METHOD FOR ASSESSING AND IMPROVING THE INITIAL STABILITY OF THE SHIP UNDER CONDITIONS OF INCOMPLETE INFORMATION ON THE CARGO LOADED

A practical method for assessing and restoring (building up) the initial stability of a vessel in conditions of incomplete information about the loaded cargo has been proposed. This method is based on the procedure of sequential filling with liquid ballast of two low-lying and symmetrical tanks relative to the center plane of the vessel. At the same time, the selection of the tanks size (the amount of ballast received) is carried out on the basis of the conditions of guaranteed non-capsizing of the vessel, on the one hand, and increasing its initial stability, on the other. Before starting ballasting, as well as after filling each of the selected tanks, it has been proposed to measure the draft and heel angle of the vessel, as well as to quantify the upper and lower limits (range) of possible values of the metacentric height and the corresponding values of the heel angle of the vessel. At the same time, at the beginning (before ballasting), the lower limit of the metacentric height is determined from the condition that the ship’s heel is caused by the ship’s negative initial stability. Using the simple logical rules formulated in the paper, it has been proposed to compare the actual and calculated values of the ship’s heel angles during ballasting, and then make a decision on the value of its actual initial stability. The necessary calculation formulas that make it possible to practically implement the proposed method, both when choosing the size (volume) of ballast tanks, and when calculating the ranges of possible values of the ship’s heel angles and its initial metacentric height are provided in the paper. For a ship of a typical design, a numerical example of the implementation of the method has been given. It, among other things, has shown that the accuracy of assessing the initial stability of a ship based on the results of ballasting depends significantly on the volume of the selected tanks: the larger this volume, the more accurate and sensitive the proposed method.

initial stability of the vessel, incomplete information about the cargo loaded, sequential ballasting of tanks, measurement of heel angle, metacentric height, heel angle, possible values, calculation and measurements

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