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Thread: Sanding Rounded Body Lines ('73 Firebird)

  1. #1

    Default Sanding Rounded Body Lines ('73 Firebird)

    First off, I am by means no professional body and paint man but I have done my fair share of both over the past 20+ years. The car I am working on is a 1973 Firebird. I understand how to get nice straight body lines but the problem is the body line in the center of the body is not a crisp line, it's slightly rounded. I have blocked the panels down to the point I actually have a crisp line, but now I need to go back and round it off but I can't for the life of me figure out how to do this with out destroying the nice straight lines I have. I'd GREATLY appreciate some ideas on this.

  2. #2
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    Quote Originally Posted by firstyearta View Post
    First off, I am by means no professional body and paint man but I have done my fair share of both over the past 20+ years. The car I am working on is a 1973 Firebird. I understand how to get nice straight body lines but the problem is the body line in the center of the body is not a crisp line, it's slightly rounded. I have blocked the panels down to the point I actually have a crisp line, but now I need to go back and round it off but I can't for the life of me figure out how to do this with out destroying the nice straight lines I have. I'd GREATLY appreciate some ideas on this.
    Where on the car? Pictures?

  3. #3

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    Center body line between both wheel wells.
    Here's a picture of the car:
    http://www.flickr.com/photos/2356310...7625604161317/
    Last edited by firstyearta; 03-07-2011 at 08:51 PM.

  4. #4
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    My best filler man (Mike) uses a piece of tape to mark the center of the peak then applies filler on one side, board or block sands then moves the tape and fills the other side then sands that side. You want to be sure to use a guide coat so that you can see exactly what you're doing.

    You would make the peak then round it off using a 16" or longer block.

  5. #5

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    That is exactly how I got the nice straight peak. I was afraid if I sanded the peak off with a long block it would just make it flat or make the straight line wavy.

  6. #6
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    Quote Originally Posted by firstyearta View Post
    That is exactly how I got the nice straight peak. I was afraid if I sanded the peak off with a long block it would just make it flat or make the straight line wavy.
    It probably would make it flat if you sanded straight back and forth but to round it off evenly you should sand along and around it at the same time kinda like //// then \\\\ but a little more horizontal than these lines and use 80 grit to do the shaping then finer grit to remove the 80 scratch before priming.

  7. #7

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    Okay, great. I'll give it a shot and hope for the best.

  8. #8
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    I find spray on guide coat to work better for making lines. It leaves more of a defined area of guide coat. The powder seems to make the edge cloudy so to speak. It also helps to spray it a little heavier directly on the line. This will tell you without a doubt how straight your line is. I also find for flat surfaces leading to an edge you can at times angle your block and sand it straight so part of your block hangs over the edge. This however will lend a hand to an uneven surface away from the line if you do it too long, but it contributes greatly to a very perfect edge and body line so it's worth to throw a few of those strokes in there.


    However, that's not the problem here. If you're trying to make a sharp line more dull you can use a softer block with 180-220 and cross hatch lightly over it equally and use guide coat This has worked well for me. If it's waay sharper then I'd carefully start with some 180. Just be glad you're facing the problem of needing to dull it out rather than it not being sharp enough. When it's sharper it's easier to see how straight it is and easier to dull it out and leave it straighter. So in my mind you've taken the right approach.
    Last edited by tech69; 03-13-2011 at 02:51 PM.

  9. #9
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    Quote Originally Posted by tech69 View Post
    However, that's not the problem here. If you're trying to make a sharp line more dull you can use a softer block with 180-220 and cross hatch lightly over it equally and use guide coat This has worked well for me. If it's waay sharper then I'd carefully start with some 180. Just be glad you're facing the problem of needing to dull it out rather than it not being sharp enough. When it's sharper it's easier to see how straight it is and easier to dull it out and leave it straighter. So in my mind you've taken the right approach.
    When making a sharp line it doesn't pay to start with 180-220, you'll want to start coarse and end with a finer grit. A coarse grit will help cut the line and make it easier to get a sharp straight line, if you start fine you'll have a tendency to cause irregularities like waves. And if the line is straight the blocks you use should be hard not soft.

  10. #10
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    I said 180-220 to dull the body line, not make it. Dulling the bodyline with 80 grit would be too aggressive in my opinion as there's a real small area of contact, or if you do it I'd do it lightly. Making the bodyline would be from anything from 40-80, for me anyways.

    Waves are not a problem of mine. I have more experience in that aspect than anything else.

  11. #11

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    Sorry for not reporting back sooner. In the end the method discussed above worked well. I sanded the line to a point them cross-hatched over it a few times to knock the point down to a curve. This was maddening though as I was worried I was going to ruin the straight line I'd worked so hard to create. Just today I picked up the main body from the paint shop (a friend of mine sprayed it).


  12. #12
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    Quote Originally Posted by firstyearta View Post
    Sorry for not reporting back sooner. In the end the method discussed above worked well. I sanded the line to a point them cross-hatched over it a few times to knock the point down to a curve. This was maddening though as I was worried I was going to ruin the straight line I'd worked so hard to create. Just today I picked up the main body from the paint shop (a friend of mine sprayed it).
    It looks like you did a good job on he body line that you were worried about.

    Was the front end painted at the same time as the rest of the car? If not it should be interesting to see if you get a perfect match.

  13. #13

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    Thanks.
    The fenders and hood were not painted at the same time but the painter assures me they will match.
    I'll post some pictures when it's back together (but it will be a few months as I have a bunch of detail work to do before the front clip goes back on).

  14. #14

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    Sorry I have not got back to this thread till now. The project ended up taking much longer than I'd planned (don't they all). In the end everything looks great. The paint turned out great and is a perfect match (fenders to doors). Here are a few shots:




  15. #15
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    Default Looks Great!


    How did everything match? It's hard to tell in the pictures.

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