Common to see bonding strip though paint?
 

On my recently acquired '78, I can see and feel where the bonding strip is on the ds rear quarter. It's a long narrow line following the curve of the rear about two inches below the top edge. I would not be surprised if someone replaced this panel. The car has been repainted. Is this common? Sorry, no pix yet.

Yes, it's common. That's a factory bonding strip, sooner or later they show through the paint.

I can see mine very faintly. I tried to show it to my wife, but she can't see it. :lol:
I can't feel it though, it's kind of strange.

Thanks fellas. Makes me feel a little better. I'll get you some pix asap.

Jay

Common, almost EXPECTED with original paint.
With a repaint, you'd think they would have cleaned up the bonding areas before paint. MAYBE that rear panel that still shows WAS a repair that shrunk after the new paint.

The latest issue of Vette Magazine has a small article about how to repair the area. They say you should grind it down and apply 3 layers of fiberglass mat (not cloth) to the areas. I'm not sure if this should be done automatically when you get ready to repaint or only if it shows?

http://i106.photobucket.com/albums/m...e/scan0012.jpg

81 shown; other years are similar. These bonding seams have been smoothed but not yet been sanded down. With age, the bonding resin shrinks and the seams begin to show.

:)

:lol: I swear my seams are going away with age.....

I can only see them now when I have my bifocals on.....:lol:..:cheers:

Stock vettes are sometimes a wavy mess...when a car is too straight and slick then we know it's had all kinds of body work,

Didnt I hear somewhere the NCRS looks for wavys and such?

Only way to make sure they won't show in the new paint is to glass them. 3 layers is not enough, IMO. They should be ground down to the bonding strip behind the panel so all traces of seam filler are gone, then built back up with as many layers of glass it takes to be flush with the panel.

http://www.imagesup.com/usr/84/IMG_0244.JPG
http://www.imagesup.com/usr/84/IMG_0380.JPG

:iagree:

Pretty poor repaint if they didn't fix imperfections at that time.

They probably did but the lines will keep coming back until it is glassed. Glassing the seems is not part of a regular paint job. It's quite a bit of work.

:iagree:

When I took my car in for paint the body shop told me the one thing I need to address are seems and gaps. I could take a pass on it and just paint the car but the car will not look right down the road. I had them do seems and door gaps

I guess I should of said pretty poor body shop not to inform the customer on what the car will look like if they don't fix seems.

All the quarter panel bonding strips show on my original paint '78. Maybe the one that shows on yours is the only one that hasn't been repaired in the past?

Whether the bond strip areas are just filled with a resin adhesive/filler or glassed in (strands of any configuration) doesn't matter.
It is a common misconception.

It is the resin only that shrinks and causes the eyesore.
Glassing will make it stronger and is a very easy way to solve the problem. Improper curing, will still show with this method.
One can also use any of several none shrinking thickeners to make a filler.

Epoxy again, is the best to use since it shrinks the least. The stuff I use is rated at 1% shrinkage (still noticeable after curing and before sanding). Polyesters and vinylesters have much more shrinkage.
When these cars were built the resins were old tech and no where near the properties of current epoxies. They get better every year.
Optimum strength and minimal long term shrinkage is almost completely reduced with the use of a heated postcure curing process.

Hobbyists can ideally set the completed repair in as hot an environment as available (up to 120° for at least 24 hours, preferrably a few days before grinding or sanding.
I used to use a big kerosene salamader in a paint booth at over 100°.

Body shops usually don't want to take the time or take up the space for that length of time and it won't show for a long time down the road so......

Usually only the earlier cars (C1 and C2). The newer fiberglass panels used on C3s were much smoother than the older cars and required far less body work at St. Louis. The SMC panels used after 73 often needed nothing more than scuff sanding.

Not necessarily.

:)

SMC started before '73, but not all panels were SMC. The first, I believe, were the quarter panels in '71.

I have a NOS quarter panel on my car and it didn't need much before paint.

Correct. 71 rears. Additional panels in '72; by '73 they were all SMC.
:)