fiberglass repair

[Chester M.]

bracket holding headlight assy.in place. rivets sweling,lifting panel.

[Gene M.]

Re: fiberglass repair

My '68 started to show thru again. That really ruins the looks of the car. But I shouldn't have attempted to "fix" it years ago the way I did. I was told that grinding out the rivets completely and bonding in the brace instead of rivets would correct the problem. But I'm not going to do anything to fix it. I learned to live with it. I guess it just does not bother me enough any more...........

[Chuck S.]

Re: fiberglass repair

My '68 started to show thru again. That really ruins the looks of the car. But I shouldn't have attempted to "fix" it years ago the way I did. I was told that grinding out the rivets completely and bonding in the brace instead of rivets would correct the problem. But I'm not going to do anything to fix it. I learned to live with it. I guess it just does not bother me enough any more...........

Sorry for your pain, Gene.

I know this problem happens, but could you elaborate...If the rivet heads are completely gone, what is causing irregularities to show through on the top surface again?

Actually, if I remember my 70 correctly, the center nose reinforcing beam is riveted to a fiberglass "bonding strip" that is then bonded to the underside of the nose.

[Terry B.]

Re: fiberglass repair

My '68 has the same problem. I have at least 10 rivet bulges on the nose plate that supports the headlight bezel. I have been through the judging process a few time with this problem and the more experienced judges have said this was typical of the '68 that had not been restored. They do not ding me too bad on it. I'm curious if other '68 owners with original unrestored front nose area are seeing it too. I would love to fix it but not sure what works.

I would like to hear from others who have had the problem.

Terry

[Pat M.]

Re: fiberglass repair

My 70 has 'em, but they're not real noticeable. Unless they get much worse, I'm not foolin' with it. I fear the "fix" will end up being worse than the problem.

[Michael G.]

Re: fiberglass repair

To the best of my knowledge, this is common with most of the early sharks. My 71 has them also. I inqired to someone with a 70 with fresh paint and no dimples. He explained that his body-shop had to reinforce the bond from underneath the body and then remove the dimples. He did not know much about the process and just recommeded I use his man. I know they don't look so great but I'm not sure we should be removing them. It seems they are either a factory flaw or a result of the curing process of the fiberglass. I have read that the curing continued for some time after these bodies were completed. Mike

[Steven G.]

Re: fiberglass repair

My early 70' reveals front nose panel rivets and always has, after 30+ years, they do seem more noticeable. On a 72 project car, the rivets seemed to be corroded and filler cracking at the pins, the header bar was very rusted, I will replace rivets and header bar for a lasting paint job. A good underside inspection may be required. Steve

[Erik S.]

Re: fiberglass repair

a very well known and experienced corvette painter here in the Netherlands is arguing that one should simply get the rivets out and just glue the piece together. Has someone ever done this as well?

[Jack H.]

Re: fiberglass repair

OK, boys and girls, this is a COMMON issue with Shark cars. It's created by electrolsis.

You've got a steel reinforcement bar that was painted black. It's held in place by aluminum rivets going through fiberglass. That gives the basis for a 'battery'...dissimilar metals separated by a dielectric insulator.

Now, log some miles/years on the car and let the thin black paint on the reinforcement bar wear away to expose the underlying steel. Then, throw some water up into the nose (salt water from near-the-ocean, or off winter roads accelerates the process) and you've added the finishing touch to the 'battery'...an electrolyte solution!

Over time the aluminum rivet will corrode from the process and 'salt' (the unintended byproduct of an oxidation/reduction process) forms on the rivet and migrates to point of minimal field strength--the TOP of the rivet.

The added material (rivet + salt) causes the overlying fiberglass to 'bulge' and we get the customary 'ringed dome' deformations that early Shark cars are known for...

If you cut away the upper fiberglass where it's bulged, you'll find a quantity of white powder beneath (the 'salt' from the oxidation/reduction process). One 'fix' is to suck the salt out with a vacuum cleaner and fill/sand the access holes cut into the fiberglass with bond.

This 'fix' WILL NOT LAST! It's a fool's errand in futility because it doesn't address the root cause. It might make the car pretty enough for a quick sale, but those bulges ARE going to return with time...

The way to stone cold kill the problem is reasonably simple:

(1) Cut out the bulged fiberglass

(2) Drill out and completely REMOVE the aluminum rivets. They were only there to hold the reinforcement bar in place prior to the final assy of the car's front clip...

(3) Now, fill the holes with FIBERGLASS (not bond!) and sand the surface flush prior to touch-up painting.

If you insist on preserving the factory originality of the car (bottom of rivets visible via inspector's mirror in the nose area), you're looking at a MAJOR chore. The only way you can get from here to there is to clean up the 'salt' and touch-up paint the reinforcement bar where it's likely to make physical contact with the rivet(s) to electrically insulate the system.

BUT, a 'cleaver' short cut here is to fake it! Take the rivets that've been drilled out and cut off their lower tips. Now, fill the holes as outlined with fiberglass. Last, glue the cut off lower rivet tips in place so savvy judges will 'see' what they expect to find in the nose area that's characteristic of factory original construction techniques...

