The stability of a damaged roll-on roll-off vessel with water on deck

The stability of a damaged roll-on roll-off vessel with water on the vehicle deck is discussed. It is shown that the heeling moment that heels the ship beyond the static angle of equilibrium in calm water comes from water on deck, elevated above sea level by the dynamic action of waves. Three methods of calculating the heel angle with water on deck are discussed. In addition, the critical heel angle associated with the point of no return is analysed. Finally, the paper argues that the GZ curve for the damaged ship should correspond to the concept of minimum stability, which is not very well known within the profession.