The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship. It is the distance between center of gravity (c) and Metacenter. It is the measure if static stability of floating body. Large the metacentric height more is the stability. AIM: To determine the meta-centric height and position of the meta-centric height with angle of heel of ship model. APPARATUS REQUIRED: Water tank.

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Technically, there are different metacentric heights for any combination of pitch and roll motion, depending on the moment of inertia of the waterplane area of the ship around the axis of rotation under consideration, but they are normally only calculated and stated as specific values for the limiting pure pitch and roll motion.

By means of the inclining experiment, the ‘as-built’ centre of gravity can be found; obtaining GM and KM by experiment measurement by means of pendulum swing measurements and draft readingsthe centre of gravity KG can be found. Distance of movable mass at left of center mm. A larger metacentric height on the other hand can cause a vessel to be too “stiff”; excessive stability is uncomfortable for passengers and crew.

Then I brought the body in the water tube and changed the horizontal moving load distance first towards right.

Water Hammer – Definition and Factors Affecting it. The centre of vetermination is at the centre of mass of the volume of water that the hull displaces.

In contrast, a “tender” ship lags behind the motion of the waves and tends to roll at lesser amplitudes. The centre of gravity of determintaion ship is commonly denoted as point G or VCG. The metacentric height also influences the natural period of rolling of a hull, with very large metacentric heights being associated with shorter periods of roll which are uncomfortable for passengers.

KM is the distance from the keel to the metacentre. It follows that is the center of buoyancy in the first position, the center of buoyancy in the second inverted position, and the center of gravity in both positions. When a floating body is given a small displacement it will rotate about a point, so the point at which the deterkination rotates is called as the Metacenter.


Builder’s Old Measurement Moorsom System. We shall now demonstrate that these positions are setermination both stable, or both unstable, provided the body is of uniform density.

Hence, and. Coast Guard Technical computer program support accessed 20 December kf Stay informed – subscribe to our newsletter. Work must be done to roll a stable hull. They then calculate the righting moment at this angle, which is determined using the equation:.

Metacentric height – Wikipedia

Email The subscriber’s email address. Similarly, the downflooding angle is the angle at which heught will be able to flood metacentrid into the vessel. The metacentric height of a conventional ship whose length greatly exceeds its width is typically much metacenttic for rolling i. Criteria for this dynamic stability effect remain to be developed. Desirable and Undesirable Characteristics of Offshore Yachts. This page was last edited on 22 Novemberat Metacentres are usually separately calculated for transverse side to side rolling motion and for lengthwise longitudinal pitching motion.

Experimental study of Laminar, Transitional and Turbulent Flow. Depending on the geometry of the hull, Naval Architects must iteratively calculate the center of buoyancy at increasing angles of heel. When an edge is tipped, the water rushes to that side, which exacerbates the tip even further.

A ship with low GM is less safe if damaged and partially flooded because the lower metacentric height leaves less safety margin. The meatcentric though which the force of buoyancy is supposed to pass is called as the center of buoyancy.

Because the vessel displacement is constant, common practice is to simply graph the righting arm vs the angle of heel.

Hence, a sufficiently, but not excessively, high metacentric height is considered ideal for passenger ships. Such a deterination can be thought of as a very crude model of a ship. An overly stiff vessel rolls with a short period and high amplitude which results in high angular acceleration. Displacement Loaded displacement Standard displacement Light displacement Normal displacement. A ship with a small GM will be “tender” – have a long roll period.


Suppose that the body now turns through a small angle about the -axis.

Stability and Metacentric Height

Current Deadweight tonnage Twenty-foot equivalent unit Intermodal containers. It is necessary for the stability of a floating body, If metacenter is above center of gravity body will be stable because the restoring couple produced will shift the body to its original position. The righting couple on the ship is proportional to the horizontal distance between two equal forces.

For this reason, maritime regulatory agencies such as the International Maritime Organization specify minimum safety margins for seagoing vessels. The metacentric height GM is a measurement of the initial static stability of a floating body.

Hence, hfight submerged volume is. The metacentre deermination a direct relationship with a ship’s rolling period. Ignoring the ballastwide and shallow or narrow and deep means that the ship is heignt quick to roll and very hard to overturn and is stiff. By using this site, you agree to the Terms of Use and Privacy Policy. This is because the stiff vessel quickly responds to the sea as it attempts to assume the slope of the wave.

Very tender boats with very slow roll periods are at risk of overturning, but are comfortable for passengers. The effect is similar to that of carrying a large flat tray of water. It is easily demonstrated that. A simple extension of the previous argument reveals that if the body turns through dtermination small angle about the -axis then the metacentric height is. First of all I adjust the movable weight along the vertical rod at a certain position and measured the distance of center of gravity by measuring tape.

Tonnage Gross tonnage Compensated gross tonnage Net meatcentric.

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