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carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Sun Oct 04, 2009 4:17 pm Post subject: tuft/stall testing (with video)

http://www.youtube.com/watch?v=afPCxoogLic

Had some fun with wool tufts on my Model 2 wing today.  I've always been impressed with the stall characteristics of if and wanted to see just how the stall progressed out the wing.  



First thing everyone will notice is how the fabric, especially at the root seems loose and does a lot of oil canning.  I had no idea this was happening until I saw this vid and quickly checked the fabric tension after this flight.  It's nice and tight so I wonder if some of it is due to normal wing flexion and some is due to the violence of the slip stream where the prop wash interacts with the wing.  Remember also that this plane was built in 1991 (by me) and at that time, Denney shipped the lightest Stits fabric available (1.7 oz) which I see now is reserved for ultralight use only.  All Kitfox's since use the 'medium' weight 2.4 oz fabric.  At least I think they do.



Anyway, the 1.75" twist I built into the wing seems to be working and the stall is nice and linear as it spreads from root to tip.  



Next step.  Vortex generators!



Chris Carlisle

Model 2, Rotax 582

Sioux Falls, SD

Last edited by carlisle on Sun Oct 11, 2009 10:28 am; edited 2 times in total

Lynn Matteson

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

Posted: Sun Oct 04, 2009 4:47 pm Post subject: tuft/stall testing (with video)

1.75" ? WOW...that seems like a lot. Is this normal for the model II?  

Seems like my model IV was 0.75" on each side.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062, 786.8 hrs

Countdown to 1000 hrs~213 to go

Sensenich 62"x46" Wood prop

Electroair direct-fire ignition system

Rotec TBI-40 injection

Status: flying

On Oct 4, 2009, at 8:18 PM, carlisle wrote:



 	  Quote: 	
		   



 Had some fun with wool tufts on my Model 2 wing today.  I've always  

 been impressed with the stall characteristics of if and wanted to  

 see just how the stall progressed out the wing.



 First thing everyone will notice is how the fabric, especially at  

 the root seems loose and does a lot of oil canning.  I had no idea  

 this was happening until I saw this vid and quickly checked the  

 fabric tension after this flight.  It's nice and tight so I wonder  

 if some of it is due to normal wing flexion and some is due to the  

 violence of the slip stream where the prop wash interacts with the  

 wing.  Remember also that this plane was built in 1991 (by me) and  

 at that time, Denney shipped the lightest Stits fabric available  

 (1.7 oz) which I see now is reserved for ultralight use only.  All  

 Kitfox's since use the 'medium' weight 2.4 oz fabric.  At least I  

 think they do.



 Anyway, the 1.75" twist I built into the wing seems to be working  

 and the stall is nice and linear as it spreads from root to tip.



 Next step.  Vortex generators!



 Chris Carlisle

 Model 2, Rotax 582

 Sioux Falls, SD

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Sun Oct 04, 2009 5:07 pm Post subject: Re: tuft/stall testing (with video)

Checked the manual again.  1.75 inches of twist is correct.



Chris

Fox5flyer
Guest

Posted: Sun Oct 04, 2009 6:00 pm Post subject: tuft/stall testing (with video)

Excellent video, Chris.  The most informative I've seen yet on this forum. 

It makes me wonder if all of our Fox wings are doing the same thing when 

under load.  Of course, in your video there was no wing tank as most of the 

later models have.  Still, it would be interesting to see the same video of 

later models.

Deke Morisse

Mikado Michigan

S5/Subaru/CAP 438+ TT

"If you put the federal government in charge of the Sahara

Desert, in five years there'd be a shortage of sand."

-- Nobel prize-winning economist Milton Friedman (1912-2006)

 	  Quote: 	
		   



 HTTP://www.youtube.com/watch?v=xIODNmGuQ0Y

 Had some fun with wool tufts on my Model 2 wing today.  I've always been 

 impressed with the stall characteristics of if and wanted to see just how 

 the stall progressed out the wing.



 First thing everyone will notice is how the fabric, especially at the root 

 seems loose and does a lot of oil canning.  I had no idea this was 

 happening until I saw this vid and quickly checked the fabric tension 

 after this flight.  It's nice and tight so I wonder if some of it is due 

 to normal wing flexion and some is due to the violence of the slip stream 

 where the prop wash interacts with the wing.  Remember also that this 

 plane was built in 1991 (by me) and at that time, Denney shipped the 

 lightest Stits fabric available (1.7 oz) which I see now is reserved for 

 ultralight use only.  All Kitfox's since use the 'medium' weight 2.4 oz 

 fabric.  At least I think they do.



