The Curved Shaft Propulsion System

The Curved-Shaft Propulsion System was invented and prototyped independently by Mark Drela and Rick Willoughby.

>>>Mark Drela and his group prototyped the transmission at the Massachusetts Institute of Technology (MIT), in 1995, after the successful Decavitator Project. Professor Drela then donated the concept to the Open Waterbike Project in 2008, see dedicated page.

>>>The same concept was independently discovered and prototyped by Rick Willoughby. Rick also designed the successful V-Series monohulls and helped to create the user-innovators community. The 24–hour distance record is held by a V-Series stabilised monohull (Greg Kolodziejzyk, 2008) propelled by the Curved Shaft Propulsion System.


The invention is based on the deceptively simple concept of using a curved shaft enabling the transmission gearbox to be located close to the crank assembly and above the waterlevel, and the propeller to be spun perpendicular to the waterflow, while the load flexing the shaft also stabilizes it, avoiding vibrations and whipping phenomena.

A number of successful prototypes of V-Series stabilized monohulls have been built and tested by the user-innovators community.

An identical propulsion system is now fitted to the OpenCat prototypes ready for testing.

The components of the Curved-Shaft Propulsion Systems are:

  • The Gearbox 
  • The Curved Shaft 
  • The Propeller
  • The Crank Assembly


We are seeking collaboration with manufacturing firms and user-innovators. For details, or if you can provide or recommend curved shafts: Please contact us!


Our boat is better than mine.