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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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 Posted: Wed Mar 19, 2014 4:56 am Post subject: Drag Reduction Paradox/VGs |
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There are quite a few different models of VGs on the market, as well as VGs
fabricated by the aircraft builder/owner/flyer. How does one decide which
style VG is best for their particular Kolb?
How about placement, angle and distance back from the leading edge of the
wing to get the most out of them?
Is there hard evidence VGs are enhancing performance as much as folks say
they do?
One of the VG manufacturers and marketers shared with me the following, "The
only reason I have them on my Kolb is because I sell them. Wouldn't look
good if I didn't." I know they work because I have flown a Kolb several
times with VGs installed. I know they enhance landing performance, but have
no idea if they increase cruise and top airspeed.
Still satisfied with the performance of my MKIII, low, cruise, and top speed
(top speed really doesn't make any difference to me). If I ever get to the
point I need VGs, I'll be standing in line to buy the best VGs available for
my MKIII.
john h
mkIII
Titus, Alabama
The dramatic difference in all aspects of flight below 40 mph have convinced
me of the VG's worth on the MK -3C. You only have to fly it with & without
to see it.
G. Aman MK3C jabiru 800+hrs
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Wed Mar 19, 2014 6:30 am Post subject: Drag Reduction Paradox/VGs |
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Two of my neighbors partnered up to build two Legal Eagles over the winter. Pat built wings, Tim built fuselages. At first both had VG's. Tim took his off and says he gained 5 mph. Pat is still working engine issues with the half VW but as soon as those are solved it will be a good time to look at nearly identical aircraft with and without VG's. Will report back when I know more.
Rick Girard
do not archive
On Wed, Mar 19, 2014 at 7:53 AM, John Hauck <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)> wrote:
| Quote: | --> Kolb-List message posted by: "John Hauck" <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)>
There are quite a few different models of VGs on the market, as well as VGs
fabricated by the aircraft builder/owner/flyer. How does one decide which
style VG is best for their particular Kolb?
How about placement, angle and distance back from the leading edge of the
wing to get the most out of them?
Is there hard evidence VGs are enhancing performance as much as folks say
they do?
One of the VG manufacturers and marketers shared with me the following, "The
only reason I have them on my Kolb is because I sell them. Wouldn't look
good if I didn't." I know they work because I have flown a Kolb several
times with VGs installed. I know they enhance landing performance, but have
no idea if they increase cruise and top airspeed.
Still satisfied with the performance of my MKIII, low, cruise, and top speed
(top speed really doesn't make any difference to me). If I ever get to the
point I need VGs, I'll be standing in line to buy the best VGs available for
my MKIII.
john h
mkIII
Titus, Alabama
The dramatic difference in all aspects of flight below 40 mph have convinced
me of the VG's worth on the MK -3C. You only have to fly it with & without
to see it.
G. Aman MK3C jabiru 800+hrs
===========
arget="_blank">http://www.matronics.com/Navigator?Kolb-List
===========
http://forums.matronics.com
===========
le, List Admin.
="_blank">http://www.matronics.com/contribution
===========
|
--
Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
[quote][b]
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kolb-List |
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_________________
The smallest miracle right in front of you is enough to make you happy.... |
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Wed Mar 19, 2014 11:11 am Post subject: Drag Reduction Paradox/VGs |
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That would be a good comparison. Are both aircraft 1/2 VW powered?
john h
mkIII
Titus, Alabama
From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of Richard Girard
Sent: Wednesday, March 19, 2014 9:29 AM
To: kolb-list(at)matronics.com
Subject: Re: Re: Drag Reduction Paradox/VGs
Two of my neighbors partnered up to build two Legal Eagles over the winter. Pat built wings, Tim built fuselages. At first both had VG's. Tim took his off and says he gained 5 mph. Pat is still working engine issues with the half VW but as soon as those are solved it will be a good time to look at nearly identical aircraft with and without VG's.
Will report back when I know more.
