What do you mean by metacentric height?
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 and its metacentre. A larger metacentric height implies greater initial stability against overturning.
What is GM in ship stability?
The distance between G and M is known as the metacentric height (GM). A stable vessel when upright is said to have a positive metacentric height (GM), i.e. when the metacentre (M) is found to be above the centre of gravity (G). This is usually referred to as having a positive GM or a positive initial stability.
What is the use of metacentre?
If the metacentre is above the centre of gravity, buoyancy restores stability when the ship tilts. The stability increases with the distance between metacentre and centre of gravity, called the metacentric height. If the metacentre is below the centre of gravity, the boat is unstable, and a tilt results in capsizing.
What is a GM in a ship and how do we get it?
GM – Metacentric Height: This measurement is calculated by subtracting KG from KM (GM = KM – KG). GM is a measure of the ship’s initial stability. BM – Metacentric Radius: The distance between the Center of Buoyancy and the Metacenter.
What does it mean if metacentric height is negative?
The metacentric height can become negative if the centre of gravity is too high. Even with negative metacentric height, ships with certain forms can still find a position of stable equilibrium at an angle of heel called angle of loll. The moving masses transversally can endanger the ship.
What is minimum GM?
Initial GM or metacentric height should not be less then 0.15 m. Righting lever GZ should be at least 0.2 m and angle of heel Ѳ ≥ 30̊. Maximum righting lever should occur at heel >30̊ preferably but not less than 25̊.
What are the applications of metacentric height?
Metacentric height is a parameter to measure the static stability of a floating body, as it is defined as a distance between the center of gravity of a body and its metacenter. It has a direct relationship with the stability of the body. So, larger the metacentric height, more is the stability.
What is GZ or righting arm?
GZ is known as the righting arm. The plot of the righting arm GZ calculated as the function of the heel angle, at constant displacement and vertical centre of gravity KG values, is used to measure the ship stability at large angles of heels. It is called the curve of statical stability.