This is just a prototype. I tested, and printed with some model with it, but the duct's form is not the best. The fan hole is sized to an 5015 blower fan.
Print with brim to better adhension and for nicer holes.
Min. perimeters 2
Bottom solid min. 3
Top solid min. 2
Infill 10%
Slower speed is recommended on small perimeters for better screw holes and make attention to the overhanging perimeters. Use the screws from the extruder's package to attach the duct to the extruder.
UPDATE: added some variations.
Latest variation is: Hurricane buddy - dual 5015 blower.
Position it to in one line with the upper end of the nozzle!
Hurricane buddy is can be fastening with only one screw, so be aware!
The author marked this model as their own original creation.