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dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Dec 21, 2006 10:35 am Post subject: Older Kitfox cruise speeds

Hey no problem.

you can be the man today



Seasonal greetings to all.



Dave



PS   and i will include links to help others. Glad you enjoyed the videos !! 





 Here links to the factual SKi video  http://www.cfisher.com/kitfox/

        and the factual info on NGK plugs  http://www.cfisher.com/ngk/

that was backed up by Bob Robertson the Rotax guru.



---

_________________
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Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Thu Dec 21, 2006 1:14 pm Post subject: Older Kitfox cruise speeds

On Dec 20, 2006, at 2:57 PM, Paul Seehafer wrote:

 	  Quote: 	
		   Sure, the newer Kitfox (Riblett) airfoil helps to make the newer 

 Kitfoxes cruise faster, but even if you were to put a new Riblett wing 

 on an older Kitfox, my guess is you wouldn't see a lot of cruise speed 

 increase, because there is just too much positive wing incidence 

 causing a lot of drag.


	


Hello Paul,

Since I read your email, yesterday, I have been thinking about this and 

I just can't figure out how it works. From the X-Plane flight 

simulator, I am used to make digital models. I don't know how it is 

done in real life but I guess it is done in relation to a reference 

line. Let's say, a line going from the prop hub to the end of the 

fuselage. From that, various airfoils can be built, each with a 

different angle of attack. I think angle of attack (AoA) is usually 

used as the angle to that reference line, where angle of incidence is 

the actual angle made by the apparent wind and the airfoil.

If we look at the AoA, we see that, as it increases, the coefficient of 

lift and the coefficient of drag increase too. As speed increases and 

lift increases to the square of the speed, one has to push the stick to 

keep the plane at level flight.

Now, if the actual attachment of the wings' root to the fuselage is 

different from one model to another, it means that, for the same speed, 

one plane will fly with a slightly greater nose-down attitude. But how 

does that influences the maximum speed you can achieve for a given 

engine horse power? My understanding is that an airfoil has a constant 

lift/drag ration for a given AoA. Did I miss something?



Cheers,

Michel

_________________
Kitfox 3 - Jabiru 2200

akflyer
Guest

Posted: Thu Dec 21, 2006 1:36 pm Post subject: Re: Older Kitfox cruise speeds

If the tail has to come up higher in flight to get the wing level, then you have more drag.  THe fuse is not "straight" in the airflow, the horizontal stab is a big brake back there, the struts are now at a nose down attidute which means they are not straight with the relative wind etc..  It all adds up to a slower plane.

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Thu Dec 21, 2006 2:43 pm Post subject: Older Kitfox cruise speeds

On Dec 21, 2006, at 10:36 PM, akflyer wrote:

 	  Quote: 	
		   If the tail has to come up higher in flight to get the wing level, 

 then you have more drag.  THe fuse is not "straight" in the airflow, 

 the horizontal stab is a big brake back there, the struts are now at a 

 nose down attidute which means they are not straight with the relative 

 wind etc..  It all adds up to a slower plane.


	


Thank you for your answer, Leni. What you are saying, basically, is 

that a higher AoA attachment point of the wings won't increase induce 

drag but parasite drag, right? It makes sense. However, if I may ask:

You wrote: The horizontal stab is a big brake.

  Yes, it is. But if say, you decide to install a stronger engine that 

gives you more speed, can't you adjust the angle of your horizontal 

stab accordingly?



This is only a theoretical question because while my model 3 with its 

new Jabiru can easily exceed  Vne, only looking at the thin lexan 

windscreen makes me throttle back long before that! 



