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- Category: Archive 2014
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- Georges Matherat
- Sympo Special
- 2013 World Cup Links
- Face Book Vortexes
- 2014 USA Junior Team Standings
- King Orange Results
Georges Matherat
I use to fly with him in the 50s he was a great friend .My condolence to is wife "Minouche"
Pierre Brun
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Available only while supplies last
World Cup Links
A FB Picture of Jim Parker's new F1A wing with triangular “post” turbulators drew the following comments
Hernan Alarcon Herrera Turbulator ??
John Lorbiecki A little bit of sandpaper would get rid of those bumps...wonder what that would do on a power model?
Hernan Alarcon Herrera Jim, Tony uses a circules an you use triangles, same aerodynamic effects ?.?
Jim Parker I can't say-- I was not scientific-- only date is one flying session on a model with no previous history. This photo certainly has started a good discussion and we'll see if others experiment with turbulator "dots", triangle, squares and spacing. I chose triangular because of an old article I had seen on a stepped triangular LE turbulator (sorry no other info-- perhaps Lee Hines will know and a France WC story about Roy S. (F1C Champion) turning a poor performing folder model into the WC winning fly-off flight with "Danish?" triangular cut tape turbulator (again- that's all I know). As Javier Abad said-I approached it from a "blackmagic" direction. It was great getting the input from the science / aero smart guys. PS, Ken Bauer gets credit for doing the most experiment with "dot" turbulators-- see other FB posts.
Tony Mathews I'd like to see some dried out alphagetti pieces added to the leading edge spelling out a story. Or maybe a prayer to the thermal gods? "Please oh Hung, let me max this flight"...
Discuss...
Javier Abad Triangles made from medical foam tape?
Lee Hines Leeper reporting in. Hoffsass' Espada WC Wakefields is most famous user of stepped tri-cut turb LE. Also Doring's Espada WC Wakes. Have seen balsa A2s use same stepped tri-cut turb setup. Tri-cut stickons likely work to creat that vortex street thing (?name?) mentioned in Ken's comments in SEN & elsewhere.
Jim Parker Javier-- yes cut from medical tape. OK- going scientific-- I did not have the 2009 ref but then saw Brian E's ref the 2004 NFFs Sympo-- surely I reviewed it back in 2004-- but its a F1K-- not a macho F1A-- but perhaps the knowledge was swirling in my head. I then went to the absolute place of truth-- You Tube: http://www.youtube.com/watch?v=Gq-sUhP3kDI This shows Karman Vortex simulation coming off a rectangular "dot" at RE 1000. So the Karman Vortexs are not limited to cylindrical shapes-- likely the math / simulation is easier with the cylindrical shape. Also a cylindrical Dot" at RE 20,000. http://www.youtube.com/watch?v=QouhxL-qfo0 Have to stop this YouTube Science and go to the work shop and "re-turbulate" a long model to the Triangle ones to see what happens on a "known" model.
Tony Mathews The video shows why the wide spacing was not supposed to work. I think ideally you should figure out the width of the vortex "street" at the Reynolds number and pin diameter used and create a spacing that will allow the streets to mix. Full turbulation in between the pins should result. The wide spacing is black magic.
Jim Parker KarmanVortexArt-- as much black magic and art as science. To the previous TubeTube simulation of the rectangular object- noting questionable application to F1A RE etc, it is interesting to note the vortexes do not spread out (span wise) as the cylindrical objects do. The other ref YouTube shows the vortexes spreading span wise as Rudolf Hobinger sketch in the 2004 Symbo-- 15 to 20 degrees. So what are my triangle objects (turbulators) doing??????
Brian Eggleston On an airfoil with laminar flow a wedge of turbulent flow will form behind a spot that is above a critical size. The local included angle of the wedge depends the pressure gradient - if the flow is speeding up maybe about 6 deg, if it is slowing down maybe >12 deg.
Brian Eggleston I seem to recall Ken Bauer (years back) telling me he had flown in misty morning conditions and afterwards could see the transition wedges behind the pins due to greater scouring action in the turbulent region. I'd expect you would want the edges of the wedges(!) to overlap somewhere forward of 50% chord and that suggests less than 1cm spacing for 12 deg wedge. If the pin turbulator wake is more vigorous in spreading laterally then spacing could increase.
Ken Bauer Thanks Brian for remembering that pattern left in the moisture on my wings! Must have been 2008 or 09 when I did these first experiments using a hand launch glider built with a 9% BE F1A airfoil. Wish I would have taken a picture as it was amazing to see the triangle shaped marks on the wing following each pin. After seeing that the pins still give good effect even with the wide spacing I'm wondering if just having sections of the wing turbulated is enough to delay the separation bubbles over the whole wing?
Brian Eggleston Worth doing in the damp again, Ken. Then we will know if the wedge angle is much broader for the pin turbulators. I'll certainly do some flow viz next time in the wind tunnel.
USA 2014 Junior Team Standings
2013 King Orange FAI Free Flight Events Report
Jim Bradley, FAI Events Director
Unlike last year this year King Orange had very flyable weather all three day. The first day was overcast and had on and off light rain showers. Most weren’t even hard enough to get out of. We only had one hard shower but it only lasted about 15 minutes. The winds were generally 7 to 10 MPH with gust to 15 MPH when the one hard shower came through for the mini events held on the first day. This year we had no entries in F1G which is usually a popular with a lot of guys flying there older locked up Coupes.
F1J was interesting as the eventual winner, Gil Morris, switched the lead back and forth with Jean Pailet. Neither was having a great which is very unusual for both of these veteran fliers. The winner wasn’t decided until the last round.
The second day for F1A, B, C, P, and Q had the best weather of all three days with winds mostly 5 to 7 MPH all day and no rain. It was decided that the maxes would be reduced to 2 minutes because from where were flying from 3 minutes maxes would have taken the models into the dreaded Pepper trees in a strong thermal. F1Q was the exception as Dale Elder and Duncan McBride decided to start flying in round 5 when the winds were the lightest and they flew 3 minute maxes. Dale was flying his E-36 and I believe Duncan was flying an AMA Electric A model.
Rnd. 1 Rnd.2 Rnd. 3 Rnd. 4 Rnd. 5 Total
F1G, No Fliers
F1H, 2 Fliers
1. Jean Pailet 092 083 120 028 111 439
2. Tom Bell 062 044 120 000 000 226
F1J, 2 fliers
1. Gil Morris 119 071 110 068 120 488
2. Jean Pailet 110 077 120 067 073 447
Rnd. 1 Rnd.2 Rnd. 3 Rnd. 4 Rnd. 5 Rnd. 6 Rnd. 7 Total
F1A, 2 fliers
1. Bob Hanford 111 038 062 000 000 000 000 211
2. Tom Bell 120 000 000 000 000 000 000 120
F1B, 1 Flier
1. Jim Bradley 120 120 120 120 120 120 120 840
F1C, 2 Fliers
1. Tom Bell 098 012 120 118 103 120 000 679
2. Gil Morris 120 000 000 000 000 000 000 120
F1P, No Fliers
F1Q, 2 Fliers
1. Duncan McBride 000 000 000 000 131 155 156 447
2. Dale Elder 000 000 000 000 120 130 124 374
............
Roger Morrell