An old server PC case had openings for dual SCSI ports (full-sized 50-pin connectors) and not enough cooling for modern components. Solution: remove the knock-outs for the SCSI ports and snip the center section between them, then install this fan duct. This duct could also be useful with re-purposed external SCSI drive enclosures.
The 80mm fan .step file uses #4-1/2 sheet metal screws that self-tap into plastic, and the fan is offset slightly (Y - 8mm) to allow better fit. Print this with something heat-resistant, like ABS or ASA. I used 8 walls and no infill with a 0.4mm nozzle.
Created with FreeCAD Link Branch. In the FCStd file, the fan and screw sizes are parametric. The fan sketch is on a separate plane from SCSI outlet, so it can be angled and translated to fit. Feel free to adjust and remix your own!
Released under CC-0 (public domain, no warranty) license.