Twisted fin offers power and fuel savings for fast ships

Power savings of around 3 per cent are said to be possible on fast ships such as container ships that are fitted with the Becker Twisted Fin, a variation of Becker Marine Systems’ established Mewis Duct.

It said in a statement that it has been developed because its original model loses its effectiveness above speeds of around 20 knots and this new version is suited to ships such as fast container ships that have a bulbous stern.

Its Mewis Duct, which has been fitted on more than 150 vessels over the past three years, can save up to 6 per cent of power, the company said, but is best suited to ships such as tankers and bulk carriers. It reported that it has received “heavy demand for a similar device for faster vessels” and has used feedback from experience with that original version to support two years of research developing this counterpart, which it is marketing for ships of 18 knots and above.

Like the Mewis Duct, the Twisted Fin has no movable parts and is installed in front of the propeller to generate a pre-swirl in the water flow into the propeller. But its nozzle ring is significantly smaller than the original version and has a flat profile with much lower drag, the company’s literature notes.

The fins extend outwards beyond the nozzle and, to prevent the formation of a swirl and cavitation at the ends of the fins, they are fitted with end caps to reduce tip vortices. The nozzle ring generates thrust, provides stability to the fins and reduces vibrations.

Each installation will be designed to match hull geometry, propeller design and engine data and takes into account current class society strength, fatigue and vibration requirements and Becker offers a similar performance guarantee as it does for its Mewis Duct.

Further fuel savings are said to be available if the fin is paired with Becker’s established TLKSR twisted rudder, although the company has not published figures for that extra enhancement. MP