For the hull sway force and yaw moment coefficients - cfyh and cmzh - a reference is made to [15]. However, the original hull derivatives (covering rather normal limits of the drift angle and yaw velocity) are extrapolated to the so-called 'four-quadrant' range (a hypothesis to be better verified in the future) and converted to suit the formula (23) by the following expressions (the case of yaw moment included only):

　

　

where:

　

　

 The charts of cfyh and cmzh are displayed in Fig.3 and Fig.4.

　

　

　

 To come as close as possible to full scale sea trial data (35°rudder turning, 10°/10°and 20°/20° z-tests), the five tuning parameters (kept originally equal to unity) cm and c1 to c4 have been changed by means of the least square optimisation to the following values: cm=0.8 (Tab.1), c1=1.35, c2=1.00 (preserved), c3=c4=0.8.

　

 Though the relationships (17) are quite complex, the investigations made in the previous chapter enable to formulate some patterns (trends and magnitudes) of the wave second order forces as being just enough to check their importance in ship manoeuvring - the wave incidence angle is maintained exclusively however. The surge second order force is not subject to the analysis and has been assumed (due to a smaller effect and for the model completeness) as the cosine dependence with the wave incidence angle. The sway force and yaw moment are written as:

　

 where the variable coefficients at the end of both expressions are presented in Fig. 5 (two distinct cases for sway force) and in Fig. 6 (three characteristic choices for yaw moment) - they reflect relatively low wave/ship length ratios as being connected with larger forces. The most inspiring for such selections were [5], [8], [16].

　

 All above six mutual combinations have been run with wave heights: h=2[m] (wave amplitude ζ0=1[m]) and h=4[m] (ζ0=2[m]) and the wave radiating in the south direction (the ship initially goes thus against the wave). The simulation results of the turning manoeuvre at 35°rudder are varing much. Firstly, the wave second order yaw moment has little (even negligible) influence upon the ship manoeuvring motion - likely due to a magnitude, the manoeuvre appearance is dependent almost entirely upon the second order sway force. That is why Figs. 8 to 11 show the simulation results in relation to only one option of the yaw moment. The legend in Fig. 8 refers also to subsequent Figs. 9 to 11 - 's1' and 's2' stand for the both sway force coefficients as of Fig. 5, 'm1' denotes the first case of yaw moment by Fig. 6.