About this 3D model

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.