The current version
of PropDesign is 1.1.
PropDesign program last updated: 03 Feb 2004
(added images of airfoil profiles)
page last updated: 21 Sep 2010 (installed on this server)
PropDesign is a Windows port of Ed Dokus' DOS/BASIC propeller design program. It calculates propeller pitch, diameter, chord, thrust and efficiency when given a propeller type (planform, airfoil, number of blades, etc.) and cruise conditions (airspeed, altitude, etc.). Output is in graphical or tabular form, allowing an experimental aircraft designer to ask "what if?" without having to carve/bolt on/fly each new design.
Use of PropDesign is free. The program has been donated to the public domain by Ed Dokus. The version on this site is the current (latest) version and is about a 1 MB download.
Ed Dokus writes this about PropDesign:
"The prop is treated as a rotating wing. As such the relative air velocity increases linearly with distance from the hub to the tip. The tip velocity is limited to a value that is subsonic, hence the suggested value of 800 fps. From the lift equation, we are required to find a value of blade area for the lift and subsequent thrust required. Since we have established the blade length by virtue of the tip velocity, it now becomes a matter of defining the blade chord."
"The blade length is divided into fifty elements and subsequently integrated by means of Simpson's Rule. There is one less number of equations than the number of unknowns so it reduces the problem to one of trial and error. Therefore an initial value of chord is provided, .5 ft in this case, and the value of lift, drag, thrust, and torque is computed. The resulting value of power is then compared to the input horsepower and if there is a discrepancy exceeding 1 percent, an increased or decreased value of chord is used to calculate a new set of lift, drag, thrust, and torque values."
"Since the air is accelerated by the previous blade, (for want of a better explanation), the angle of attack is changed and this induced angle, theta, must be included in the overall determination of pitch angle. The equation used to determine theta is nonlinear and causes problems at high values. High values are generated at low tip speeds, hence the tip speed is limited to those that avoid the problem."
"I find that progressively reducing the tip speed for any design results in progressively lower values of efficiency. I'm reluctant to omit the inclusion of theta in the calculations, (as others have), as this would eliminate the crashing problem, in order to preserve the accuracy of the overall approach."
Instructions for Installing PropDesign:
Please report any problems in downloading PropDesign or errors on this web page to Joe Dubner at the link below. Problems or questions about propellers or the PropDesign program should be directed to Ed Dokus at the Email address listed in the PropDesign program.
Click here to contact
(Be sure to remove NOSPAM from the "TO" address before sending.)