On empirical methods to predict the rolling period of ships

A reliable prediction of the roll period is crucial, as it forms the basis of the calculation of the roll motion and transverse accelerations. Both are extremely important for the comfort and safety of passengers and crew as well as the loads on the cargo and their lashings. At present, some prediction methods are quite unreliable, with sometimes errors in the predicted roll period of 5 to 10 s. This paper describes and compares eight methods. It shows that the four best performing methods have a mean absolute error of less than 1.4 s for the three validation cases evaluated, making them considerably more reliable than some of the other methods used in the industry.