Cheers,

Michel



do not archive

_________________
Kitfox 3 - Jabiru 2200

henrysfork1(at)msn.com
Guest

Posted: Thu Dec 21, 2006 4:23 pm Post subject: Older Kitfox cruise speeds

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->  Just a quick note for those who may be interested. A guy from Rexburg,  Idaho just crashed a P-51 on the interchange closing both north and south lanes  of traffic. All that is left is two short pieces of the wing still  connected to fuselage with the gear down and  staring straight in the air.   No tail section or engine/prop anywhere to be seen. Its strung around  pretty good but the guy walked away from it. The word is they just completed an  engine install. 

  

 Its always nice to see someone walk away from one of these even if is not a  Kitfox.

  

 Dee Young

 Model II

  

  

 Do not archive

  

  



   [quote][b]

akflyer
Guest

Posted: Thu Dec 21, 2006 4:25 pm Post subject: Re: Older Kitfox cruise speeds

Sure you could, but wouldnt it be better to drop the leading edge of the wing back down so you were not looking down when in cruise ???



Then you get into the adding more ponies, stretching it out, cruising faster, costing more, taking alot longer to get off the ground, and get away from the original spirit of the Fox.....



Why not just go buy a 180 and get it over with lol...

dosmythe(at)cox.net
Guest

Posted: Thu Dec 21, 2006 4:49 pm Post subject: Older Kitfox cruise speeds

Sure you could WHAT???  No reference to a previous post.  Where is this 

thread going.  I'm lost



Don Smythe



 	  Quote: 	
		   Sure you could,

dosmythe(at)cox.net
Guest

Posted: Thu Dec 21, 2006 4:52 pm Post subject: Older Kitfox cruise speeds

Hmmm, Older Kitfox cruise speeds and a P-51 crashed.   Sounds interesting.  Where is this thread going?

  

 Don Smythe<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]-->

 [quote]      Just a quick note for those who may be interested. A guy from Rexburg,    Idaho just crashed a P-51 on the interchange closing both  



[b]

akflyer
Guest

Posted: Thu Dec 21, 2006 5:50 pm Post subject: Re: Older Kitfox cruise speeds

Sure you could....... He asked about changing the AOI on the horizontal stab.  I replied that Sure you could, but it would be easier (or better) to lower the AOI on the wing ie. drop the leading edge of the wing....Either way you would have to do some welding right ?????



As all of this is hypothetical, the thread is really going nowhere quick.  



Must have put a bigger engine in the thread huh...



I forgot where I was for a moment.  I forgot that this was a strictly business only site... 



nobeerchugforgettingofftopic

roncarolnikko(at)hotmail.
Guest

Posted: Thu Dec 21, 2006 6:56 pm Post subject: Older Kitfox cruise speeds

Hi Michel I think the undercamber in itself creates drag.  This as well as 

the lift on top from "Bernoulli's principle" or whatever make the wing 

prefer to lift even at 0 AOA.  The Riblett Airfoil has no undercamber, is 

slippery, and glides forever.  Sorry to but in, but I'm stoked on how fast 

the Speedster really is.  Ron NB Ore

ps  Merry Christmas

 	  Quote: 	
		  From: Michel Verheughe <michel(at)online.no>

Reply-To: kitfox-list(at)matronics.com

To: kitfox-list(at)matronics.com

Subject: Re: Older Kitfox cruise speeds

Date: Thu, 21 Dec 2006 22:14:13 +0100

On Dec 20, 2006, at 2:57 PM, Paul Seehafer wrote:

>Sure, the newer Kitfox (Riblett) airfoil helps to make the newer Kitfoxes 

>cruise faster, but even if you were to put a new Riblett wing on an older 

>Kitfox, my guess is you wouldn't see a lot of cruise speed increase, 

>because there is just too much positive wing incidence causing a lot of 

>drag.

Hello Paul,

Since I read your email, yesterday, I have been thinking about this and I 

just can't figure out how it works. From the X-Plane flight simulator, I am 

used to make digital models. I don't know how it is done in real life but I 

guess it is done in relation to a reference line. Let's say, a line going 

from the prop hub to the end of the fuselage. From that, various airfoils 

can be built, each with a different angle of attack. I think angle of 

attack (AoA) is usually used as the angle to that reference line, where 

angle of incidence is the actual angle made by the apparent wind and the 

airfoil.

