In this study, we conducted turning tests with rudder angles \(\pm 35^\circ\) and \(\pm 20^\circ /20^\circ\) zig-zag maneuver tests in deep and shallow water using a model of a 3,600 TEU container ship called KCS. Through the comparison of these test results with the free-running test results of three other ships, the shallow-water effect on the maneuverability was investigated. The shallow-water effects obtained during the turning and zig-zag maneuvers are as follows: Turning: The advance ( \(A_D\) ) decreases slightly when the water depth-to-ship draft ratio (h/d) is approximately 2.0 and increases significantly as the water depth decreases. The tactical diameter ( \(D_T\) ) (up to \(h/d = 2.0\) ) is approximately the same as that in deep water and becomes significantly larger when h/d becomes smaller than 2.0. Thus, there is a slight difference in the appearance of the shallow-water effects in \(A_D\) and \(D_T\) . Zig-zag maneuvers: The overshoot angle increases slightly near \(h/d = 2.0\) compared with that in deep water and becomes significantly smaller as the water depth becomes shallower. The forward distance ( \(l_{20}\) ), until reaching the heading \(+20^\circ /-20^\circ\) after steering, was approximately the same as that in deep water or decreased slightly, until approximately \(h/d = 2.0\) . Furthermore, it increased as the water depth decreased. This is because the course stability of the ship deteriorated at approximately \(h/d = 2.0\) .
