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Old Dec 14, 2014, 12:33 PM
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Aerogance's Avatar
United States, CA, Ventura County
Joined Sep 2008
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Joe Wurts' theories of DS from years ago

I found an old issue of RC Sport Flyer from 2008 that reprinted an much older article by Joe Wurts on Dynamic Soaring. In the article, Joe postulates that in a 60 mph wind a properly built DS plane can achieve 448 mph. This is not too far off from reality!

He goes into some calculations and comes to the conclusion that wing loading "drops out of the equations". Fascinating, because in practice this is normally true! In other words, a light plane can be faster in lower wind because it will turn tighter than a heavy and spend less time losing speed. Of course in super high wind you need more weight and a stronger (aka heavier) structure to fly but that is the exception and not the rule.

Joe then drops the bomb that, like any glider, L/D is king for a DS ship. The current trend with the Kinetic is to maximize L/D through clever airfoil design and very high aspect ratio wings. The results are proven, as the K2M often flies at 12x wind speed and the K130 also pulls up to 12x windspeed. Previously, 10x was the holy grail for dedicated DS ships.

My favorite statement in the article by Joe is "All you have to do is build an airplane that is capable of the air loads imposed on it and have the reflexes to keep up with the responses of the airplane". So true, and planes like the Dynamic and Kinetic certainly keep up with the stresses. Pilots like Spencer and Bruce have the reflexes. It only took 15 years to get there!

The article was written in the very early days of DS and Joe even mentions that flying above 200mph could be catastrophic for the planes of the era. But he makes a very interesting assumption that "you could potentially fly an RC sailplane at about 0.60 Mach!". Not only was this statement absolutely true, but it turns out to be understated by 20%!

I believe the future of high speed DS will depend on flying a 12x + ship in lighter wind (50mph or less) in warm air (warm = lower mach). This will require a low wingloading and high L/D design. Maybe a 200 inch Kinetic will do the trick!
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Last edited by Aerogance; Dec 14, 2014 at 04:36 PM.
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Old Dec 16, 2014, 12:46 PM
Mark Robbins
United States, SD, Watertown
Joined Nov 2007
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id like to read this if you have a link?
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Old Dec 16, 2014, 02:15 PM
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1000MPH's Avatar
USA, NV, Reno
Joined May 2003
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This is great!

http://www.charlesriverrc.org/articl...micsoaring.htm
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Old Dec 16, 2014, 03:00 PM
Get your build on!
Aerogance's Avatar
United States, CA, Ventura County
Joined Sep 2008
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Quote:
Originally Posted by Mark Robbins View Post
id like to read this if you have a link?
I cannot find a link or way to view back issues. Here is a thread about this particular issue of the magazine:

http://www.rcgroups.com/forums/showthread.php?t=902181
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Old Dec 16, 2014, 09:56 PM
Brett
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So Cal
Joined Apr 2002
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There's a video interview with Joe where he states pretty much the same thing. I think it might be on one of Paul Naton's "Endless Lift" videos, or perhaps on one of the "Lift Ticket" series. I just remember he's sitting in a lawn chair at Parker.
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Old Dec 17, 2014, 12:52 AM
Registered User
Carlsbad, CA
Joined Sep 2004
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Quote:
Originally Posted by bjaffee View Post
There's a video interview with Joe where he states pretty much the same thing. I think it might be on one of Paul Naton's "Endless Lift" videos, or perhaps on one of the "Lift Ticket" series. I just remember he's sitting in a lawn chair at Parker.
lift ticket, great interview and great early DS videos with the progression of speeds.
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Old Dec 17, 2014, 02:49 AM
Marseille: the DS city
France, PACA, Marseille
Joined Aug 2011
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Quote:
Originally Posted by rockbus View Post
lift ticket, great interview and great early DS videos with the progression of speeds.
Yes Absolutely a must have.
Available from Reese Productions http://www.reeseproductions.com/
Lift Ticket Director's cut Slope and Dynaming Soaring
Joe Wurts interview at Parker Mountain. the 45 last minutes are all about chasing the DS speed record.

You can also order Lift Ticket to Norway.
R/C road trip with some DS on the most beautiful slopes ever flown.(Lofoten)

Watch it again and again...
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Old Dec 17, 2014, 02:52 AM
Brett
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So Cal
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Ah yes, you guys are correct, Lift Ticket!
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Old Today, 12:44 AM
launch low, fly high
New Zealand, Hawke's Bay, Havelock North
Joined Dec 2004
1,885 Posts
Just ran across this thread. I remember when I had hair...

The basic physics for DS is still unchanged. My early conjectures (from nearly 20 years ago) assumed FAI limits on the airframe (5 kg, 75 g/dm2, etc.). I had thought that with these limits the pilot ended up being the limiting factor, although I may have underestimated the Tebo factor in pilot reactions! (big smiley) As DS speeds have increased, the manufacturing technology and pilot skill has definitely matured. As Aerogance (cool RCG handle!) notes, the optimal day will be a rather warm day in order to decrease the mach number for a given airspeed. For record purposes, the wind speed is very much a HUGE factor though. More than a little bit cool to see where people have gone in regards to speeds, although my DS love is not speed but acro stuff.

I had my first DS experience for a while last week. Gawd I miss Parker!!!
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Old Today, 12:10 PM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
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So cool Joe, where did you get your DS fix last week?
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Old Today, 12:26 PM
gas tires and oil
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malad, idaho
Joined Dec 2004
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this one of the best DS acro vidoes out there. the sound is the best! Ian really had a nice set up this day. you can even hear our conversations in the background. even if you've watched this before, it's worth watching again!!! awesome Ian!
The Weldon Dynamic Soaring experience (10 min 0 sec)


marty
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Old Today, 04:00 PM
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Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
29,109 Posts
My original inspiration for DS acro, was of course videos of Joe W, tearing it up
at Parker with a JW or Crossfire.
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Old Today, 04:49 PM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
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I got to see Joe do some DS Acro in person with his Crossfire. So cool!
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