To put it bluntly: the curved shaft is a flexible rod in a casing which is mounted between the gearbox and the propeller, nothing more.

As such, it is a simple, yet critical component: should it break during operation of the boat, or should it vibrate or cause too much friction inside the casing, it would spoil all the fun… and maybe cause further damage to equipment and/or persons.

Therefore the engineering challenge is to get the power from the cranks to the propeller with as little transmission loss and as little added drag as possible, using raw material that is as reliable as possible.

Rick Willoughby writes that it «must be durable» and that its quality is «…related to torsional stiffness, fatigue life, corrosion resistance, (and) ability to survive collision… .»

After extensive theoretical work and testing, three different raw materials can be recommended for producing the curved shaft:

  • purpose woven carbon fibre
  • spring steel
  • machinable aluminum

We are open to cooperation with firms able to provide curved shafts for our OpenBoats.

For details, please contact us!


Our boat is better than mine.