[Michael D.]

Re: fiberglass repair

I agree with Jack. The fix is to remove the rivets, otherwise the reaction between the rivets and the steel header will continue.

PITA.

[Terry B.]

Re: fiberglass repair

Jack,

Thanks for your complete response to the repair. Your explanation makes a lot of sense. I would assume that a number of early sharks have developed this problem and it is nice to know the best way to fix it.

I have a question about the repair. If I drill out all the revits, is there anything holding the backing plate to the fiberglass or am I missing something?

Thanks, Terry

[Michael G.]

Re: fiberglass repair

Thanks Jack. I appreciate your detailed process to the fix. Now just let me know when you are available to assist me in doing this to my 71. Thanks, Mike

[Pat M.]

Re: fiberglass repair

My fear is that anytime you put holes in the fiberglass there is the danger of the filler eventually shrinking, like I've seen on many cars that used to have luggage racks. You could then have a bunch of little depressions where you had a bunch of little domes before. Is that any better?
I'm sure if that happened you could repeatedly fill the holes until the shrinkage stopped, but you're talking about a lot of filling, leveling and painting. Think I'll just live with mine - at least for a good while.

[Jack H.]

Re: fiberglass repair

"My fear is that anytime you put holes in the fiberglass there is the danger of the filler eventually shrinking"

You are 100% correct! That's why I specifically said NOT to use bond to fill the holes...fill them with FIBERGLASS.

That means taking actual glass mat (NOT 'boat' cloth), ripping it down into small 'clumps' of fiber strands, mixing the strands with resin, hand pressing out excess resin and applying a THIN layer to sand out before you repeat the process with your next layer.

You might have to lay down 12-20 individual layers to get the job done RIGHT, but when it is done right the repair will be as strong/durable and unchanging as a factory original press molded panel.

The typical reasons for why repairs that use actual fiberglass instead of bond tend to become visible over time are simple. The body man took a short cut and tried to fill a hole with 1-2 layers.

Plus he probably didn't get right recipe for the glass to start with (correct strand size/correct resin ratio/correct resin to glass uniformity mid). Then, he probably laid in the fill WAY too thick.

Over time, with such a thick and incorrect 'fill' the resin outgasses and the fiberglass shrinks leaving telltale(s).

When you build the repair up in multiple, sucessive, THIN layers with the resin properly hand pressed to the correct consistency (glass to resin ratio + uniformity), you begin to approach the structural density of the original press molding process using hand-laid glass techniques. When it's done right, it's right...

[Chester M.]

Re: fiberglass repair

OK, boys and girls, this is a COMMON issue with Shark cars. It's created by electrolsis.

You've got a steel reinforcement bar that was painted black. It's held in place by aluminum rivets going through fiberglass. That gives the basis for a 'battery'...dissimilar metals separated by a dielectric insulator.

Now, log some miles/years on the car and let the thin black paint on the reinforcement bar wear away to expose the underlying steel. Then, throw some water up into the nose (salt water from near-the-ocean, or off winter roads accelerates the process) and you've added the finishing touch to the 'battery'...an electrolyte solution!

Over time the aluminum rivet will corrode from the process and 'salt' (the unintended byproduct of an oxidation/reduction process) forms on the rivet and migrates to point of minimal field strength--the TOP of the rivet.

The added material (rivet + salt) causes the overlying fiberglass to 'bulge' and we get the customary 'ringed dome' deformations that early Shark cars are known for...

If you cut away the upper fiberglass where it's bulged, you'll find a quantity of white powder beneath (the 'salt' from the oxidation/reduction process). One 'fix' is to suck the salt out with a vacuum cleaner and fill/sand the access holes cut into the fiberglass with bond.

This 'fix' WILL NOT LAST! It's a fool's errand in futility because it doesn't address the root cause. It might make the car pretty enough for a quick sale, but those bulges ARE going to return with time...

The way to stone cold kill the problem is reasonably simple:

(1) Cut out the bulged fiberglass

(2) Drill out and completely REMOVE the aluminum rivets. They were only there to hold the reinforcement bar in place prior to the final assy of the car's front clip...

(3) Now, fill the holes with FIBERGLASS (not bond!) and sand the surface flush prior to touch-up painting.

If you insist on preserving the factory originality of the car (bottom of rivets visible via inspector's mirror in the nose area), you're looking at a MAJOR chore. The only way you can get from here to there is to clean up the 'salt' and touch-up paint the reinforcement bar where it's likely to make physical contact with the rivet(s) to electrically insulate the system.

BUT, a 'cleaver' short cut here is to fake it! Take the rivets that've been drilled out and cut off their lower tips. Now, fill the holes as outlined with fiberglass. Last, glue the cut off lower rivet tips in place so savvy judges will 'see' what they expect to find in the nose area that's characteristic of factory original construction techniques...

Jack thanks for your info.