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Old 04-28-2018, 06:31 AM   #1
WISDAN
 
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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.
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Old 04-28-2018, 06:50 AM   #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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Old 04-28-2018, 07:15 AM   #3
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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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Old 04-28-2018, 07:27 AM   #4
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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.
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Old 04-28-2018, 08:57 AM   #5
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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.
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Old 04-28-2018, 09:06 AM   #6
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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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Old 04-28-2018, 12:25 PM   #7
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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
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Old 04-29-2018, 04:49 AM   #8
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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.
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Old 04-29-2018, 03:06 PM   #9
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Default Re: Vne for KF model 4/1200

Is the 140 mph for the standard wing span Larry?
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Old 04-29-2018, 07:57 PM   #10
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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.
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