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Kitfox Control Surface Flutter Mitigation
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Patrick.Best(at)telus.com
Guest

Posted: Tue Apr 21, 2009 5:46 am Post subject: Kitfox Control Surface Flutter Mitigation

Hi Everyone;  

  

 I am looking at a  Kitfox and a CH750.  Given the recent problems zenith has with flutter  (killing pilots, etc), I was wondering if the kitfox uses a mass-balanced  approach on their control surfaces, or uses simply cable tension to mitigate  this.

  

  

  [quote][b]

MDKitfox(at)aol.com
Guest

Posted: Tue Apr 21, 2009 6:04 am Post subject: Kitfox Control Surface Flutter Mitigation

Patrick,



The Kitfox uses mass balance weights (2 per flaperon.) The control system for the flaperons (ailerons and flaps combined) do not use any cables, they are all steel pushrods.  Careful adjustment of the rods ensures no flutter issues.  The rudder uses cables, but there are no flutter issues with it.  Overall it's an excellent system.



 Rick Weiss

N39RW Series V Speedster, 912ULS

SkyStar S/N 1

Port Orange, FL



 



On Apr 21, 2009, at 9:44 AM, Patrick Best wrote:

 	  Quote: 	
		    Hi Everyone; 

  

 I am looking at a Kitfox and a CH750.  Given the recent problems zenith has with flutter (killing pilots, etc), I was wondering if the kitfox uses a mass-balanced approach on their control surfaces, or uses simply cable tension to mitigate this.

  

  

  	  Quote: 	
		  



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http://www.matronics.com/Navigator?Kitfox-List

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=  [quote][b]

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Tue Apr 21, 2009 8:09 am Post subject: Re: Kitfox Control Surface Flutter Mitigation

Patrick,



The Kitfox is a far Superior airplane to the Zenith Air CH-750.  The CH750 is slow, and a real dog in the air compared to the Kitfox.  The Kitfox is faster, more agile, and does everything the CH-750 will do but better.



The ridiculously fat wing of the CH-750 is horrible for a lot of reasons.  Flutter would not be my concern here, flutter problems can be easily solved as I am sure Zenith Air will now quickly do.  The bad design of the CH-750 is something that can not be fixed.



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

Fox5flyer
Guest

Posted: Tue Apr 21, 2009 8:32 am Post subject: Kitfox Control Surface Flutter Mitigation

I believe the flutter problem was with the 601 only.  Someone correct me if 

I'm wrong.

Deke

do not archive

---

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Tue Apr 21, 2009 8:41 am Post subject: Re: Kitfox Control Surface Flutter Mitigation

JetPilot -



Uh,  hmm ... Well I would definetly not go so far as to say that ...



Being a builder of BOTH a Kitfox, and a Zenith I see it slightly differently.



Regards,

Jeff

Last edited by n85ae on Tue Apr 21, 2009 8:46 am; edited 1 time in total

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Tue Apr 21, 2009 8:43 am Post subject: Re: Kitfox Control Surface Flutter Mitigation

Deke -



The 601 has the flutter/wing shedding problem.



Jeff

Patrick.Best(at)telus.com
Guest

Posted: Tue Apr 21, 2009 9:13 am Post subject: Kitfox Control Surface Flutter Mitigation

Jeff, what are you impressions of both?  Which models did you own? 



The reason why I'm very much interested in the 750 is because I am a large guy (6'5 , 260lbs) and the bubble doors appealed to me.  Also, I was interested in using an O-200 but still having a good useful load.



--

Patrick.Best(at)telus.com
Guest

Posted: Tue Apr 21, 2009 9:17 am Post subject: Kitfox Control Surface Flutter Mitigation

Mike, what about the design of the 750 has turned you towards the kitfox?



 



--

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Tue Apr 21, 2009 9:43 am Post subject: Re: Kitfox Control Surface Flutter Mitigation

I posted that info here the other day  

http://forums.matronics.com/viewtopic.php?t=57186



Kitfox had flutter issues as well in the early days and not all Kitfox have 2 counter weights per flapperon only the Speedster did. Others have one for each flapperon.. 



