Extrude-Scale by Function: Propeller

WilliamAAdams suggested, quite rightly, that the various extrusion parameters I've been doodling with could be controlled by functions... and I pointed out that the thing being extruded could be any 2D shape at all.As a semi-practical application of these two ideas, this is a four-blade propeller made by extruding the union of a square and four rectangles while scaling that union according to the cosine of the extrusion height (with some twist thrown in, of course).The layers are 1/4 mm thick. --- Imported from Thingiverse: https://www.thingiverse.com/thing:8688 Original creator: Function: Propeller by syvwlch