NACA Duct for RC airplanes, well anything really.....

thingiverse

Still building an Ansley Peace Drone. Decided to add some NACA ducts on the sides to keep its innards cool and comfortable. :) Pretty close to a standard NACA duct. Copied the drawing from here as closely as possible: http://www.formula1-dictionary.net/naca_duct.html. The scoop is an optional feature, but it gives the drone a sleek finished look. My scoops are simply attached flush with the foam, allowing the front of the scoop to protrude slightly for better airflow at the expense of more drag. Print the ducts standing up with their widest ends facing downwards and supports will be minimal. Oriented the STL file accordingly. "THE BEER-WARE LICENSE" (Revision 42): https://www.thingiverse.com/kwg08/ created this drone design. As long as you retain this notice, you can do whatever you want with this stuff for non-profit uses only. If we meet some day and think this drone is worth it, you can buy me a beer in return.