I have decided to repair the visible bond lines on my 69 coupe ( after much thought) and deal with the over restoration points loss. I just can't bring myself to leave them visible. My question is what is the best way to repair them so the repair won't be visible 5 years down the road.
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Re: bond line repair
It's called "'glassing the seams". Buy yourself a good fiberglass repair book; I liked Eckler's book, but now I believe they are selling the information in high-dollar CDs. (NCRS isn't the only one that's discovered there's gold in "them thar CDs"!)
Grind a v-shaped depression along the seam...you should end up with a shallow swale about 2+" wide along the joint, and nearly to the bonding strip in the center of the seam. Cut 2+" wide strips of fiberglass mat to fit the ground area...some people insist the mat should be torn to facilitate feather edging the repair. I find that tearing the mat is a RPITA...it makes it impossible to have any kind of consistency in the strips, and you're going to end up grinding the entire repair down anyway.
Laminate the mat strips over the ground area by saturating the mat with catalyzed polyester resin, applying the mat, and rolling the lamination thoroughly to remove air bubbles. Repeat until you have at least three layers...I like to put four, or as required to bring the lamination back up to the fender contour. Let it cure, then grind and sand the lamination to contour. Finish off with body filler as required.
Plan on doing this repair early in the restoration and letting it "gas out" in the sun for about a year before painting. -
Re: bond line repair
How is one suppose to handle the seam issue if he is going to restore the body of a car to original specs? Just paint over the seam? Maybe gel coat?Comment
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Re: bond line repair
Sure...you can do those things; however, it's unlikely that you will (1) fill the visible crack with those materials, and/or (2), having been successful at filling the crack, make a repair that will stand the test of time. Even if the crack doesn't return at the original location, a seam that has already cracked is just as likely to crack again at another location a few inches away.
"Glassing the seams" is the conventional approach, and it was not invented by people looking for the easy way out; it's a very labor intensive repair. The reason short-cuts for this repair never caught on, irrespective of seam originality, is because people that do body work for a living grew weary of seeing that Corvette drive back up in the front IMO. This procedure eliminates those crude, original sunken seams that we all love by essentially making the fender one continous piece of fiberglass.
You can't have it both ways. Pick your poison...choose either non-original seams or non-original cracks in the seams. No judge can honestly claim that NO car came out of St. Louis with perfect seams; OTOH, anybody should be able to tell you they didn't come off the assembly line with cracks in the seams.Comment
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Re: bond line repair
Thanks Chuck, do you recomend stshting with a narrower strip and progressing to wider strips on second and third coats? What are yor feelings on gelcoat as a sealer? My car was striped to the bare glass when I got it. I don't know how long it was sitting and I am concerned about contamination in the glass although it appears to be clean. If you recomend gelcoat which one would you recomend? Thanks BradComment
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Re: bond line repair
Yes, I adjust the width of the successive layers to avoid excess thickness at the edges of the ground area. You can expect the width of the mat strips to grow about 20 percent or more once they are saturated with resin and you roll them, but I don't consider that in cutting them to size.
The biggest problem with having the body stripped for a long time is oils from your hands or from other projects going on in the same space. Dust should wash right off with a good soap and hot water bath. I keep mine covered with a car cover. Inspect the fiberglass carefully for oily hand or finger prints, splashes, etc. and wipe those areas with lacquer thinner. If it makes you feel better, wipe down the entire body with lacquer thinner...it won't hurt the fiberglass.
If the oil wasn't applied real wet (drips, splashes, etc), you can at least clean it off the surface and maybe entirely. If you have oily spots that remain after a lacquer thinner wipe down, I would consider grinding/sanding those areas deep enough to remove the oil, and then rebuild with mat and resin as necessary. You can't leave it there, because your paint won't stick to it...better to deal with a fiberglass touchup repair than paint problems later.
Gel coat...I'm still thinking about it. I will probably use it at least on the fiberglass repairs; but as I said before, elapsed time after the repairs will be your best friend. Eckler's would probably be my choice since I'm unfamiliar with other options that use PVA.Comment
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