Tip speed

RPM X Diameter Inches X .00436 = tip speed (Ft/Sec)

The normal maximum for a wood prop is 900 Ft/Sec

2700 X 68 X .00436 = 800 Ft/Sec

Geometric Pitch

RPM X Pitch Inches X .000947 = Speed (MPH)

This approximates the aircraft forward speed.

2700 X 60 X .000947 = 153 mph

Blade Angle

Pitch/Circ. = the arc. tang. = angle (Degrees)

To find the angle needed at any blade station for a desired pitch.

Example: 60 pitch, 68 diameter (214" Circ.)

60/214 = .2804, then arc. tang of .2804 = 15.70 Degrees

Great Plains Index

Link to Sonerai Aircraft