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Rudder specialist Becker Marine Systems has announced that the first sea trials of its 'fuel-saving' Mewis Duct® device have been completed.

The Mewis Duct® is a propulsion improvement device for full-form ships, ie tankers, bulk carriers and multi-purpose vessels.

The company developed the device after research found that the wake field of full-form vessels, such as tankers, reduces the propeller’s propulsion efficiency. The water flow velocity was found to have such an unfavorable characteristic that the propeller did not get a uniform water flow.

The Mewis Duct® consists of two strong fixed elements mounted on the vessel: a duct positioned ahead of the propeller together with an integrated fin system within. The duct straightens and accelerates the hull’s wake into the propeller and also produces a net ahead thrust. The individual placed fins have a stator effect by generating a pre-swirl in the counter direction of the propeller’s operation, recovering the rotational energy from the propeller slipstream.

Ships are propelled by combustion engines whose power output is dimensioned by the ship’s hull resistance, the propeller efficiency and the desired speed range. The Mewis Duct® is said to reduce the power requirement by improving the water inflow towards the propeller in order to achieve an higher overall propulsion efficiency.

The achievable power savings from the Mewis Duct® are strongly dependent on the propeller thrust loading. According to Becker Marine this ranges from 3% for small container vessels up to 10% for large tankers and bulk carriers.

"The duct combines very consequentially different theories of fluid dynamics. Countless calculations, dozens of tank tests and final true scale tests have proven the enormous fuel saving potential of the product," Becker Marine said.

First Installation

The first installation was carried out at China's Chengxi shipyard. The 46,000 dwt Star Instid runs with a 36sqm Becker Flap FKSR Rudder and was the first of three vessels to be equipped with the new product.

A Becker Service team member was present on site and supervised the installation for Norwegian ship owner Grieg Shipping Group AS.

Following the first sea trials, Becker Marine said the outcome of the first sea trials fully confirmed the predictions from CFD calculations and model tests. Becker Marine Systems has since then installed two further Mewis Ducts®, one of them for Grieg Shipping group and the other for Laurin Maritime. The sea trial results are due to be published soon.

About Becker Marine

Hamburg-based company Becker Marine Systems is a leading manufacturer of high performance rudders and manoeuvring solutions for a wide range of ships. Becker’s rudder systems are used in luxury yachts, super tankers, container ships, passenger ferries and large cruise vessels.

The company’s turnover reached 100 Million Euros in 2008 when over 300 rudder systems were delivered to 25 countries.