Toroidal propeller 3D print model

A toroidal propeller is a type of propeller that is ring-shaped. Toroid propellers are significantly quieter (especially at audible frequencies, which lie between 20 Hz and 20 kHz), and are claimed to be more efficient than traditional propellers both in air and water. Toroidal propellers are promising for their potential to reduce noise pollution through quieter aviation and maritime transport, but they have always been difficult to manufacture and therefore very expensive.