post by chimpvalet » Wed Oct 22, 2014 12:00 am

I'm restoring a '79 Lotus and seek advice on preparing the body for paint. It's in its original skin, an acrylic metallic in generally fair shape, and I'm thinking that it will be sufficient to just clean and scuff up in order to be ready for a modern paint job. In other words, there's no particular reason to sand down to the gelcoat, correct?
Steve

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Re: To Paint a Fiberglass Car

Post by Bubstr » Sat Oct 25, 2014 2:33 pm

If there are no adhesion problems with the paint on the car and it's not too thick. Sand it, waterborne primer/ sealer and paint. If it's not adhering or thick build up including primers, strip it if you want it to last. Just like all re-paints. The waterborne sealer insures the Acrylic enamel doesn't get attacked buy the newer solvents in the paints. With out that, you can get ring around the repair, anywhere you break the surface of the Acrylic.
Older I get the less I know for sure

chimpvalet
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Re: To Paint a Fiberglass Car

Post by chimpvalet » Wed Oct 29, 2014 1:26 am

Thanks, Bubstr, looks like I'll be wet sanding the car through about 1 mil of old acrylic down to the factory primer so shouldn't be too tough.
Steve

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Re: To Paint a Fiberglass Car

Post by Bubstr » Wed Oct 29, 2014 6:11 pm

How did you determine how thick the paint was as most gauges work off magnetic readings? I don't think we will find metal in the fiberglass. If you have a rock chip or scratch, which most do, block sand that and the ring will be more accrate at telling paint build up. Spray paint a guide coat over the area and any ring over 1/4 to 3/8 is with in tolerances for the build up of modern urethane paints that are low build paints. 1/2 inch ring says take it off. It will chip badly when done.

Hand sanding a Acrylic paint job off is not a easy task. I really don't like the strippers for fiberglass either. I prefer to use a 3M Mickey Mouse Pad on a low speed grinder with 80 grit to get most of it. Then a palm sander with 150 and finally hand sand wet with 400. This will save on tennis elbow. Still I would prefer the waterborne Sealer, just in case. If you have the palm sander mastered, you can do most of the 400 work with it. I sand clear coats before buffing with it but have done it for almost 60 years. Keep it flat to the surface just like you where using a block. I prefer Hutchens sanders. Better balance.
Older I get the less I know for sure

chimpvalet
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Re: To Paint a Fiberglass Car

Post by chimpvalet » Thu Oct 30, 2014 2:21 am

Thanks again for your wisdom, Bubstr. One mil was the opinion of an experienced old bodyman who noticed the topcoat had been rubbed through on one of the crisp edges at the top of a fender. My best guess is that rub-through occurred because the car had been stored outside, with a plastic tarp flapping onto the fabric car cover from time to time. It's the original factory paint from '79 and colour rubs off with a rag wetted with lacquer thinner. So if that means it's not urethane, then it would be what Lotus called "nitrocellulose". I hear ya loud and clear as to avoiding tennis elbow - already got that going on, left side. Since the body is real smooth from the factory and the color coat is thin I wonder if you are sure you'd stick with the dry 80 grit?
Best regards,
Steve

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Re: To Paint a Fiberglass Car

Post by Bubstr » Thu Nov 06, 2014 2:02 pm

80 Grit is my choice. You need sander control. Keep it almost flat. If you get too flat, the sander will jump around on you. Keep that sander moving also. you don't want it to dig in. Each change of grit will erase the last sand scratches. The last set of scratches is your adhesion for your sealer. You would be right on the old GM being Nitrocellulose lacquer. The good thing about it, is it isin't prone to ring around the repair as enamels are, in case you miss some. If it was Steel. I would start with 40 grit stopping short of the bare metal.
Older I get the less I know for sure

chimpvalet
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Re: To Paint a Fiberglass Car

Post by chimpvalet » Thu Nov 06, 2014 7:31 pm

Thanks Bubstr. I'm still weeks away from getting at the paint, the way things are going right now. I'll check back in once I've had some results to share.
Steve

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Re: To Paint a Fiberglass Car

Post by F-BIRD'88 » Sat Mar 14, 2015 11:40 am

If the paint can be rubbed off by wetting with a laquer tinner soaked rag, it is Laquer.

If its that old its finished . Time to strip it off. As it will now surly be checked.
The checking will show up in the new finish.
Remove it. You can power saned it off with 180 paper on a D A. ( dual action air sander.)
DO NOT REmove the gelcoat. Just the paint and primer.
STAY OFF THE EDGES AND BODY lines with the D A sander. Mast
k them off with masking tape if nessessary. Do these edge-bodyline areas last, by hand. 180 dry or wet.
Then when all stripped off wash the gelcoat with wax and grease remover.
Repair all cracks etc with fiberglass cloth and resin. Repair any gouges, scratches with body filler and 2K putty
to a 240 grit finish
Coat with a premimum 2part epoxy primer. Usually 1 to 2 coats. You do not want a heavy coat.
Then, prime with a premimum 2 part 2K urethane primer surfacer.
usually 3-4 good coats.
Water sand or dry sand block sand to a 600-800 grit finish. ( usually start with 400 and work up)
A black charcoal dust power guide coat or thin black paint mist guide coat helps you see the surface
when sanding. If/when final sanding you find any small pin holes in the primer surface you can fill them with 2K putty
or the old school red lacquer putty and wet sand in by hand 600-800grit. Be sure you find and fill any all of these tiny pin holes before painting. (tiny pin holes that are in the fiberglass gelcoat and or body filler, that you don;t find before initial primer coat)
There are always a few. You MUST fill these tiny PIN HOLES. Or they show up in the new paint finish and cannot be sand
and polished out.

