Question: Err, Stress Cracks, anyone?

[richross]

Does this look familiar to any other shark owners out there? I've got these fine cracks about an inch tall along the upper curve of my forward driver's side fender. They are so uniform and match the curve of the fender so well I figure they're stress cracks from where the two fiberglass sheets come together. If I sight along the car from about the driver's side door, I can see a very light ribbon-like depression of similair dimensions running in that direction. I've checked thouroughly under the wheel well for any sign of mis-color or body work and she looks clean as a whistle. Any ideas? :confused

 

[White75]

Looks about where the bonding strips are if memory serves me right. My dad's 78 SA with no body work has a similar ribbon that you mention. Could be related to shrinkage over time?

 

[richross]

Yep, I think you're right. I've since seen a picture a stripped-down 78 Pace Car that had the bond-strips right where I see the cracks... I'm guessing that you're right: probably expansion-shrinkage over time...

 

[JohnZ]

Here's where the bond seams are on late C3's.

 

[gmjunkie]

Here's where the bond seams are on late C3's.

I Likey the Photo John!!

 

[richross]

John- That's one slick photo- saved it to My Pictures! I am perpetually amazed at how much people know out there... It's the 'Information Age' at work!
THANK YE!

 

[bill81vette]

YUP!!! I had them show up after mine was repainted,I figured that the body
flexes there...I have them on ALL 4 quarter panels

 

[richross]

Are the cracks just as likely to show up after a repaint as appear in the original paint, or is there something about the body-work process prior to a new paint job that increases the likelihood that the cracks will appear?

 

[Evolution1980]

Are the cracks just as likely to show up after a repaint as appear in the original paint, or is there something about the body-work process prior to a new paint job that increases the likelihood that the cracks will appear?

When I had my car repainted, I was told that if there's cracks in the fiberglass, even if they smooth 'em out or whatever they do, they will eventually come back. A few small ones on my car came back within the year. When I inquired about them, I was told that the only way to get rid of them is to remove/replace the entire part that's cracked. Kinda like getting rid of rust I guess...

 

[6880 Mike]

Are the cracks just as likely to show up after a repaint as appear in the original paint, or is there something about the body-work process prior to a new paint job that increases the likelihood that the cracks will appear?

The cracks you reference are probably not in the fiberglass body panels. Although I've never seen the specific pattern in your photograph (strangely uniform), you are apt to find the bonding resin used between the upper surround panel and the fender has shrunk with age. Bond shrinkage is a common older Corvette problem and usually more noticeable on the rear fenders.

At the time of repaint, you can fill the low areas, sand them back to body contour, prime and paint.

Here's a pic of the fender/surround panel joint from the same series of pics as posted by JohnZ ('81 production at St. Louis). Dark area is bonding compound sanded to contour and ready for primer.

BTW: There is a series of plant photographs taken at St. Louis in December of 1980, possibly two dozen or so. They are in the public domain on the internet and you can probably google up the whole series. Since they are already available free, no sense buying them from the dude on ebay who's trying to sell them.

 

[jims427400]

I'd like to see those production pics, does anyone have the link to those..

 

[richross]

Yeah, me too. Mike, do you happen to know the link to the plant production photos? I would happily sacrifice some computer memory or zip drive those photos.

 

[6880 Mike]

I believe I pulled down the pics from Corvette Forum. They may even be on C3VR. Hop over and check the archives.