Summary

This OpenSCAD script generates a form for molding a propeller suitable for use on lightweight rubber band powered indoor model airplanes. The form is used to warp flat sheets of balsa into a curved and twisted shape needed to produce efficient propeller blades. The cover photo shows a 7" x 22" prop form and template for a Limited Pennyplane class model.

The usual procedure involves carving a wooden block for forming. This script automates that part of the process by generation such a mold from design parameters.

Details on design and construction of propellers for various endurance classes of rubber band powered model airplanes can be found on several websites, such as //indoornewsandviews.files.wordpress.com/2012/10/inav_121_press.pdf
Note, some competitions require that you use commercially manufactured propellers, so this scripts might not be useful there.

The basic design parameters for a propeller are its diameter and pitch, or theoretical distance traveled in one revolution. The block width is also needed as this indirectly sets the blade's chord.

Additional options include whether the blades are flat plates or curved cross sections. Currently the script does not support other airfoil shapes, but that could be added. Finally, a parameter specifies the number of sections along the length of the blade. I suggest not increasing this too much (at least while adjusting the other parameters) as the script may become unresponsive. Values of about 50 seems like a good number here.

Update 10/13/2022
Uploaded a new version of the script with option for embossing the dimensions on the block and another for minimizing print volume. Also added an STL file for the 14" x 22" example