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Sinha Deturbulator Progress Reports

Progress Articles
9/17/2003 First successful test of Sinha deturbulator on a glider
10/18/2003 Further drag reductions on Standard Cirrus wing
  Baseline polar for performance testing
2/8/2004 Progress Report: SSA Convention in Atlanta
2/28/2004 First outer-span test
5/27/2004 Wind tunnel goes into operation
8/31/2004 Stereolithography used for wind tunnel wing sections
12/3/2004 First success on upper surface of Standard Cirrus wing
12/12/2004 More success on upper surface of Standard Cirrus wing
2/18/2005 First Sink-Rate Measurement
(revised 3/13/2005)
2/26/2005 Second Sink-Rate Measurement: Some Encouraging Data
3/19/2005 First Parallel Flight - vs. ASW-28
3/19/2005 Measurements with Full Top Surface Deturbulation
9/12/2005 A Performance Endurance Issue
10/29/2005 It’s Deturbulation Time Again
1/9/2006 Paper Presented at AAIA Annual Conference
2/3/2006 Talk Presented at SSA Annual Convention
5/6/2006 Paper Presented at AAIA Flow Control Conference
7/1/2006 Notes on Endurance and the Temperature/Humidity Issue
10/21/2006 Measurements Show 20% Improvement!
(revised 1/3/07)
12/13/2006 Deturbulator Performance Confirmed!
1/2/2007 Calibrated Airspeeds
12/13/2006 Summary of Johnson Flight Test
(revised 2/10/2007)
12/13/2006 Details of Johnson Flight Test
(revised 12/26/2007)
12/01/2007 Johnson Effect Confirmed
(revised 12/26/2007)
06/7/2008 Third Parallel Flight - vs. Diana 1
(revised 8/3/2008)

Publications and Presentations
1/2006 Sailplane Performance Improvement Using a Flexible Composite Surface Deturbulator - Sinha
(PDF, 1174 KB)
6/2006 Drag Reduction of Natural Laminar Flow Airfoils with a Flexible Surface Deturbulator - Sinha
(PDF, 757 KB)
2/2007 Wing Surface Deturbulators - Johnson
(PowerPoint, 2140 KB)
2/2007 Revolutionary Aerodynamics - Sinha
(PDF, 856 KB)
6/2007 Optimizing Wing Lift to Drag Ratio Enhancement with Flexible-Wall Turbulence Control - Sinha
(PDF, 588 KB)
8/2007 Improving Automotive Fuel Efficiency with Deturbulator Tape - Sinha
(PDF, 1368 KB)


Baseline polar for performance testing

Figure 15. Baseline Polar for Performance Testing
on Standard Cirrus #60
Preliminary sink rate measurements have been performed to establish a baseline for measuring performance gains with SinhaFCSD. Sink rates were measured for three test flights. Data scatter from vertical air motion was reduced by dropping a few points that were clearly out of bounds and averaging the three resulting polars. The result is shown in Fig. 15 where the red curve is the average. The black curve is from Standard Cirrus #267 (N5CC) as reported by Dick Johnson.

The difference in these curves is due to the fact that in these tests only the ASI is calibrated, not the Pitot/static system. Since total ASI system calibration is not necessary for performance comparisons on the same glider, and since I do not have a trailing bomb of known quality, it was decided to proceed using ASI instrument calibration only. Total system calibration will be done later when #60 is tested by an independent party.

To verify that the deviation from Johnson's, and Bikle's polars (not shown), is due to the Pitot/static system, correction data reported by Johnson for #267 was applied to the baseline polar for #60. The result is shown in Fig. 15 as a broken purple line. It is expected that correction data measured on #60 will bring the baseline polar more in line with the black curve.

The aircraft configuration for these and future test flights is as follows:

  • All up weight = 728 lbs
  • Wing loading = 6.8 lbs/sq ft
  • All control surface gaps sealed with tape on hinge side, mylar on other side
  • Tail boom inspection ports open
  • Canopy/fuselage gap not sealed
  • Standard wing tips
  • Soft wing tip skids in addition to standard skid pads
  • Tail wheel instead of standard skid
  • Pilot relief tube extending 1/4th inch through gear door
  • Drag rake installed on right wing with connecting tube taped to trailing edge, under wing fillet and down fuselage side

Jim Hendrix
Oxford Aero Equipment




Airspeeds shown in graphs are instrument calibrated. The aircraft airspeed system is not calibrated. Errors in the Standard Cirrus static/Pitot system bias the data towards higher speeds. This makes polars seem better than they really are. However, this is not an issue when the purpose is only to show comparitive data on the same glider.


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