CALCULATION THE CENTER OF MASS COORDINATES OF BULK CARGO STACK WITH AVAILABILITY OF VESSEL’S TRIM

Abstract

In practice of simultaneous transportation of several types of bulk cargo by coaster type vessels between ports of Northern Europe and Norway in the North Sea, Norwegian Sea and Baltic Sea areas, and also placement of such cargo in the hold by separate stacks is carried out by the «natural» separation method. In accordance with such loading, cargo mate believes that each mound is a separate load and has its own mass, the center of mass coordinates, creates a moment relative to the midship section, etc., during calculations of seaworthiness of a vessel. Voyage observations of the simultaneous transportation of several types of bulk cargo by m/v «Wilson Bilbao» were made. It is found that, if the ship has no trim and
loading is performed on an even keel, the load is placed, most often, as follows. In fore and aft of the vessel’s hold a stack has the shape of a right triangle or rectangular trapezoid, and has the shape of an isosceles trapezium or an isosceles triangle in the central part of the hold, depending of its volume. There is a moving and pouring if the ship has a trim, when loading bulk cargo especially. The angles at the base of these cargo stacks change in the angle of trim: one of the angles increases, the other one decreases. There is moving of stack center of mass of shifted cargo that can not be ignored in the calculation of the stability of a vessel after completion of loading. The mathematical model that allows to calculate a coordinates of the center of mass of a shifted cargo depending of the hold linear dimensions, angle of repose of a cargo and the initial trim of the vessel, is considered in the article.