Inspired by https://www.thingiverse.com/thing:3340414 I decided to design my own Fan duct.
It fits for an original E3D V6 Hotend but was designed to also fit for the original Hotend which is longer (not tested). The bottom shold be leveled approx. 1mm above the nozzle to avoid collision while parts are warping or curling.
It was designed to fit a Sunon 5015 (MF50151VX-A99) blower.
Added a V2-Version:
-Increasing air velocity by reducing number of holes to get a more focused air jet.
-optimized the center position to make all jets meet just below the nozzle in reality.