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Old 09-25-2016, 05:38 PM
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Vette Fiberglass Prep Question

I'm brand new to this, but I'm planning to prep and paint my 85 Vette. It was hit on one side, and I just want to change colors completely after repairing it.

How far down should I be sanding it? I'm planning to hit it with epoxy primer, then a bc/cc. I see a few layers, and I'm not sure if I should stop early, or sand all the way down to the glass? Is there gelcoat on these vettes, and if so, which layer is it?

Also, in the front, there may have been work done already, I can't tell (where the little square is cut out). There appears to be a yellowish layer that's also present in the flexible rear part through some paint cracks. What is this?

What sandpaper would you suggest? I was just sandblocking with 80 grit, and then planning to move to 220. I can also DA. Would this be sufficient?

Any other advice would be appreciated. I only know bodywork in theory, and am pretty unfamiliar with fiberglass as a whole. I know its a ton of questions, but I'm just trying to get it close to perfect. Thanks for any advice in advance!
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Old 09-26-2016, 02:17 PM
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The gel coat is always on the visible side. To repair a crack you should taper the area (from the back side) 10 times as wide as the material is thick. Fill the area with layers of cloth and resin. (on the back side) Then use an epoxy filler on the visible side to fill and smooth the crack. From there it is going to be primer, color and clear to your mood.
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Old 09-26-2016, 02:51 PM
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Quote:
Originally Posted by OldTech View Post
The gel coat is always on the visible side. To repair a crack you should taper the area (from the back side) 10 times as wide as the material is thick. Fill the area with layers of cloth and resin. (on the back side) Then use an epoxy filler on the visible side to fill and smooth the crack. From there it is going to be primer, color and clear to your mood.
So then the gelcoat would be the white layer? Or is it the last layer before the fiberglass?
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Old 09-26-2016, 03:23 PM
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The gel coat is under the paint and on top of the glass. If you hit glass you have penetrated the gel coat.

The gel coat is sprayed into the mold before anything else (well there is release agent on the mold). The gel coat gives a nice smooth finish but very little strength. The resin is then sprayed onto the gel and the fiberglass is laid up on that. To finish the color, paint is sprayed over the gel coat (unless the gel coat is the finished color).
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Old 09-26-2016, 03:37 PM
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Quote:
Originally Posted by OldTech View Post
The gel coat is under the paint and on top of the glass. If you hit glass you have penetrated the gel coat.
Thanks for the replies. So out of the 3 layers between the paint and fiberglass on my car, its logical to say the one directly on top of the fiberglass is the gel coat...what would the other two be? A sealer and primer?

If you look at my pictures you'll see the layers go:
Fiberglass < Gray Layer < Dark Blue Layer < White Layer < Blue Paint

I'm trying to deduce what each layer is, and what would be the best layer to sand down to. I'm assuming that just reaching the gel coat would be the smartest thing for a new paint job? And in this case, that has to be the gray layer?
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Old 09-26-2016, 03:48 PM
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The gray layer is probably the resin. The dark blue is likely the gel coat. The white is primer-surfacer or sealer?? The gel coat should be thick compared to the others.
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Old 09-26-2016, 04:17 PM
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Quote:
Originally Posted by OldTech View Post
The gray layer is probably the resin. The dark blue is likely the gel coat. The white is primer-surfacer or sealer?? The gel coat should be thick compared to the others.
Hmmm...I don't really see any layer that's much thicker than the others. Doing a little more research, I've found a lot of people saying that Corvette's don't leave the factory with gel coat. Now I'm more confused than ever.

If the white is indeed primer-surfacer or sealer, do you think I would have a problem blocking it out and spraying paint right on top? Should I epoxy over it first? Or should I just sand to the gelcoat (if there is one?)
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Old 09-26-2016, 07:22 PM
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I think I can help, but unfortunately the right question hasn't come up so theres still an 800 lb gorilla in the room, hiding behind the curtain if you know what I mean.

Your hood ought to be junked, its hurt too bad. Thats my 800lb gorilla opinion.

But they are a thousand bucks, you say. That does not change my opinion.

Its probably made of SMC, sheet molded compound, which is about the same as fiberglass but its molded on both sides rather than just one. So its smooth on both sides and may not have been gelcoated in the traditional sense but primered instead. Repair materials and methods for that are essentially the same as fiberglass, which is called FRP.

In your first pic, the layers are clear, base color, primer.

In the third pic, layers are clear, base color, primer from when it was painted, and the black is a primer that was applied when the part was made.

Hope this clears things up. The hood is badly structurally damaged and a proper repair would be quite laborious even for a seasoned technician. The amount of damage there actually kinda caps the potential quality achievable in a repair... meaning even if you fix that or get it fixed... its likely to show up later and look awful. A less damaged salvage item would be my first idea and there are plenty of those around. A local find would really be the only practical thing because imagine shipping one.

There are fullblown fiberglass experts and Corvette experts in here but they aren't me. But I do have some experience with repairs. A fiberglass expert might suggest cutting away a large section and splicing it in. Again, very laborious and dependent upon what you can locate.
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Old 09-26-2016, 08:09 PM
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SMC is a different material and requires fillers and adhesives made for SMC. On a job like that just DA it with 80 grit, feather any foobobs and 2 wet coats of epoxy and go for it. And vettes do not have gel coat on them. the glass is a brown color of SMC is an off white.

