The empirical formulae of equation (8) can be applied to normal commercial ships for full load and ballast conditions. But there are some difficulties to obtain precise prediction results for the container ships at ballast condition and full ships whose Cb is over 0.83 and Cb×B/L is over 0.155 because these ships are distributed at the end edge of database.

　

 In equation (8), SR, BPS and BP07 are introduced to define the stern hull form as shown in Fig. 9.

　

　

 As SR is large, it is apparently shown that the stern hull form becomes more U type. Therefore, SR gives easy comprehension to ship designer in modification of stern hull form for ship's maneuverability. The stern hull type coefficient SR is closely related to all linear hydrodynamic coefficients. But relationship with nonlinear hydrodynamic coefficients is difficult to be defined and the prediction accuracy is not improved although applied to some coefficients.

　

 The nonlinear and cross coupling coefficients are as follows:

　

　

 The interaction coefficients and the gradient of lift coefficient for rudder are obtained as below:

　

　

where

　

∇'=∇/L³