Best make your
entire fan 1 script_object (an entity can have more than 1 brush). To do so, first select the blades, then selection -> ungroup brush. Then, select the center section and press N, see if it still is a script_object. If it is, follow the instructions below
very accurately:
- unselect everything (esc)
- select the center section
- select the blades
- selection -> add to entity
done
The above steps need to be followed exactly, i.e. if you misselect something you cannot unselect it again (you can but then it won't work

), so you gotta start from the beginning (unselect stuff) when something goes terribly wrong.
To check if all went right, select the center section and press ctrl + e. The blades now should automatically be selected, too
