Hey guys,

I finished the metal work on the quarter panels of a ’72 Dodge Demon; got every dent to within 1/16” of the surface. Now the panel just feels a little wavy when you run your palm over where the dents were.

Since then, I spread some 3M Platinum Plus body filler over the area that I worked and beyond, then with a 8” Mudhog, cut down the top glaze of the filler with 80 grit sandpaper.

I then finished hand sanding the filler, going from 120 grit to 180 grit with a combination of Durablocks, a flat wooden block sander, and Mirka guide coat.

After all that, I sprayed four coats of Slicksand, then blocks with 120, 180, and finally 320 grit.

Yet when I ran by palm down the side of the quarter panel, I still felt the waviness. I confirmed it when I sprayed some w&g remover over the area to see the gloss with a work light.

So I rough sanded the area and reapplied more filler and blocked that to 180 again. Yet I’m still feeling the waviness.

What should I do differently? I didn’t think I was sanding too much because elsewhere I only broke through the Slicksand in a few spots, which were still flat.

Should I go ahead and apply a couple more coats of Slicksand then start with a finer grit instead, like 180 and finally 320?

Or should I just move on with high build primer? I would have thought the Slicksand would have taken care of the problem.

Is cutting with a 80 grit on a 8" mudhog too much? Should I do my initial cut with a finer grit?

Thanks!

I think I would have skipped using the hog and cut it with the 80 grit by hand with a long board and guide coat. I have a flexible long board that works great for lightly contoured panels. either way you need to be careful not to cut flat spots. with the body filler and 4 coats of slick sand your body work must not have been as close as you thought. when you cut the body filler did you cut until you started to see metal.
Jay D.

I would use the longest board that fits the area within reason. And as mentioned above, I would also block it down with 80 grit until I started to just get a hint of the Epoxy Primer or metal and then use the polyester primer to fill the scratches. It sounds like you are following the contours instead of leveling them.

I agree with what has been said above. The most important thing when trying to get a panel straight is not to press too hard on the sanding block. Use the longest sanding block that allows you to comfortably sand the panel. Too long and you will struggle, too short and you will follow the contours rather than remove them.
You must change the sandpaper often. As soon as it starts losing its cutting action you will start pushing hard on the sanding block. This flexes the panel inward and the result is that you keep adding more filler but nothing changes.

To get panels straight you need to use a coarse grit (80 works fine) and let the paper do the cutting.

Guide coat is your friend and IMHO absolutely necessary to get a panel straight. Read the sticky on Guide Coat at the top of this forum. It will save you tons of sanding and aggravation.

Coronet, I'm not trying to sound rude at all but please read my OP. I'm using guide coat AND 80 grit to do the initial cut.

badsix wrote: with the body filler and 4 coats of slick sand your body work must not have been as close as you thought.

No, I measured it myself. The deepest dents were 1/16" from the surface, and they were more like waves than actual dents when I was done.

You said you were using a Mudhog and I think that is about as far as I read. In my minds eye I see hills and valleys. LOL

With all the material you have put on the car it ought to be straight as a laser.

I would put 80 grit on a 9" long (minimum) sanding block then sand down to the epoxy primer. Remember to let the sandpaper do the work and just apply a steady firm pressure to the sanding block but don't lean too hard on it. (By the way I am not a fan of the durablocks for getting a panel straight. The round and teardrop blocks work well on curved surfaces though.)

One other tip is to sand at an 45 degree angle across your panels.

Once you start seeing the epoxy primer move to another panel. Things should start shaping up pretty quickly.

When done shoot 2 coats of 2k primer (polyester if you prefer). When dry apply guide coat (I use 3m Dry) and then sand with 180 - 220 until the guide coat is gone. If necessary repeat the process but you should get to the place where the guide coat is gone and no metal or low spots are showing.

Don't trust your hand and feeling the panel. I have only met a couple of body guys who were that good.

GOODPOST ^^ I'm sure when he said to sand at a 45 he means to hold the long board horizontal to the panel then up and down at a 45, it also helps to go the other way also. lightly curved quarter panels can be a challenge even for the experienced. and use the 2k its much easier to work with and will give good results. when you make the transition for 80 grit to the 2k take some 180 and lightly cut the 80 grit down. I don't like to prime over 80 grit if the primer doesn't have enough time to cure good it may shrink after the top coat something you don't want. its just a little safety factor.
Jay D.

'68 Coronet R/T wrote: (By the way I am not a fan of the durablocks for getting a panel straight. The round and teardrop blocks work well on curved surfaces though

If you are not a fan of Durablocks what would you recommend to get long panels straight?

I prefer this style for block sanding large panels by hand:


I have a 9" version of the above that gets used on every job.

Also have a Hutchins 16" air sander that works nicely for final sanding and feathering of filler.

^^^ I use the same. you might try and do most of the cutting at the 45deg. we are talking about, but do both ways. it's real hard to sand a long quarter that has a slight curve to it. with out getting flat spots, experience really helps here. but doing a 45 one way then the other will help.
Jay D.