 Anyway, the 1.75" twist I built into the wing seems to be working and the 

 stall is nice and linear as it spreads from root to tip.



 Next step.  Vortex generators!



 Chris Carlisle

 Model 2, Rotax 582

 Sioux Falls, SD





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 66493#266493

carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Sun Oct 04, 2009 6:10 pm Post subject: Re: tuft/stall testing (with video)

Thanks Deke.  I've got the 13.5 gal fiberglass tank in the opposite wing.  I agree it'd be interesting to see the fabric over there.  The camera is still mounted.  Maybe I'll turn it around and see what that looks like on my next flying day.



Chris

hlang(at)bluewin.ch
Guest

Posted: Mon Oct 05, 2009 2:16 am Post subject: tuft/stall testing (with video)

Thanks a lot Chris. Please do the same with the Vortex Generators. That

will be even more interesting.

Regards:



Heinz

carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Sun Oct 11, 2009 10:25 am Post subject: Re: tuft/stall testing (with video)

http://www.youtube.com/watch?v=gor7LhsAILs



OK, here's the new video with Stolspeed vortex generators added.



Stall now happens around 30 mph instead of 35 and I can't get it to progress out to the tip of the wing, even trying to hold it (at) high pitch for a while with power on.  The last stall does fall off to the right a little and this vid is of the left wing so I wonder if it didn't go ahead and go out to the tip on that side.



Also note; the flexing/flapping/oil canning fabric is no more.  I did take a heat gun to the entire upper surface after seeing the first vid but couldn't really tell that that made much difference, at least to the 'feel' of the fabric tension. I suppose the fabric might have loosened over the years a little. One has to wonder though if the vg's are at least partially responsible for smoothing out the boundary layer and therefore the fabric a little too.



Guess I'll leave them on.



Chris

Fox5flyer
Guest

Posted: Sun Oct 11, 2009 5:26 pm Post subject: tuft/stall testing (with video)

Again, another great video, Chris.  Thanks.  Please tell us more about your 

VGs.  Where you obtained them, how much you paid, etc.  Also, how did you 

determine exactly where to place them on the wing, especially the spacing. 

Any other observations welcome.

Deke Morisse

Mikado Michigan

S5/Subaru/CAP 439+ TT

"If you put the federal government in charge of the Sahara

Desert, in five years there'd be a shortage of sand."

-- Nobel prize-winning economist Milton Friedman (1912-2006)





---

MichaelGibbs(at)cox.net
Guest

Posted: Sun Oct 11, 2009 9:43 pm Post subject: tuft/stall testing (with video)

 	  Quote: 	
		   Again, another great video, Chris.


	


I agree!  Do you have a picture of your camera rig (or did I miss it)?



Mike G.

N728KF, Kitfox IV-1200 Speedster

Phoenix, AZ

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Mon Oct 12, 2009 3:39 am Post subject: Re: tuft/stall testing (with video)

I did some testing of Stol speed's  V G's a few years ago. 

I have used both Stop Speeds and Harrison VGs.  STolspeed are the best  value as the adhesive comes with it  and they have a less sharp trailing edge.  



Mine are placed at 10%  MAC -- I have never moved them around to optimize them.  Mine are on a Model IV that has a different wing than yours. 

I saw about 1 to 2 mph  stall reduction at  the most,  no cruise speed loss.   The biggest  differance I found was  there is no buffet on power off or power on stalls.  You will just mush during power off stalls.   Power on stalls when more aggressive there is no buffet or warning signs until the nose drops and usually a wing will drop as well.  



http://www.cfisher.com/cowl.html

http://www.cfisher.com/vg.html



I got cooling gains by using VGs under the cowl after some cowl mods.



All the being said , I have over 700 hours in last 2 years and have not removed them or changed them yet. 



If you do some searches on this forum you will find my comments likely about his topic. 



 	  carlisle wrote: 	
		  http://www.youtube.com/watch?v=gor7LhsAILs



OK, here's the new video with Stolspeed vortex generators added.



Stall now happens around 30 mph instead of 35 and I can't get it to progress out to the tip of the wing, even trying to hold it (at) high pitch for a while with power on.  The last stall does fall off to the right a little and this vid is of the left wing so I wonder if it didn't go ahead and go out to the tip on that side.



Also note; the flexing/flapping/oil canning fabric is no more.  I did take a heat gun to the entire upper surface after seeing the first vid but couldn't really tell that that made much difference, at least to the 'feel' of the fabric tension. I suppose the fabric might have loosened over the years a little. One has to wonder though if the vg's are at least partially responsible for smoothing out the boundary layer and therefore the fabric a little too.



