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pj.ladd(at)btinternet.com
Guest

Posted: Wed Jun 24, 2009 3:20 am Post subject: R: VGs

I>>



 If I put on the wings the VGs, the speed cruise increases or decreases?



Charly

you will not notice any difference in the cruise but the stalling speed will 

be lower by  about 5mph



Pat

?

sky-king(at)inbox.com
Guest

Posted: Wed Jun 24, 2009 12:39 pm Post subject: R: VGs

My stall speed lowered by 10 mph.



[quote] --

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Wed Jun 24, 2009 3:51 pm Post subject: R: VGs

Subject: Re: R: VGs

 	  Quote: 	
		   



 My stall speed lowered by 10 mph.


	




Brad S:



That is an impressive improvement.



What was your stall speed prior to, and after installation of

VGs?



At what altitude did you conduct your tests?



What were the differences in stall characteristics prior to and after 

installation of VGs?



How did the VGs affect speed at your normal cruise power setting?



Did you test stall in ground effect, before and after?



What airplane are you flying?



Would you please expand on your experience flying this airplane before and 

after?



If I could get a 10 mph reduction in stall speed in ground effect, I could 

land at 20 mph.



john h

mkIII - Always impressed with the dramatic improvements in aircraft 

performance and handling after installation of VGs.

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

pj.ladd(at)btinternet.com
Guest

Posted: Thu Jun 25, 2009 1:36 am Post subject: R: VGs

Always impressed with the dramatic improvements in aircraft

performance and handling after installation of VGs. >>



John,

you are fighting a rearguard action but by crackey you are doing it very 

well.



Pat

jbhart(at)onlyinternet.ne
Guest

Posted: Thu Jun 25, 2009 3:08 am Post subject: R: VGs

At 06:50 PM 6/24/09 -0500, you wrote:

 	  Quote: 	
		  

If I could get a 10 mph reduction in stall speed in ground effect, I could 

land at 20 mph.


	


John,



The only way to find out is to try them.  Why depend on others to do the 

research for you?  It only takes about $10 for materials and a few minutes 

of your time to make them.



See "Vortex Generators" at:



http://www.jackbhart.com/firefly/fireflyindex.html

sky-king(at)inbox.com
Guest

Posted: Thu Jun 25, 2009 3:38 am Post subject: R: VGs

Hi John, 



To answer some of your questions,I will first throw in a disclaimer.Iam not a 1000 hr or more pilot,just a dumb old country boy who likes to fly. 

My stall speed prior to vg's was 42mph indicated and 32mph after,there is very possible a + or - a few mph because of all the things that we know that can cause errors. 

There is not a lot of difference in stall handling before or after,Iam flying a Kolb mk3 and she has a very gentle stall, and no tendency to drop a wing,there never was any violence as reported by some others. 

In ground effect before vg's in the 42-45mph range the plane would just drop to the runway,after the vg's I can get down into the 32-35mph range and the plane just seems to settle to the runway. 

I hope this helps someone. 



[quote] --

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 25, 2009 4:48 am Post subject: R: VGs

 	  Quote: 	
		   

 >
	


 	  Quote: 	
		   The only way to find out is to try them.


	




Morning Jack:



I have tried  VG's, several times.  I have also done a side by side flight 

comparison between my fat old bird and a much lighter MKIII.  The results of 

those flights did not convince me to install VGs on my airplane.



This last flight West was interesting.  There were times when I could have 

used a lot more lift.  Then there were times when I wished I had spoilers 

installed on my wings.  At the Rock House, in the desert of SE Oregon, we 

watched our Kolbs attempting to fly and flying while tied down.  Then there 

was the difficult time at Grants, NM, where we were trying to deal with a 

density altiutude of 9,300 feet, severe turbulence, cross wind, and dust 

devils, on take off.  I don't know if VGs would have helped me at Grants or 

not.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 25, 2009 5:06 am Post subject: R: VGs

> My stall speed prior to vg's was 42mph indicated and 32mph after,there is 

very possible a + or - a few mph because of all the things that we know that 

can cause errors.