If we look at the AoA, we see that, as it increases, the coefficient of 

lift and the coefficient of drag increase too. As speed increases and lift 

increases to the square of the speed, one has to push the stick to keep the 

plane at level flight.

Now, if the actual attachment of the wings' root to the fuselage is 

different from one model to another, it means that, for the same speed, one 

plane will fly with a slightly greater nose-down attitude. But how does 

that influences the maximum speed you can achieve for a given engine horse 

power? My understanding is that an airfoil has a constant lift/drag ration 

for a given AoA. Did I miss something?

Cheers,

Michel

_________________________________________________________________

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Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Sat Dec 23, 2006 4:22 am Post subject: Older Kitfox cruise speeds

Hello Leni and Ron,



On Dec 22, 2006, at 3:55 AM, ron schick wrote:

 	  Quote: 	
		   Hi Michel I think the undercamber in itself creates drag.


	


Of course! But maybe I misunderstood what was in that scanned article. 

I understood that if Denney had used a lesser AoA at the fixation of 

the wing's root to the fuselage, the models 1, 2 and 3 would fly 

faster. And that is what I don't understand. But if I misread then ... 

I understand! 



Happy holidays,

Michel

_________________
Kitfox 3 - Jabiru 2200

av8rps(at)tznet.com
Guest

Posted: Sat Dec 23, 2006 5:28 am Post subject: Older Kitfox cruise speeds

Michel,



I'm not sure about your X-plane flight simulator, but if you check out books 

on the subject of aerodynamics and aircraft design it might clear this up 

for you better than I can.  But I do think Leni did a pretty good job of 

explaining it. By getting the wing incidence out of wack it makes the tail 

have to compensate, and adds further drag.



This whole scenario was played out somewhat years ago when Piper created 

their PA-12 Supercruiser.  One of the things they did to make their new Fat 

supercub airframe fly faster was to reduce the amount of positive wing 

incidence.  And it worked.  Although they did lose a bit of the Supercub 

STOL performance.  But not much.  Today with the higher horsepower 

conversions done to both the PA-12 Supercruiser as well as the Supercub, you 

can hardly notice any STOL loss on the SuperCruiser.  Somewhat similar to 

what we've experienced with the Kitfoxes.



Paul Seehafer



---

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Sat Dec 23, 2006 1:19 pm Post subject: Older Kitfox cruise speeds

On Dec 23, 2006, at 3:05 AM, Paul Seehafer wrote:

 	  Quote: 	
		   By getting the wing incidence out of wack it makes the tail have to 

 compensate, and adds further drag.


	


Yes, Paul, I understand that and while I will always take a simulator 

with a grain of salt, mine does a pretty good job at modelling things 

like that. I am always amazed to see how changing one degree in the AoA 

of the horizontal stab, or moving the CoG a couple of inches, changes 

entirely the flight model, stall, etc.



I am not contesting the Kitfox article, nor the Piper engineers, I 

merely try to understand how this works because if I learn something 

today, then it is a good day.



Here is an hypothesis: The day Mr Denney sat and drew the first Kitfox, 

as he made the line that would define the AoA of the wing, a fly came 

to rest on his pencil. In a quantum of time, two different universes 

came to exist: One where he drew the intended line, as it as now; and 

another one where he was distracted by the fly and his ruler slid 

slightly down thus making a line with a lesser AoA.



In both universes, now moving in their own individual existence, it 

resulted in a constructed plane. In the first one, Mr Denney - after 

the first test flight - realises that to keep a proper balance, the 

horizontal stab has to be modified to keep the nose slightly  up. In 

the other universe, he decides - for the same reason - that it has to 

be modified to keep the nose slightly down.



