I have designed a replacement propeller for my fan, which had broken. It works perfectly and silently, it measures 36cm in diameter and it fits an 8mm shaft. It's fully 3D printable without supports, and it doesn’t require any glue or screws for assembly. It stays together thanks to the pressure from the nut. I printed it in PETG. The bottom part has 3 perimeter walls and 20% honeycomb infill; the top part has 3 perimeter walls and 10% honeycomb infill; and the blades have 2 perimeter walls and 10% rectilinear infill.