These lists identify people who are known to be participating in this project or doing related work.

Tabulation of Feedback
Glider Airfoils Climbing
Tape + -
Tape + -
Genesis 2
white 0 1
clear 0 0
white 0 1
clear 0 0
white 0 0
clear 0 0
white 1 0
clear 0 0
Salto V1
white 1 0
clear 0 0
white 1 0
clear 0 0
Standard Cirrus
Cirrus 75
white 3 1
clear 0 0
white 9 1
clear 0 3
Name Comments
_Hyvärinen, Jari and Ann

Project Page
Standard Cirrus: FX S 02-196 mod, FX 66-17A II-182
Modeling aeroelastic modes of deturbulator panels, the near and far effects of leading-edge rear-facing steps

(8/31/2011): Jari and daughter, Ann, Hyvärinen have made significant progress this year in their effort to discover, model and document deturbulator flow dynamics. For details, go to The Hyvärinen Project project page.


  • We spent some flights developing a procedure for repeatable measurements.
  • 3 flights completed with a clean wing, in which we checked that we got repeatable results, and a good reference for the continued work.
  • 1 flight with leading edge tape installed (wraped around the nose).
  • 1 flight with deturbulator only installed (no leading edge tape).
  • Today, we will complete a flight with both leading edge tape and deturbulator.
All flights are about 1 hour long with tow up to 2000 m. What our flights show is that the tape is sending dynamic, clearly identifiable signals downstream to the microphone we have installed. The question is if and/or how the boundary layer development is influenced by this ?

If we can trigger the membrane to vibrate at specific frequencies as a function of velocity, then I can start to evaluate the dynamics. If we get this to work, we will also install our wake probe and study how the airfoil performance is influenced by an active membrane. We will have a the GoPro HD camera installed to check that the membrane is not ballooning.

I have after the 2011 regional competition repeated the last task that we flew (181 km speed task) and performed a 19.5 and 38.2 km final glides (I hit a thermal averaging 3.5 m/s so I took a couple of turns in it.) the average climb speed of the day 1.4 m/s. The average speed of the first part of the final glide was 121 kph with L/D 35 after the strong thermal the average speed increased to 146 kph with L/D 22. My average speed on the task was about 72 kph (I had a slow second leg.). Winds were rely weak during the day. SeeYou calculated the there was only a 2 kph tail wind on the final glide.

I have over the years learned that I get L/D of about 26 if the average speed on the final glide is 120 kph, which is a typical mid-Sweden summer average with 1.5 m/s average thermal strength.

So, my impression from my last 3 cross country flights still is that I need to increase speed with about 15-20 kph to have the same glide path that I had with the clean wings (Almost clean, I removed lower surface mid-coord turbulator tapes I had installed for 8-years). I have been flying competitions many years and my cirrus has performed well compared with others, so no big negatives with the turbulator.

Maybe 3 flights is to few and I have not yet flew against the best club class pilots in the country (This will have to wait until next year.).

(7/27/2011): I am attending a regional soaring competition this week. We have completed 3 days so far. The first day ended in an outlanding in tricky weather conditions. Yesterday, I won the day and today I was second. I am flying with the lower side tape on the wings. I have done 2 final glides of 30-40 km length and used my IPAQ as calculator. This is the same system that I have used during the past 10 years. Both final glides have ended in a 300 to 400 m overshoot. So, something has dramatically changed in the glider!!!
A Discus 2 pilot, that I did not see following me, told me that he did not gain on me during fairly long glides at 110-120 kph (60-65 kts). After a few climbs he lost track of me, I left a thermal he entered and I got home before him.

(6/27/2011): We did the first flight with the National Instrument DAQ system on board and the new surface microphone installed on the wing. The initial goal is to do a few flights and learn how to best use the equipment to produce repeatable results. We are also evaluating, what we can catch with the mic located at the reattachment point where the deturbulator panels were tested by Jim Hendrix.

After the initial flights we will install a few meters of 70 um tape, and test if we can catch/measure the amplitude and frequency of pressure fluctuations appearing, due to the backward facing step generated vortexes, at the location of the mic.

What is installed so far:

  • A 4-channel National Instrument Compact DAQ system.
  • A mini PC with LabView Signal Express software that drives DAQ system.
  • iPone 4, used to start, stop, and monitor the data.
  • A Vireless router.

On a second channel differential pressure (total-static pressure) will be monitored. There is still some work to be done on the wake probe that will sweep the wake during flight. This will be completed soon. The probe is not required during the current work in which we focus on trying to catch the dynamics.

We are now studying:

  • Is it possible to catch the vortex frequency due to the backward faceing step.
  • Can we detect the frequency at which the deturbulator vibrates at specific velocities.
  • If this works out, then using LINFLOW it should then be possible to study the type of modes involved.

If/When the above is "clear" we can start to use the wake probe to study the effect on drag due to excitation of different kinds of deturbulator panel modes. "There are many waypoints to be past before we reach the final glide on this task" but we are on the move!!!!

