Curved fin stabilisers matching the performance of hydraulic ones, with easier fitting and functionality, could be a game-changer. Hugo Andreae reports
After years of resisting calls to develop an electric version of its popular hydraulic Vector stabilising fins, Sleipner has finally bowed to pressure from boatbuilders and revealed a brand new range of all-electric fins. Over four years in development and featuring a number of new innovations to maximise the efficiency, quietness and safety of both the actuators and the fins, Sleipner is confident that its latest offering will not only match the performance of its existing hydraulically driven fins but also outperform its electrically driven competitors.
Speaking to Motor Boat & Yachting, Sleipner CEO, Ronny Skauen, said that it had taken this long to develop the new system because of his determination to ensure the same high levels of safety and reliability inherent in the company’s hydraulically activated fins.
“Hydraulics are very powerful, very quiet and very reliable and can cope with shock overloads,” said Skauen. “Even if they do fail you can always release the pressure to let the fins return to their neutral position. Electromechanical systems tend to be noisier and there’s a greater risk that the motor or gearbox could seize, leaving them stuck in the up or down position. It took us a long time to find effective solutions to these issues.”
SAFETY FIRST
One of those solutions is a very unusual gearbox design called a Harmonic Drive Strain Wave gear that uses a unique elliptical cog bearing that can withstand extreme loadings while delivering exceptional reliability and very high gearing ratios. It can even slip without destroying its interlocking teeth. Skauen admits it is a costlier and marginally more power hungry solution than traditional planetary gears but points out that there’s a reason the Mars Rover space vehicle and Lockheed F35 fighter jet also use the same type of gearing.
Resolving the noise issue also took some lateral thinking as the problem isn’t just the sound of the motor and gears accelerating and decelerating causing a distinctive (and more noticeable) rise and fall in pitch than the near silence of a hydraulic piston or background thrum of a generator, but also the actuator’s tendency to reverberate through the hull.
Skauen says that the hull moulding can act like a loudspeaker membrane with certain resonant frequencies causing it to vibrate and create noises in areas of the boat some distance from the actuator itself. However, unl
