C-Job Naval Architects has delivered the design for a wind-assisted general cargo vessel to Dutch shipping company Switijnk Shipping.
The 8500 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%.
Flettner Freighter 8500
C-Job was approached by Switijnk Shipping following its involvement in the European Union Interreg project S@IL, for which C-Job developed the design of a 4500 DWT Flettner Freighter. This smaller vessel was designed 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
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 Rotor Sails were chosen for this project because they are easy to use, safe, reasonably quiet, with no need for extra crew, and cheaper in investment compared to other systems. In addition, the effectiveness of Rotor Sails has been successfully proven.’
Hybrid Power
The main engines of the FF8500 have yet to be decided upon. Space has been reserved for LNG engines, but this will be dependent on LNG bunkering infrastructure along the vessel’s sailing routes.
Velocity Prediction
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.