Propeller design

Propeller design

The main reason for the performance of our electric drivetrains is that we control their design from A to Z. Everything is optimized to achieve exceptional performance while keeping costs down. Designing a boat's electric motor means optimizing the entire propulsion system, so that each "stage" operates as close as possible to its maximum efficiency:

  • The battery
  • The engine
  • Motor controller with power electronics
  • The propeller
  • The propeller fairing

At Kahe Nautic, we also have a patented system that allows us to do without a gearbox: the propeller is directly connected to the electric motor. This means no reduction in performance with a gearbox, no maintenance on our propulsion systems, and excellent reliability.

Today, some details of the Kahe POD 600's propeller design, as well as its fairing:

1) Blade profile 

Our propeller blades have specific profiles, which we design digitally to achieve 2 objectives: 

- Minimize the drag generated by the blade profile at all operating points of the propeller (from low power to maximum power).

- Never cavitate. Cavitation is a phenomenon that occurs when the vacuum generated by the blade is so great that water vaporizes around the blade! The blade then rotates in the midst of water vapor bubbles, and its performance is severely degraded. Our profiles are designed to ensure that the negative pressure is evenly distributed across the entire profile, and never exceeds the critical value that leads to cavitation. 


 2) Blade geometry 

The 3D geometry of the blade is an optimization of many factors: the evolution of the chord of the profiles used, the evolution of the profiles themselves, the twisting and the deflection of the blades. We use numerical optimization methods to achieve the best possible compromise. 

3) Propeller fairing geometry 
The propeller fairing has a dual function: 
- Protecting the propeller and users: safety comes first, and a propeller fairing offers very important protection by making access to the propeller much more difficult.
- And this propeller fairing can be optimized so that the propeller operates more efficiently than without a fairing, and the fairing itself contributes to the propulsion of the whole. This propulsive force generated by the fairing under the influence of the propeller is far from negligible. On the Kahe POD 600, it accounts for around 33% of dynamic thrust (and almost 50% of static thrust)! 


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