 	  Quote: 	
		   In ground effect before vg's in the 42-45mph range the plane would just 

 drop to the runway,after the vg's I can get down into the 32-35mph range 

 and the plane just seems to settle to the runway.


	




Brad S:



A 10 mph decrease in stall speed is still a very impressive number.



In ground effect I get the same flight characteristics as you on the FSII I 

was flying with VGs.  The break at stall was very gentle.  Other than that, 

I could not find any other improvements in flight over a FSII without VGs.



My experience with Kolb aircraft indicates they fly as well without as they 

do with VGs except for the very gentle break on landing.  As far as extra 

steep climbs, steep turns, and great control right through the mush/stall, 

they all do it without VGs.



I have discovered I can make good landings if I stall the airplane closer to 

the ground.  If I stall it a foot above the ground, it will drop a foot.  If 

I don't want to take the chance of dropping in, I can always fly the Kolb to 

the ground above stall speed.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 25, 2009 5:08 am Post subject: R: VGs

> you are fighting a rearguard action but by crackey you are doing it very

 	  Quote: 	
		   well.



 Pat


	




Patrick:



No fight intended.



Trying to learn.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

robcannon

Joined: 22 Jun 2008
Posts: 39
Location: British Columbia

Posted: Thu Jun 25, 2009 6:25 am Post subject: Re: R: VGs

Kolb Mark II, Hks 700 E, 550 lbs empty, 180 lb pilot, 2000'asl.  Initial flights with no vg's I was surprized and unhappy with my high stall speed of 38 mph power off.  I added vg's as an experiment with low expectations.  You should have seen my face when I landed after the first flight with vg's.  Ten dollars worth of hardware store flashing and a days messing around and my stall dropped minimum 10 mph.  That's right TEN mph !  TEN DOLLARS - TEN MPH.  Stall characteristics did not change that much - clean break around 26, but will mush along in full control right down to 26.  

   The advantages here are obvious. The disadvantages are minuscule.  Top speed does not seem affected, but my testing would not be very accurate as my plane is easily goes over vne, and low speed is my focus, so I didn't do very scientific testing. I thought washing the wing would be a hassle but the soft bristle brush I use doesnt seem to notice the vg's.

   If anyone wants to make there own I'll send you a pattern one and instructions. I tested different adhesives and decided upon indoor/outdoor carpet tape from wallmart.  It's sticky shit that is never coming off and is much cleaner to use than any liquid adhesive ( just happens to come in a roll the same width as the vg's). I put a rivet in the ones in front of the prop just in case but in hindsite I don't think it was necessary.  Try it you'll like it !!   Rob Cannon

robcannon

Joined: 22 Jun 2008
Posts: 39
Location: British Columbia

Posted: Thu Jun 25, 2009 6:45 am Post subject: Re: R: VGs

Oh yeah, forgot the landing part. I can now land at fifteen mph in ground effect.  ............. Just kidding ..... With my 26 mph stall, I cant land this slow as my tail will be too low.  I built tall gear legs and I can get down pretty slow (32 - 35) but any slower and the tail hits first. 

  The advantage is a huge safety margin at slow speeds.  Theoretically I could fly approaches at 39 mph ( with a 1.5 safety factor), but I fly them at 45 - 50.   If I have an engine failure, I can do a 180 at 45-50 and be around quicker and higher.    blah,blah,blah, Rob

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Thu Jun 25, 2009 9:34 am Post subject: R: VGs

At 10:26 AM 6/25/2009, robcannon wrote:

 	  Quote: 	
		  ...my stall dropped minimum 10 mph.... The disadvantages are minuscule...


	


Perhaps... but one thing concerns me.  My UltraStar supposedly stalls at 

25mph (it's 30mph indicated).  It gets risky to fly an airplane when the 

wind is a significant fraction of your stall speed (one half is the usual 

rule of thumb).  As a PPG pilot also, you can imagine I'm quite sensitive 

to this.  As it is, I hesitate to fly on breezy days; I'd hate to lower 

that flyable threshold at all.



