REFLECTOR:Vortex Generators on XL
Jim Sower
reflector@tvbf.org
Sat, 06 Dec 2003 10:51:17 -0600
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Alex Balic wrote:
Was said"
> You shouldn't assume that, because the airfoils are different.
The fact that there are nearly twice as many VGs on the main wing would tend to ensure
"balance" (whatever that is).
> What you want
> to avoid is sticking the flow to the top of the canard more than it was
> designed to since the canard is supposed to stall before the main wing.
.... sticking ... more than it was designed to ...
What exactly does "sticking" mean and how much "sticking", precisely, was the canard
designed to tolerate? Is there a report somewhere in the Velocity archives that you
can quote or I can read?
The canard airfoil does have more chamber than the main wing, precisely to make it
stall at a lower AoA than the main wing. I don't believe VGs alter that.
> If the canard becomes more stall resistant (better flow adhesion due to well
> placed VG's), you will have a big problem unless the wing has the same or
> better improvement,
Which is why I used the same placement of VGs on the canard and wing - neither is more
"well placed" than the other.
> since there is some leeway built into the design, you
> hopefully won't have a problem, but really, you should get the situation
> analyzed professionally before venturing out,
That is what I thought I was doing when I consulted with Dr. Price
> otherwise, stick to VG's on
> the mains only......... The VG's will not change the center of lift
> appreciably,
I disagree. It may not move the CL of the wing, but by increasing the lift of the
wing, will move the CL of the airplane aft, having the effect of a forward CG and
defeating the purpose of installing the VGs
> just move the point of flow separation further back, and allow
> the airfoil to fly at a higher angle of attack.
If you move the point of separation further back, doesn't that cause the CP to move
back?
What I would appreciate hearing is less unsupported generalities and vague terms like
"sticking" and "balance" and all and more specific engineering and hard science.
A lot of folks have been alluding (rather vaguely) to "factory approved" placement of
VGs. I would really appreciate someone comparing the way I did mine and how,
precisely it differs from how "the factory" did theirs. We could then have a rational
discussion as to what effect my departures from the "gospel according to Duane" might
have on the flight characteristics of my airplane. I am at quite a disadvantage here
in that I have no specifics at all on how the factory does this, but you folks have
all the details on my approach. I can't make specific comparisons, and until now, for
some reason you folks won't. I feel that further discussion, if it is to be rational
and useful, must involve specifics. Absent details and some engineering principles
applied to them, it's all bullshit and black magic.
I can't learn much from unsupported generalities. That's why I went to Jim Price ....
Jim S.
>
>
> -----Original Message-----
> From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
> Behalf Of John Dibble
> Sent: Friday, December 05, 2003 3:50 PM
> To: reflector@tvbf.org
> Subject: Re: REFLECTOR:Vortex Generators on XL
>
> Jim Sower wrote:
>
> >
> >If one were to install VGs on the wing or canard and not the other, it
> might "mess up"
> >the "lift ratio". I used the same VGs in the same pattern and location on
> both
> >surfaces. No reason to believe that would "mess up" anything.
> >
> My SRG is aft cg when I fly solo. Could I install vgs on the main wing
> only to reduce the aft cg situation?
>
> John
>
> _______________________________________________
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>
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--
Jim Sower
Crossville, TN; Chapter 5
Long-EZ N83RT, Velocity N4095T
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Alex Balic wrote:
<br>Was said"
<blockquote TYPE=CITE>You shouldn't assume that, because the airfoils are
different.</blockquote>
The fact that there are nearly twice as many VGs on the main wing would
tend to ensure "balance" (whatever that is).
<blockquote TYPE=CITE>What you want
<br>to avoid is sticking the flow to the top of the canard more than it
was
<br>designed to since the canard is supposed to stall before the main wing.</blockquote>
.... sticking ... more than it was designed to ...
<br>What exactly does "sticking" mean and how much "sticking", precisely,
was the canard designed to tolerate? Is there a report somewhere
in the Velocity archives that you can quote or I can read?
<br>The canard airfoil does have more chamber than the main wing, precisely
to make it stall at a lower AoA than the main wing. I don't believe
VGs alter that.
