120mm laminar flow fan stator duct with Bezier cone

remixed fan duct by Segelkram to include a 40mm diameter bezier cone in the center (the size of a typical fan center hub) which should reduce turbulence and improve laminar flow.

recommend printing with supports enabled. The cone base needs to 'float' a little bit to facilitate removal from the print bed without breaking the fins.

See also the velocity stack generator for a matching velocity stack for this: https://www.thingiverse.com/thing:6659902