ASW-22DB (Eta Biter) Evolution

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Presentation by Dick Butler about the extensive modifications that he made to his ASW-22 in the early 2000s. This was presented at the 2003 Soaring Society of America (SSA) convention in Atlanta, Georgia.

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ASW-22DB (Eta Biter) Evolution

  1. 1. ASW22DB (ETA BITER) Evolution Feb98 to Jun03
  2. 2. Project Phases• Phase I- Build ASW22BL with 30% Less Horizontal Tail Area• Phase II- Modify HQ17 Airfoil Inboard Wing• Phase III- New Vertical Stabilizer and Retractable tail wheel• Phase IV- New Outboard Airfoil Profile, Span Increase to 28m, Internal Air Flow Improvement
  3. 3. Anticipated Performance Gains From Project Phases• 9% Performance Gain at Best L/D• 11% Performance Gain at High Speeds, (160km/hr)• Improved Climb Performance From Reduced Span Loading• Equal flying qualities with 28m Span by Maintaining Vertical Tail Volume Coeff. (V/S.b)
  4. 4. Phase I- Build ASW22BL With Smaller Horizontal Stabilizer• 2.6% Less profile drag relative to wing• Good stability/elevator authority on tow & low speed flight (Minimum pilot wt. 88kg)
  5. 5. Phase II- Modify HQ 17 Airfoil• Prof. Loek Boermans Designs Modification to HQ17 Airfoil Lower Surface for 7.5% Less Skin Friction Drag at High Speeds (6.0 percent relative to wing).
  6. 6. Momentum Rake Installation
  7. 7. Flight Test Verify Theoretical Calculations Parasite Drag ASW22DB 0.9 0.8 flap -8.6deg, HQ17M,zz tape TE 80% , no blowing 0.7 Flap -8.6deg, HQ17, blow holes at 73% 0.6 0.5 Cl 0.4 0.3 0.2 0.1 0 0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 Cd
  8. 8. Blowing Articulation• Blow Holes at 72%• Blowing Set as a Function of Flap Position• NACA Ducts Opened & Closed by Servos Mounted Over Plenum
  9. 9. Delft HQ17M Airfoil DesignWas Implemented and Flight Tested
  10. 10. Phase III- New Vertical Stabilizer & Retract Tail Wheel• Reasons For Building -Drag reduction with modern profile -Maintain 22BL tail volume coefficient(V/S.b) with 28m span (add 30cm tail boom, 10cm span) -Center hinged rudder -Drag reduction with retract tail wheel• Benefits - 25% Less profile drag - 2.2% Less drag relative to wing - Better handling from new profile and center hinged rudder
  11. 11. Vertical Stabilizer Construction
  12. 12. Tail Boom Construction
  13. 13. Stabilizer Alignment
  14. 14. Vertical Stabilizer Construction
  15. 15. Perspective
  16. 16. Phase IV- New Airfoil on Outboard Wing, Span to 28m• Reasons for Changes - Improve lift distribution to near elliptical - Less profile drag with Delft DU99-138 - Improve low speed, 1.8m more span - Strengthen wing for 850kg max weight• L. Boermans & M. Hulst designed new airfoil and winglet for outer wing panel• 2% Less profile drag at high speeds & 4% at low speeds relative to wing.
  17. 17. Skin Removal & Contouring
  18. 18. Skin Replacement & Aileron Construction
  19. 19. New Airfoil & Wing Contouring
  20. 20. Wing Tip Construction
  21. 21. Removable Tipand Perspective
  22. 22. Internal Airflow Improvement
  23. 23. Ship met All ExpectationsWinning 03 Open ClassNationals
  24. 24. Remaining Work• Build Lighter Weight Ailerons• Build and Test Delft Winglets per Boermans & Hulst Design• Obtain Performance Polar for Completed ASW22DB
  25. 25. ASW22BL, wt 1279, New VS, Retract Tailwheel, Exhaust in Turtle Deck,New Delft Airfoil to Sta 8.25, NACA Duct Driven by Servo, No Winglets, W/S 7.13lb/sq ft 700 flap -8.6deg, no blowing" 600 flap -6.5deg, blowing Measured factory polar for ASW22B corrected to BL 500rate of sink, ft/sec flap -4.4deg, blowing 400 Flap 0deg, blowing 300 flap- 2.2deg, blowing 200 100 0 0 20 40 60 80 100 120 140 airspeed, kts
  26. 26. Comparisons ASW22BL Nimbus 4 ASW22DB ETASpan 26.4m 26.4m 28.0m 30.9mWing Area 16.7m^2 17.8m^2 17.0m^2 18.6m^2Aspect Ratio 41.8 39.2 46.1 51.3MTOW 750kg 750kg 750 (850)kg 850kgWing Loading 45.0kg/m^2 42.1kg/m^2 44.1kg/m^2 44.8kg/m^2Span Loading 28.4kg/m 28.4kg/m 26.7kg/m 27.5kg/mV/sb .05 .04 .05 ?
  27. 27. Design Team

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