-Dana





--

  Question Authority and the authorities will question you!

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Thu Jun 25, 2009 11:32 am Post subject: Re: R: VGs

 	  Dana wrote: 	
		  At 10:26 AM 6/25/2009, robcannon wrote:

 	  Quote: 	
		  ...my stall dropped minimum 10 mph.... The disadvantages are minuscule...



	


Perhaps... but one thing concerns me.  My UltraStar supposedly stalls at 

25mph (it's 30mph indicated).  It gets risky to fly an airplane when the 

wind is a significant fraction of your stall speed (one half is the usual 

rule of thumb).  As a PPG pilot also, you can imagine I'm quite sensitive 

to this.  As it is, I hesitate to fly on breezy days; I'd hate to lower 

that flyable threshold at all.



-Dana



Dana,



Your understanding of this is wrong.   What you do not want is a gust causing a loss of airspeed and stall in the airplane.   VG's expand your flying envalope and increase your safety margain aginst gust induced stall.  Lets take a Firestar, say it stalls at 30 MPH.  If you approach at 40 MPH, a 10 MPH gust could place you at the stall speed.   With the same firestar with VG's, if you stall at 22 MPH with VG's, a 10 MPH gust would not cause a stall, it would take an 18 MPH gust to put you at stall speed.  This equals increased safety.



You have taken something that is generally true, and misapplied it.  The danger is when an airplane stalls very slow, and is ALSO have a very low approach speed.   The VG's do not mean that you have to fly your approaches slow if you are in windy weather.   VG's actually INCREASE safety and your protection against gust induced stalls.



Mike





--

  Question Authority and the authorities will question you!

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

Kolb MK-III Xtra, 912-S

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Thu Jun 25, 2009 11:34 am Post subject: Re: R: VGs

 	  Dana wrote: 	
		  At 10:26 AM 6/25/2009, robcannon wrote:

 	  Quote: 	
		  ...my stall dropped minimum 10 mph.... The disadvantages are minuscule...



	


Perhaps... but one thing concerns me.  My UltraStar supposedly stalls at 

25mph (it's 30mph indicated).  It gets risky to fly an airplane when the 

wind is a significant fraction of your stall speed (one half is the usual 

rule of thumb).  As a PPG pilot also, you can imagine I'm quite sensitive 

to this.  As it is, I hesitate to fly on breezy days; I'd hate to lower 

that flyable threshold at all.



-Dana



Dana,



Your understanding of this is wrong.  You are misapplying a generality that applies to slow flying airplanes where the approach speed is very close to what its stall speed is.  What you do not want is a gust causing a loss of airspeed and stall in the airplane.   VG's expand your flying envelope and increase your safety margin against gust induced stall.  Lets take a Firestar, say it stalls at 30 MPH.  If you approach at 40 MPH, a 10 MPH gust could place you at the stall speed.   With the same Firestar with VG's, if you stall at 22 MPH with VG's, a 10 MPH gust would not cause a stall, it would take an 18 MPH gust to put you at stall speed.  This equals increased safety.



You have taken something that is generally true, and misapplied it.  The danger is when an airplane stalls very slow, and is ALSO have a very low approach speed.   The VG's do not mean that you have to fly your approaches slow if you are in windy weather.   VG's actually INCREASE safety and your protection against gust induced stalls.



Mike



--

  Question Authority and the authorities will question you!

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

Kolb MK-III Xtra, 912-S

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Thu Jun 25, 2009 11:35 am Post subject: Re: R: VGs

 	  Dana wrote: 	
		  



Perhaps... but one thing concerns me.  My UltraStar supposedly stalls at 

25mph (it's 30mph indicated).  It gets risky to fly an airplane when the 

wind is a significant fraction of your stall speed (one half is the usual 

rule of thumb).  As a PPG pilot also, you can imagine I'm quite sensitive 

to this.  As it is, I hesitate to fly on breezy days; I'd hate to lower 

that flyable threshold at all.