Guess I'll leave them on.



Chris

_________________
Realtime Kitfox movies to separate the internet chatter from the truth
http://www.youtube.com/user/kitfoxflyer
Hundreds of Kitfox Movies
Most viewed Kitfox on youtube
Most popular on youtube
Highest rated on youtube

carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Mon Oct 12, 2009 6:28 am Post subject: Re: tuft/stall testing (with video)

I used Stolspeed VG's. Kind of a cute little Mom/Pop operation out of Australia where the guy apparently got started using them on his Zenith in place of the big leading edge slat those planes have.  He claims the vg's work better than the slat. The web page is very informative though and IMO has sound aerodynamic theory backing their installation.



http://www.stolspeed.com/



A generic set which includes 130 vg's, templates for installation, and some cool sheets of 3M adhesive that holds them tight but can be overcome with steady pressure so you can move them around is $97 (US).  He doesn't charge for shipping.  



The best evidence for an average plane is that they work about the same if placed within a certain range of the total cord of the wing (including flaperons), the best overall number being around 7% back from the leading edge.  That's where I put mine and I haven't moved them.  Stolspeed is very candid about how the experimentation he did within the recommended range didn't make much difference in overall performance.



The templates that come with are just simple rectangles of cardboard with slots cut out.  The first 15 vg's beginning from the tip are spaced 30mm apart and are at a 30 deg angle to the slipstream.  This is to ensure that the stall occurs at the wing tip last so as to preserve flow over any ailerons one might have (not applicable for us but still a good idea).  Remaining are placed at the same angle but at 60 mm intervals all the way to the root.



I'll try and get a pic of the camera setup.  Mean time, here's one of the wing showing the vg's more clearly than in the vid.

IMG00016.jpg

Description:

Model 2 Kitfox with vortex generators, left wing

Filesize:

580 KB

Viewed:

12339 Time(s)

hlang(at)bluewin.ch
Guest

Posted: Mon Oct 12, 2009 11:51 am Post subject: tuft/stall testing (with video)

Hello Chris

Thanks for the very interesting message and video. Meanwhile I have also

put VGs on the elevator (5 and wings (68)and flown the first time with

them yesterday. I have a Kitfox IV with Rotax 582LC and warp drive 3

blade 70". My observations are: stallspeed 3..5mph lower, but only with

power on. This means, similar as yours. Secondly, the stall seems to be

better controllable, smoother as before. I have the feeling, that the

aircraft is more stable, specially in thight turns. I also will leave

the VGs on, because I think that it is an improvement and helps to land

"uphill" at mountain airfields and glaciers. 



Heinz

carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Mon Oct 12, 2009 2:25 pm Post subject: Re: tuft/stall testing (with video)

Here's the camera setup.  Just a cheap webcam shoved up through a hole drilled in the roof Lexan just where it meets the turtle deck.  Gonna replace the Lexan this winter anyway.  Everything held in place with nylon tie wraps.  Laptop sits on passenger seat where I can fuss with it in flight.  Plan to do some more vids with it facing foward and backwards!



Chris

IMG00017.jpg

Description:

Cam mount

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539.37 KB

Viewed:

12304 Time(s)

FlyboyTR

Joined: 04 Nov 2006
Posts: 215
Location: Mobile, Alabama

Posted: Wed Oct 14, 2009 7:51 am Post subject: Re: tuft/stall testing (with video)

Chris,

Great video's.  Thanks for sharing with us!  I've got to get me some VG's for my 5 (Vixen).  I've got cracks in the paint showing up aft of the fuel tanks.  I wonder if I'm having the same fabric flutter you were having?



If anyone has VG's on a 5 (or higher), please let me know your experience with them.



Thanks again!



FlyboyTR

_________________
Travis Rayner
Mobile, AL
Skystar Vixen, N-789DF
Continental IO-240, Prince P-Tip Prop
ADI-II Autopilot
AnyWhereMap Navigation with weather
www.enotam.net (My Flying Info Website)

Lynn Matteson

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

Posted: Thu Oct 15, 2009 4:14 am Post subject: tuft/stall testing (with video)

What kind of paint did you use, Travis? If it was an automotive  

paint, I've heard that could be the cause of the cracks.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062, 795.1 hrs

Countdown to 1000 hrs~207 to go

Sensenich 62"x46" Wood prop

Electroair direct-fire ignition system

Rotec TBI-40 injection

Status: flying

do not archive



On Oct 14, 2009, at 11:51 AM, FlyboyTR wrote:



 	  Quote: 	
		   



 Chris,

 Great video's.  Thanks for sharing with us!  I'm got to get me some  

 VG's for my 5 (Vixen).  I've got cracks in the paint showing up aft  

 of the fuel tanks.  I wonder if I'm having the same fabric flutter  

 you were having?

