Repellers convert thrust of a fluid stream into rotation and thus allow for energy harvest, while propellers convert rotation into thrust. The difference: Repeller blades are mounted with reversed pitch to the shaft.

Wanted to print my own repeller designs for testing some stuff, but I didn't find anything usable in this forum - especially no code.

Building upon some of my previous libraries it took just a couple of lines in OpenSCAD to get good results comprising proper airfoil data with camber and twist.

Finally I packed everything into a new OpenSCAD library for conservation and later reuse.

The code is more or less straight forward and has just a few lines. I decided to expose only the most important parameters and used consequent defaulting giving you fast results. Of course one can always introduce more design parameters to serve further needs and purposes. I leave that up to you.

What you get:

• Consistent defaulting, easy to understand code
• A full blown and easy to use library with many parameters for tuning and creating your own propeller and repeller designs
• A bunch of examples showing the library’s range
• Help text with module signatures in the command window

What you need

• OpenScad 2015 – one of the sublibraries uses it
• My NACA4 library. It contains all the airfoil stuff and is easy to use.
• My ShortCuts library. Sorry for that, but it makes programming in 3D space so fast and easy.

If you want to do more specialized propeller and repeller designs you should throw an eye at my sweep library. It allows you to program your own smooth transitions between different airfoils along your own path.