C-Job completes design of wind-assisted Flettner Freighter
C-Job Naval Architects has delivered the design for a wind-assisted general cargo vessel to Dutch shipping company Switijnk Shipping. The 8,500 DWT vessel will be equipped with two Norsepower Rotor Sails that will supplement the main engines and is expected to achieve fuel savings of approximately 14 per cent.
C-Job was approached by Switijnk Shipping following its involvement in the European Union Interreg project S@IL, for which C-Job developed the earlier design of a 4,500 DWT Flettner Freighter.
C-Job designed this smaller vessel with four Rotor Sails. However, after studying the prevailing wind patterns on Switijnk’s proposed sailing routes, C-Job decided to design a new vessel, called the FF8500, with two larger Rotor Sails.
Rotor Sails are deck-mounted rotating cylinders that utilise the Magnus effect to create a propulsive thrust. The Magnus effect is a force that acts on a spinning body in a moving airstream. Because the Magnus effect acts perpendicularly to the direction of the airstream, the optimum wind direction for Flettner ships is at 90 degrees to the direction of the sailing.
“Our experience from the Project S@IL study showed that Rotor Sails were the most viable choice compared to other wind assisted propulsion systems,” explains C-Job Business Manager Jelle Grijpstra. “And then, together with Finnish Rotor Sail supplier Norsepower, we concluded that two larger Rotor Sails were most effective for this project. This was because these would yield a comparable propulsive force to four smaller units. Also, with two Rotor Sails, one on the bow and one on the stern, there would be no chance of wind shadows affecting performance.”
The subject of the main engines of the FF8500 has yet to be decided upon. “Switijnk has a well-defined vision of sustainable shipping and we are glad to sit down and share our knowledge with them. We have an extensive track record of integrating mission equipment, and we have looked at all the options available to help them achieve their ambitions. We have reserved space for LNG engines; although this will be dependent on LNG bunkering infrastructure along their sailing routes.”
With the concept design of the vessel complete, the next stage of the project will consist of testing at Maritime Research Institute Netherlands (MARIN). The intention of this velocity prediction research is to validate the design and to quantify the fuel savings to be gained. “Once investors are convinced and the financing is arranged, then Switijnk can continue with the process of selecting a shipyard to build the vessel,” Mr Grijpstra added.
By Jake Frith
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