Note: I wound up making a 3rd version that I'm using now. (http://www.thingiverse.com/thing:228536) (See also http://www.thingiverse.com/thing:216229 -- Version 2; it's mount can be used with this cowl.) Designed for a 60x60x10mm fan (what I had on hand). Mounts to the X carriage using the existing side screw. The "top" and "side" parts slide together with a tight friction fit, and allows for some forward/backward adjustment. The cowling directs the airflow at the extruder nozzle. Ironically, you'll probably need a print cooling fan to print this print-cooling fan cowling; the slope gets pretty shallow near the tip... I wound up "manually" using a heat gun (heat off) to print my first one.