Model Airplane Propeller Form

thingiverse

This OpenSCAD script generates a mold for shaping propellers suitable for use on lightweight rubber band powered indoor model airplanes. It transforms flat sheets of balsa into the curved and twisted shape needed to produce efficient propeller blades. The cover photo shows a 7" x 22" prop form and template used in Limited Pennyplane class models. Typically, you carve a wooden block for forming. However, this script automates that process by generating such a mold from design parameters. You can find details on designing and building propellers for various endurance classes of rubber band powered model airplanes on websites like inav_121_press.pdf. Note that some competitions require the use of commercially manufactured propellers, so this script may not be useful there. The basic design parameters for a propeller are its diameter, pitch (theoretical distance traveled in one revolution), and block width. The block width indirectly sets the blade's chord. You can also customize options such as whether the blades are flat plates or curved cross sections. Currently, the script only supports flat plates and curved cross sections, but other airfoil shapes could be added. Finally, a parameter specifies the number of sections along the length of the blade. I recommend not increasing this too much (at least while adjusting the other parameters) as the script may become unresponsive. A value of about 50 seems like a good starting point here.