The ship performance play an important role is safety of ship in seaways. Therefore the International Maritime Organization (IMO) develop the Second Generation Intact Stability Criteria (SGISC) based on ship dynamics in waves. The hydrodynamics characteristics is crucial correspond to analysis and simulation of ship and wave interaction. Several methods to estimate the hydrodynamics forces and moments are available recently but the applicability depending on the ship geometry.
In case of dead ship condition, the damping coefficient of roll motion and the effect wave slope coefficient are necessary to assess ship stability invulnerability criteria level 1 and level 2, even in the direct assessment. Those hydrodynamics coefficients are also important for the excessive acceleration failure mode mainly for ships with large breadth-to-draught ratio with passenger and crew accommodation located in high position. The damping coefficient can be estimated from the data of roll decay test and the effective wave slope coefficient is estimated based on roll test in beam waves with damping obtained by the roll decay test.
The roll decay test and the roll test in beam waves had been conducted on an Indonesian ro-ro ferry with breadth-to-draught ratio larger than 4.5. The purpose of the experiment was to determine the damping coefficient and the effective wave slope coefficient to be used on the stability assessment correspond to the dead ship and excessive acceleration failure mode.
