KAPPEL Propeller. Development of a Marine Propeller with Non-planar Lifting Surfaces

The principle of non-planar lifting surfaces is applied to the design of modern aircraft wings to obtain better lift to drag ratios. Whereas a pronounced fin or "winglet" at the wingtip has been developed for aircraft, the application of the non-planar principle to marine propellers, dealt with in this paper, has led to the KAPPEL propeller with blades curved towards the suction side integrating the fin or winglet into the propeller blade. The combined theoretical, experimental and practical approach to develop and design marine propellers with non-planar lifting surfaces has resulted in propellers with higher efficiency and lower levels of noise and vibration excitation compared to conventional propellers designed for the same task. Conventional and KAPPEL propellers have been compared for a medium sized container ship and a product tanker. In total nine of these unconventional and two conventional propellers have been designed and models of all propellers have been examined with respect to cavitation and efficiency in the open water and behind conditions. Casting procedures, measurement procedures and stress analysis methods for the unconventional geometry of the KAPPEL propeller have been developed. The manufacture of the first full scale propeller of this type is completed. Comparative sea trials with this propeller and the conventional propeller for the same 35,000tdw product carries are imminent.