It was just the 601 xl this note was about and a serious issue as they have had more than 1 inflight break ups .

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n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Tue Apr 21, 2009 10:04 am Post subject: Re: Kitfox Control Surface Flutter Mitigation

I built and fly a Series 5 Kitfox with an IO-240B, and am most of the way 

through building a CH801. Given your size, you will be VERY cramped in a  Kitfox. I am quite a bit smaller, and I find it cramped (and yes I have

the bubble doors). I can't speak for the 750, but the 801 has a LOT more

room inside.



Kit quality is the same, just different. The manuals I got for the Kitfox

were better than those for the Zenith. However the Zenith has a lot of 

good drawings.



My hangar neighbors have a Murphy Moose, they complain just as much

about the Murphy kit as do I about Zenith, or previously the Kitfox. So

I would say - They're all about the same with regard to building. The

kits are all ok, but none of them are perfect.



The Zenith IS a draggy plane, BUT it is probably less affected by weight

than the Kitfox. The Kitfox flies great light, but the wing is NOT a load 

hauler. So they are different flyers. The Zenith will take off shorter, and

land shorter than a Kitfox, but it won't go as fast. I really hate to say it,

but I really don't think of the Kitfox as being STOL. I think of it as being

a pretty straight forward tube and fabric high wing taildragger. I've been

flying it for almost 7 years now, so I think my opinion is pretty well

formed.  



Light weight, solo, the Kitfox gets of the ground really fast. But put two

in it, and it's just another airplane. 



I think if you want to haul a load, and get in and out of small places

and aren't worried about cruise speed (or looks). The 750 & 801 are

better planes than the Kitfox. If most of your flying is solo, and you 

like flying in and out of grass strips, etc. The Kitfox is the plane.



If you weigh 260, I'd seriously look at the Zenith's. The Kitfox is very

small inside. 

 

I like both planes, they are different. I definetly would not say one is

better than the other. 



Regards,

Jeff 



 	  Quote: 	
		  Jeff, what are you impressions of both? Which models did you own?



The reason why I'm very much interested in the 750 is because I am a large guy (6'5 , 260lbs) and the bubble doors appealed to me. Also, I was interested in using an O-200 but still having a good useful load.

lcfitt(at)sbcglobal.net
Guest

Posted: Tue Apr 21, 2009 11:34 am Post subject: Kitfox Control Surface Flutter Mitigation

Jet Pilot,



Just curious,  Have you flown Both??.  Or are you just passing on some 

internet hearsay.  Not to get me wrong, I love my Kitfox, but, I like to 

post where I have some personal experience.  To simply pass on rumor or 

hear-say as fact sounds pretty much like most internet information.  FYI, I 

know some dedicated and experienced Kitfox folks who are experimenting with 

a "fat" wing.  I really don't know if anyone can simply look at a wing and 

decide if it will enhance performance or hurt it.  Some enterprizing soul 

will prove the concept.  Until then we will get lots of opinions.



Another question,  do you always have to trash anything you don't personally 

own?



Lowell



---

Patrick.Best(at)telus.com
Guest

Posted: Tue Apr 21, 2009 8:34 pm Post subject: Kitfox Control Surface Flutter Mitigation

Thanks so much for your insight.  Very appreciated.

________________________________________

From: owner-kitfox-list-server(at)matronics.com [owner-kitfox-list-server(at)matronics.com] On Behalf Of n85ae [n85ae(at)yahoo.com]

Sent: Tuesday, April 21, 2009 2:04 PM

To: kitfox-list(at)matronics.com

Subject: Re: Kitfox Control Surface Flutter Mitigation

I built and fly a Series 5 Kitfox with an IO-240B, and am most of the way

through building a CH801. Given your size, you will be VERY cramped in a  Kitfox. I am quite a bit smaller, and I find it cramped (and yes I have

the bubble doors). I can't speak for the 750, but the 801 has a LOT more

room inside.

Kit quality is the same, just different. The manuals I got for the Kitfox

were better than those for the Zenith. However the Zenith has a lot of

good drawings.

