APPLICATION AND DEVELOPMENT OF A LARGE DUCTED PROPELLER FOR THE 280,000-DWT TANKER MS THORSAGA

The phenomenal growth in tanker size has resulted in increased propeller loading which causes reduced propeller efficiency and vibration problems. The ducted propeller appears as a good solution for tanker propulsion. At the sea trials of the largest ducted propeller tanker to date, the 280,000-dwt MS THORSAGA, a considerable speed increase and a reduction in vibration were attained compared with conventional sister tankers. This paper presents a summary of the THORSAGA ducted propeller's research and development involving design analysis, model tests, sea trials, and propeller cavitation observations. The importance of the ducted-propeller-hull interaction is stressed. Comparisons of the THORSAGA and sister tanker propulsive performance, maneuverability, structural, and vibrational responses are discussed along with cavitation correlations of the THORSAGA and NSMB VACUUMTANK observations. Duct quality control efforts in the shipyard and the impact of the ducted propeller on tanker economy are presented.