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Thread: Rear edge stiffeners ?

  1. #1
    Senior Member Kitfox Pilot's Avatar
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    Default Rear edge stiffeners ?

    Did most you add these 3/8 pipes to the trailing edges ? I read they keep the rear edge from deforming when covering? Is this a problem when covering? I just read this on another build and had not heard of it.
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    Harlan and Susan Payne
    Sold Piper Archer
    Flying FarmFox STI Kitfox N61HP
    Rotax 915is, Airmaster prop
    https://www.youtube.com/channel/UC5A...oCVUP15G0uB-Yw

  2. #2
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    Default Re: Rear edge stiffeners ?

    What type of covering are you doing? Not needed with Oratex but recommended with poly.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  3. #3
    Senior Member efwd's Avatar
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    Default Re: Rear edge stiffeners ?

    I used them. I used Oratex. The last thing I wanted to see was a trailing edge resembling the Batman logo.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  4. #4
    Senior Member jrevens's Avatar
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    Default Re: Rear edge stiffeners ?

    I used them with Oratex too, Harlan. As an aside, the first time I was folding my wings in the 3-point attitude (before the first flight) I stupidly let a wing rotate back & slam into a cabinet with the trailing edge. The result was a relatively minor repair. I believe that if I hadn’t had the stiffening tubes I would’ve probably had to replace a section of the trailing edge.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  5. #5
    Senior Member jiott's Avatar
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    Default Re: Rear edge stiffeners ?

    In my opinion the stiffeners are a must; the 350F final fabric shrink pulls on that edge with a LOT of force. Some folks, I have heard, stop at 250F or so, but I have seen several in-flight videos of the top surface of the wing bulging up; so I personally want maximum fabric shrink and tightness on the wings. Even with the stiffeners I put a straight edge on the trailing edges after 350F shrink (I used Polyfiber) and found them slightly bowed inward about 1/8" at midspan, which was not visually noticeable.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  6. #6
    Senior Member jiott's Avatar
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    Default Re: Rear edge stiffeners ?

    One other idea I saw on this forum was instead of the 3/8" tubes he used carbon fiber arrow shafts at midspan hysoled between the trailing edge and the rear spar; an interesting lightweight solution he claimed did the job. Maybe the member/s who posted this quite a while ago will chime in and verify.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  7. #7
    Senior Member Kitfox Pilot's Avatar
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    Default Re: Rear edge stiffeners ?

    Thanks guys I will get some ordered. I am using oratex.
    Harlan and Susan Payne
    Sold Piper Archer
    Flying FarmFox STI Kitfox N61HP
    Rotax 915is, Airmaster prop
    https://www.youtube.com/channel/UC5A...oCVUP15G0uB-Yw

  8. #8
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    Default Re: Rear edge stiffeners ?

    I will play devils advocate.......unnecessary weight in my opinion but do what makes you most comfortable. Both of our planes we did not use them. We shrunk both wings to 450F and trailing edges are both straight. Wings are tight as a fiddle! When you shrink your wings you go longitudinally and start at the front of the wing so there is not much pulling on trailing edge verus pulling against the ribs. Of course we did a lot of things different than others on here like no rib stitching and minimal finishing tape. On another note this is what drove me crazy about kitfox. Where is the secret menu to order these "must" items? If something is required then include it with the kit!
    Last edited by Shadowrider; 06-13-2020 at 11:35 AM.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  9. #9
    Senior Member Kitfox Pilot's Avatar
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    Default Re: Rear edge stiffeners ?

    Quote Originally Posted by Shadowrider View Post
    I will play devils advocate.......unnecessary weight in my opinion but do what makes you most comfortable. Both of our planes we did not use them. We shrunk both wings to 450F and trailing edges are both straight. Wings are tight as a fiddle! When you shrink your wings you go longitudinally and start at the front of the wing so there is not much pulling on trailing edge verus pulling against the ribs. Of course we did a lot of things different than others on here like no rib stitching and minimal finishing tape. On another note this is what drove me crazy about kitfox. Where is the secret menu to order these "must" items? If something is required then include it with the kit!
    I had no idea about the little pipes, just ran across them looking at the builders logs. I thought oratex might pull harder since its a tougher material but I guess not if you've done two you should know.
    Last edited by Kitfox Pilot; 06-13-2020 at 03:24 PM.
    Harlan and Susan Payne
    Sold Piper Archer
    Flying FarmFox STI Kitfox N61HP
    Rotax 915is, Airmaster prop
    https://www.youtube.com/channel/UC5A...oCVUP15G0uB-Yw

  10. #10
    Senior Member Dave S's Avatar
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    Default Re: Rear edge stiffeners ?

    Harlan,

    I believe the instructions to include the aluminum tubes as an option was mentioned in my build manual (early S7); and, at the time I ordered them from aircraft spruce following the demise of skystar.

    I see the addition as a way to increase the ruggedness of the trailing edge as well as dealing with the fabric shrinking stress as mentioned in the manual. I have seen way too many OOPS! happen in various hangars with visitors and I would rather see a dent in the perpetrator than the wing if at all possible.

    Overall I think it is well worth the trouble but everyone's mileage certainly varies. Regarding weight - I just try to avoid eating too much stuff I shouldn't.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

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