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Thread: Need another way to set diehedral.

  1. #1

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    Need another way to set dihedral.

    IF:
    I level my inner and outer wings.
    measurer 56 5/16" from the attach point/pivot out the bottom of the outer wing.
    Raise the outer wing 4" at that point.

    Will my wing have 4 degrees dihedral?
    Last edited by BobMo; 02-23-2012 at 08:18 AM.

  2. #2
    bsdunek's Avatar
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    arcsin 4/56.3 = 4 deg. so you will have 4 deg per wing, or 8 deg total. This is of the outer wings. Not knowing what you're building and the length of inner and outer wings, I don't know what the average diehedral would be.

  3. #3
    Eric Witherspoon's Avatar
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    Another way to do this, so you aren't hunting around at that 56 inch point wondering what exactly 4" of lift looks like, is to cut a board at the 4 degree angle - maybe make it half of the 56.3" measurement and 2" high on the short side. Put that angled board on the wing panel to be lifted. Put a high-precision level on top of that. Then just shim up the outer wing panel until the level shows - level.
    Murphy's 13th: Every solution breeds new problems...

    http://www.spoonworld.com

  4. #4
    Neil's Avatar
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    Another way to measure 4 degrees is to use the sine of 4 deg. which is .06975" and multiply that by the length of a long level, say 48" and that comes out to 3.348 or really close to 3 and 11/32. Make a shim to go under the end of the level and it will measure 4 degrees all day. I generally measure dihedral with the wings leveled to zero degrees of incidence. On my biplane (which has 2 deg. dihedral and 1.5 deg. of incidence) that means the fuselage is propped up to 1.5 deg. tail high. This really matters a lot with a swept wing.

    Got no idea what you are building but with any design measurement accuracy suffers if you don't start with a zero deg X Y base line.

    A degree board as Mr. Witherspoon describes works well too. You just have to know how to get the 4 degrees and know all other plains are at zero.

    Back to your original question, 56 5/16" or 56.3125" x .06975=3.9147 or about .085"(less than 3/32") short of 4". Probably close enough as long as the rise measurment is taken from the same plain as the attach point.
    Last edited by Neil; 02-24-2012 at 05:55 PM. Reason: additional comments

  5. #5

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  6. #6

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    Thank for the tips. I had not found my digital level and I remembered the 56 5/16" = one degree for every one inch rise. Plus, I just wanted another way to double check my digital levels accuracy. I'll try them all before I drill my attach plates.

    Thanks,
    Bob

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