Critical Design Review

1. Critical Design Review Team 2: Balsa to the Wall and the TFM-2 Ashley Brawner Neelam Datta Xing Huang Jesse Jones Matt Negilski Mike Palumbo Chris Selby Tara Trafton

2. Presentation Overview • Aerodynamics • Propulsion • Structures • D&C • Specifications Summary

3. Aerodynamics Overview • Airfoil Selection • Taper Ratio • Aspect Ratio • Drag Model • Parasite, Induced, Viscous • Max CL & Flaps • Aero Design Summary

4. Airfoil Selection: Main Wing • Wing Section • Design Requirements • Gives approximate 2D Cl needed for dash • Relatively thin for minimizing drag • Thick enough for structural considerations • Other Considerations • Availability of empirical data • Conclusion: NACA 1408

5. Airfoil Selection: Tail • Tail Sections • Horizontal Stabilizer • Symmetric with low Cd over a wider range of α (0 - 5 degrees) • Conclusion : Jones airfoil (8% t/c) • Vertical Stabilizer • Symmetric with low Cd at low α (0 degrees) • Conclusion : NACA 0006

6. Taper Ratio • Ideal lift distribution is elliptical (minimizes induced drag) • λ=0.45 gives closest elliptical lift distribution • Less than 1% higher induced drag than ideal (Raymer) Figure from Raymer textbook

7. AR Trade Study • High CL • Drag-due-to-lift dominates • High AR • Low CL • Parasite drag dominates • Low AR • CL design≈ 0.083 • AR needs to be small

8. Drag Build-up Method • Cfc= Component skin friction coefficient • FFc= Component form factor • Qc= Component interference effects • Swet,c = Component wetted area • Sref = Wing planform Method from Raymer textbook

9. Component Friction Coefficient Figure from Nicolai paper

10. Aircraft Drag Polar • Takes into account having a cambered wing. • Minimum drag occurs at some non-zero CL • Models inviscid and viscous drag-due-to-lift. • K′ is the inviscid drag-due-to-lift factor • Due to trailing edge vortices (induced drag) • K′′ is the viscous drag-due-to-lift factor • Due to transition and increased skin friction Method from Nicolai paper

11. Aircraft Drag Polar (cont.) More involved (next slide) Assumes that the zero lift angle of attack is the same for 2D and 3D Method from Nicolai paper

12. Aircraft Drag Polar (cont.) Method from Nicolai paper

13. Effect of Flaps Figure from Nicolai textbook

14. Aerodynamics Summary

15. Propulsion Overview • Ducted Fan Basics • Propulsion System • Thrust Model • Duct Design

16. Ducted Fan Applications • Wind Tunnels • Hovercraft • Tail Rotor • Similar to: High Bypass Turbofan

17. Ducted Fan Basics • Pros • No Propeller Tip Downwash • Direct Drive • High Static Thrust • No Landing Gear • Hand Launch / Belly Landing • No Landing Gear Drag • Cons • Duct Profile Drag • High RPM • Duct Weight • High Amperage • Dangerous Belly Landing

18. Propulsion System • WeMoTec Midi Fan • Fan Dia: 3.5 in • Max RPM: 35,000 • Weight: 0.25 lbf

19. Propulsion System Cont’d • Electrifly Ammo 36-50-2300 • Kv: 2300 RPM/Volt • Max Cont. Current: 60 Amps • Max Surge* Current: 100 Amps • Max Cont. Power: 1.5 hp • A123 Systems M1 Li-Ion Cells • 5 cells in Series • Capacity: 2300 mAh • Voltage: 18 Volts • Max Cont. Current: 70 Amps • Max Surge* Current: 120 Amps * - Surge is 10 sec

20. Thrust Model Cont’d Stall Speed = 30 ft/s Thrust Required Max Speed 107 ft/s ( 72 mph ) Thrust at Max RPM (35,000 RPM) Thrust at Operating RPM (30,000 RPM)

21. Duct Design • Duct Inlet • 129 % of Fan Swept Area (FSA) • Converging Nozzle • Ensure Sufficient Mass Flow • Ingest Boundary Layer • Duct Exit • 85 % of FSA • Converging Nozzle • Raise Exhaust Velocity • Optimized for High Speed FSA highlighted in blue DFan = Diameter of Fan DHub = Diameter of Hub