My hangar neighbors have a Murphy Moose, they complain just as much

about the Murphy kit as do I about Zenith, or previously the Kitfox. So

I would say - They're all about the same with regard to building. The

kits are all ok, but none of them are perfect.

The Zenith IS a draggy plane, BUT it is probably less affected by weight

than the Kitfox. The Kitfox flies great light, but the wing is NOT a load

hauler. So they are different flyers. The Zenith will take off shorter, and

land shorter than a Kitfox, but it won't go as fast. I really hate to say it,

but I really don't think of the Kitfox as being STOL. I think of it as being

a pretty straight forward tube and fabric high wing taildragger. I've been

flying it for almost 7 years now, so I think my opinion is pretty well

formed.

Light weight, solo, the Kitfox gets of the ground really fast. But put two

in it, and it's just another airplane.

I think if you want to haul a load, and get in and out of small places

and aren't worried about cruise speed (or looks). The 750 & 801 are

better planes than the Kitfox. If most of your flying is solo, and you

like flying in and out of grass strips, etc. The Kitfox is the plane.

If you weigh 260, I'd seriously look at the Zenith's. The Kitfox is very

small inside.

I like both planes, they are different. I definetly would not say one is

better than the other.

Regards,

Jeff

 	  Quote: 	
		   Jeff, what are you impressions of both? Which models did you own?

 The reason why I'm very much interested in the 750 is because I am a large guy (6'5 , 260lbs) and the bubble doors appealed to me. Also, I was interested in using an O-200 but still having a good useful load.

Read this topic online here:

http://forums.matronics.com/viewtopic.php?p 40513#240513

lcfitt(at)sbcglobal.net
Guest

Posted: Wed Apr 22, 2009 9:07 am Post subject: Kitfox Control Surface Flutter Mitigation

Jeff,



Excellent post.  Comparing apples and oranges by someone who has eaten both 

sure beats a lot of the stuff we read here.



I have a comment, though.  Pardon me for maybe stepping on some toes, but 

the Kitfox history reminds me of Ford's transformation of the Thunderbird 

from a neat little two seater to a four seat monster - not that the Kitfox 

has four seats yet, but I am pretty sure it has been considered.



The early Kitfoxes were STOL in the purest sense of the word.  The Model IV 

was close, especially if the builder had STOL in mind.  My friend's, with 

everything needed for long cross country and lots of close in flying, 

weighed 604 lbs.  I would bet that the newer offerings, if put on a very 

restricted diet could still be built in the mid 600 lb. range, but add all 

the goodies plus a heavy engine requiring ballast to boot with the same wing 

as a Model IV and empty weights approaching - and occasionally exceedin 900 

lbs.  and performance in the STOL catagory does suffer.



Deke introduced an interesting thread on tool kits, with lots of comments on 

how to maximize utility and minimize weight.  Would someone who has the 

adjustable rudder pedals  in one of the later Kitfoxes offer an opinion as 

to their utility vs. the weight penalty.



Lowell



Do not Archive

---

Fox5flyer
Guest

Posted: Wed Apr 22, 2009 9:55 am Post subject: Kitfox Control Surface Flutter Mitigation

Would someone who has the

 	  Quote: 	
		   adjustable rudder pedals  in one of the later Kitfoxes offer an opinion as 

 to their utility vs. the weight penalty.



 Lowell


	


I have them and only because they came with my kit that I purchased 

unstarted from someone who had buyers remorse.  Thinking they would be a 

nice option I installed them, but after putting the pedals where they were 

comfortable for me, it's rare that I ever change them.  Perhaps if I was 

using the airplane for dual instruction they might be useful, but otherwise 

the extra weight and complexity could have easily been avoided and they 

would not have been missed.  Add to that my CD player and G meter. 

Sheesh...

Deke Morisse

Mikado Michigan

S5/Subaru/CAP 405+ TT

"The aim of an argument or discussion should not be victory, but progress."

- Joseph Joubert

n981ms(at)yahoo.com
Guest

Posted: Wed Apr 22, 2009 10:58 am Post subject: Kitfox Control Surface Flutter Mitigation

I can't compare to without but I like them. I fly from either side.  Bottom line is if you are the only one to ever fly your plane, you will be happy without them and you will have saved weight (I don't think its much though) and complexity.  But keep in mind you might want to sell it someday.



