The model is defined by four variables, that can be changed to generate new variations of the geometry.
Go to Insert->Tools->Equations to open the dialog box showing equations and variables.
Here you see the equations I have set-up in this particular model.
Change any value and observe how the geometry changes when the model rebuilds.
You can create some pretty groovy variations...
...but be aware that some values will destroy the geometry. In that case re-open Equations and change back to the default values.
The default values are 60 degree angle, 200 mm spacing, 3 blades and 750 mm diameter.
This is the default model.