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Old 09-26-2016, 08:38 PM
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Quote:
Originally Posted by OneMoreTime View Post
SMC is a different material and requires fillers and adhesives made for SMC. On a job like that just DA it with 80 grit, feather any foobobs and 2 wet coats of epoxy and go for it. And vettes do not have gel coat on them. the glass is a brown color of SMC is an off white.

Sam
3M has an adhesive that works with SMC and FRP.

I don't see how this is getting fixed with primer though-



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Old 09-26-2016, 11:23 PM
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Your hood ought to be junked, its hurt too bad. Thats my 800lb gorilla opinion.
Hmmm, that's a pretty sobering thought. I don't doubt you're right, simply for the fact that I bought this car with a salvage title. The damage didn't look too incredible to me, but I've heard that most insurance companies just wrote off Corvettes when the hood was damaged.

What kind of problems do you think will show through with a repair, and why do you think it probably won't work? I was under the impression that the way fiberglass is applied makes it pretty easy to create a shape, and that any minor deviations can be fixed with filler? These are all theories of course, I've never repaired fiberglass. I'm going to attempt the repair anyways, just for the educational value, regardless if I fail or succeed. What part of the repair do you think is just going to make me want to throw in the towel?

You're right about the layers by the way. I finally found a thread on a Vette forum with an owner going step by step through the prep process. He sanded just below the base coat, and applied urethane primer on top of the sanded factory primer. I'm going to do the same, except just sand the factory primer layer with guide coat, lay down some epoxy, and then the basecoat/clear....assuming I make it through the repairs that is...
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Old 09-27-2016, 07:14 AM
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If you're going to try it anyway, you'll find out for yourself. I don't know you so speculation about what makes you change your mind would be silly.

Tell us about the repair plan as it stands in your mind. Tell us about the materials you plan to use, and how you will use them. Tell us what makes you anticipate success. Tell us what the panel is made of and how a proper repair is done. Tell us your expectations for the repair. Gather more input. Ignore advice as you wish and proceed. It's your car so you can't fix it wrong, seriously.

I did not say I think it won't work, nor did I say anything about you throwing in the towel. I did say a repair will show up later on regardless of how it's done. Cracks, bubbles, pits.

If I see a kid zooming down a driveway on a bicycle toward a busy street, I'll try to at least knock them down before they get run over. If the kid gets up, waits for the next car then deliberately tries to get killed.... I'm not trying again because there's something I obviously don't understand going on. All I can do is hope all the cars miss them and that I don't get sued for trying to save a person from themselves. You go play with fiberglass and I'll just keep walking.
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Old 09-27-2016, 11:19 PM
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No need to be melodramatic, nobody is going to get killed over this project lol. You're probably correct though, I honestly have no knowledge or experience with fiberglass. I just don't think I should scrap the hood without at least trying no?

From my limited research of fiberglass and how fiberglass repairs work, it just seems as if it's possible to fix the damage on my vehicle. I've watched videos of people successfully (at least short term) patching cracks and even holes on corvettes and other cars. They seem to have come out alright (at least short term), and it seems like fiberglass is meant to repair to not show up later on, if done correctly. I can't imagine that heavy fiberglass damage is impossible to repair. Now as to WHY my damage is irreparable as opposed to other "minor" damage...I'm ignorant to the science, and I'm hoping to be educated by people like you.

I'm not saying that I'm going to have drastically different results than you've ever had...I'm just trying to put this puzzle together in my mind so that I have the greatest chance of success...

Improbable? Definitely. But Impossible? Until someone gives me a legitimate reason why this repair is impossible, I can't accept that...
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Old 09-28-2016, 01:14 AM
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Fiberglass prep

I was a certified GM body tech when this Vette was new, I will tell you that Sam is 100% correct, THIS CAR IS NOT repeat NOT fiberglaas, it is Sheet Molded Compound(SMC). Corvettes have NOT been fiberglass since the new body style came out in the '84 model year. If you try to repair it with fiberglass, you are not only wasting your time, but also your money on materials. You asked a legitimate question, and he gave you a truthful, legitimate helpful answer. I guess if you are dead set on doing it this way, WHY did you ask?? Sorry to blow my cool, but it seems like ANYONE who can throw bondo, and sand it smooth thinks they are a "bodyman"
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Old 09-28-2016, 07:00 AM
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Quote:
Originally Posted by 928Vette View Post
No need to be melodramatic, nobody is going to get killed over this project lol. You're probably correct though, I honestly have no knowledge or experience with fiberglass. I just don't think I should scrap the hood without at least trying no?

From my limited research of fiberglass and how fiberglass repairs work, it just seems as if it's possible to fix the damage on my vehicle. I've watched videos of people successfully (at least short term) patching cracks and even holes on corvettes and other cars. They seem to have come out alright (at least short term), and it seems like fiberglass is meant to repair to not show up later on, if done correctly. I can't imagine that heavy fiberglass damage is impossible to repair. Now as to WHY my damage is irreparable as opposed to other "minor" damage...I'm ignorant to the science, and I'm hoping to be educated by people like you.

I'm not saying that I'm going to have drastically different results than you've ever had...I'm just trying to put this puzzle together in my mind so that I have the greatest chance of success...

Improbable? Definitely. But Impossible? Until someone gives me a legitimate reason why this repair is impossible, I can't accept that...
Dogmatic individuals stump me every time. I told you it was probably SMC because the advice you were getting was heading in the wrong direction. When you insisted, I used a strong analogy. SMC repairs that I'm familiar with are spliced, not ideal for a hood. Look before you leap, but don't look for my assistance.
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