The question then is: Will the Kitfox in one universe - with the same 

engine, etc. - fly slower than the Kitfox in the other universe?



Cheers,

Michel



do not archive

_________________
Kitfox 3 - Jabiru 2200

akflyer
Guest

Posted: Sat Dec 23, 2006 3:12 pm Post subject: Re: Older Kitfox cruise speeds

has someone been hitting the kitfox holiday eggnog a little early????

or are they watching kitfox Xfiles????

eskflyer(at)lvcisp.com
Guest

Posted: Sat Dec 23, 2006 4:26 pm Post subject: Older Kitfox cruise speeds

I can answer this one .

In one universe the air is more dense than the other so both Kitfoxes are 

flying at the same speed .



 Cheers

Merry Christmas everyone

IN the holiday spirit uhhh holliday spirits in me lol

John Perry



DO NOT ARCHIVE

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Wed Dec 27, 2006 5:24 am Post subject: Older Kitfox cruise speeds

 	  Quote: 	
		   From: kurt schrader [smokey_bear_40220(at)yahoo.com]

 When aircraft are designed, they are usually initially

 layed out to be most efficient at a given cruise speed

 and weight.


	


Thank you for this comprehensive explanation of all the challenges an aircraft designer meets, Kurt. It is, indeed, always a compromise. Maybe I misunderstood the article that Paul published for us on the list. I think I understood that if the models 1 to 3 were designed with a lesser wing AoA, the would fly faster but loose STOL capacity. I am sorry, I still don't understand.

Yes, the shape of every object in the airflow will contribute to more or less parasite drag. Yes it could be that the fuselage, being at a more nose-down attitude when the wings have a greater AoA, has a greater drag. But the author of the article doesn't know that, does he?

Likewise, I don't understand how a greater wing AoA increases STOL capacity. I have been told that there isn't such a thing as a stall speed, only a stall AoA. STOL means that you can land slower, right? Will the wing AoA make it stall at a greater AoA? I don't understand. I will make the fuselage more nose-up when stalling on landing. It can make your 3-points landing with a tailwheel touching first. But so can gap-sealing elevators, your CoG, your wheels' diameter, etc.



I am sorry, I don't get it and if I am the only one on the list not to get it so let it be. Maybe I am slow and in a few months I'll wake up in the middle of the night and shout: EUREKA! 



Cheers,

Michel



do not archive

<pre><b><font size  color="#000000" face="courier new,courier">

_________________
Kitfox 3 - Jabiru 2200

mscotter

Joined: 15 Jan 2006
Posts: 49
Location: Winston-Salem, NC

Posted: Wed Dec 27, 2006 6:23 am Post subject: Older Kitfox cruise speeds

Michel, I'll chime in for a moment and share my understanding of this, which

I **believe** to be correct from what I've read.  

I think what was said was that the wing incidence was increased to give

better visibility over the nose.  In other words, the wing incidence was

increased so that at any given time the fuselage would be flying at a lower

angle of incidence, hence allowing the nose to be lower and us to see over

it better.

As for wing Angle of Attack/Incidence and its relation to STOL capability, I

think what is being said is that since the earlier models had the wing

mounted at a greater angle of incidence on the fuselage then those aircraft

would, upon taking off, be at a greater angle of attack sooner (with respect

to the later model kitfox) and thus be developing lift and flying sooner.

Personally, I'd bet that you'd be hard pressed to measure the difference in

two otherwise comparably equipped aircraft, as these airplanes get off the

ground so quick already.  But I digress...

Mark Scott

Elkton, MD  USA

Merry Christmas to all



--

_________________
Mark Scott
Winston-Salem, NC

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Wed Dec 27, 2006 12:18 pm Post subject: Older Kitfox cruise speeds

On Dec 27, 2006, at 3:23 PM, mscotter wrote:

 	  Quote: 	
		   <SNIP> hence allowing the nose to be lower and us to see over

 it better.