It is now ready for final primer sealer and Urethane paint. 1 stage colour or base clear.
Most shops are using water bourne base clear now.

Do not bother painting over old cracked lacquer paint. You are wasting your money as the cracked finish will show up in any new finish.

lacquer paint remelts when wiped with lacquer thinners. "thermoplastic"
Enamels will not remelt. "thermoset" The rag should come up clean beyond simple old top oxidied paint removal by the rag.
Most enamels EG acrylic enamel, from 1979 will be beyond refinisheing also. Time to strip off the old stuff
and start over.
Do not dig into the gelcoat. Paint sripper is nasty. If you got to use paint stripper use proper body protection, gloves etc etc.
Machine air DA sanding it all off takes a bit longer, bit the result is a lot nicer.
Do not use super course paper. You want a 180grit finish to prime over.

if you are skilled with using a DA sander you can start sanding with 120 grit on the DA.
Then progress to 180GRIT.
Do not use 40 or 80grit on fiberglass for stripping.
Its too course. you want a nice 180GRIT DA sanded surface when done. Again finish any bodyfiller-2K putty work to 240grit.

It's a good idea to follow a paint brand System. If you are going to paint with Dupont paint, use Dupont primers and sealers.
and follow their tech directions. If you are going to use BASF use all BASF undercoats too and follow their directions.

If you want a show car finish "Colour sand" "sand and polish" the Clear coat with 1500 -2000 wet sand paper and Polish it..
This stuff is the best for Polishing new Paint Clear coat.
www.farecla.com

G-3, then G-10. Use the G Mop polishing pad on your machine polisher.

chimpvalet
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Re: To Paint a Fiberglass Car

Post by chimpvalet » Sun Mar 22, 2015 10:53 pm

Awesome response, leaves nothing to chance, most appreciated! Now, if only I could find time away from business duties :(

Steve

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Re: To Paint a Fiberglass Car

Post by chimpvalet » Mon Nov 02, 2015 4:51 pm

Have finally just begun paint stripping and seem to be facing up already to a bit of a dilemma. I'm hand sanding to start, working on a small section aft of the rear wheelwell first with a sanding block and 80 grit dry for a short time then moving to 220 wet as these are what I have on hand. The sticking point seems to be a question of blocking, or flatting, as opposed to paint removal. I am a novice and would welcome further advice as it relates to what's going on. Specifically, the small body section in question seems to have high sections along its edges even though the surface does not look concave. To my eye it seems the section should be either flat or slightly convex for best aesthetic. In the lower edges I have cut through the gelcoat, which is pink, exposing raw fiberglass. So I'm concerned that either a lot of rectification may be needed by the time the whole body's been prepared, or I need further coaching on my approach.
Thanks,
Steve
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chimpvalet
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Re: To Paint a Fiberglass Car

Post by chimpvalet » Mon Nov 02, 2015 9:52 pm

On reflection, decided to tilt toward paint removal over blocking / flatting. Switched to a narrower block with a strip of fairly stiff foam behind the paper. As a result I could focus removal on the areas where paint was remnant with a fair bit of control, using wet 220. Tomorrow will get some supplies in 120, 180 and 240 wet/dry so should be able to pick up the pace a bit. No DA air sander in the picture as I ran out of space for a compressor within the garage long ago owing to household and business needs competing with the car project. Picked up a small orbital electric sander dirt-cheap which I may be able to use but not sure whether it will offer much over wet sanding in terms of effort or pace. Nice aspect of the wet sanding is that it's dustless and not too difficult to moderate removal of material.

Steve

chimpvalet
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Re: To Paint a Fiberglass Car

Post by chimpvalet » Mon Nov 02, 2015 9:57 pm

p.s. - paint looks to be enamel, not lacquer. Looks like rather thin layers of gelcoat, primer and top coat over the fiberglass.

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Re: To Paint a Fiberglass Car

Post by chimpvalet » Tue Nov 03, 2015 7:38 pm

OK, school's in and here's what I'm starting to appreciate about the task ahead. The finishing layers are quite thin, which I suppose is to be expected. Block sanding while removing paint has revealed that the body surface is less even than I thought and so I'm through the surface layers to glass in high spots before all traces of topcoat are removed from the low ones. 220 wet offers plenty of control but is slow to remove material, so I've gone to 100 dry for quicker progress. If I'm seeing things correctly it appears that levelling out the skin is likely to be needed far more extensively than I had thought. In other words, the car is less consistently finished from the factory than my eyes could see. Question to more experienced members: Is this what one should expect for a '70's import?S
Thanks,
Steve

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Re: To Paint a Fiberglass Car

Post by Brian P » Tue Nov 03, 2015 8:13 pm

It's unlikely that the manufacturer (i.e. the assembly workers) put effort into making the car flawless. Light weight and low cost would have been more important than having flawless surfaces and gaps.

That car was not mass-produced in the modern sense. Not painted by robots - means the paint won't be a consistent thickness and not consistent from one vehicle to the next.

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Re: To Paint a Fiberglass Car

Post by pdq67 » Fri Nov 06, 2015 11:21 pm

May I throw this out here.

I was at a car show somewhere sometime and walked by a tent where a guy was holding a pop can. He was hawking, "media blasting". He handed me the can and told me that he took it down color layer by color layer using his system. Never roughed up the aluminum can at ALL!!!!!

He went on to say that it was safe enough to use on F/G and that was why he was talking about/selling it, etc., etc... 'Vette's and such cars body work...

Anyway, it impressed me to say the least.

pdq67

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