Exotic Propellers:

Precision machining of propeller blades; Subhuman III Human Powered Record Challenger. 

This HPV sub featured two, twin blade, counter rotating propellers of an extremely sophisticated design. Blades were machined from 6061-T6 billets. The blades fit into a clamped retention system in the hubs. Also of interest, the entire propeller assembly including fins could be pivoted to provide vectored thrust for directional control.