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Thread: Wing Twist & 5 vs. 7 rigging differences

  1. #1
    rcbif's Avatar
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    Default Wing Twist & 5 vs. 7 rigging differences

    I rigged the wing of my model 5 last night, but I have to say, the only step I’m not 100% sure of the intent of is the first step in setting wing twist. The manual has you place the level, 3” from the root, place the level touching the front spar, and measure the difference between the level and the bottom of the rear spar.


    Both my wings were level for this location, and being so close to the fuselage, I’m not entirely sure why they shouldn't be?




    The only reason I can come up with the purpose of this step is if for some reason your spars are floating a bit over the fuselage lug/attachment points? Is this sound reasoning?



    Regardless, I proceeded to measure level at the wingtip with my ½” block on the level for the ½” washout.


    This morning I decided to review the same steps in the model 7 manual the previous owner bought for this model 5 to reference for some updates and I noticed the model 7 uses a different reference for the dihedral.


    The 5 uses the rear spar to measure the 1 deg dihedral, while the 7 uses the front spar to measure the1 deg dihedral.

    This is followed by the 5 adjusting the front lift strut bracket position to set twist, and the 7 adjusting the rear lift strut bracket position.

    I would think the leading edge would be the logical place to measure dihedral, and I’m guessing that’s why Kitfox changed it to that way, but I’m no aeronautical engineer.

    I ran the numbers (scary trig, lol) and the difference would be .17 degrees in dihedral. So the 5 has a bit less. I think since I already rigged according to the 5 manual, I’m just going to go with that unless anyone has any comments.
    Building a Kitfox V Outback in NE Ohio

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    Senior Member HighWing's Avatar
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    Exclamation Re: Wing Twist & 5 vs. 7 rigging differences

    My thoughts. At this stage of the build you are likely setting wing twist to get you through the initial stages of your flight testing without excessive roll corrections needed with the stick. I recently did a half turn adjustment on a lift strut rod end to reduce a bit of left roll tendency. Which spar to adjust? A friend told me it was best to adjust by flattening the lifting wing rather than increasing dihedral on the dropping wing. I went a half turn tighter in the right forward strut.
    Lowell Fitt
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    Senior Member Maverick's Avatar
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    Default Re: Wing Twist & 5 vs. 7 rigging differences

    Did that do the trick?

    I followed the series 5 manual guidance. The first series 5 build I did long ago was certainly by the series 5 manual instructions given it was the latest model at the time and that plane flew very well with no adjustments to the washout or dihedral necessary. I'm hoping for the same this time around (I should be so lucky).

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    Senior Member HighWing's Avatar
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    Default Re: Wing Twist & 5 vs. 7 rigging differences

    Not quite there, it seems, but want to evaluate further as I still have the tendency to want to correct what appears to be no longer there - the old "one wing low" phenomenon.
    Lowell Fitt
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    Senior Member rv9ralph's Avatar
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    Default Re: Wing Twist & 5 vs. 7 rigging differences

    It seams there is a maturation of the process from the Series 5 to the Series 7. The front spar is used to set dihedral and the rear spar is used to set twist. As a note to the interpretation... if the rear spar is used for both, both will change when trying to adjust just one attribute.

    Just my thoughts and interpretation.

    Ralph

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    Default Re: Wing Twist & 5 vs. 7 rigging differences

    I ran into this exact same scenario. Any other thoughts on this? How did it it turn out? Anyone building a 5 use the newer model 7 wing rigging instructions?

    I am tempted to use the front spar for the dihedral and the rear for the washout.

  7. #7
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    Default Re: Wing Twist & 5 vs. 7 rigging differences

    Quote Originally Posted by Jerrytex View Post
    I ran into this exact same scenario. Any other thoughts on this? How did it it turn out? Anyone building a 5 use the newer model 7 wing rigging instructions?

    I am tempted to use the front spar for the dihedral and the rear for the washout.
    Well I will be building my series 5 with 7 instructions but I haven't started my wings yet.

    I actually own the plane at the beginning of this thread. The OP mis-drilled the strut attach fittings so I'm building wings from bare tubes and new ribs/tanks.

    I've read far enough into the manuals to see the twist (washout) is incorporated into the wings when you shim the outboard end of the rear spar 1/2" when you bond the ribs in place. Of course it won't be super rigid at that point and adjusting the rear strut length would alter that somewhat.

    I agree that using the front spar for the dihedral would remove variations in washout from the equation.
    Kitfox 5 (under construction)
    Commercial SE/ME, CFII

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