<blockquote TYPE=CITE>If the canard becomes more stall resistant (better
flow adhesion due to well
<br>placed VG's), you will have a big problem unless the wing has the same
or
<br>better improvement,</blockquote>
Which is why I used the same placement of VGs on the canard and wing -
neither is more "well placed" than the other.
<blockquote TYPE=CITE>since there is some leeway built into the design,
you
<br>hopefully won't have a problem, but really, you should get the situation
<br>analyzed professionally before venturing out,</blockquote>
That is what I thought I was doing when I consulted with Dr. Price
<blockquote TYPE=CITE>otherwise, stick to VG's on
<br>the mains only......... The VG's will not change the center of
lift
<br>appreciably,</blockquote>
I disagree. It may not move the CL of the wing, but by increasing
the lift of the wing, will move the CL of the airplane aft, having the
effect of a forward CG and defeating the purpose of installing the VGs
<blockquote TYPE=CITE>just move the point of flow separation further back,
and allow
<br>the airfoil to fly at a higher angle of attack.</blockquote>
If you move the point of separation further back, doesn't that <b>cause</b>
the CP to move back?
<br>What I would appreciate hearing is less unsupported generalities and
vague terms like "sticking" and "balance" and all and more specific engineering
and hard science.
<p>A lot of folks have been alluding (rather vaguely) to "factory approved"
placement of VGs. I would really appreciate someone comparing the
way I did mine and how, precisely it differs from how "the factory" did
theirs. We could then have a rational discussion as to what effect
my departures from the "gospel according to Duane" might have on the flight
characteristics of my airplane. I am at quite a disadvantage here
in that I have no specifics at all on how the factory does this, but you
folks have all the details on my approach. I can't make specific
comparisons, and until now, for some reason you folks won't. I feel
that further discussion, if it is to be rational and useful, must involve
specifics. Absent details and some engineering principles applied
to them, it's all bullshit and black magic.
<p>I can't learn much from unsupported generalities. That's why I
went to Jim Price .... Jim S.
<blockquote TYPE=CITE>
<p>-----Original Message-----
<br>From: reflector-admin@tvbf.org [<a href="mailto:reflector-admin@tvbf.org">mailto:reflector-admin@tvbf.org</a>]On
<br>Behalf Of John Dibble
<br>Sent: Friday, December 05, 2003 3:50 PM
<br>To: reflector@tvbf.org
<br>Subject: Re: REFLECTOR:Vortex Generators on XL
<p>Jim Sower wrote:
<p>>
<br>>If one were to install VGs on the wing or canard and not the other,
it
<br>might "mess up"
<br>>the "lift ratio". I used the same VGs in the same pattern and
location on
<br>both
<br>>surfaces. No reason to believe that would "mess up" anything.
<br>>
<br>My SRG is aft cg when I fly solo. Could I install vgs on the
main wing
<br>only to reduce the aft cg situation?
<p>John
<p>_______________________________________________
<br>To change your email address, visit
<br><a href="http://www.tvbf.org/mailman/listinfo/reflector">http://www.tvbf.org/mailman/listinfo/reflector</a>
<p>Visit the gallery! www.tvbf.org/gallery
<br>user:pw = tvbf:jamaicangoose
<br>Check new archives: www.tvbf.org/pipermail
<br>Check old archives: <a href="http://www.tvbf.org/archives/velocity/maillist.html">http://www.tvbf.org/archives/velocity/maillist.html</a>
<p>_______________________________________________
<br>To change your email address, visit <a href="http://www.tvbf.org/mailman/listinfo/reflector">http://www.tvbf.org/mailman/listinfo/reflector</a>
<p>Visit the gallery! www.tvbf.org/gallery
<br>user:pw = tvbf:jamaicangoose
<br>Check new archives: www.tvbf.org/pipermail
<br>Check old archives: <a href="http://www.tvbf.org/archives/velocity/maillist.html">http://www.tvbf.org/archives/velocity/maillist.html</a></blockquote>
<p>--
<br>Jim Sower
<br>Crossville, TN; Chapter 5
<br>Long-EZ N83RT, Velocity N4095T
<br> </html>
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