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VNE on a mod 4 1200 and high speeds

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jeburke94je(at)direcway.c
Guest

Posted: Tue Mar 21, 2006 3:32 pm Post subject: VNE on a mod 4 1200 and high speeds

I have been reading this discussion and trying to figure out how in the 

world you guys are getting all this speed from your Kitfox's. I've got to 

say I am so jealous of your speeds I'm just beside myself. I have a IV-1200 

ser# 1830 with a 582,575 lbs empty,long wings,faring on the struts and 

landing gear support. I don't have wheel pants, I'm sure they would help a 

bit. I think the only way I could reach VNE of 125 MPH would be pointing 40 

degrees down and full power. I don't think I have ever seen over 110 MPH on 

the speed indicator even in rough air. It could be I need to replace my 

speed indicator or at least have it checked. I usually cruse at 70 MPH (at)5600 

Rpm and 75 mph (at) 6000 rpm.  my Gamin confirms a matching ground speed on a 

clam evening. So does the 912ul make that much difference with a increase of 

15 HP or do I need to make some major changes? I don't mean to say I'm not 

happy with my Kitfox  performance, But all those high speeds boggle the 

mind. Like always all your input is a plus. If someone has a set up similar 

to my Fox, I would also welcome your input.



Jim N94JE

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lcfitt(at)sbcglobal.net
Guest

Posted: Tue Mar 21, 2006 4:42 pm Post subject: VNE on a mod 4 1200 and high speeds

Hi, Jim,



I think the biggest speed drag on the Model IV is the absence of elevator 

trim - using the flaperons for pitch trim.  Flaps are usually designed to 

increase lift and drag.  To use flaps for pitch trim would increase drag 

significantly and this is how the early KFs were designed.  The later models 

use a movable horizontal stab for pitch trim.



When I bought my kit, I opted for the trim tab in the elevator and closed 

the gaps in both the vertical and horizontal tails with foam and fiberglass. 

That is where I believe I get most of my cruise performance and in my 

opinion, that is where the later models get theirs also.  Lift Strut 

fairings help as do other fairings, but the big improvement is in the trim 

system.  I don't remember the math, but to increase performance, a little 

bit of drag reduction helps as much as a lot of extra horsepower.



On the way back from a trip once, I played a bit with the trim.   I trimmed 

for a little nose up with the trim tab and then trimmed for level using the 

flaperons and speed definitely degraded.   I don't remember how much.



Lowell



---

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Tue Mar 21, 2006 6:18 pm Post subject: Re: VNE on a mod 4 1200 and high speeds

I suppose that the extra 15 hp could be a big difference but I have to throttle way down to hold 75 so I'm guessing that you're flying with considerably more parasitic drag. Next time I'm up I'll note the RPMs and manifold pressure at 75mph.  Cross reference against the Rotax charts will tell me how much power it's taking to fly at that speed. That would give us more to go on.

mike
Guest

Posted: Wed Mar 22, 2006 8:27 am Post subject: Re: VNE on a mod 4 1200 and high speeds

I do have trim in the elevator.  I have strut fairings.  I will say that my best rpm is 5200, the speed is great around 100, it is quite, that's the best part.  In fact it worries me a little when I put it up to 5800 and climb, I get vibration, kind of unnerving, but that's normal also.  It's just so smooth and quite at the lower rpm, that it's now my prefered.  So nice and smooth, quite, stereo a blarin, lots of IFR, wow! what a life.

mike
Guest

Posted: Wed Mar 22, 2006 8:48 am Post subject: Re: VNE on a mod 4 1200 and high speeds

here is a pic of my IFR

IFR.JPG

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f.miles.tcp.833(at)clearw
Guest

Posted: Wed Mar 22, 2006 9:34 am Post subject: VNE on a mod 4 1200 and high speeds

Is that Felts Field?



Frank LWS



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mike
Guest

Posted: Wed Mar 22, 2006 9:51 am Post subject: Re: VNE on a mod 4 1200 and high speeds

no, a farm house about 15mi south.  I'll get a pic of felts when I can and post. want to see spokane international, here you go.

international.JPG

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f.miles.tcp.833(at)clearw
Guest

Posted: Wed Mar 22, 2006 10:05 am Post subject: VNE on a mod 4 1200 and high speeds

Excuse me . . .the fifth picture you have posted is no farm house. Must be

GEG?



--

mike
Guest

Posted: Wed Mar 22, 2006 10:13 am Post subject: Re: VNE on a mod 4 1200 and high speeds

I'm new to this posting stuff, trying to see the fifth pic

mike
Guest

Posted: Wed Mar 22, 2006 10:15 am Post subject: Re: VNE on a mod 4 1200 and high speeds

If you are writing about the pics on the frapper. the fifth pic is fairchild AFB.

mike
Guest

Posted: Wed Mar 22, 2006 10:30 am Post subject: Re: VNE on a mod 4 1200 and high speeds

I think I know whats going on, I'm posting on the BBS forum interface and my attatchments are being shown on that forum and maybe not on the regular list.

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