New design of coastal feeder ship wins Japan award

A coastal container vessel featuring a novel, aerodynamic bow form has been voted ‘Best Small Cargo Ship’ at the Japanese Ship of the Year event hosted by the Japan Society of Naval Architects and Ocean Engineers (JASNAOE).

Deployed since delivery in December on the Japanese feeder network operated by Imoto Lines, the 548 teu Natori won the award on account of its energy-saving and safety features. The vessel is highly unusual in appearance, by virtue of a hemispherical-like prow, with integral, rounded forward bridge and superstructure, rendering a highly unusual appearance.

According to builder Kyokuyo Shipyard, the patented ‘semi-spherically shaped bow’(SSS-b) design reduces wind pressure by 30% compared to ships of conventional hull shape, saving up to 5% in fuel consumption under average sea conditions. The yard claims that the vessel is 9.5% more efficient overall as a result of an improved underwater hull form, high-efficiency propeller and ultra low-friction antifouling paint, together with the unique bow construction.

The JASNAOE accolade closely followed the award for ‘Development of Technology that Reduces the Environmental Impact for Logistic Operations’, conferred on the shipowner by the Japan Association for Logistics and Transport(JALoT). This recognised the Natori’s innovative energy-conserving measures, including the SSS-b and special propeller, as well as the ship’s contribution to efforts to achieve a modal shift of freight from road to sea in Japan.

Indicative of the modest size of vessels engaged in regular Japanese coastwise container transport, the 7,300gt Natori is the largest feeder in domestic service, and offers scope for 100 refrigerated units in a maximum cargo payload of 548 teu. The ship connects the Keihin port collective(Tokyo, Yokohama and Kawasaki) and Hanshin port(Kobe and Osaka) with Kitakyushu and Hakata, linking the major international hubs and industrial areas of Honshu island with Kyushu island to the west.

The integration of the bridge and accommodation into the ship’s forepart gives better visibility and habitability, due to minimised noise and vibration from the propulsion machinery aft. The configuration also helps maximise container loading efficiency within main hull dimensions of 136m length by 21m breadth.

Natori is powered by an MAN seven-cylinder S35MC two-stroke engine, produced by Japanese licensee Hanshin Diesel and giving a speed of 17 knots.

The feedership’s unusual forward design draws on Kyokuyo’s experience in developing and building two shortsea car carriers incorporating the SSS-b concept, the 2011-completed City of St Petersburg and City of Rotterdam.

Vehicle carriers have a characteristically very bluff form. The rounded shape of the bow in the two 2,000 car-capacity ships from the Shimonoseki yard was intended to cut wind resistance by 50% relative to a conventional design. Resistance was also lessened at the vessel sides by using a radiused transition from the uppermost side plating to the weather deck.

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