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Thread: Vne for KF model 4/1200

  1. #1
    WISDAN's Avatar
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    Default Vne for KF model 4/1200

    I'm currently using a Vne of 125 mph flying my 4/1200 with 32 ft wing span. What's the groups thoughts on this? I'm currently cruising at 110-115 mph indicated.
    Dan G.
    Model IV 1200 - Tri-gear
    Jabiru 2200
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  2. #2
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    Default Re: Vne for KF model 4/1200

    My first question is this: How accurate is your ASI? Second is: What does Kitfox say the VNE supposed to be on the Kitfox 4? JImChuk

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    Default Re: Vne for KF model 4/1200

    My pilot handbook, if I remember correctly, says 120 mph for the standard model 4 1200 and 140 mph for the Speedster. I assume the airfoil shape of the tail surfaces of the Speedster handle higher airspeed a little better than the standard model 4's flat surfaces. James Thomas

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    Administrator DesertFox4's Avatar
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    Default Re: Vne for KF model 4/1200

    My understanding is it has more to do with the thickness of the windshield material.


    DesertFox4
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  5. #5
    WISDAN's Avatar
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    Default Re: Vne for KF model 4/1200

    Thanks for the replies. My ASI is correct. I don't plan on faster than 120mph but when I got my kit vne was listed at 125 in my limitations (skystar). Of course we keep speeds down in rough condions.
    Dan G.
    Model IV 1200 - Tri-gear
    Jabiru 2200
    Flying

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    Default Re: Vne for KF model 4/1200

    You're probably right DesertFox4 about the windshield thickness. I just figured the airfoil tail surfaces might be less likely to flutter at higher speeds. I do remember that the Speedster called for a thicker windshield. I suspect we're both right. James Thomas

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    Default Re: Vne for KF model 4/1200

    Just as a comparison, the Avid MK IV had a VNE of 135. They never did use any wood ribs in the tail feathers on the Avids. Avid wings are 2' shorter than the standard Kitfox 4. I have noticed the .060" thickness windshield start to buckle in at about 100 MPH though. JImChuk

  8. #8
    Super Moderator Av8r3400's Avatar
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    Default Re: Vne for KF model 4/1200

    My IV-1050 stated 125 mph.

    My IV-1200 Classic has listed 140.


    I agree with Steve, it is all about the windshield. The earlier kits had a thin (.062"?) Lexan (polycarbonate) sheet the w/s was made from. This would begin to stove in at around 115-120 mph. The later kits had a thicker piece (.087'?) or the molded acrylic piece from LP Aeroplastics which was much more rigid.
    Av8r3400
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  9. #9
    WISDAN's Avatar
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    Default Re: Vne for KF model 4/1200

    Is the 140 mph for the standard wing span Larry?
    Dan G.
    Model IV 1200 - Tri-gear
    Jabiru 2200
    Flying

  10. #10
    Super Moderator Av8r3400's Avatar
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    Default Re: Vne for KF model 4/1200

    I don't know that the wingspan has any effect on the VNE.
    Av8r3400
    Kitfox Model IV
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