Parametric Savonius Rotor

typical wind turbine Savonius
some parameters
-The twist,recommended between 0 ° and 90 °
-The number of blades
-The blade type, choose rotor1() or rotor2() in Savonius module ()
Attaches directly to a brushless motor, fan-type PC
for the ratio between the total diameter and the standard medium,
see:http://en.wikipedia.org/wiki/Savonius_wind_turbine (see the french version)
![alt text](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Savonius-rotor_en.svg/1100px-Sa