The old rudder types that have been used a lot for inland vessels have been subjected to an investigation into energy saving. After a real life test on an inland tanker with a new type of rudder designed by the R&D department, drag tests were performed at Marin and a location study was conducted at TU Delft. Following positive results from all investigations, the Easyflow rudders have now been introduced to the maritime world.
The old type of rudder that has been used under most vessels from 1985 to 2013 was based on optimum manoeuvrability. This was achieved, but fuel consumption was never considered. The rudders were provided with a semi-fishtail on the outside and were usually quite big around the rudder stock. The blade has a lot of shape. By preserving the optimum manoeuvrability characteristics, and still making the model energy efficient, the Easyflow rudder is created.
Up to January 2016, 37 vessels have been converted and 17 new vessels have been fitted with Easyflow rudders. They all show positive results and consume less gas oil. The very large rudders in particular, that for a large part are in the propeller radius, are able to achieve fuel savings from 15 to 18%. This is a maximum result. The average is a little lower, due to different navigational areas.
The heavier the vessel, the more return is to expect. On the other hand, there may be less return on still water (no current). On average, these vessels will achieve fuel savings between 10 and 12%. For these vessels, streamline plates were also used, or the cabinets above the rudders were opened to achieve a better current around the vessel. Up to now, all vessels made with the new rudders achieved fuel savings that vary between 5 and 15%, making this a sustainable solution.