Obtained hydrodynamic derivatives and coefficients are expressed by simple formulas to get them easily for arbitral fishing vessels.

　

4.1 Linear hydrodynamic derivatives

　

 For the expression of linear derivatives, well-known Kijima's formulas [6] are used in principle. However, the formulas are based on the conventional merchant ships, some modifications are required. The linear derivatives are generally affected by trim. The effects of trim on linear derivatives are plotted in Fig.7 comparing with Kijima's trim corrections. From these figures, it is pointed out that the following trim corrections are more suitable for these fishing vessels.