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Thread: Pitotube routing hole...

  1. #1

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    Default Pitotube routing hole...

    I’m currently restoring a model 2 Kitfox and now I am recovering the wing.

    I also decided to replace the pitotube as it is 26 years old....the previous owner had drilled a hole through the Aluminium wing bar and routed the tube there in to the cockpit.

    I enlarged the hole slightly to fit the new tube...but then I started thinking if this could affect the strength of the wing bar?

    Is reinforcement with aluminium sheet now required or some other sort of reinforcement or is it not necessary?




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  2. #2

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    Default Re: Pitotube routing hole...

    I found this in the build manual so I guess it is ok then?




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  3. #3
    Senior Member Delta Whisky's Avatar
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    Default Re: Pitotube routing hole...

    If I'm seeing the pictures correctly:

    1. It appears that the builder followed the instructions.
    2. The hole appears to be on the neutral axis.

    And,

    1. if it isn't larger than17/64 in height, and
    2. there aren't any sharp edges or burrs,

    You should be good to go.

  4. #4

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    Default Re: Pitotube routing hole...

    The hole is slightly bigger now on the highest point, 11.5 mm in height.

    Maybe email kitfox and get opinion?

  5. #5
    Senior Member Delta Whisky's Avatar
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    Default Re: Pitotube routing hole...

    I'm not familiar with the rib numbering convention for the Model 2. Is the hole inboard or outboard of the lift strut attachment?

  6. #6

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    Default Re: Pitotube routing hole...

    The hole is inboard from the attachment.

    I emailed kitfox and they don’t recommend any drilling in the spar.

    Deaney Aircraft however did...Kitfox recommended structural repair according to Ac 43-13


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  7. #7
    Senior Member Delta Whisky's Avatar
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    Default Re: Pitotube routing hole...

    The inboard loads on the spar of a strut braced, high wing aircraft are a tad more complex that one might think; maybe there is someone lurking here that has the background to supply enough information to help you make a decision. Clearly Denny aircraft called for the hole but the issue now is that it is larger - how much larger is too much larger? That is the question. I couldn't spend much time in AC43-13 this evening but I couldn't find any instruction related to repairing a spar, let alone a round spar. My only suggestion is to see if you can get in touch with a DER (or, equivalent) for his/her advice or analysis. It may cost you a bit but might be a lot cheaper than the time and cost of a new spar/wing panel. Or, maybe a structures engineer is reading this and can assist.

  8. #8

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    Default Re: Pitotube routing hole...

    I have decided to to replace the spar, the other wing has a dent in the front spar as well so will be replacing that one to.


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  9. #9
    Senior Member Delta Whisky's Avatar
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    Default Re: Pitotube routing hole...

    I'm sure you put a lot of effort and time into making the decision and it wasn't easy - BUT - I'll bet you'll sleep better. Keep us posted on progress through your rebuild.

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