Since the rotors are easily fabricated via 3D printing they should be easy to ... or this one that only uses a single propeller. The toroidal propeller, one of the Lab's @RD100Awards winners ...
Naturally, if you’re [Daniel Riley] of RCTestFlight, then you have to 3D print a few of them, and make a video covering a handful. Most famous of these is probably the toroidal propeller that ...