Old fender repair, info please?

[conesare2seconds]

Is there a trick to making a fender repair last?

My car had a fender cracked years ago with a prior owner. Although the paint is nice, I could see the repair underneath and had it redone. The body guy said the first shop used cheap filler and he had the material to do the job right, etc.

Fast forward a few years and I can see the repair work again. The old crack isn’t visible, but the skim coat is showing imperfections I didn’t see when the panel was refinished. I kept an eye on the repair as it was done and the panel seemed well finished before paint.

It’s something I’ve observed with other C4s, too - over time, any filler seems to keep shrinking and though smooth at first, eventually shows through the finish.

What’s going on and is it inevitable? Was the repair just not done properly again? Am I going to have to track down a whole fender and have a replacement bonded in?

[lfalzarano]

I have never heard of filler on fiberglass Corvette unless it is resin and fiberglass mat. I did my 68 427 and it never cracked after primer and painting.


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[Carnutdallas]

Shrinkage due to material differences. Extremely hard to do right. Practically impossible unless you prep, repair and wipe the entire panel. I own a Collison center and steer away from Corvettes, even though I own 4 of them, LOL.


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[Flyman 27]

That would happen if they used a fiberglass resin to make the repair.
A C4 is made with a SMC resin which is not compatible with standard fiberglass resins.

[lfalzarano]

That would happen if they used a fiberglass resin to make the repair.

A C4 is made with a SMC resin which is not compatible with standard fiberglass resins.



Didn’t know that... Fortunately I don’t have a need to repair the fiberglass on my Z!


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[fred]

That would happen if they used a fiberglass resin to make the repair.
A C4 is made with a SMC resin which is not compatible with standard fiberglass resins.

C4s require SMC compatible resins, epoxys and fillers to get the "bite" needed to make repairs and be able to feather edge the repair. I've had better luck using epoxy adhesives in place of resins. Always use epoxy primer/fillers, and use matt instead of mesh or screen. C4s were the first generation to not use bonding strips to join panels, but hid the joints.

[billschroeder5842]

C4s require SMC compatible resins, epoxys and fillers to get the "bite" needed to make repairs and be able to feather edge the repair.

This is 100% spot on. Last year I had a small fender bender that required some work on the hood. The insurance company was willing to pay for cheap fiberglass/bondo materials while my shop insisted on SMC compatible products.

Eventually the insurance company caved and my hood got repaired the correct way.

[conesare2seconds]

Thanks for the info. The old crack repair isn’t visible, but the glaze coat that was used to feather in the repaired area shows through the paint now. Looks like I’ll have it re-done.