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TARBO-PANDA
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4,910 Posts
Discussion Starter #1
So I've got me some bondo and I've been reading up on it and watching lots of videos...

I have a buddy who has used it for lots of things, but never a car...

I'm finally getting over the eff'd up passenger door and going through with it. Going to take the palm sander to the car again and fix up all her dings from the years of hardship. lol.

I'm curious if any of you bondo pros have any tips. I have plenty to play with and learn, and I'm not afraid to sand it back down and try again. So monkey see, monkey hear, monkey do...

[cheers]
 

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Premium Member
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Best when used over primer, not straight on metal.

Bondo uses talc as a cheap, light, filler material and that attracts moisture. Hold moisture by the steel & it'll eventually rust, with the Bondo then falling off eventually as the panel rusts underneath.

Encapsulate by painting before as well as the usual paint on top to avoid the problem as much as possible.


Learned a lot about the properties when researching repair on my Boat, with constant water contact there Bondo is absolutely NFG as a filler for glass work. Needed glass bead (powder size) as an additive to epoxy resin to make a good filler, but that's HEAVY stuff & more expensive. (Bondo is Polyester resin & talc)


I use an old plastic cutting board as a palette/mixing board, scrape it as clean as possible after each use so it's reusable. The flexible applicators can be flexed & peeled clean once it solidifies.

Hdwe. store rasp, of the type with holes/replaceable blade, works best for taking down the rough bumps to do the basic smoothing for me. Less mess than trying to sand it all down with power tools. (don't need it if you put it on smooth enough) I've got an old rasp type file that I use for basic smoothing on all convex surfaces, rounded back works on some concave areas as well.

Your hands & tools that have some stiffness help shape things without getting a wavy effect, soft sanding backers don't work well for taking off the high spots as desired.

It's always a fill, smooth to feather edges & repeat to fill low spots/voids process. Mixing the filler by working it easy helps avoid getting bubbles in the material to cause holes that need filling again.
 

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Bondo brand filler is junk. I wouldn't bother with it. It will shrink.

Rage Gold is what the pros use and isn't hard to find. Vastly superior.
 

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TARBO-PANDA
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Discussion Starter #5
Thanks guys. Keep sending the tips. Looking forward to making her look better.
 

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TARBO-PANDA
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Discussion Starter #6
After reading some more...it sounds like a bad idea to try and do it in parts.

I was planning on doing a little each weekend...but if it rains....I'm not sure how to protect the bondo. Some say primer will, others say no way. So much conflicting information out there.
 

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After reading some more...it sounds like a bad idea to try and do it in parts.

I was planning on doing a little each weekend...but if it rains....I'm not sure how to protect the bondo. Some say primer will, others say no way. So much conflicting information out there.
primer holds moisture...that's why it is used before you paint because it helps absorb the liquidity of the paint. If you use primer it's going to get wet and hold rain and eventually rust...making things worse.
 

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TARBO-PANDA
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Discussion Starter #9
Good to have some confirmation from people here...

So if I have to do it in parts I will have to cover the primer with some paint.
 

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Vince your Moderator
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Rage Gold sands very well.
 

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When your talking about doing it in parts, I'm assuming that you are using your car as a DD. If you are free on a weekend, do it then. It is easier to do all at once then in parts. If you could put up some pics, that would help greatly. If there is bare metal, then the first coat of filler you want to put on is body filler mixed with a fiberglass.
They make fillers, such are Duraglass, that works wonders for that because it prevents the bare metal from rusting by essential sealing the the metal. Think of it as putting on a rain coat and walking in the rain.

Also if your using, filler try to picture a golf ball of it. If you have a golf ball of filler, then use about an inch of the catylist the filler comes with. Also if you can, try mixing the body filler on a flat, smooth surface. When you are applying it, trust me, put the filler on smooth and flat; it will be easier to sand. Repeat as needed. Wait about 10-15 minutes for it to cure. You'll know if it isn't ready to sand due to the filler being tacky and gummy, if it is stop sanding and wait. Again pics would be great then I could diagnose what exactly you would need to do. If you can't, It's fine, just follow those rules and it should turn out fine.
 
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