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Thread: Wing tips

  1. #1
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    Default Wing tips

    I am in the conondrum of trying to decide if I want to keep the KF IV that I originally purchased for my son or if I should sell it. I already have way too many projects but will admit, I have always liked the KF. I just do not need it right now as I have a 172, a RANS S7, and a couple of Murphy Rebel projects along with this recently acquired KF.

    Lately my thoughts have been towards keeping it and getting it flying. Having given this winded explination of my mixed up mind, I am wanting to get your guys comments on the droop tips verses the Hoerner type wing tips. Is one better than the other?

    My KF has the droop tips on it and I previously had them on my Champ floatplane. The only downside I ever noticed was they do block visibilty somewhat. But that plane was nearly stall proof. Not sure if it was the tips, VG's, or the combination but it would just sink without breaking if I guy held the stick fully back.

    So, after my long winded rambling...

    Pro's and cons of Droop tips verses the Hoerner type. What say the experts?

  2. #2
    Senior Member HighWing's Avatar
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    Default Re: Wing tips

    Keith,
    Personally all my experience has been with the Hoerner tips. I do have friends with the droop tips and have flown alongside them many times. I think practically, you have mentioned the basic benefit of the Hoerner - visibility. In practice, I don't think one performs better than the other cruise wise. I do think one real benefit of the droop tips, at least in the early days where everyone was flying with the squirrely bungy gear, is the relative ease of trimming the tip where it struck the ground after the ground loop - something like a skid.
    Lowell Fitt
    Goodyear, AZ


    My You Tube Channel

  3. #3
    Senior Member jiott's Avatar
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    Default Re: Wing tips

    According to Mr. Hoerner who developed the wing tips they are a much improved design developed to smooth the wingtip vortex and maintain better lift all the way to the tip, among other claims. I have these tips and my plane seems to float somewhat farther (more lift?) than others when I fly with friends with identical SS7's and standard tips.
    Don'y know much about the droop tips; seems not a lot of real research out there that I can find, other than they look kind of cool and a lot of personal anecdotal claims. Either way I think the difference in performance would be hard to measure. If I were to do it over again, I think I would go with the standard tips with built-in recesses for nav/strobe lights. Gluing on and fairing in the light adapters for the Hoerner tips was a lot of work.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  4. #4
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    Default Re: Wing tips

    Jim has it, but to expand on that: the purpose is to add efficiency to the wing by pulling that vortex inboard, instead of it sliding off the end of the wing and in doing so, effectively increasing the L/D without adding wing length.

    At speeds under 80, you'd be hard pressed to see any difference between any of them and a standard wing as far as both lift and drag go. As speed increases, say up into the 120 to 130mph range they increase efficiency quite a bit.

    Either tip can add up to 15% equivalent wing length at higher speeds which equates to higher efficiency without adding the length or associated weight. A 32' wingspan would effectively then be over 36'. Again - at higher speeds.

    For that matter, you could put a rhomboid or circular flat end plate on the end of the wing and achieve the same results.

    Greg

  5. #5
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    Default Re: Wing tips

    Thanks guys! One of the reasons for the question was my long term thinking of posibly keeping the plane. The droop tips are on it now, but saw Dan's posting for the standard tips and I was interested in them. Mostly due to my past owning a plane with the droop tips and remembering how they were a little obstructive for viewing during turns and landings.

    Guess I'll just stay with the droop tips as the 'con' of them is easily fixed by just lifting the wing a bit more for clearing turns.

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