On the roll radius of gyration of Ro-Ro passenger ships

The present paper is based on a study of the Ship Design Laboratory of NTUA concerning the specification of the Roll Radius of Gyration in the framework of the implementation of the so-called Equivalent Model Test Method following Res. 14 of the new SOLAS 95 regulations for Ro-Ro Passenger Ships. The objectives of the study were specifically to outline a methodology for the correct estimation of the roll radius of gyration of existing and new ships, to apply this methodology to a characteristic sample of existing Ro-Ro passenger ships, to review existing semi-empirical formulas for the determination of the roll radius of gyration of Ro-Ro passenger ships, as suggested by IMO, and to conclude, finally, on the practical implications of the correct estimation and reproduction in model scale of the roll radius of gyration to the validity of the Model Test results. The principal findings from the NTUA investigation were that existing, semiempirical formulas and approximations for the roll radius of gyration do not account for the special features of typical Ro-Ro passenger ship designs and can lead to significantly erroneous results, that the radius of gyration of modern Ro-Ro passenger ships is comparatively large, and that an underestimation of the actual roll radius of gyration and its modeling according to Res. 14, SOLAS 95, will eventually lead to an increased tendency to capsize the ship model in the specified seastate conditions.