Hydrodynamic rudders ordered for ammonia-fuelled box ships

The Singapore shipping arm of AL Group Asiatic Lloyd ordered the six 7,100-TEU feeders at Dalian Shipbuilding Industry Co, and the yard will deliver the vessels between 2023 and 2025. Length between perpendiculars of the four identical vessels is 255 m, with 43 m breadth, 15 m design load draught and a design speed of 21 knots. Damen will provide the tailor designed rudder for each of the vessels, measuring 61 m² and generating 3,300 Kilo-newton metres of torque.

DMC said when the vessels are in forward thrust, the propeller has a fixed rotation direction, meaning the asymmetric leading edge will improve the water flow by directing turbulent water along the rudder blade more efficiently.

More hydrodynamic optimisation is achieved by the bulb. In the wake of the propeller axis, turbulent water can circle and cause vibrations in vessel’s hulls and rudders. The rudder bulb is positioned directly behind the centre of the propeller and eliminates this turbulence to create a better flow along the rudder blade, according to DMC.

"This reduces ship’s resistance in the water and it also improves torque of the rudder when it turns. A stable and directional water flow generates more thrust than turbulent water," DMC said.

"The advanced rudder technology adds to the sustainable ambition of the shipowner and charterer to operate vessels that cause minimal emissions. The choice for ammonia as a propulsion fuel expresses this ambition. Reducing drag, exemplified by the application of ART Atlantic rudders with a bulb allow further fuel and emissions savings."

“We will benefit from this highly optimised and high efficiency Van der Velden rudder design by DMC to realise our goal of achieving vessel efficiency to the highest possible emission ratings” said AL Group fleet director Tonci Zdunic.

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