(6/2011): I and Ann have made some flights with the 70 um tape on lower side of the wing and got a good feeling (no facts) about it. My first cross country flight with the tape installed can be seen on OLC Flight Log of 2011-05-14 I had a strong headwind on the return leg but managed to get home. If you click on the info-icon to the right you can download the igc-file etc.

ANKER-ZEMER Engineering AS
Sinha, Sumon Invented the FCSD Panel
Commercializing FCSD Panels
SinhaTech, SinhaDeturbulator
Aholt, Justin
Finaish, Fathi
Modeling a plasma actuator with a rear-facing step.
Predicts same bubble modifications as seen in passive step (see oil-flow visualizations).
Aerospace Engineering, Missouri S&T, Rolla, MO
Flight Testing
Name Comments
Arndt, Steven Leading-edge tape
Concord, NH
Bange, Brian Leading-edge tape
Magnolia, TX
Barker, Kenneth Leading-edge tape
Bester, Andrew Salto h101: FX 66-17A 182, Leading-edge tape
Andrews, Ken Standard Cirrus: FX S 02-196 mod, FX 66-17A II-182,
lower-surface leading-edge tape
(9/20/2011): The Cirrus did great… what an awesome little ship! Johann and I soared together for quite a while including thermaling in the same thermals, etc. In the end, I only came down because a German was on the radio yelling to come down or my ride home would be leaving! I could have stayed up there all day...Johann said the Cirrus was doing better because the Grob was so dirty which may have been a factor but I'm not thinking the only one. I definitely noticed that my sink rate was about .25 to .5 knot less than he was doing. That sustained me better between thermals as they were cycling. The other part that I think helped a lot was that I could thermal at a slower airspeed and tighter than him which really helped that day since the thermals were fairly tight and bubbly probably due to the wind...In the end, I noticed that the Cirrus seemed quite a bit more nimble than I remembered and my sink rate was definitely lower that before. That really showed up in the you know, the spoilers aren't great so I usually start my pattern at 800 and now I'm noticing that even at 800 it doesn't come down as fast as before. I'd attribute that to the cleaner airflow and associated reduction in drag.
Bravo - I think you made a great glider better. I had no idea that you could add tape like that to make such a difference!!!
Barsby, Rob
Lintott, Tony

Project Page
Libelle 201B: Wortmann FX 66-17A 11-182
Lower-surface leading-edge tape
The Gliding Centre, Husbands Bosworth, UK
Braun, Erik Salto V1 (13.6m): Akaflieg Karlsruhe,
(6/2011): Since I installed the leading edge tape I did several cross country flights often together with other gliders. ... Combining the leading edge tape (LET) and winglets ... seems to give a big performance boost to the Salto (13.6m). I flew against our AK-5 (15m ship with HQ-17 airfoil) with gear extended, against a LS-1c and ASW-15 on flights of 200 to 300 km. In climb there was no difference and to my surprise almost none in cruising. Wing loading was slightly higher on the Salto because of the small wing, so it did very well in fast cruising especially compared to the ASW-15.
Douglas, Hugh Schreder RS-15: Wortman FX 67-150/170, leading-edge tape
Toronto, Canada
Firth, John PIK 20E self launcher: Wortmann FX67K170
Fowler, Roger Libelle: Lower-surface leading-edge tape
Fox, Charlie RC Models
Hamey, Stewart Standard Cirrus SN 489: leading-edge tape
Brisbane, Australia
Hendrix, Jim Standard Cirrus: FX S 02-196 mod, FX 66-17A II-182
(9/11/2011): On the 2nd day of a local contest, I cruised 74 nm (137 km) in dead air with sparse thermals, 76% more than other competiters. (Don't ask why!) Two other gliders landed out. I made it home cruising at 110 kts (204 kph) the last 12 nm (22 km). The last 37 nm (69 km) was flown into a 14 kt (26 kph) headwind, during which I tested various airspeeds against my differential altitude (height above/below computed glide slope). As I have experience in past years with full deturbulator configurations, my best performance, cruising into a strong headwind was achieved from 42-45 kts (78-83 kph). A normal polar should have performed best around 60 kts (111 kph)! (8/28/2011): Flew vs. PIK-20D thermalling and cruising better. Flying at 75 kts, I overtook the PIK who was flying 60 kts. Still, I gained altitude over the PIC all along the way, starting about one mile back.

It appears that there is a low speed hump in the modified polar that is good for thermalling and scratching your way home. Other sweet speed ranges appeared to include 60-65, 70-75 and 80-85 kts (111-120, 130-139 and 148-157 kph). These subjective observations need to be confirmed by measurements.

(8/28/2011): Flew vs. PIK-20D thermalling and cruising better. Flying at 75 kts, I overtook the PIK who was flying 60 kts. Still, I gained altitude over the PIC all along the way, starting about one mile back.

