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Thread: Lift strut attach brackets off center

  1. #1
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    Default Lift strut attach brackets off center

    I am rigging my wings and got everything dialed in correctly. When I pulled the wings off, I noticed that the lift strut brackets are not exactly centered on the "wear lines" anymore. I had to loosen the brackets to set the dihedral, twist, etc. On one wing I can still see the line through the tooling hole, on the other wing, I noticed that it is about 1/8" off the line on both brackets. Is this normal?

  2. #2
    Senior Member Dave S's Avatar
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    Default Re: Lift strut attach brackets off center

    Jerry,

    Maybe just me; but, I believe they need to be right on the line.

    1/8" might put the rivets in a weaker position. The correct alignment takes into account where the rivets will end up in relation to the web and the edge of the insert.

    If the brackets are a bit off center, the forces on the lift strut and spar will be off center bu the same amount. The attach bolts through the rod ends will also be at a slight angle and not square with forces they are intended to carry.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  3. #3
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    Default Re: Lift strut attach brackets off center

    Thats kind of what I was thinking. I drilled a few of the holes already before noticing it. I haven't drilled the holes in the bracket that go in the I beam yet so I could adjust accordingly. I am going to have to do some thinking now. I bet I measured 100 times and inspected 1000 times. Little frustrating.

  4. #4
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    Default Re: Lift strut attach brackets off center

    Drilling the holes for the lift strut brackets is probably the most nerve racking part of mounting the wings.

    Rick

  5. #5
    Senior Member jiott's Avatar
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    Default Re: Lift strut attach brackets off center

    I agree with Dave; there is not much wiggle room to get the strut bracket rivets to go thru both flanges of the I-beam insert with proper edge clearance. An 1/8" off may be too much. This area of the wing structure is by far the most critical item that hold you up in the air thru turbulence and g limit loads.

    I may be a little nerdy about this subject being an engineer, but during my build I badly scratched the inside of one of my spars trying to position a stuck I-beam insert. Because of its critical nature I could never fly comfortably knowing this, so I spent the money and got a brand new spar. I was building my own wings, not factory quick build wings.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  6. #6
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    Default Re: Lift strut attach brackets off center

    Well after being almost nauseous over this, I am leaning towards remounting the wings, clocking the brackets 1/6"-1/8" to line up with "drag lines" more accurately. Its look like I will be able to drill out the the holes to 3/16" on the few that I already drilled and use a few oversized rivets. Since I didn't drill the holes in the bracket for the I-beam hole yet, I can get those centered where they need to be.

    If I wrote the build manual, there would definitely be BOLD notes around important items to quadruple check! One being......Important.....after rigging and before drilling.....check the lift strut brackets to make sure they are still lined up with the "Drag Line"!

  7. #7
    Senior Member Dave S's Avatar
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    Default Re: Lift strut attach brackets off center

    Jerry,

    We're all going to have our moments of frustration, just keep on doing

    I had a little spar kerfuffle during my build where one of the completed spar tubes rolled off the sawhorses and dinged the spar. In that case the spar was beyond repair so off to get a new tube and insert. Stuff just happens once in a while.

    In my defense, I now have a really, really sturdy yard light pole in front of our house.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  8. #8
    Senior Member bbs428's Avatar
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    Default Re: Lift strut attach brackets off center

    "We're all going to have our moments of frustration, just keep on doing

    In my defense, I now have a really, really sturdy yard light pole in front of our house."


    That is just hilarious Dave!

    I'm feeling your pain Jerry. I read the manual and darn when I read it again there is a little nugget - not highlighted - but there it is, letting me know I just stepped in it.

    Hope you get it sorted out.
    Somebody said that carrier pilots were the best in the world, and they must be or there wouldn't be any of them left alive. — Ernie Pyle

    Brett Butler
    Flying: 1998 Model 5 Outback, 912ul Zipper 110hp, G3x avionics, ss7 upgrades

  9. #9
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    Default Re: Lift strut attach brackets off center

    Thanks everyone.

    When in doubt call the factory. I spoke with Mr. McBean this morning. I felt like an idiot explaining to him what was going on, but it was determined that the small amount that I am off won't hurt anything since I am still able to rivet into the I-beam. Also the Eyelet connectors swivel so the load pressure is variable and the .5 of a degree the bracket is off, isn't going to effect anything.

    Bottomline.......make sure the reference line is visible in the witness hole before drilling.

  10. #10
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    Default Re: Lift strut attach brackets off center

    Huge relief. I'm sure there are plenty of us sweating this one out with you.
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

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