Traditionally a racing yacht is designed with as low radii of gyration as possible, especially regarding the pitch radius. A small radius normally provides less relative velocities between hull and water and thus less added resistance. Recent model tests at SSPA with a sailing yacht in head seas have indicated that a minimum of the added resistance can be found for a certain radius of gyration. The relation between the radius of gyration and the added resistance is of course best investigated by extensive model tests. However this is expensive and time consuming. A cost effective procedure is to combine model tests with computer based velocity predictions. There are a number of different Velocity Prediction Programs (VPP’s) available around the world today. Most of them are based on equations of equilibrium, one for each degree of freedom, that are explicitly solved. These programs work well as a basis for the judgment of the calm water characteristics for a sailing yacht. Many of them also have algorithms for estimating the added resistance in waves, which is normally based on regression formulas, derived from frequency based strip theory calculations. At SSPA a time domain dynamic prediction program has been developed , a DVPP (Dynamic VPP), that provides possibilities to study also the dynamic characteristics of a sailing yacht. The input data are the same as for a conventional VPP, however, also the hull form is entered in the form of sectional coordinates. The principles for the program is that all the horizontal hydrodynamic forces are expressed in the same way as in the conventional program, however the velocities in the different degrees of freedom are corrected for the wave particle velocities. Additional wave induced forces are also obtained from wave particle accelerations and by pressure integration over the whole momentary wetted surface.