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Thread: Is it really that hard to block a 55 Chevy laser straight????

  1. #21
    Registered Member MP&C's Avatar
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    I'm certainly no expert and I'm sure there's someone somewhere that can provide valid reasoning to support that. But these door skins, much like most of the other body panels, have a noticeable crown in the vertical direction. Sand enough in the horizontal direction and you will be adding flat spots, despite the overlap you may use. The other point to consider is the angle of your cross hatch. Here is a sample of a 45....





    In this example let's go on the assumption that the spacing is approx. 1" apart. Now if we use a 30* angle on the cross hatch, and maintain the same one inch spacing in the horizontal direction, it gives us a closer overlap in the vertical direction for a more effective blocking session to remove those "flat spots" being added by a flat sanding board.





    Where this has a better overlap and does a better job of getting rid of those flat spot issues, you can still feel the ridges in the primer after a session of horizontal only blocking. By performing a few vertical blockings, it cuts those ridges down, but also now look at the overlap... which should give the best results in blocking the panel.











    Perhaps this method isn't suitable for all panels, but for the door removed from the car, it did well in removing the ridges..
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  2. #22
    Registered Member chevynut's Avatar
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    Robert, looking at your crosshatches I think I sand more at 30 degrees than 45 degrees. I think the point is you should sand at an angle, not straight.
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  3. #23
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    I never sanded vertical and may be the reason it took so long to get my doors straight. Will give it a try on my quarter panels, hope it helps cause these dogs are fighting me big time. Thanks Robert!

  4. #24
    Registered Member MP&C's Avatar
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    Quote Originally Posted by chevynut View Post
    Robert, looking at your crosshatches I think I sand more at 30 degrees than 45 degrees. I think the point is you should sand at an angle, not straight.

    True. And even though the sanding blocks in the pictures are shown as parallel to the edge, they are pulled at a slight angle to kinda sorta match the 30* cross hatch pattern shown. But in some instances, I have also turned the sanding block at a slight angle to parallel and pulled it straight to the panel. All depends on the shape of the panel that you have to contend with. As long as your "cutting edge" is at an angle to the pull, all is good. I should also point out that the vertical blocking was using minimal pressure, only enough for the sanding block to match the contour. Then, it was only used enough to smooth the ridges we could readily feel..
    Last edited by MP&C; 08-05-2015 at 07:59 AM.
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  5. #25
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    To my way of thinking, as an extensions of the thoughts already said - it seems to me that if there's more crown vertically than horizontally, which is the case on most doors and quarter panels on any car, especially a 55-57 - then sanding vertically is the most likely way to create low spots because you have to get the block, especially if it's a long one to conform to the contour. So from that line of thinking, the 30º horizontal crosshatch is also better than a 45º crosshatch.

    The other half of this is that you never want to make too many consecutive strokes in one place (maybe none), no matter what your pattern is.

    The hardness and flexibility of the sanding block also plays into this.

  6. #26
    Registered Member MP&C's Avatar
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    Here's a video taken yesterday using the 36" AFS sander. Note how the sander is grasped and the fact that this promotes letting the sandpaper do the work without "leaning" on it. Applying downward force through your palm to get the job done more quickly runs the risk of deflecting the sander downward at that point, causing low spots...


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  7. #27
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    I think your point about letting the sandpaper do the work without a bunch of pressure is very important. No matter how you build it, a flexible long block won't sand evenly if you push hard on it. And if it's rigid, it only sands in the center or on one end. Pressure may work when you're first leveling the filler, but not as you get closer to the finished contour.

  8. #28
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    I apply way more pressure then in your video. Maybe why it takes me so long to make a panel straight. Thanks for the info.

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