Customizable Vertical Axis Wind Turbine

This is customizable and stackable [Vertical Axis Wind Turbine](https://youtu.be/07_d94n-MTM).

The provided files are just an example, you can customize most of its aspects and experiment with it.

[Customize the design](https://www.openjscad.xyz/?uri=https://www.thingiverse.com/download:11452147)

__Udate (2020/02/05)__:

* Fixed issue when the arm radius is bigger that the bearing height.

__Udate (2020/02/12)__:

* Replaced blades' airfoil with [NACA 23012](https://en.wikipedia.org/wiki/NACA_airfoil#Five-digit_series).
* Made the insert circular.
* Fixed issue with parameter names.