Rick Girard
do not archive
On Wed, Mar 19, 2014 at 7:53 AM, John Hauck <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)> wrote:
--> Kolb-List message posted by: "John Hauck" <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)>
There are quite a few different models of VGs on the market, as well as VGs
fabricated by the aircraft builder/owner/flyer. How does one decide which
style VG is best for their particular Kolb?
How about placement, angle and distance back from the leading edge of the
wing to get the most out of them?
Is there hard evidence VGs are enhancing performance as much as folks say
they do?
One of the VG manufacturers and marketers shared with me the following, "The
only reason I have them on my Kolb is because I sell them. Wouldn't look
good if I didn't." I know they work because I have flown a Kolb several
times with VGs installed. I know they enhance landing performance, but have
no idea if they increase cruise and top airspeed.
Still satisfied with the performance of my MKIII, low, cruise, and top speed
(top speed really doesn't make any difference to me). If I ever get to the
point I need VGs, I'll be standing in line to buy the best VGs available for
my MKIII.
john h
mkIII
Titus, Alabama
The dramatic difference in all aspects of flight below 40 mph have convinced
me of the VG's worth on the MK -3C. You only have to fly it with & without
to see it.
G. Aman MK3C jabiru 800+hrs
===========
arget="_blank">http://www.matronics.com/Navigator?Kolb-List
===========
http://forums.matronics.com
===========
le, List Admin.
="_blank">http://www.matronics.com/contribution
===========
<![if !supportLineBreakNewLine]><![endif]>
--
Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
01234567890123
[quote][b]
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kolb-List |
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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johngilpin
Joined: 23 Mar 2011
Posts: 93
Location: 004
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| Posted: Thu Mar 20, 2014 2:12 am Post subject: Drag Reduction Paradox/VGs |
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| Quote: | One of the VG manufacturers and marketer
shared with me the following, "The only
reason I have them on my Kolb is because I sell them. Wouldn't look good if I
didn't" |
Well that manufacturer would probably be me. I manufacture the Stolspeed VGs, and have spent some good times yarning with JH.
But I do have to correct some misremembering here. I certainly never would have said, "Wouldn't look good if I didn't...", cause that's not my attitude and I never do anything just for image..... I don't remember my exact words, but as I remember, the wording would have been more like. "Of course I had to put my VGs on my Kolb, cause I make 'em..." But that's because I'm a curious and avid experimenter, and want to test VGs on any aircraft I get my hands on. I also would have said that. " The VGs didn't give any effective landing advantage on the FireFly...", but that has to do with the FireFly design rather than the effect of the VGs. Now I must explain......
The addition of the VGs did lower the stall speed several mph (I don't have the actual figures any longer). This was the stall speed measured at altitude. Of course a lower stall speed also means a higher Angle of Attack, and with the VGs the FireFly was very stable at this higher AofA and lower airspeed. The stall was very benign and gentle, but then it was so before, characteristically due to the low aspect ratio of that short rectangular wing, which tends to give such stall characteristics.
But I found that I wasn't able to use that higher AofA and slower speed for landing, due to the landing gear design on the FireFly. It sits very flat on the ground, nowhere near the AofA at stall speed. When I tried to do full stall landings with VGs at the slowest speed, the tail wheel touched down first while the mains were way off the ground, then the mains came down with an almighty thump....... I'm used to regularly doing full stall landings - hold off, hold off, hold off, with the mains a few inches from the ground, AofA increasing and speed decreasing until it stalls on as slow as possible with no energy left to bounce or swerve. But with the FireFly had to learn to 'fly it on', and at the three-pointer attitude that was considerably faster than a stall landing. It's still a fairly short landing but not near as short and slow as it could be. I can well understand why some Kolb owners have gone to taller main gear legs.....
But point is that the VGs actually couldn't help any at that flat attitude, so they were fairly useless on the FireFly, as regards to slow landings. The VGs did give crisper aileron authority at slow speed, and much more stability in very slow speed turns, but then you shouldn't be doin' them anyhow, eh....
