Voith Schneider Propellers
On a Voith-Schneider Propeller the blades project below the ship hull and rotate about a vertical axis, having an oscillatory motion about its own axis superimposed on this uniform motion. The blade's oscillating movement determines the magnitude of thrust through variation of the amplitude, the phase correlation determining the thrust direction
between 0 and 360 degrees. It is mounted inside a protective nozzle on the bottom of the ship to protect it against underwater obstructions and from ships hulls.