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Thread: locating correct elevation points of front spar and rear spar .

  1. #1

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    locating correct elevation points of front spar and rear spar .

    All,
    I have tried to search for information on the correct elevation differences between the front and rear spar. My plans do not have the sizes for the spars.
    I need this to check my attachment points for each spar on the frame as well as make a jig for the wing to check the wing structure as well as the root points on the frame / fuselage.

    1. From the plans that I have it appears that the bottoms of the front and rear spars are level with each other at the root. If this is true them the attachment points for the spars are offset in the vertical direction by a set amount of distance due to the difference in spar height bolt hole location at the root attachment point. Is this Correct?

    2. If #1 is correct and the spars are in parallel and vertical with each other at the root attachment point, then the spar bolts would be horizontal with each other and offset vertically by the difference in height of the spar and would be rotated or set at a inclined degree amount from horizontal from the frame of (? 1.75 degrees?) Is this correct?

    3. If #1 and #2 is correct , what is the offset difference in height of the front spar to the rear spar at the bolt / root locations. I do not have that measurement on my plans nor have I been able to locate measurement via search on this site.


    Thanks for the help in advance ,
    Ken

  2. #2
    Steve Pierce's Avatar
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    What plans are you using? The bottoms of the spars are parallel to each other at the root before you put the twist in the wing.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  3. #3
    Southern Aero's Avatar
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    Ken

    I'm guessing since you are on this site its a SC build. If so, the front and rear fittings are parallel with each other with rear 1 1/2" below centerline of the front. The spars are both 13/16" or .813 wide. You can make a temporary fixture with threaded rods and wooden or aluminum blocks to hold the 1 1/2" dimension. (The spars are square to centerlines in the fixture)....... Plus will hold the 31" centers of the mounts for welding. This pretty much holds true for most of the aluminum spar Piper type builds, J3 and PA11 are different. If its a SC the front attach point is 24 3/4" and rear 22 1/4" above the HRL. This would EQUATE to a degree number but I would use the dimensions rather than degrees unless you had a reason or purpose to change them.

    I think this is what you were asking..................

    I have seen builders before make the front and rear attach points on the same centerline that will not work. Would need a big hammer...................
    ......... It doesn't cost any more to go first class! You just can't stay as long.

  4. #4

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    Quote Originally Posted by Southern Aero View Post
    Ken

    I'm guessing since you are on this site its a SC build. If so, the front and rear fittings are parallel with each other with rear 1 1/2" below centerline of the front. The spars are both 13/16" or .813 wide. You can make a temporary fixture with threaded rods and wooden or aluminum blocks to hold the 1 1/2" dimension. (The spars are square to centerlines in the fixture)....... Plus will hold the 31" centers of the mounts for welding. This pretty much holds true for most of the aluminum spar Piper type builds, J3 and PA11 are different. If its a SC the front attach point is 24 3/4" and rear 22 1/4" above the HRL. This would EQUATE to a degree number but I would use the dimensions rather than degrees unless you had a reason or purpose to change them.

    I think this is what you were asking..................

    I have seen builders before make the front and rear attach points on the same centerline that will not work. Would need a big hammer...................
    This is exactly what I was looking for., Yes it is a Super Cruiser rebuild. I should have stated that in the first post.

  5. #5
    Southern Aero's Avatar
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    Ahh

    Super Cruiser and not Super Cub. Experimental? 2+2?
    ......... It doesn't cost any more to go first class! You just can't stay as long.

  6. #6
    AkPA/18's Avatar
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    Quote Originally Posted by Southern Aero View Post
    Ken

    I'm guessing since you are on this site its a SC build. If so, the front and rear fittings are parallel with each other with rear 1 1/2" below centerline of the front. The spars are both 13/16" or .813 wide. You can make a temporary fixture with threaded rods and wooden or aluminum blocks to hold the 1 1/2" dimension. (The spars are square to centerlines in the fixture)....... Plus will hold the 31" centers of the mounts for welding. This pretty much holds true for most of the aluminum spar Piper type builds, J3 and PA11 are different. If its a SC the front attach point is 24 3/4" and rear 22 1/4" above the HRL. This would EQUATE to a degree number but I would use the dimensions rather than degrees unless you had a reason or purpose to change them.

    I think this is what you were asking..................

    I have seen builders before make the front and rear attach points on the same centerline that will not work. Would need a big hammer...................
    Hello Southern Aero
    I believe it is 2 1/2 inch differential for the Super cub and 1 1/2 for the 12. In reading your post it appears you just mistyped.
    Thanks, Mark
    http://thrustline.com/

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  7. #7
    Southern Aero's Avatar
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    Ken/Mark

    Didn't really mistype just mind was on Super Cub not Cruiser. But you're right on the 12, with 23" in the front and 21 1/2" in the rear from the HRL for the mount positioning centerline. Big difference in AOA!
    ......... It doesn't cost any more to go first class! You just can't stay as long.
    Thanks AkPA/18 thanked for this post

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