Maxwell Duke

S6/TD/IO240

Dublin, GA



--- On Wed, 4/22/09, fox5flyer <fox5flyer(at)idealwifi.net> wrote:

  	  Quote: 	
		  From: fox5flyer <fox5flyer(at)idealwifi.net>

Subject: Re: Re: Kitfox Control Surface Flutter Mitigation

To: kitfox-list(at)matronics.com

Date: Wednesday, April 22, 2009, 1:54 PM



 	  Quote: 	
		  --> Kitfox-List message posted by: "fox5flyer"

<fox5flyer(at)idealwifi.net>



Would someone who has the

 	  Quote: 	
		   adjustable rudder pedals  in one of the later Kitfoxes offer an opinion as

to their utility vs. the weight penalty.
	


 	  Quote: 	
		   

 Lowell


	


I have them and only because they came with my kit that I purchased unstarted

from someone who had buyers remorse.  Thinking they would be a nice option I

installed them, but after putting the pedals where they were comfortable for me,

it's rare that I ever change them.  Perhaps if I was using the airplane for

dual instruction they might be useful, but otherwise the extra weight and

complexity could have easily been avoided and they would not have been missed. 

Add to that my CD player and G meter. Sheesh...

Deke Morisse

Mikado Michigan

S5/Subaru/CAP 405+ TT

"The aim of an argument or discussion should not be victory, but

progress."

- Joseph Joubert

	
	


           [quote][b]

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Wed Apr 22, 2009 12:52 pm Post subject: Re: Kitfox Control Surface Flutter Mitigation

Lowell -



The only reason I don't really think of MY Kitfox as STOL is:



It isn't STOL at max weight, it's GRYHND (i.e. as in bus)



The landing performance is a huge issue. There is simply

no real way to dump lift, and get a lot of drag for landing short. The

flaperons, don't really work well for generating drag. At least in notch

1, the second notch I find to be scary to use so I don't. Slips are pretty

usefull, but that's more pilot technique, than airplane.



However, MY plane, will make a Schweitzer sailplane pilot green

with envy if I come in hot as it floats, and floats, and floats, and ... 



I think to be really STOL in the purest sense, it needs big barn door 

flaps, AND the ability to fly and perform at Max GW.



AGAIN - Light with half tanks, I can be airborne by the first runway 

light, and at pattern altitude by the end of the runway (3000 ft.). Which

never fails to impress the line of Cessna drivers where I fly. The

view out the side window and the wing looks to be 45 to the horizon

at 65 mph. SO maybe it is STOL. I might be just so used to it that

it feels normal now 



Jeff 



 	  Quote: 	
		  The early Kitfoxes were STOL in the purest sense of the word. The Model IV

was close, especially if the builder had STOL in mind.

n981ms(at)yahoo.com
Guest

Posted: Wed Apr 22, 2009 2:25 pm Post subject: Kitfox Control Surface Flutter Mitigation

Jeff,  

   You may have already found this but my Fox has a dramatic change in sink rate at around 50 kts.  Uncomfortable at first (feels like being in an elevator) but there is plenty of elevator left for the flare.  Ready with the power just in case.  I usually land with full flaps but I usually do not deploy them until on final.  My home strip is 2000ft with trees on one end.  With head wind of 10-12kts I have landed over 40-50ft trees on a 1000ft strip.  Maybe not as good as a Zenith but still seems short.



Maxwell Duke

S6/TD/IO240

Dublin, GA



--- On Wed, 4/22/09, n85ae <n85ae(at)yahoo.com> wrote:



  	  Quote: 	
		  From: n85ae <n85ae(at)yahoo.com>

Subject: Kitfox-List: Re: Kitfox Control Surface Flutter Mitigation

To: kitfox-list(at)matronics.com

Date: Wednesday, April 22, 2009, 4:52 PM



 	  Quote: 	
		  --> Kitfox-List message posted by: "n85ae" <n85ae(at)yahoo.com>



Lowell -



The only reason I don't really think of MY Kitfox as STOL is:



It isn't STOL at max weight, it's GRYHND (i.e. as in bus)



The landing performance is a huge issue. There is simply

no real way to dump lift, and get a lot of drag for landing short. The

flaperons, don't really work well for generating drag. At least in notch

1, the second notch I find to be scary to use so I don't. Slips are pretty

usefull, but that's more pilot technique, than airplane.



