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1. 03:12 AM - Re: Drag Reduction Paradox/VGs (JC Gilpin)
2. 05:48 AM - Re: Re: Drag Reduction Paradox/VGs (John Hauck)
Message 1
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Subject: | Re: Drag Reduction Paradox/VGs |
*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
Message 2
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Subject: | Re: Drag Reduction Paradox/VGs |
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@matronics.com
[mailto:owner-kolb-list-server@matronics.com] On Behalf Of JC Gilpin
Sent: Thursday, March 20, 2014 5:12 AM
Subject: Kolb-List: Re: Drag Reduction Paradox/VGs
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
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