Older fiberglass damage, flex body filler

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PostPosted: Tue Jul 24, 2018 9:31 pm
Ok, this will go against the grain with some of you (me included) but bear with me. My 71 corvette has some past damage on the passenger door resulting in circular stress lines thru all layers of paint and re-paints. It looks like the panel was flexed inward but came back out to normal or close to normal profile. Curved stress lines, about 12 inches long telegraph through several layers of paint, light filler and primers all the way to the substrate. I had the door almost finished today and found a couple light cracks, couldn't leave them and subsequent investigation left me with a spot ground down with a DA and 80grit to the bare grey glass.
Situation is, there's really no way to repair it properly short of a new door skin which ain't happening for this paint job. I'll get a new skin later, and months or years down the road I'll change it or the new owner will. So my question is, since I know regular polyester filler will telegraph these stress lines as will the new paint, (btw... you can't really see the lines in the glass panel but that's where they're they're coming from) but I'm thinking of trying a flexible polyester filler like for bumper covers etc... to maybe put off the inevitable, or maybe a premium (expensive) body filler. Any recommendations?

Since the pics shown, I've sanded the area down to bare glass with the stress lines following all the way thru past the first layer of primer. I put a layer of Crest Polyester Glazing Putty on but I could easily take it back off to go with something else.

All help would be much appreciated.
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PostPosted: Tue Jul 24, 2018 11:10 pm
Well, man, I think you thought this through pretty well. And yeah, short of replacement you are doing about all you can do. I've had a similar situation with an aftermarket mono-tub style old kit body with problems a lot like this....not even an option of replacing a "part" for me so.... I did indeed use USC's Poly Flex (it is an even more flexible version of their Body Icing) worked out over a pretty large area. Before I did that filler I took one of our industrial super glues and "wicked" that into the micro cracks I was seeing, let that set for a minute or so then hit it with our matching chemical accelerator so I knew I didn't have any trapped liquid in there. I just saw the car in pictures about a year ago and it had been 7 years since I did the work....no changes. I even blew the pictures up on my 29 inch monitor and put colored filters over it. No cracks and I could tell by the cut and buff it had not been repaired again.....
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!



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PostPosted: Wed Jul 25, 2018 3:34 pm
Hey Darrell thanks much!
I'll try the super glue trick also, but if that flexible filler will buy me even a few months I'd be happy. I'll be getting some Poly Flex, thanks again for the info.

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PostPosted: Wed Jul 25, 2018 4:11 pm
It's worth a try. They claim that once it cures it can handle a 100 degree flex without cracking. I had a bumper on an old Acura Integra that I repaired with it. About 6 months later an idiot hit me in the same spot. Bumper flexed in, bumper flexed out....paint scraped up but the filler did not loose adhesion or crack. That's pretty good case for using it......
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PostPosted: Wed Aug 15, 2018 1:14 pm
I know I am late to the thread for comment BUT...

I have played with more than my fair share of Vetts and many more Boats / Water craft and Aircraft fiberglass parts over the years.
I have always Cut or Grind out the Cracks with a die grinder and lay the edges back beveling the edges at a 45 degree angle and then Lay a Flat piece of fiberglass cloth with resin over back side over the entire damaged area. Then fill the beveled grove with Strands of Fiberglass pulled from Fiberglass Matt and resin.
Sand the mess flush after curing and Repeating as necessary till the Grove is fully filled and Flush with work piece, Finish as desired.

Method has always worked for me and Cracks never reappear.
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Sun Aug 26, 2018 8:22 pm
DoRight, thanks for the reply. I cut my teeth in the mid 70's with boats too. Lots of boats and aircraft in fact. And of course your method is definitely the correct way to do this other than re-skinning the door.
I actually removed all the previous paint and filler I had on to bare glass, used the Poly Flex filler. It looks like it's going to work great (hope I didn't just jinx it), I have to buy some time here as my Dad is now 85yrs, his Corvette... 6yr project.
Ls1 and T56 into a base 350/auto car. Everything done right, engine bay and bottom stripped to glass and sprayed with Lizard Skin, then Zero Clearance foil over that. New suspension F&R, rebuilt 3:55, big axles, Wilwood calipers, adj suspension etc... Got to get this thing painted and driving!

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PostPosted: Sun Aug 26, 2018 9:35 pm
Nice....really nice....good drivetrain selection and well thought out for a "real" driver type car. I know you are buried in it right now but when you get a chance flip some pic.s up here for us. Getting ready to Poly-Flex repair a bumper that a family member had a large "rock" encounter with.....
Metal, wood, fiberglass, we work it all... www.furniturephysicians.com We can restore the irreplaceable!

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