Underwater wing and bulbous bow lifts passenger vessel fuel efficiency

The 12-year-old 'Valais' achieved a 24% reduction in fuel consumption following a retrofit with a bulbous nose and an underwater foil. (Image: Jari Ott)The 12-year-old ‘Valais’ achieved a 24% reduction in fuel consumption following a retrofit with a bulbous nose and an underwater foil. (Image: Jari Ott)

Retrofitting a 12-year-old 30 metre passenger vessel with an underwater wing and a bulbous bow reduced the vessel’s resistance and contributed to a 24% improvement in fuel efficiency.

The patented Hull Vane, an underwater wing which reduces resistance, was fitted to a freshwater passenger vessel, CGN’s Valais at CGN’s workshop in Lausanne, Switzerland, in 2019.

The retrofit included the replacement of the vessel’s engines with new MAN Energy Solutions V8 engines and the installation of a bulbous bow.

Despite the significant amount of added weight, including the Hull Vane, bulbous bow construction and ballast, the results showed that the fuel consumption of the vessel was reduced by 24%.

The improved fuel efficiency, reduced engine speed and new engines have made the vessel quieter, with the greatest improvements (of up to 6dB) seen in the passenger lounge. The reduced resistance means that the vessel now also makes significantly less waves. The added weight and added submerged surfaces also improve the stability and seakeeping of the vessel.

Irwin Gafner, technical director of CGN says: “We selected the 30m passenger ship Valais and commissioned a ship optimisation study by means of Computational Fluid Dynamics software, comparing several possible hydrodynamic improvements at our operating speed of 25 km/h. In the study, the benchmark hull (which has a trim wedge) was compared to various retrofit alternatives for the stern, such as ducktail extensions, interceptors (a vertical blade protruding below the transom) and a Hull Vane, which is a rather novel solution and can be described as a “spoiler for ships”. The best alternative to come out of this optimisation was the Hull Vane, promising a resistance reduction of 15%. We also asked to optimise a bulbous bow for the ship with Hull Vane.”

The device was optimised by Hull Vane BV for the Valais. Bruno Bouckaert, sales director of Hull Vane BV, said: “There are a lot of small passenger ships ranging from 20 to 100m in use worldwide, on rivers, lakes and servicing islands. Because of their length and displacement, they often operate at excellent speeds for Hull Vane effectiveness, making a retrofit very worthwhile.”

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