175 mm fan and 180mm Duct for retrofitting window fans.

thingiverse

I had an issue with the performance of my window fan. If you really want efficient transfer of air from inside your house to outside your house you should be using a ducted fan design. Rounded fans in an open environment is good for stirring air in a general direction, but the squared off blades with a duct really made a difference in airflow in my apartment. First check if you need CW or CCW fan blade. You can change this fan by mirroring it on the build plate, turning it around on the shaft is not the same thing. Also this can be tricky to print. The blade can be very thin at the trailing end and you need to make sure there is enough overlap that each layer connects to the one below. Support was necessary. Customized version of https://www.thingiverse.com/thing:2536887 Created with Customizer! https://www.thingiverse.com/apps/customizer/run?thing_id=2536887 I have included a version of the STL where I have hollowed out the hub that allows you to use a zip tie to tighten the fan to the shaft. I would put the zip tie on first, tighten it a bit, then place it on the hub.