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

ruebd(at)skymail.csus.edu
Guest

Posted: Thu Oct 15, 2009 6:40 am Post subject: tuft/stall testing (with video)

Chris:



It looks like you enjoyed a sooner liftoff and possibly a better climb with the generators.  

Did you fly at cruise? Did you fly at any of the speeds in the yellow region?  



Duane N24ZM



--

FlyboyTR

Joined: 04 Nov 2006
Posts: 215
Location: Mobile, Alabama

Posted: Thu Oct 15, 2009 9:05 am Post subject: Re: tuft/stall testing (with video)

Lynn,

I didn't paint the plane (I'm the second owner).  However the logs show that is was a Poly.....something...???  purchased from Aircraft Spruce.



Travis

_________________
Travis Rayner
Mobile, AL
Skystar Vixen, N-789DF
Continental IO-240, Prince P-Tip Prop
ADI-II Autopilot
AnyWhereMap Navigation with weather
www.enotam.net (My Flying Info Website)

Lynn Matteson

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

Posted: Thu Oct 15, 2009 12:00 pm Post subject: tuft/stall testing (with video)

Probably Polytone, one of the Poly Fiber final color products.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062, 796.4 hrs

Countdown to 1000 hrs~207 to go

Sensenich 62"x46" Wood prop

Electroair direct-fire ignition system

Rotec TBI-40 injection

Status: flying

On Oct 15, 2009, at 1:05 PM, FlyboyTR wrote:



 	  Quote: 	
		   



 Lynn,

 I didn't paint the plane (I'm the second owner).  However the logs  

 show that is was a Poly.....something...???  purchased from  

 Aircraft Spruce.



 Travis



 --------

 Travis Rayner

 Mobile, AL

 Skystar Vixen, N-789DF

 Continental IO-240,  Prince P-Tip Prop

 ADI-II Autopilot

 AnyWhereMap Navigation with weather





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 68088#268088

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Thu Oct 15, 2009 5:40 pm Post subject: Re: tuft/stall testing (with video)

Duane...Hard to say about the takeoff and landing rolls and how they were effected by the vg's.  The wind here in South Dakota, especially this time of year is quite variable and I don't get a lot of choice when it comes to flying conditions.  The plane got off the ground in such a short time without the vg's, I'm not sure I could tell!



Cruise speed seems down a couple of mph.  I usually cruise right at 75 which is the beginning of the yellow arc on the Model 2.



An interesting idea that's been tossed out is to try VG's on the UNDERsurface of the wing.  Theory is that because of the convex undercamber of the early Kitfox wings (through model 3) , there are areas of very low relative pressure that might be smoothed out and decrease overall drag (at) cruise speeds and angles of attack.  I think I'll try some tufts there next time and see what happens.



Chris

thesupe(at)hotmail.com
Guest

Posted: Thu Oct 15, 2009 7:05 pm Post subject: tuft/stall testing (with video)

Be sure to put lots of tuffs around where the lift struts connect to the wing.  Got to be some interesting turbulance between them.  I know I see small ripples in the fabric in that area while flying on my Avid B.  And thanks for doing these videos C it sure is interesting to see what is going on with the wings.  Take care C  Jim Chuk

[quote] Subject: Kitfox-List: Re: tuft/stall testing (with video)

 From: carlisle_99(at)yahoo.com

 Date: Thu C 15 Oct 2009 18:40:26 -0700

 To: kitfox-list(at)matronics.com

 --> Kitfox-List message posted by: "carlisle" <carlisle_99(at)yahoo.com>

 Duane...Hard to say about the takeoff and landing rolls and how they were effected by the vg's. The wind here in South Dakota C especially this time of year is quite variable and I don't get a lot of choice when it comes to flying conditions. The plane got off the ground in such a short time without the vg's C I'm not sure I could tell!

 Cruise speed seems down a couple of mph. I usually cruise right at 75 which is the beginning of the yellow arc on the Model 2.

 An interesting idea that's been tossed out is to try VG's on the UNDERsurface of the wing. Theory is that because of the convex undercamber of the early Kitfox wings (through model 3)  C there are areas of very low relative pressure that might be smoothed out and decrease overall drag (at) cruise speeds and angles of attack. I think I'll try some tufts there next time and see what happens.

 Chris

 Read this topic online here:

 http://forums.matronics.com/viewtopic.php?p=268153#268153

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