The Caterpillar and OMT-patented TwinFin propulsion system has been retrofitted on ‘Polarcus Naila’, which is a 90 m seismic survey vessel operated by Polarcus. The TwinFin propulsion system replaces two azimuth thrusters and, in addition to lower noise and higher reliability, the system has proven to provide 30% less fuel consumption at same bollard pull.  

The replacement of the two azimuth units with the TwinFin propulsion system was carried out by Damen Shipyard in Amsterdam. The retrofit upgrade was designed by OMT, Caterpillar Marine and Scandinavian Marine Group and included two ducted propellers with an inner diameter of around 4,500 mm.

The TwinFin propulsion system is an innovative fuel-saving propulsion system designed and patented by Caterpillar Marine, Odense Maritime Technology and Scandinavian Marine Group.

Many of today’s modern offshore vessels have azimuth thrusters as their preferred propulsion system. Azimuth thrusters feature marine propellers, which can be rotated to any horizontal angle. This eliminates the need for a rudder and provides greater manoeuvrability compared with a fixed propeller and rudder system. However, the azimuth thrusters can make a vessel more vulnerable, especially in tough Arctic seas and weather conditions where a breakdown to the angle gears or other mechanical parts usually means a time-consuming and costly period in dry dock for repairs. Conventional diesel-electric or diesel mechanical propulsion with a long shaft and machinery positioned inside the hull is often seen as a more reliable alternative, but the gears and electric motor occupy valuable space.

The TwinFin propulsion system is a compact propulsion system, which has proven to offer significantly higher fuel efficiency compared to azimuth thrusters and with a compact design based on proven, robust components and tested technologies.

The TwinFin propulsion system comprises a compact electric motor and gearbox configuration connected via a short drive shaft, rotating two controllable pitch propellers with performance-enhancing tailor-made fins attached to the hull. Major transmission parts are accessible from inside the vessel, which makes maintenance easier and removes the need for repairs in dry dock.

The TwinFin propulsion system can be applied to various vessel types and is offered via the global Caterpillar dealer network for both newbuilding and retrofit applications.

Based on successful full-scale experience from ‘Polarcus Naila’, the TwinFin propulsion system provides around 30% lower fuel consumption at same bollard pull, which is as result of the large propellers running at low shaft speed. The twin-fin system can be specified with tunnel thrusters, attached either to the fins or the central skeg running between them, to provide dynamic positioning capabilities.

Based on the experience with the propulsion system, the TwinFin concept is ideal for various ship types typically operated by azimuth thrusters, hereunder vessels operating in shallow water where propeller trust and propeller protection is of high importance. In addition, the TwinFin concept is ideal for vessels operating in arctic conditions, where safety and reliability are critical.