I fixed some stress cracks on the 70 by grinding a V into the cracked glass
and then filling with resin and glass in layers to the surface. I then blocked everything, applied polyester glazing putty over the whole area, blocked again, shot polyester primer (PE Sprayfiller) guide coated, blocked,
then 2 coats of Standox 2khs fill primer, guide coated and wet sand. It looked
as smooth as a mirror. I then sprayed the bc/cc. Now after about 2 weeks If
you lok at the right angle with the sun just right, you can see the damn repair!
This whole process was done in about a months time., Ican't believe I still got some shrinkage! Any advice on how to avoid this next time? How long should you wait before sanding the last coat of fill primer?

Thanks Spoke!

 

Did you spot paint the area or did you paint the whole car. In my experance, if you just tried to fix and spot paint the repaired area it is very hard to paint it without if being seen at differant angles. Good luck

 

painted whole car

 

Body and paint is about five percent tools, materials, and knowledge. The other 95 percent is art and experience.

I wouldn't feel too bad about a repair that can only be observed under very stringent conditions. My limited experience is that even though you block and block and block, it will never be perfect because you did the best you can not the best a talented professional with 30 years experience can.

Both of my projects have those flaws but I've learned to live with my regrets. After all, body and paint is not what I do but I did it anyway.

 

Assuming you blocked as stated, I figure your problem is in the filler you used. Fiberglass contracts and expands. I filled in my paint project and have not had any swelling.

In large spots, where I actually used a Dremel Tool, I used 3M Short Strand Fiberglass Reinforced Filler.

For the smaller nicks, imperfections, I used Evercoat Platicworks Vette Panel Adhesive (PN 1234).

It's also important to consider the surface you put the filler on. Fillers will react differently to the surface applied. I put my filler on top of a layer of PPG DP48 Sealer.

 

spokewrench; you state that you ground a V in the cracked glass. How far back on each side of the crack did you taper? It should be tapered back at least an inch or more and at the crack it should be ground nearly through if not totally through. Another thing, did you use a fiberglass roller on each layer of matte to squeeze out excess resin and tighten the matte. This makes a much more solid repair. As far as how long to wait to sand primer, today's 2K primers can be sanded as soon as they cure which is usually a few hours. For a Vette I would wait several days just to make sure all solvents are gone. I hope you used matte and not cloth fiberglass. Cloth repairs will almost always show. I hope this helps. Craig

 

spokewrench, I can feel your pain. I thought u may have did a spot repair. I just painted my 69 last weelend. Well After spending 10 months doing then same as u did, I am showing the wife the car the other day, She looks down and notices a spot where it looks like there is still a crack about 10mm long close by where the hood blolts to the front fender. Lucky for me it is in the seem and really not that noticeable. I just hope it does not lift. I was told by a painter once, u will always have a "Oh poopie area".

 

I did not taper more than the 1/2"groove- but , I think fiberglass and the fill primer shrunk due to insufficient heat, because of the cold spring in the northeast, and then the exsposure to our recent heat and now cold weather again!
Body work can really suck!

 

Yes. Body work is an art. Have you heard the saying, "paint it black to paint it . . ."? Street rodders and other showcar folks will paint their rod black, wet sand and polish just to locate those types of problems. I've never done that on any of my projects, and yes, like another member said, you always seem to have at least one oh s h i t. I'll be painting mine black before I paint it . . .

As for cure time, fiberglass really depends on the mix and the abient temperature. Early on when I'm still a year or more from painting, I'm not real critical when I mix the resin. In the last month, I tend to measure carefully and mix it a little hotter for the temperature to try and avoid delayed shrinkage. I also try to put repairs in direct sunlight as much as possible.

Did you spray metallic or pearl? If not, you could rework the area and blend in the solid color.

 

It is silver mist mettallic- I will have to repaint the whole front clip minus the hood. I did the glass when it was a little cool and never let it sit in the sun, until now! I thought the chemical reaction with glass eliminated delayed shrinkage. I guess I will let everything cook in the sun for the next month, then guide coat the clear and block it with 220 grit then shoot some fill primer
and guide coat and wet sand with 600 grit- I would never want to own a body shop!

 

Nice to hear that some people do their own body work. Anyone can take an alternator off and call themself a mechanic. But give the guy a body hammer, auto puddy, and a few grades of sandpaper and tell him to pull this dent perfect, different story. Then theres the guys that talk about painting like they know everything where in reality they've never layed a skin on a car in their life. Nice to hear you do your own work. Nothin annoys me more than a car at the car show with a list of things the owner has had done to the car but the owner hasn't lifted a finger just his $$. Sorry kinda had to get that off my chest. Your problem is expansion contraction. Thats forsure, theres ways of minimizing it for example the material your chose is very important. Some puddy's contract more than others. And people don't realize that the fibre glass expands too, and it certainly has different properties than that of the sheet metal on other cars. The other thing, when I'm doing something like that on a corvette, depending on the location of the damage, and people who know autobody know that it's a art but only where you see it. Depending on the color your painting, and how low on the body a "pit" is, you can get away with leaving it. I've done so called "perfect" paint jobs with at least 10 hours that could be done on the bottom. An no one has ever seen it. You want to make money at it, well you gotta find short cuts. Back to your problem, the materials expand and contract, but what you should do, and I always do this on vettes, is where your Vgroove is, you should have puddy on at least an inch and a half both sides along the trench. When you block sand this out, you leave it such that there's a slight slight bumb, make it jsut so you can feel the bump, then give it a few more strokes. Then as the material contracts it is distributed over a larger area and voila your mistakes are hidden. Just an after thought I hope you put a quality primer, because if you don't use primer, the paint is sucked in by the pudy and you see a dry spot. I've seen people critisize a guys body work becuase of that when the body work was actually perfect. Make sure you use primer on the putty.

 

I'm so sorry to hear that! Hang in there . . . it will get done and you will be proud. :yesnod:

Since it's silver, I hope your using the original mix. Also, have the can shaken again by the shop. And try and follow your past practice. If the paint was shaken 3 days before you sprayed the color coat, have it shaken 2-3 before again, not hours before. And match your previous setting on air pressure and flow on the gun. Metallics can shade on you and I'd hate to see the hood and clip end up a different shade. A converstaion with the paint shop may help as well, they usually can provide good advice to avoid shading issues.

Oh yeah. WE WANT PICS! :cool: :cool: :cool:

 

Thanks for all the help! Their are NO! shortcuts in bodywork!