A vessel's capabilities at different trims and loading conditions, as well as in shallow and restricted waters (channels, banks, and other constrictions), change significantly from those in deep water and in a complex fashion. This section begins by describing the operational results of maneuvering capabilities in deep water. In general, much greater sophistication is required to accurately model trajectories than at other conditions.

Turning, turn recovery, and course-keeping abilities are closely related to the level of dynamic course stability, a characteristic of hull form and rudder. In general terms, dynamic stability is the ability of a vessel to return to steady heading (or initial turning condition) after a disturbance. Figure D-1, for example, shows the response of stable and unstable ships with the rudder fixed, after a

FIGURE D-1

Paths of stable and unstable ships after a yaw disturbance of 1 degree (t' = ship length of travel).

Source: Eda and Landsburg (1983).