However, MY plane, will make a Schweitzer sailplane pilot green

with envy if I come in hot as it floats, and floats, and floats, and ... 



I think to be really STOL in the purest sense, it needs big barn door 

flaps, AND the ability to fly and perform at Max GW.



AGAIN - Light with half tanks, I can be airborne by the first runway 

light, and at pattern altitude by the end of the runway (3000 ft.). Which

never fails to impress the line of Cessna drivers where I fly. The

view out the side window and the wing looks to be 45 to the horizon

at 65 mph. SO maybe it is STOL. I might be just so used to it that

it feels normal now 



Jeff 

 	  Quote: 	
		   The early Kitfoxes were STOL in the purest sense of the word. The Model IV

 was close, especially if the builder had STOL in mind.


	






Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=240791#240791





	
	


         [quote][b]

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Wed Apr 22, 2009 4:57 pm Post subject: Re: Kitfox Control Surface Flutter Mitigation

Maxwell -



I take it you're doing this with 1 notch of flaperons? Winds permitting I

might work on this tommorrow after work. I generally slip it in around

60, and then start flaring after the slip. 50 seems slow, but still there's

probably about 10 mph left. If I bend the gear, I'll blame you. 



Definetly don't want to do that if it's gusting at all. Even with my normal

style landings, I've had some wind shift and pretty dramatic sink at

times.



Regards,

Jeff

n981ms(at)yahoo.com
Guest

Posted: Thu Apr 23, 2009 4:02 am Post subject: Kitfox Control Surface Flutter Mitigation

I use full flaps to land short.  Full flap has not scared me.  Maybe I don't know enough to be scared but I use full flaps almost all the time. Again, I usually do not use any flap until on final.  Try getting slow at altitude to get the feel for it.  (I may not be able afford new gear for you right now.)  There is a change in the feel of the plane that takes a little getting used to.  Nose is very high and once you get slow enough it feels almost like you are going down more than forward.  But there is still elevator authority to flare.  Not having that extra speed at flare really shortens the glide and landing distance.



Maxwell Duke

S6/TD/IO240

Dublin, GA



--- On Wed, 4/22/09, n85ae <n85ae(at)yahoo.com> wrote:

  	  Quote: 	
		  From: n85ae <n85ae(at)yahoo.com>

Subject: Kitfox-List: Re: Kitfox Control Surface Flutter Mitigation

To: kitfox-list(at)matronics.com

Date: Wednesday, April 22, 2009, 8:57 PM



 	  Quote: 	
		  --> Kitfox-List message posted by: "n85ae" <n85ae(at)yahoo.com>



Maxwell -



I take it you're doing this with 1 notch of flaperons? Winds permitting I

might work on this tommorrow after work. I generally slip it in around

60, and then start flaring after the slip. 50 seems slow, but still there's

probably about 10 mph left. If I bend the gear, I'll blame you. 



Definetly don't want to do that if it's gusting at all. Even with my

normal

style landings, I've had some wind shift and pretty dramatic sink at

times.



Regards,

Jeff





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=240836#240836





	
	


         [quote][b]

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Thu Apr 23, 2009 5:32 am Post subject: Re: Kitfox Control Surface Flutter Mitigation

Maxwell -



I'm comfortable with the nose high attitude the plane gets when slow, so

that's no problem. 



What I don't like is the full flaperons. I think at full nose up trim I still have 

to hold a lot of back stick, plus it really screws up the roll control. I'll let

you be the expert on this subject.



Can we just start calling you Madmax on the forum from now on?



By the way, I think you have the same gear I have, so ... If you're

lacking funds you can just ship me yours.



Regards, 

Jeff

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