22. Duct Design Cont’d • Duct Intake Area • 9.81 in2 • Duct Intake Diameter • 3.53 in • Duct Intake Length • 3.57 in • Duct Exit Area • 6.85 in2 • Duct Exit Diameter • 2.95 in • Duct Exit Length • 3 in

23. Duct Integration

24. Propulsion Summary

25. Structures Overview • V-n Diagram • Analysis of Wing Loads • Wing/Boom Structure • Fuselage and Tail • CATIA Model

26. Preliminary Weight Estimate

27. V-n Diagram Maximum Design Load Factor = 7.5

28. Structural Properties of Wing • Discretized wing into ten sections • Initially, elliptic airfoil approximation • Bending and polar moments of inertia found at each station using XFOIL • Foam core, fiberglass skin construction • Foam neglected in analysis

29. Bending Analysis M = bending moment y = vertical distance from neutral axis I(t) = moment of inertia, a function of skin thickness, t

30. Twisting Analysis T = Torque Cm = Moment coefficient c = Chord length phi = Twist angle/unit length

31. Wing Structure Core: Expanded Polystyrene Foam Skin: 2 oz E-glass Cloth EZ-Lam Epoxy

32. Wing Structure • Shaped balsa blocks integrated into wing foam at boom, fuselage, and motor/duct mount interfaces • Carbon fiber composite arrow shafts for booms • Fiberglass over wing/boom structure

33. Fuselage and Tail • Fuselage • Foam core on CNC due to advanced geometry • 3 oz satin weave fiberglass and epoxy • Horizontal and vertical tails • Hot wire cut foam cores • 2 oz plain weave fiberglass and epoxy

34. Component Integration

35. CATIA Model Contribution • Visualization of design • Wetted areas • Aircraft weight • Accurate CG calculation/placement • Moments and products of inertia • Manufacturing necessity

36. Structures Summary • Dual boom design contributes significantly to structural design of wing • Twist is dominant constraint • Foam core/fiberglass skin construction • Value of CATIA model

37. D&C Overview • Tail Sizing • Control surface sizing • Trim diagram • Yaw rate feedback control system

38. Horizontal Tail • Longitudinal X-plot • Tail area = 90 in2 • Chord = 5 in • Span = 18 in • AR = 3.6 • Static margin 18 %

39. Vertical Tail – Twin Tail Config. • Directional X-plot • Tail area = 30 in2 • Chord = 5 in • Span = 6 in • AR = 1.2 • Weathercock stability = 0.102 rad-1 • Total vertical tail area 60 in2

40. Control Surface Sizing • Elevator • 25% of chord = 1.25 inches • Elevator effectiveness (Cmδe) = -1.28 rad-1 • Rudder – Only one rudder on twin-tail • 50% of chord = 2 inches • Rudder effectiveness (Cnδr) = -0.031 rad-1

41. CLmax α = 7o CL α = 3o α = -1o Cm0.25c Trim Diagram Cm = 0 Xcg forward Cm = 0 Xcg nominal Cm = 0 Xcg aft • Limitations • Tail Stall at α = 7.2º • CL,max = 1.06 • Trim Velocity • 92 ft/sec • From Trim Diagram • δe range -1º-8º

42. Feedback Control System • Dutch roll mode damping ratio required to be at least 0.8 • Without feedback control system damping ratio is 0.212 • Integration of feedback controller with control law gain of -0.45 increases dutch roll mode damping ratio to 0.81

43. Futaba Servo + - -0.45 1 Control Law and Rate Gyro Gains Feedback Control System Yaw Rate Aircraft Transfer Function Yaw rate [r/s] δr [rad]

44. D&C Summary • Horizontal tail area 90 in2 for static margin of 18% • Vertical tail area 60 in2 for weathercock stability • Feedback control system with control law gain of -0.45 needed to meet dutch roll mode damping of 0.8

45. CATIA Model 3-View

46. Summary

47. Questions?

48. Appendix

49. Aerodynamics Appendix

50. Airfoil Selection: Main Wing (cont.)