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Tue Jan 21, 2014 8:19 am

Hey guys, I just got the motor in my bug after a mild rebuild, and I need to address the body work. I don't have a rust problem, really, just a couple of places where a PO had put on a thick layer of bondo and it let go of the metal underneath. Both places are right behind the doors on either side. I assume I need to get the remaining bondo off, and try to push the metal further out from inside the car. Once I do as much of that as I can, what is next? I figure more bondo, but how do I keep it from cracking this time around? How can I ensure that it will adhere to the metal? I am sure I can push the dents out to need a lot less of the stuff, so that alone may help...

Tue Jan 21, 2014 9:55 am

Keys to bondo sticking are
1) Proper thickness
2) Bare metal.

If it is due to dents and not rust, pushing the metal out so your bondo is thin, and making sure you strip the surface to clean bare metal it should be just fine.

Tue Jan 21, 2014 11:14 am

bare metal with a good bonding surface, say 50 to 80 grit sanding paper, proper panelbeating so you do not have to use thik bondo.

Tue Jan 21, 2014 11:20 am

Hyperspace wrote: bare metal with a good bonding surface, say 50 to 8 grit sanding paper, proper panelbeating so you do not have to use thik bondo.

True that, I found bondo in places on mine that a hammer to the back side was enough to straighten it out.

Tue Jan 21, 2014 11:22 am

When applying Bondo you never want the layer to be more than 1/8'' thick, and only apply it to bare metal. That is how you keep it from cracking.

-Sam

Tue Jan 21, 2014 11:25 am

I've seen tests where they compare the strenght of the bonds in straight to metal and over primer. bare metal won hands down for everything from chip damage to small dents.

Tue Jan 21, 2014 10:14 pm

Thanks guys! This crap was like 1/4" thick, although I think I can push the metal out far enough to need very little of it. Is fiberglass better for this than bondo? Or is bondo ok as long as I don't need to gob it on so thick?

Wed Jan 22, 2014 1:15 am

fibreglass was never intended for this purpose.