![]() The side it leans on depends on the weight distribution of the vessel. If GM is negative, that is, below the center of gravity then the boat is unstable and leans to either the port or starboard side. As the value of GM gets smaller the vessel becomes less stable and it tends to roll more easily. ![]() If the metacentric height GM is much higher than the COG and COB, then you have a stiff and stable vessel that easily stays upright but a vessel with a higher GM will be tougher to maneuver. Metacentric Height and its relation to COG and COB The bigger the value of righting lever the better chances the vessel comes back to its initial condition. If you measure the distance the COB moves from its initial location, and subtract the distance the COG moves from its initial position, the difference is called the righting lever. The Righting lever and its relation to COG and COB The vessel can be brought back to its stable upright condition by shifting weights on board. The center of buoyancy is no longer under the center of gravity, and the vessel is in an unstable or heeled condition. Technically it can be defined as the point obtained by drawing an imaginary line vertically through the center of buoyancy and the center of gravity, then heeling the vessel to a few degrees and again drawing an imaginary vertical line through the new center of buoyancy along the center of gravity, the point at which these two imaginary lines meet is called as the metacenter and the height from the center of gravity to the metacenter is called as the metacentric height (GM).Īs the vessel heels, the underwater area changes which correspondingly changes the underwater volume and the center of buoyancy moves from its initial location to a new one. To make it easier, relating the vessel to a pendulum, is the point about which the pendulum swings can be considered as the metacenter. The metacenter is a theoretical point at some height above the center of gravity measured from the keel of the vessel. ![]() It is the center of the underwater volume of an object.Įffects of the center of gravity and center of buoyancy on floating objectsīefore we get into how the center of gravity and buoyancy effects a vessel, let’s learn about an additional term that plays a huge role in correlating both the forces called metacenter. The center of buoyancy (COB) can be defined as the theoretical center of the immersed part of an object where the upward buoyant forces act on. If you could balance the boat on a certain point, this would be the point where it balances, similar to the center of a seesaw we see in playgrounds. The direction of this force acts downwards and its location totally depends on how the weights are arranged. The center of gravity (COG) of any object can be defined as the theoretical point at which the object’s total weight is assumed to be concentrated due to the presence of gravitational forces. The balance between the two determines if a body is in stable or unstable conditions. The two terms are most commonly found in relation to the stability aspects of floating bodies.
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