This is a simple fan duct i designed for use with two old compuer fans (80mm x 25mm) I had laying around. It is designed for a 89 mm hole in an acrylic/plexiglass window, I cut the hole with a wood hole saw with a lot of water for cooling. I designed it to work with 105mm aluminium (stiff) ducting withoout having to use a hose clamp, I simply slit and bent out small peices of the end the ducting (with regular siccors) and secured in place with the locking ring and 3 screws.

It requires 3 screws (30mm x 3mm shaft x 5mm head), some contact glue to fasten the window adapter to the window, a small electronic switch (I used a 12mm round switch that presses into place), two 80mm x 25mm computer fans, a 12 volt (or other matching your fans) power supply, I just used an old charger, and some wire and basic soldering/crimping. I also sealed mine with some silicone between the acrylic and 3d print but that is not strictly neccisary.

It is printed with standard prusa slicer pla settings and quite low infill (5-10%). it doesnt need a lot of strength so 4 perimiters, top and bottom layers should be fine. The cap however has quite a high infil (20%), 7 top, bottom and perimiter layers and a few solid infil layers to up the insulation. I had some diffuculty with the screws ripping through the locking ring when screwing into place so it may be wise to up the perimiters to strengthen that part.

I used paint on supports to support the inner overhang on both the fan enclosure and the window adapter (see pictures). Attached pictures also show suggested print orientation.

I also attached a dfx file if you want to change the design to suit your needs (maybe another switch or other fans). I appologise for the messy file bur i didnt anticipate i would post it online hehe.