Cracks in body work

[Stewart A.]

Hi there
I am used to metal cars not f/glass. I am seeing alot of Corvettes with hair line cracks in the paint work. Is this normal ! Is it normally the paint thats cracking or the glass. I am re painting my bonnet to get rid of these hairline cracks but not sure if the cracks in the paint work because of the f/glass. I was only going to sand the pant off and highfill the bonnet then paint. I am scared the cracks could be in the glass and will show their hiddious face again. Is there a prduct I can put on the f/glass to eliminate this from happening. Someone said its the shriking and expanding from the suns heat that causes it. Metal cars dont suffer as much shrinking and expanding so its not as common ? Any body experts out there I need advice.

[Donald S.]

Re: Cracks in body work

your gonna have fun . i have been doing fiberglass repair a long time . if the laquer is the problem striping it [do not use chemical stripper] priming and re spraying will solve your problem . but if they are stress cracks in the glass or gelcoat fiberglass repairs are nessacary in order to permanantly remove the problem . any fillers or primers put over cracked glass or gelcoat is temporary without proper fiberglass repair being done first the cracks will come back....Don .

[Chuck S.]

Re: Cracks in body work

No claim to expertise here, but most likely those cracks in the paint are from stress cracks in the fiberglass. New paint will crack over them just like the old paint did.

If there are only isolated instances of stress cracks in the fiberglass, they should be ground out and repaired with resin and mat. If they are too numerous to repair individually, then you'll proabably have to gelcoat the entire panel. If you haven't heard of gelcoat, it's like a thick catalyzed polyester primer that is difficult to apply, and even more difficult to sand smooth again.

Stress cracks are not due to expansion and contraction in the sun. Stress cracking in Corvette fiberglass is due to combined dynamic and static loads exceeding the strength of the fiberglass in local areas.

Depending on the generation of the Corvette, the areas of stress cracking are predictable...on early C3s, you will find stress cracks at the corners of the headlight door openings, at the front edge of the hood opening, and possibly along the front fender peaks (under some conditions).

[Stewart A.]

Re: Cracks in body work

Thanks Chuck and Donald.
Hey guys do you think I can use a product called polyester. I have used it before on things like laminex before painting 2 pak gloss and its worked great its very adhesive and sticks like shi_ to blankets. If its a fine crack in the gelcoat do you think I could drizzle resin over crack when dry sand it back before high-filling. How does that sound!
Your knowledge on this has been great so far thanks guys !

[Gary C.]

Re: Cracks in body work

Stewart, recommend a search of the archives on gelcoat. Lots of good information pros/cons about gelcoat and other alternatives Members have used. Personally, I prefer gelcoat. Gelcoated my '57 ten years ago. It's fiberglass had alot of fractures. So far so good - no cracks or spiders. Good luck, Gary....

[Chuck S.]

Re: Cracks in body work

Thanks Chuck and Donald.
Hey guys do you think I can use a product called polyester. I have used it before on things like laminex before painting 2 pak gloss and its worked great its very adhesive and sticks like shi_ to blankets. If its a fine crack in the gelcoat do you think I could drizzle resin over crack when dry sand it back before high-filling. How does that sound!
Your knowledge on this has been great so far thanks guys !

Polyester is a general class of chemical resins...not a specific product. A lot of the terminology you're using is foreign to me...you would pretty much have to experiment with what you are proposing. Like any experiement, the result may be favorable, or unfavorable. Others may be able to comment on your proposal.

For your general information, Corvettes before 1973 were mostly made of fiberglass known as FRP or Fiberglass Reinforced Plastic. Polyester resin is the "plastic" that binds the glass fibers together. Corvettes AFTER about 72 are made of a different material called SMC...technically speaking I think the resins used in SMC are STILL polyester resins, but because of the addition of fillers and other additives, adhesives and gelcoat formerly used for the old FRP can not be used on SMC Corvettes after 72.

Gelcoat is a polyester based product...using gelcoat is like spraying the body surface with catalyzed resin. Many body repair products, e.g. body filler, are polyester based.

To my knowledge, Eckler's is the sole supplier of the type gelcoat typically used on Corvettes. For the gelcoat to cure properly, air must be excluded from the process. With Eckler's gelcoat, this is accomplished by a waxy substance that migrates to the surface after the gelcoat is sprayed on the fiberglass. After curing, this waxy coating complicates sanding the gelcoat smooth.

When I mentioned stress cracks too numerous to repair, I meant a condition like Gary described where you have very shallow general cracking over the entire fiberglass surface. If you have discrete individual cracks that are deep into the fiberglass, those cracks are the result of loads on the body panel. Those kind of cracks must be repaired by taper grinding out the crack, then laminating several layers of fiberglass mat and resin to build the surface back up with reinforcement. The surface is then finished back to contour by grinding and sanding. It seems like a draconian solution when there are lots of band-aids you can apply, but if you don't take the extra measures, you may see a crack in the same place again soon.

[Stewart A.]

Re: Cracks in body work

Chuck thanks for the the tech tips you sound like you have been there before and don't you love it. I am doing this as a bit of a quick clean up. I am extremly fussy and just bought the broom broom from Pro Team put it in a container and shipped it 10,000 miles away to Australia. I bought it sight unseen. I am ordering parts like a mad man, so I can rip off the frame and do a full body off resto. The car is in terrible condition but its complete at least. (a complete basket case). I cant bring myself to drive around in it the way it presents itself so I am just giving it a little TLC for the time been. The car is red but its originally black so I will be changing it back to black after the parts collection. I figure it will take me about one to two years to collect all the parts.

[Edward M.]