	


Aha! Now we are getting closer, Mark! I am sorry, I didn't read 

entirely the article Paul provided, mostly what he underlined in red. I 

have then missed the point in the high AoA.



 	  Quote: 	
		   <SNIP> and thus be developing lift and flying sooner.


	


Good Lord! Then I have to revise my take off technique. I fly from a 

long asphalt runway so STOL is not very actual. But, at occasions, I 

need to take off from short grass runways. Now, I was instructed to 

take off by pushing the stick full forward, if anything, to see sooner 

over the cowling. Once I was with a passenger, on a hot summer day, on 

a short grass field and I pulled the stick back a bit too soon, the 

plane wasn't ready to take off. We did a few hop and I didn't like it 

(nor my passenger, for the matter! 

After that, I tried to improve the technique which is: Full throttle 

and stick full forward. As soon as the plane is level, I wait for Vso 

then pull the flaps and keep the plane a few inches over the ground 

until speed is enough to go ballistic toward the sky, after pushing in 

the flaps.

Is this wrong? Because if the high AoA is to help STOL, then I should 

take off with the tailwheel still on the ground, right? I thought it 

was important, on short fields, to be horizontal as soon as possible, 

to have as little as possible induced drag and pick up speed fast.



Cheers,

Michel



do not archive

_________________
Kitfox 3 - Jabiru 2200

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Wed Dec 27, 2006 5:39 pm Post subject: Older Kitfox cruise speeds

You've been flying a lot longer than I have, Michel, but my takeoff  

technique is different. I was instructed to hold neutral elevator,  

full power, then at about 30mph, forward stick only until tail  

raised, then hold neutral elevator until liftoff, or pull back  

slightly to induce liftoff. Then either forward for ground effects  

(shortfield) and quicker achievement of Vy, or back for Vx, but only  

when Vy speed has been achieved. Of course my cowl is the Skyfox  

cowl, and easier to see over (even for this 5' 6" pilot), so I don't  

have to...or WANT to...push that stick forward too far, let alone  

full forward. My soft field technique is to hold stick full back,  

firewall the throttle, and hold stick back until it lifts off by  

itself, then forward until Vy is achieved, then use stick to hold  

Vy.  As my instructor says, "as soon as you leave the ground, your  

soft field is over."

Lynn

On Dec 27, 2006, at 3:18 PM, Michel Verheughe wrote:

 	  Quote: 	

 On Dec 27, 2006, at 3:23 PM, mscotter wrote:

> <SNIP> hence allowing the nose to be lower and us to see over

> it better.

 Aha! Now we are getting closer, Mark! I am sorry, I didn't read  

 entirely the article Paul provided, mostly what he underlined in  

 red. I have then missed the point in the high AoA.

> <SNIP> and thus be developing lift and flying sooner.

 Good Lord! Then I have to revise my take off technique. I fly from  

 a long asphalt runway so STOL is not very actual. But, at  

 occasions, I need to take off from short grass runways. Now, I was  

 instructed to take off by pushing the stick full forward, if  

 anything, to see sooner over the cowling. Once I was with a  

 passenger, on a hot summer day, on a short grass field and I pulled  

 the stick back a bit too soon, the plane wasn't ready to take off.  

 We did a few hop and I didn't like it (nor my passenger, for the  

 matter! 

 After that, I tried to improve the technique which is: Full  

 throttle and stick full forward. As soon as the plane is level, I  

 wait for Vso then pull the flaps and keep the plane a few inches  

 over the ground until speed is enough to go ballistic toward the  

 sky, after pushing in the flaps.

 Is this wrong? Because if the high AoA is to help STOL, then I  

 should take off with the tailwheel still on the ground, right? I  

 thought it was important, on short fields, to be horizontal as soon  

 as possible, to have as little as possible induced drag and pick up  

 speed fast.

 Cheers,

 Michel

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

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