… thanks Chris_G
and here is the base-construction of the prop (with a narrow tree).
Next step is the "sweeping" of the blades by placement.
The projection of the blades profile is only "planar" - better would be the radial projection to the profile zylinder.
But this is only a visual concept, missing any calculation and profile input - for Mixed_curve demo.
https://forum.freecadweb.org/viewtopic. ... 20#p352531
Is there a way to make this blade to a real solid?