Clear Coat Split....

Anything goes in the world of fiberglass and plastic

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PostPosted: Wed Jul 18, 2018 8:52 am
A few years ago I came on this forum and with Darryl's help did a pretty nice paint job on a 76 vette. Today I drove it to the store and noticed the clear coat had a 9 inch split right on the top of the hood stemming from the cut out for my bug catcher. Well this is a bit distressing....no where else on the car did it do this. I have a heat shield under the hood, I used quality HOK products that were mixed as per manufacture's recommendations, the thing has always been garage kept and never seen the rain. I know that metal will expand when it gets hot but the entire car is fiberglass. You can run your hand over it and tell it was the clear that split, the paint is still intact underneath. Any ideas as to why this happened years later? More importantly, and ideas on how I can fix this? All opinions would be appreciated.

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PostPosted: Wed Jul 18, 2018 3:52 pm
Just for your info,
Fiberglass and plastics expand way more than steel does.
That's why Corvettes should never have more than 1 repaint on them.
I don't know why you got a split but if it's only in the clear then
I would think it's the clear at fault. Make sure you don't have a crack
under that basecoat that you can't see.
JC

(It's not custom painting-it's custom sanding)

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PostPosted: Wed Jul 18, 2018 4:01 pm
Man, that's strange.... doesn't look like the typical cracking I would see on fiberglass up in the clear coat. If the color is undisturbed it didn't come "up" from the fiberglass (well, unless the fiberglass did heat/swell, then shrink back). That looks like if you would take a 1/4th inch thick bar of steel and drug it on edge across the surface. That would kind of make a peel/crack effect. Are you sure you didn't hit something while driving or perhaps in storage???? My problem with this is....if you do repair it without knowing what did it will it simply come back.... For now I think I would measure and record the length/width of the thing and check it again in a few weeks. If has increased in size you may indeed have some type of heat/cool cycling problem with that surface...... Be curious to hear what other guys think of this......
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PostPosted: Wed Jul 18, 2018 8:23 pm
Yeah fellas, this is some strange brew. Nothing hit it or got dragged across it. I keep it in a humidity controlled garage covered at all times. With all the effort that Darrel and I put into this thing a few years ago I treat it like gold and that is the only place on the entire car it has happened. If you look at it you can tell it is just a separation of the clear. In any case, nothing is going to be fixed this year, I will wait till next spring. I was thinking about applying some clear, several coats in the crack with a fine line brush then wet sanding and buffing it out. I just don't know any other way to fix it. I will keep an eye on it and keep measuring it this summer and attack it next spring but if anyone has any suggestions on a fix for it by all means, lay it on me.
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PostPosted: Wed Jul 18, 2018 9:40 pm
The split has originated from the cut-out, and my opinion is because of the weakened structure of the cut-out. Something stressed that area, maybe from driving up or down a driveway while turning or ???. Might have even been from the hood shaking under accelleration.

I would strengthen the underside of the hood around the cutout with more fiberglass or perhaps a bonded metal strip.

Your idea of filling the split with clear might work, I'd try it, but repainting the hood might be the final solution.

Sorry about the split, looks like a fine Vette.
"If you can't move it, paint it." - U.S. Army

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PostPosted: Wed Jul 18, 2018 10:11 pm
NightTrain is on the right track (sorry, it just slipped out..... :lol: ) with that reasoning. It does look kind of a directional tear coming from that cutout. Even if it is being caused by movement I don't think I would add metal underneath as that might heat load and aggravate it again. I think I would rough up under there with grinder and go to a long hair mat with an epoxy resin rather than polyester resin.
As for the topside if I was going to try that with the brush I would still end up reclearing the whole hood again.
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PostPosted: Thu Jul 19, 2018 10:31 pm
DarrelK wrote:NightTrain is on the right track (sorry, it just slipped out..... :lol: ) with that reasoning.......

Good one Darrel. :rotfl: Everyone wants to be a comedian. lol

Good catch on the possibility of metal heat loading, didn't think of that...
"If you can't move it, paint it." - U.S. Army

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PostPosted: Sat Jul 21, 2018 8:28 am
Yeah, metal and plastics have an odd relationship. I just saw where a fairly well built kit car (Lambo Miura replica) was taken completely apart and reassembled because everywhere there was an original steel mount the fiberglass shrank and ghosted through the paint. I believe it was a black paint job so I am sure that the surface got very hot when at car shows. They ended up flipping the entire car over and layered a veil material with higher temp. epoxy resin. Then they made larger attachment bars as needed decreasing the total number of mounting points. Studs were welded into the bars so the body could be bolted to the mounting points.
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