I do not recommend using this with bare fans, you really need ducts that direct the airflow to the tip of your nozzle. This design as is will blow on the heater block and then the hot air will try to cool our print... not optimal. I will try to modify the design if I get time for it, for now I recommend using http://www.thingiverse.com/thing:780379 instead.
This is a derivative of ianlee74's 40mm Fan Mount for Mini Kossel original design is Joey Doll's 40mm fan mount for the Mini Kossel. I made it double to mount 2 fans at a 120 degree angle.
Update: made a cutoff to allow easy fitting around hot end.