-Dana

	




Dana,



Your understanding of this is wrong.  You are misapplying a generality that applies to slow flying airplanes where the approach speed is very close to what its stall speed is.  What you do not want is a gust causing a loss of airspeed and stall in the airplane.   VG's expand your flying envelope and increase your safety margin against gust induced stall.  Lets take a Firestar, say it stalls at 30 MPH.  If you approach at 40 MPH, a 10 MPH gust could place you at the stall speed.   With the same Firestar with VG's, if you stall at 22 MPH with VG's, a 10 MPH gust would not cause a stall, it would take an 18 MPH gust to put you at stall speed.  This equals increased safety.



You have taken something that is generally true, and misapplied it.  The danger is when an airplane stalls very slow, and is ALSO have a very low approach speed.   The VG's do not mean that you have to fly your approaches slow if you are in windy weather.   VG's actually INCREASE safety and your protection against gust induced stalls.



Mike

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

Kolb MK-III Xtra, 912-S

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 25, 2009 12:26 pm Post subject: R: VGs

 	  Quote: 	
		   


	


 > You have taken something that is generally true, and misapplied it.  The 

danger is when an airplane stalls very slow, and is ALSO have a very low 

approach speed.   The VG's do not mean that you have to fly your approaches 

slow if you are in windy weather.   VG's actually INCREASE safety and your 

protection against gust induced stalls.

 	  Quote: 	
		  

 Mike


	




Mike B:



So...I increase my approach speed 10 to 15 mph and I am good to go without 

VGs.



I'm not concerned over the small amount of difference in speed between "with 

and without VGs" when I stall at 30 mph IAS in ground effect.  Even if I 

stalled at 40 mph in ground effect, I still would not be concerned about my 

approach speeds of 50 to 60 mph IAS.



I'm very conservative when it comes to stall and approach speeds.  I usually 

shoot my approaches at 50 to 60 mph IAS, even on my short 750 ft strip.



VGs aren't going to do a whole lot to improve safety.  We are talking of 

very slow speeds with and without.  Most average pilots should be able to 

adjust a couple mph.



What makes landing with zero ground roll so important?



john h

MKIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Thu Jun 25, 2009 1:14 pm Post subject: Re: R: VGs

John H,



My ground roll is most assuredly longer than yours is, even with VG's..   I need bigger brakes !!!



Mike

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

Kolb MK-III Xtra, 912-S

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jun 25, 2009 1:41 pm Post subject: R: VGs

> My ground roll is most assuredly longer than yours is, even with VG's.. 

I need bigger brakes !!!

 	  Quote: 	
		  

 Mike


	




Mike B:



Get some good MATCO's with 3/4" axles and tapered roller bearings.  I have 

had mine since I wiped off the main gear 9 years ago next week.



In fact, they are so good they slow the mkIII down before touch down. 

hehehe



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

jbhart(at)onlyinternet.ne
Guest

Posted: Thu Jun 25, 2009 1:52 pm Post subject: R: VGs

At 03:24 PM 6/25/09 -0500, you wrote:

 	  Quote: 	
		  



What makes landing with zero ground roll so important?




	


John,



Zero ground roll is a splat, but it what is important is a low energy 

landing.  Where this is useful is when you are landing on an unfamiliar 

landing area.  The slower you can fly the plane at touch down the less 

likely you are going to bend something or tear out a leg socket.  Why risk 

the plane?  This does not rule out the use of a high energy approach to 

landing.  Also, this is why it is important to learn to three point.  VG's 

will knock the energy down by 5 to 10 mph.  In this case it can make the 

difference of flying or trucking it home.  I have done both and flying is 

much more fun.



Fly safe.



Jack B. Hart FF004

Winchester, IN

zeprep251(at)aol.com
Guest

Posted: Thu Jun 25, 2009 2:05 pm Post subject: R: VGs

Think I'll put 3 sets on ,then I can hover.

                G.Aman mk-3c

 

   

 

   

 

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