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  #21  
Old 12-02-2011, 12:57 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,973
Default no one said it!

Quote:
Originally Posted by rv7boy View Post
"Don't try this at home."


P.S. Just as a reminder, the grammar lesson for today is "Plural forms of English words derived from Latin." "Vortex" is singular, and "Vortices" is the plural word. An alternate plural form is "Vortexes," but there is no such word as "Vortice" often pronounced "Vor-ta-see" as a singular form of "Vortex." English is so confusing.
I checked using the search feature. You are correct of course, and it is a common error. But cudos to the RV gang that no one made that error. As Bob said, I would be agast.
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Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 700
also
1/4 share in 1959 C-182B (tow plane)
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Dec 2020
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  #22  
Old 12-02-2011, 01:01 PM
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Ron Lee Ron Lee is offline
 
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Posts: 3,275
Default

Quote:
Originally Posted by scsmith View Post
I checked using the search feature. You are correct of course, and it is a common error. But cudos to the RV gang that no one made that error. As Bob said, I would be agast.
Or perhaps "aghast"
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  #23  
Old 12-02-2011, 01:30 PM
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rvmills rvmills is offline
 
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Location: Georgetown, TX
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Default

Quote:
Originally Posted by Ron Lee View Post
Or perhaps "aghast"
Geez Ron! This is a guy that says things like, "the tangential velocity drops off as 1/r, r being the perpendicular distance from the vortex"

Give him a break, eh!

Bob
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  #24  
Old 12-02-2011, 01:38 PM
N999BT N999BT is offline
 
Join Date: May 2005
Posts: 217
Default The Germans Worked on this too... in WW2

Great post Steve!

When I frist heard about this I remembered that there is a short article on it in Hoerner's "Fluid Dynamic Drag." I scanned it and would be happy to email it to you if you don't have it, as well as anyone else who might want to look it over. He has some curves that show drag reduction as a function of lateral and vertical separation as well as number of planes in the formation. I find it interesting that he didn't think there was any benefit to the lead, and your explanation is right on!

If anyone wants a copy, PM me.
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  #25  
Old 12-02-2011, 04:22 PM
scsmith scsmith is offline
 
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Location: Ashland, OR
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Default Hoerner

Thanks Brent,

Yes, Hoerner is one of my standard desk references.

The journal article by Peter Lissemann is very good, although of course very technical. But if you are interested, some Google work should find it.

Steve.
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Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 700
also
1/4 share in 1959 C-182B (tow plane)
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Dec 2020
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  #26  
Old 12-02-2011, 10:53 PM
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JoeBlank JoeBlank is offline
 
Join Date: Mar 2005
Location: Molalla, Oregon (KOL05)
Posts: 529
Default What he said....

Steve, Nasty, All, Great thread so far and hugely informative. And, yes, Don't try this at home unless you've had training...

A couple of observations that I had while doing these flights...

The postion of "Thuh Sweet Spot" in a 2-3 ship trail position for me was to line up the H/S tip with the NACA duct on the side of the fuselage of the preceding aircraft. At 110 Kts, this put the trailing aircraft just about exactly in the Vortex (just one, right) Very controlable and maintainable. Nasty's description on how to fly that was spot on.

Another observation I made, was when KK (Ken Kreuger RV-4) and I (RV-6) were commuting down to Tracy from the Mother Ship, we had a long time (3+ hrs) to play with this. At RV cruise speeds the effect is not quite as pronounced but it was still there. KK played most of the time while I led. What I found as Lead blew me away. While at cruise power/speeds and KK in trail he was able to affect my heading! At first I thought, 'No Way'... At that altitude the air was glass though and danged if he didn't keep pulling my nose to the left and off course. From then on I could tell when he was effectively playing in "Thuh Sweet Spot" and draggin' me around the sky... Pretty weird...

I again had a chance to try this today while flying the RV-9A on a reposition flight with Gus, who was flying the factory 7A. Even at cruise speeds I was able to easily locate the spot and get in it. The 9A seemed to be a bit more controlable in that spot, possibly due to that wings different airfoil, aspect ratio, etc. I want to say that it felt just more efficient too, but without any data capture capability I can't document it. Just sayin' maybe we should instrument a -9 airframe and try it.

Great science project! Thanks to all for participating and watching. The VAF community Rocks!
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Last edited by JoeBlank : 12-02-2011 at 10:56 PM.
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  #27  
Old 12-05-2011, 06:10 AM
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newt newt is offline
 
Join Date: Jan 2011
Location: Sydney, Australia
Posts: 429
Default They missed something.

Just finished watching it.

I can't believe that they got through the entire myth without drawing attention to the fact that all the aircraft involved had "EXPERIMENTAL" written on them.

Wouldn't that have been perfect for Mythbusters?

- mark
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  #28  
Old 12-05-2011, 08:51 AM
dwilson dwilson is offline
 
Join Date: Jul 2005
Posts: 434
Default smoking vortex?

Would be interesting to see this with smoke coming off of the wingtips. It might be easier to SEE the sweet spot, (but might not be so easy to see the lead!)
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  #29  
Old 12-06-2011, 07:21 PM
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Bruce Bruce is offline
 
Join Date: Feb 2006
Location: Anywhere, USA
Posts: 1,174
Default Big Wakes



This close formation was very difficult.
Aircraft weights would be 750,000--- 385 RV's and 250,000--125 RV's.
The bow wave of the C-5 would push the 135 around
like a rag doll. Thanks for autopilot.

Joe----It would roll left and right from bow wave alone and was
controlled by autopilot.

Very hard on Boom controls in back at 50 feet back it would
fly boom up to stowed position with no help.

Just thought I would share.

Great show and thanks to the guys and
Slick----Get a hair cut.

Boomer--OUT
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  #30  
Old 12-06-2011, 08:34 PM
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tcone1 tcone1 is offline
 
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Location: Fresno, CA
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Default

Boomer,

I cut both of them, what more do you want?

I've tried tanking in a c-5 sim and it's lots tougher than most would think...who'd think a puny little kc-135 could toss three quarts of a million pounds around like that?
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