Re: Cracks in body work

Stewart, recommend a search of the archives on gelcoat. Lots of good information pros/cons about gelcoat and other alternatives Members have used. Personally, I prefer gelcoat. Gelcoated my '57 ten years ago. It's fiberglass had alot of fractures. So far so good - no cracks or spiders. Good luck, Gary....

Gary;

My 56 has the same sort of "fractures" all over. Did you grind them down and fill them with fiberglass or resin before gelcoating? What gelcoat did you use?

[Richard M.]

Re: Cracks in body work

Stewart, curious......Do you have to convert the '60 to right hand drive there. Years ago a friend of mine sold a 59 to someone in Australia and they had to convert it. I think it was the law there then. Still today?

Rich
ps good luck with the project. I have similar fbgls issues with my '62 project.

[Stewart A.]

Re: Cracks in body work

The Law states that If the car is older than 30 years old the car can stay left hand drive. The law changed about 10 years ago. Although I have a very nasty 520 hp pavement stomper 65 Ford Mustang with a stout 347 cu inch Windsor in it. ( I own a Ford just to realise how good a chev is.)
I converted it over to right hand drive. And I think I had the worlds worse
handling car. My God it was dangerous, after about one year of constant tampering with geometry I finally got it right. Now its a killer, I just love dusting those rice burners to the weeds. Although have a guess how much fuel is now here. I figure its 4 litres to the gallon. I just paid $1.70 per litre of high octane today about $6.80 per gallon. The Aussie dollar is very strong at the moment its about 95cents USA. The average wages is about 50k per year. So dont winge about Gas prices. Its killing us !! I might start boiling potatos out the back for pure alcohol, it might be cheaper to run in the car ah.

[Chuck S.]

Re: Cracks in body work

...I am ordering parts like a mad man, so I can rip off the frame and do a full body off resto...

Since you have an old Mustang, I assume you have done restoration before.

If not, be careful not to spend a fortune on parts only to become overwhelmed by the immenseness of a body off restoration. A full body off restoration seems a no-brainer when you start that first project...after all, if you're going to be replacing parts, you want them all to be new at the same time, right? A body off resto can quickly become a case of "forgetting you set out to drain the swamp when you are up to your neck in alligators (crocodiles Downunder?)"

After being committed to one of these projects for years, I would recommend (1) restoring the car mechanically to insure roadworthiness, reliability, and original performance, (2) do some cosmetic body-on restoration sans exterior paint to improve appearance, and (3) drive the car to enjoy it and get acquainted with it. This will give you a chance to learn what the car really needs, and how best to restore it when you're ready.

For example, you will quickly learn that no repro part has been made that will fit and look as good as an original part...Rule 1: Refinish and restore original parts whenever possible; use repro parts only as a last resort. Closely related to Rule 1 is Rule 2: Never throw anything away.

[Edward M.]

Re: Cracks in body work

Chuck thanks for the the tech tips you sound like you have been there before and don't you love it. I am doing this as a bit of a quick clean up. I am extremly fussy and just bought the broom broom from Pro Team put it in a container and shipped it 10,000 miles away to Australia. I bought it sight unseen. I am ordering parts like a mad man, so I can rip off the frame and do a full body off resto. The car is in terrible condition but its complete at least. (a complete basket case). I cant bring myself to drive around in it the way it presents itself so I am just giving it a little TLC for the time been. The car is red but its originally black so I will be changing it back to black after the parts collection. I figure it will take me about one to two years to collect all the parts.

Stewart;

Pay attention to what Chuck S. said. It is easy to get a project to a state where it looks so overwhelming that you lose interest.

Having been down the "completely restore it" path a number of times, I am currently working on a 56 Corvette "rat rod". Plan is to 1. Get it running. 2. Drive it. 3. Think about how it looks (much later).

Attached pic is me driving the car down the block. First time in almost 20 years that this car has moved under it's own power.

I kind of like the looks of it now, but I need to do something to protect the fiberglass. Maybe a coat of primer.

[Chuck S.]

Re: Cracks in body work

...I kind of like the looks of it now, but I need to do something to protect the fiberglass. Maybe a coat of primer.

Yep, Ed, need something on there to protect the fiberglass from UV. You know, Mike McCagh has demonstrated that even flat black primer can look good on a C1...If it has an LT5 under the hood. HaHaHa...

[Edward M.]

Re: Cracks in body work

Yep, Ed, need something on there to protect the fiberglass from UV. You know, Mike McCagh has demonstrated that even flat black primer can look good on a C1...If it has an LT5 under the hood. HaHaHa...

I like the looks of flat black primer.

I am wondering if I can get orange primer? Orange primer, then paint number 20 on the doors, and I'm set. Next stop...Talladega!

[Stewart A.]

Re: Cracks in body work

Ed and Chuck fortunatley I have grown up in oil. My father was a mechanic and we owned a workshop, then as I got older we kind of expanded into about four of them. Got off the tools and became a paper head in the office. But the passion for cars was always extremely there.
Over the years I have done about six Mustang full resto's. But I have never done a body off. I have all the tools 5 car hoists 7 trolley jacks and about half a million dollars worth of tools.(half I'm not sure how to use). Yes I plan on driving the car now and injoying it until the parts are sufficient to start the project. I bought the car as a number 3 (good driver ) but when it turned up I thought they had sent me the wrong car. It was totally stuffed. I spent the first two days working on the car just to get it started. Finally started it to find the motor was unexeptable to drive anywhere (more smoke than a Iraq oil field). So I pulled the motor and tranny and have just got the motor back from the machine shop ready to put back together and place back in car. I dont get overwhelmed with restos I enjoy the journey as much as I enjoy the finish product.