On the Prediction of Radii of Inertia and their Effect on Seakeeping

As part of the design verification, seakeeping assessments (either numerical or experimental) are performed. However if no detailed values of the radii of inertia are available and incorrect estimates are made, the predicted ship performance might be misleading. This paper describes the effect of radii of inertia on ship motions. It gives guidelines for the accuracy required to ensure that the changes in seakeeping performance are small. Various estimation methods are compared for a range of illustrative ship types. For each of the methods, advantages and disadvantages are discussed and a practical estimation method is proposed that can be used in the basic design phase.