Bondo

[BellaCoola]

I need to clean up my rear tub 1/4 panel on my 109. It is an ex-mod that obviously saw some damage and as a result has alot of dings and dents just behind the door. None of them are very severe although it looks a little nasty.

I thought that the best cure was to sand it down to metal, and just skim coat it with bondo to flatten out the pimples.

My question is what grit of sandpaper should I use? Bondo recomends 80 grit, but I am concerned that I will score the aluminum. I just redid a hardtop using 180 only to remove 4 coats of paint, and although not completely done yet (just primer) it looks very nice and smooth.

Do I need 80 for the bondo to have something to stick to, or should I use the 180?

Thanks in advance,

https://www.freewebs.com/83s3109

pics of the beast on the above link

[KevinNY]

That looks like a very clean truck, I don't see the "damage" in the pics. Chalk it to beauty marks.

[I Leak Oil]

I'd leave it as is also but if you want to do the body work keep a couple things in mind. Poly body fillers don't like to stick to the aluminum very well. It will, but it must be prepped absolutely right and kept thin. Most plastic over birmabrite I've seen has shown signs of seperatation from the metal. As for your question about grit, use what the plastic mfg. recommends. The purpose of sanding is to rough up the surface to provide a place for the plastic to "bite" into. All those scratches provide more surface area to stick to. If there are no instructions on the product for applying over aluminum then get in touch with the manufacturer to get some!
Nice truck!
Jason T.

[thixon]

Go to your local automotive paint store. You're looking for a lightweight body filler like Evercoat Rage. Tell the guy at the counter what you're up to. Do not use bondo from pep boys, you'll be sorry later. I know plenty of people will chime in that its fine, but trust me. The premium products sand nicer, easier, and smoother. They adhere better, and last longer (The product I mention is specifically made to adhere to aluminum or galvanized surfaces). A gallon of Evercoat will cost you $35.

You will need to rough up the surface. A scotch bright pad will work fine, but talk to the guy at the paint store counter and get his opinion.

I won't go into the entire process here, but if you want some help PM me.

Good luck,

[S11A]

The grit is not a big problem. Once you have prepped and filled, use a milder grit like 150 for the first sanding. It will be rough enough to knock down the filler and remove marks from the 80 grit. Then switch to a finer grit such as 220 and sand again to smooth. This will also remove any marks from the 150. Rinse and repeat.

I have polished aluminum parts on the track car by first using the angle grinder to remove casting part lines and similar excess material. At that point in the process, the first time you do it, you think, oh my God, what have I done to the part? Then after using 150, then 220, then switching to a bench grinder with polishing wheels and compounds, by moving to finer and finer grits, you can get a mirror shine out of aluminum.

Long-ish answer, but the bottom line is the 80 will be fine; just use successively smoother grits to get rid of any marks from the 80.

I have seen old Series trucks polished to a near-chrome shine in Sikkim, India. Pretty cool.

[S11A]

Oh, one more thing: The auto paint stores can also supply a very fine filler that comes in a tube. The last time I used it, I seem to remember it being red but I can't recall the name or brand. This goes over the regular filler, and fills very small voids and is also nice for small areas such as minor dings. Not sure if this will work well on bare aluminum, but will definately be good over the filler if needed.

[madp]

It's called finishing putty and it works great! Evercoat make a really good one, they have premixed finishing putty, but get the two part one, I have found it works a lot better.
S11A advice is very good, I have used Evercoat Rage, and it is worth the money. Find a good paint shop and make friends of the counter guy, most of the time they are happy to give you good advice. Also when you are working with bondo use a long-block sander, it will help your finish look perfect.

[BellaCoola]

Thanks for all the advice. have done one area so far and am really pleased with the results. After the next trip up the west coast, I'll do the other 1/4 panel.

Seems to adhere very well...sanded down to metal with 80grit.

Thanks for all the advice...very helpfull as usual.