What is Metacentric height?

This is the vertical distance between the ship’s centre of gravity (G) and the initial transverse metacentre (M).

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The GM is very important in determining the initial stability of the ship i.e. the stability of the ship at small angles of heel.

  • If the centre of gravity (G) of the ship shown was higher, the righting lever (GZ) would be smaller and the ship would be less stable (since the righting moment would be smaller!).
  • If the centre of gravity (G) of the ship shown was lower, the righting lever (GZ) would be larger and the ship would be more stable (since the righting moment would be larger!).

Consider the vertical positions of the centre of gravity (G) and the initial transverse metacentre (M) for the ship shown. M is above G.

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Whenever M is above G, GM is a positive and the ship will be in a stable condition, in other words, the ship will have positive stability.

SUNIL KUMAR