![]() So, when a ship experiences beam winds, it will till up to the angle at which the righting moment generated will cancel out the heeling moment. The moment (clockwise) created by the wind force and water pressure is the heeling moment, and the moment (anti-clockwise) created by the weight and buoyancy couple acts as the righting moment. The risk here is, at a larger angle of heel in a neutrally stable shift, an unwanted weight shift due to cargo shifting might give rise to a condition of unstable equilibrium. As shown in the figure below, in such a condition, no righting lever is generated at any angle of the heel.Īs a result, any heeling moment would not give rise to a righting moment, and the ship would remain in the heeled position as long as neutral stability prevails. It occurs when the vertical position of CG coincides with the transverse metacentre (M). ![]() This is the most dangerous situation possible, for any surface ship, and all precautions must be taken to avoid it. This is called the Righting Lever, and abbreviated as GZ (refer to the figure above).Īn important relation between metacentric height (GM) and righting lever (GZ) can also be obtained from the figure above. The lever that causes the righting of a ship is the separation between the vertical lines passing through G and B1. The moment resulting in the uprighting of the ship to its original orientation is called Righting Moment. The lateral distance or lever between the weight and buoyancy in this condition results in a moment that brings the ship back to its original upright position. So, when the ship heels to an angle (say theta- Ɵ), the centre of buoyancy (B) now shifts to B1. A stable equilibrium is achieved when the vertical position of G is lower than the position of the transverse metacentre (M). There are three types of equilibrium conditions that can occur, for a floating ship, depending on the relation between the positions of the centre of gravity and centre of buoyancy. The fundamental concept behind the understanding of the intact stability of a floating body is that of Equilibrium. Want to read about damage stability? Click below:ĭamage Stability Of Ships Intact Stability of Surface Ships:
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