(6/2011): I have one set of performance data with lower-surface only deturbulator tape (PDF) that indicates 15% better L/D. I flew four hours on 6/11/2011 and have the impression that best L/D speed is higher than normal. For example, cruising with a 10 kt quartering tailwind, the best L/D was achieved at 60-65 kts and steadily gained on the glide computer's glide slope.
Memphis Soaring Society, USA
Standard Cirrus
Oxford Aero Equipment
Hopkins, Jim PIK-30: Lower-surface leading-edge tape
Hopper, Thomas LS-1c: Wortmann FX 66-S-196 mod
(9/18/2012): On a recent 2.4 hour flight here in New Hampshire I found that if I cruised at around 45 knots in no lift that my sink rate would show a familiar reliable rate, like before I put the tape on. But when I sped up to 50 knots or more that it would show a reliably lesser sink rate. The point that this change occurs seems rather abrupt at this speed change, as I sped up approaching the 50 knot rate, the sink rate would start to respond showing a lessening sink rate, and as I continue to 50 or more knots the sink rate would lessen more enough to even feel a slight change in pitch attitude. I could repeat it again and again. Now there was some thermal lift around and even some ridge lift but I tried heading away from the ridge to eliminate at least that part. This experience makes me want to do a better job and look for this many more times and try to become more observant of the exact indicated speeds and specific changes in sink rates in particular. More later, but do you and others experience anything like this Jim? I find the insects clean off the tape very easily and it is staying in place well with good adhesion.

(9/2014): Just to comment that I am still flying with the .0025" thick tape on the underside of my LS-1c wings. This 4th of July, at Franconia, NH I was comparison flying along with several newer ships but in particular I kept my eye on an ASG 24 that a friend of mine was flying with an L/D of 43, I think. My ship is reported as built at 37/1. Of course the ship is getting old now but it does have a very good two part epoxy finish using PPG's best,applied 7 or 8 years ago. That day was very strong winds, 55 with gusts and broken lift all over. A fleet of us were hanging around at 5K to 6K facing upwind all not making much headway over the land. I was making a point of staying over 55 to 60 knots and I was not loosing altitude or flying slower then the ASG 24 that was 1000 feet off my right side and slightly ahead. I kept inching the stick forward but didn't loose altitude in relation to the ASG 24. So it seems that your concept ... has a very real basis of truth to it. I am not removing the tape, that is for sure.
Post Mills Soaring Club, USA
Hostage, Mike Silent 2 Targa
Hunger, Stefan Libelle H201b
Sutton Banks, UK
Falk Pätzold
Standard Cirrus: FX S 02-196 mod, FX 66-17A II-182
(8/2011): High quality polar measurements with clear leading-edge tapes indicates no change in performance.
Preliminary Results of Flight Performance Determination of Cirrus75 D-6607 S/N 633 at the
IDAFLIEG Sommertreffen 2011 in clean configuration and modified with leading edge tapes...(PDF)
Kotila, Chuck Pegasus 101A
Lovinggood, Ray LS1d: Wortmann FX 66-S-196 mod
Carrboro, North Carolina, USA
Noel, Richard HP 14: Lower-surface leading-edge tape
Québec, Canada
O'Donnell, Luke Standard Cirrus: FX S 02-196 mod, FX 66-17A II-182
Queensland, AUSTRALIA
Hayet, Pascal Lark IS-29D2: Lower-surface leading-edge tape
Québec, Canada
Hopper, Thomas LS-1c: Lower-surface leading-edge tape
Concord, NH
Mugleston, Andrew Lower-surface leading-edge tape
Cullompton, UK
Salvo, Bob

Project Page
Genesis2: Lower-surface leading-edge tape
(9/30/2011): I used the White 12mm tape. When I compared myself to another Genesis, that had no tape, I saw very little difference at cruising speeds. But during the Seniors competition, I found my climb to be less than usual. Removing the tape restored my climb. The Genesis airfoil is very flat on the bottom, and oil flow tests on my ship by Dick Johnson indicated laminar flow back to 90% C on the lower surface. The wing has about 3 degrees of twist, most of which comes near the root end. When circling in thermals, the AoA at the root is near 10 or 11 degrees; the tape may not work properly with such a high AoA. I'm only guessing at this point.

Jim Hendrix: I suspect that with airfoils like the Genesis has,

Shearer, David Std. Jantar: Lower-surface leading-edge tape
Shipp, Tom
Kiley, Aaron

Project Page
Standard Cirrus: FX S 02-196 mod, FX 66-17A II-182
Lower-surface leading-edge tape

(8/29/2011): We have done a before-test then installed white tape at the 45 degree position, I have flown the glider 3 times since installing the white tape and the Cirrus seems to climb better and appears to have better glide performance. An after-test will be run soon to verify any performance improvements.

Villanueva, Antonio Centrair Pegase 101a: Lower-surface leading-edge tape
Club Planeadores Zarate
Buenos Aires, ARGENTINA
Woolley, Adam Cirrus 75B: Lower-surface leading-edge tape

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