So that's the story as I remember it.....
John Gilpin
[quote][b]
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Thu Mar 20, 2014 4:48 am Post subject: Drag Reduction Paradox/VGs |
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JC G/Kolbers:
I apologize for the misunderstanding. Would like to blame it on old age, but have to admit I got things screwed up. Now that you have told me the story again, I remember what we were talking about, it was the tail wheel hitting first while the mains were well off the ground.
Most Kolbs do that when performing full stall landings. Homer Kolb designed his airplanes, except the Sling Shot, to sit fairly level on the ground. His intention was the prevent low time pilots from pulling the aircraft off the ground too soon, too slow, at too steep an angle, and stalling. Landings must be done fairly level, requiring more speed, and reducing the possibility of stalls. Any time someone got hurt in a Kolb, Homer took it personally. He wanted his airplanes to be as safe as possible. Despite that, we still manage to break his airplanes.
My MKIII doesn't have that problem because it has been modified to sit nose high. Even at the nose high attitude, it is possible to hit the tail wheel first if I get too aggressive in a full stall approach. I don't have that problem much, now days, because I am not nearly as aggressive as I was when I was younger.
Again, I am sorry for the mix up. JC has a much better memory than me. His recollection of our conversation, two or three years ago, is right on.
john h
mkIII
Titus, Alabama
From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of JC Gilpin
Sent: Thursday, March 20, 2014 5:12 AM
To: kolb-list(at)matronics.com
Subject: Re: Drag Reduction Paradox/VGs
| Quote: |
One of the VG manufacturers and marketer
shared with me the following, "The only <![if !supportLineBreakNewLine]><![endif]>
reason I have them on my Kolb is because I sell them. Wouldn't look good if I
didn't" |
Well that manufacturer would probably be me. I manufacture the Stolspeed VGs, and have spent some good times yarning with JH.
But I do have to correct some misremembering here. I certainly never would have said, "Wouldn't look good if I didn't...", cause that's not my attitude and I never do anything just for image..... I don't remember my exact words, but as I remember, the wording would have been more like. "Of course I had to put my VGs on my Kolb, cause I make 'em..." But that's because I'm a curious and avid experimenter, and want to test VGs on any aircraft I get my hands on. I also would have said that. " The VGs didn't give any effective landing advantage on the FireFly...", but that has to do with the FireFly design rather than the effect of the VGs. Now I must explain......
The addition of the VGs did lower the stall speed several mph (I don't have the actual figures any longer). This was the stall speed measured at altitude. Of course a lower stall speed also means a higher Angle of Attack, and with the VGs the FireFly was very stable at this higher AofA and lower airspeed. The stall was very benign and gentle, but then it was so before, characteristically due to the low aspect ratio of that short rectangular wing, which tends to give such stall characteristics.
But I found that I wasn't able to use that higher AofA and slower speed for landing, due to the landing gear design on the FireFly. It sits very flat on the ground, nowhere near the AofA at stall speed. When I tried to do full stall landings with VGs at the slowest speed, the tail wheel touched down first while the mains were way off the ground, then the mains came down with an almighty thump....... I'm used to regularly doing full stall landings - hold off, hold off, hold off, with the mains a few inches from the ground, AofA increasing and speed decreasing until it stalls on as slow as possible with no energy left to bounce or swerve. But with the FireFly had to learn to 'fly it on', and at the three-pointer attitude that was considerably faster than a stall landing. It's still a fairly short landing but not near as short and slow as it could be. I can well understand why some Kolb owners have gone to taller main gear legs.....
But point is that the VGs actually couldn't help any at that flat attitude, so they were fairly useless on the FireFly, as regards to slow landings. The VGs did give crisper aileron authority at slow speed, and much more stability in very slow speed turns, but then you shouldn't be doin' them anyhow, eh....
So that's the story as I remember it.....
John Gilpin
01234567890123
[quote][b]
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kolb-List |
|
_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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