REFLECTOR:Vortex Generators on XL
KeithHallsten
reflector@tvbf.org
Sat, 6 Dec 2003 14:31:14 -0800
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Scott,
It's good to know how the recommendations were developed. I sounds like =
Jim's installation has at least as much basis in science and testing!
I recall when we were talking to Lon Arnold at the Golden West Fly-In =
that he recommended that the "crowfoot" pattern of VG placement be used =
on the canard, since it has no sweep, and a little slip couldn't =
dramatically change the effect of the VGs if each pair worked either =
way. However, he suggested placing the VG's on each swept main wing all =
parallel to each other in such a way as to "trip" the spanwise flow at =
low airspeeds and high angles of attack, while being nearly parallel to =
the flow at high airspeeds. There is, of course, much less spanwise =
flow down the wing at higher airspeeds. This minimizes drag at cruise =
speeds while maintaining effective VGs at low airspeeds. If you look =
out the window of any Boeing (swept wing), sure enough, you see that all =
the VGs are parallel to each other, with the leading edge of each VG =
just a little outboard of its trailing edge.
I'm not flying yet, but unless contrary wind-tunnel testing results are =
available before I get there, I plan to follow Lon's recommendation! I =
know that he had tried several arrangements on his Long-EZ, and that's =
what he had determined worked best for him.
I am just finishing up the cowl attachment flanges on the wing roots, =
then I'll try hanging the "dummy" IO-540 that Ly-Con lent to me!
Keith Hallsten
----- Original Message -----=20
From: Scott Baker=20
To: reflector@tvbf.org=20
Sent: Saturday, December 06, 2003 12:42 PM
Subject: Re: REFLECTOR:Vortex Generators on XL
Those who are working on testing new VG placements ... keep up the =
good work!
Nothing about the Velocity placement guide is sancrosect. The company =
collaborated with the VG supplier, who recommended a pattern/placement =
guide based on (I think I'm correct on this) 20% MAC. There have been =
no wind tunnel or computer model tests to verify if the VG's are in the =
best/most efficient location - or not. So we are all giving it our best =
guess.
The VG placements on the standard wing resulted in excellent benefits =
- the stall speed was lowered a good 5-knots, with very little (no =
noticable) penalty on the top end. The VG's on the big wing (XL and =
173's) help some - but their effectiveness does not stand out as good as =
on the standard wing. I personally don't care for the performance of =
the VG's on the big wing (based on the present template).
Is there room for improvement? I'm sure of it! Lon Arnold, pilot of =
the Becker Avionic Systems aerobatic Long EZ has done a lot of field =
testing of VG's on canard aircraft - which differ from conventional =
wisdom - and he is obtaining excellent success. Ask him about this when =
you say "Hello" at some future air show.
I am really, really, really hoping that Jack Sheehan will team his =
Velocity XL up with Old Dominion University, who runs the full scale =
wind tunnel at the Langley Research Laboratory in Hampton, Virginia. =
The folks at ODU have introduced the idea to do this for free (that's a =
good price) - and it's just a matter of working out the timing and the =
details. It would be great to do actual wind tunnel testing to =
determine the best VG placements for the XL.
Scott B.
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<DIV><FONT face=3DArial size=3D2>Scott,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>It's good to know how the =
recommendations were=20
developed. I sounds like Jim's installation has at least as much =
basis in=20
science and testing!</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I recall when we were talking to Lon =
Arnold at the=20
Golden West Fly-In that he recommended that the "crowfoot" pattern of VG =
placement be used on the canard, since it has no sweep, and a little =
slip=20
couldn't dramatically change the effect of the VGs if each pair =
worked=20
either way. However, he suggested placing the VG's on each =
swept main=20
wing all parallel to each other in such a way as to "trip" the spanwise =
flow at=20
low airspeeds and high angles of attack, while being nearly parallel to =
the flow=20
at high airspeeds. There is, of course, much less spanwise flow =
down the=20
wing at higher airspeeds. This minimizes drag at cruise speeds =
while=20
maintaining effective VGs at low airspeeds. If you look out the =
window of=20
any Boeing (swept wing), sure enough, you see that all the VGs are =
parallel to=20
each other, with the leading edge of each VG just a little outboard =
of its=20
trailing edge.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I'm not flying yet, but unless contrary =
wind-tunnel=20
testing results are available before I get there, I plan to follow Lon's =
recommendation! I know that he had tried several arrangements on =
his=20
Long-EZ, and that's what he had determined worked best for =
him.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I am just finishing up the cowl =
attachment flanges=20
on the wing roots, then I'll try hanging the "dummy" IO-540 that =
Ly-Con=20
lent to me!</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Keith Hallsten</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Dsbakr@comcast.net href=3D"mailto:sbakr@comcast.net">Scott =
Baker</A>=20
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dreflector@tvbf.org=20
href=3D"mailto:reflector@tvbf.org">reflector@tvbf.org</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Saturday, December 06, =
2003 12:42=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Re: REFLECTOR:Vortex =
Generators=20
on XL</DIV>
<DIV><BR></DIV>
<DIV><FONT face=3DArial size=3D2>Those who are working on testing new =
VG=20
placements ... keep up the good work!</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Nothing about the Velocity placement =
guide is=20
sancrosect. The company collaborated with the VG supplier, who=20
recommended a pattern/placement guide based on (I think I'm correct on =
this)=20
20% MAC. There have been no wind tunnel or computer model tests =
to=20
verify if the VG's are in the best/most efficient location - or =
not. So=20
we are all giving it our best guess.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>The VG placements on the standard =
wing resulted=20
in excellent benefits - the stall speed was lowered a good 5-knots, =
with very=20
little (no noticable) penalty on the top end. The VG's on the =
big wing=20
(XL and 173's) help some - but their effectiveness does not stand out =
as good=20
as on the standard wing. I personally don't care for the =
performance of=20
the VG's on the big wing (based on the present template).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Is there room for improvement? =
I'm sure of=20
it! </FONT><FONT face=3DArial size=3D2>Lon Arnold, pilot of the =
Becker=20
Avionic Systems aerobatic Long EZ has done a lot of field testing of =
VG's on=20
canard aircraft - which differ from conventional wisdom - and he is =
obtaining=20
excellent success. Ask him about this when you say "Hello" at =
some=20
future air show.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I am really, really, really hoping =
that Jack=20
Sheehan will team his Velocity XL up with Old Dominion University, who =
runs=20
the full scale wind tunnel at the Langley Research Laboratory in =
Hampton,=20
Virginia. The folks at ODU have introduced the idea to do this =
for free=20
(that's a good price) - and it's just a matter of working out the =
timing and=20
the details. It would be great to do actual wind tunnel testing =
to=20
determine the best VG placements for the XL.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Scott B.</FONT></DIV>
<DIV><FONT face=3DArial =
size=3D2></FONT> </DIV></BLOCKQUOTE></BODY></HTML>
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