1. Propeller Design Workshop
Presented by
David J. Gall
Gall Aerospace

2. Propeller Design Workshop
Theory and design of practical propellers, Part 3. Practical Prop Design
Propeller Design Workshop
Practical Propeller Design

3. Introduction H. Dietsius, N.A.C.A. TN-127 (1923)
“The Air Propeller, Its Strength and Correct Shape,” (Translated)
F. Weick, N.A.C.A. TN-238 (1926)
“A Simple Method for Determining the Strength of Propellers,” fourth in a series: TN-235 thru TN-238
ANC-9 (1956)
Available Where???
Practical Propeller Design

4. Introduction These are the ONLY References I’ve Found
None of them account for the in-plane forces caused by modern high-compression internal combustion engines
Practical Propeller Design

5. Introduction
Practical Propeller Design

6. Practical Propeller Design
Outline: Theory and design of practical propellers, Part 3.
Reality check: Those darn physical constraints
Reynolds' number and Mach number
What about those tips?
From minimum induced loss to maximum efficiency: The effect of viscosity on all those theories
Fuselage/nacelle blockage (a.k.a. "Source-sink slowdown")
Optimum Propellers
Airfoil choices
How to make a proper hub
Proper design of pusher props
Ground and in-flight adjustable pitch and constant speed props
Structural requirements
By Request
Practical Propeller Design
Practical Propeller Design

7. 1. Physical Constraints Diameter Number of Blades Hub Thickness
Thickness of the Blank
Machine Capacity
Practical Propeller Design

8. 2. Reynolds and Mach Numbers
Subsonic Propellers
Use Rules-of-Thumb or
Calculate Your Critical Mach Number then
Adjust Diameter to Keep Tip Speeds Below MCR
Transonic Propellers
See NASA for Un-Ducted Fans, etc.
Supersonic Propellers
Yes, NASA went there, too
Practical Propeller Design

9. 2. Reynolds and Mach Numbers
Practical Propeller Design

10. 2. Reynolds and Mach Numbers
Practical Propeller Design

11. 2. Reynolds and Mach Numbers
Practical Propeller Design

12. 3. What About Those Tips? What do you have after you cut off the tip?
Winglets
Hoerner Tips
Curving Up
Curving Down
Elliptical Tips
Round Tips
“Sheared” Wingtip
Practical Propeller Design

13. 4. Viscosity
Theodorsen (and all prior) adds the viscous effects after the fact
That’s OK, especially with round blade shanks
The coefficient of drag is constant at any RPM
The effect of viscosity is minimal so long as the coefficient of drag isn’t too high…
(Ohh, those round blade shanks are soooo bad!)
However, they are in the place of least harm
Practical Propeller Design

14. 5. Fuselage/Nacelle Blockage
Larrabee et. al “De-Pitch” after the fact to accommodate the reduced inflow velocity
This loses part of the relative wind that’s used in the algorithm
So, it deviates from the Goldstein distribution
Practical Propeller Design

15. 6. Optimum Propellers
Practical Propeller Design

16. 7. Airfoil Choices The Traditional Airfoil Choices Clark ‘Y’ RAF 6
NACA “One” series
NACA “Six” series
Eppler
Others?
Practical Propeller Design

17. 7. Airfoil Choices Can You Manufacture It?
Design to What Coefficient of Lift?
No Sharp Leading Edges
Watch Out for Thin Trailing Edges
Try to Stay Within a Family
Ease of Thickness Scaling
Ease of Performance Prediction (Modeling)
Ease of Manufacture
Practical Propeller Design

18. 7. Airfoil Choices
Practical Propeller Design

19. 7. Airfoil Choices
Practical Propeller Design

20. 7. Airfoil Choices
Practical Propeller Design

21. 7. Airfoil Choices
Practical Propeller Design

22. 7. Airfoil Choices
Practical Propeller Design

23. 8. How to Make a Prop(er) Hub
Must Carry ALL Loads
Must Mate Mechanically to Engine
Prop Flange and/or Extension
Must Deliver Engine Power to Propeller
See Sport Aviation archives
Practical Propeller Design

24. 8. How to Make a Prop(er) Hub
Practical Propeller Design

25. 8. How to Make a Prop(er) Hub
Practical Propeller Design

26. 8. How to Make a Prop(er) Hub
Practical Propeller Design

27. 8. How to Make a Prop(er) Hub
Practical Propeller Design

28. 8. How to Make a Prop(er) Hub
Sensenich Website: “Wood Propellers: Installation, Operation, & Maintenance”
“Drive Lugs” DO NOT Drive the Prop
Static Friction Drives the Prop
Static Friction Must be Greater Than the Torque Forces Developed in Power Pulses
PLUS A LARGE MARGIN for Prop Strikes from Lost Exhaust Pipes, etc. (Silver Bullet ppt…)
Practical Propeller Design

29. 9. Design of Pusher Propellers
Hub Goes on “Backwards”
Center Bore on Front Face
Drive Lug Bores on Front Face
Aerodynamics Much More Difficult
NO, I don’t want to do a partially-ducted channel-wing contra-rotating asymmetrical pusher propeller with winglets
(I might consider it if it were symmetrical) 
Practical Propeller Design

30. 10. Adjustable Pitch/Const. Speed
Discussion
Practical Propeller Design

31. 11. Structural Requirements
ANC-9
Practical Propeller Design

32. 11. Structural Requirements
Practical Propeller Design

33. 11. Structural Requirements
Practical Propeller Design

34. 11. Structural Requirements
Practical Propeller Design

35. 11. Structural Requirements
Practical Propeller Design

36. 11. Structural Requirements
Practical Propeller Design

37. 12. By Request Airfoils Sweep Twist Noise Resonance Materials
Contra-Rotating (Dual Rotation)
Shrouded
Ducted
Practical Propeller Design

38. Propeller Design Workshop
David J. Gall
Gall Aerospace