Preliminary Study on Stability Parameters of Semi-Displacement Ships

Semi-displacement passenger ships operate at the speed range of 19 to 23 knots or Froude number Fn of 0.50 to 0.75. Those ships need higher engine power to maintain their speeds. The efforts should be made to minimize their higher engine powers. Most experts worked to minimize the engine power for most merchant ships. In their works, the initial metacentric (GMO) at departure condition was taken as constraint to represent stability parameters. However, this is not a general case for semi-displacement passenger ships. In this study, a parent semi-displacement passenger was designed and modified. Stability parameters were computed and evaluated as required by the rules IMO-HSC. In addition, one existing high speed passenger ship was evaluated for stability evaluation as reference also. It was found that the stability parameters at large angles of inclination such as: weather criterion, angle of GZmaxand others are more critical compared to GM0. Also, the stability parameters when ship is at arrival condition are more critical compared to those at departure condition. The study resumed that the application of criterion GM0≥ 0.15 m at optimization process of semi-displacement passenger ships should be considered again for the future.