GZ Curve M V Seamanship

The following data can be extracted from a GZ curve; The metacentric height (GM) is found by drawing a perpendicular line at 57.2° (1 radian) where this line intersects the GZ Curve a right angle is drawn and where this intersects the GZ axis of the graph the GM can...

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Bad Stability

In the diagram below G is above M and consequently when the vessel is inclined it forms a capsizing moment due to the negative GM. This is known as bad stability.

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Good Stability

Righting Lever (GZ) In the below diagram as M is above G it forms a righting lever this is stable as the ship will return to the upright and is GOOD STABILITY

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Shift of Buoyancy

Shift of Buoyancy When a vessel is inclined the waterline changes as shown below from W1 to W2 and hence the underwater volume of the vessel. Consequently, the buoyancy in the blue wedge shape moves b to b1 and B moves from B to B1.  

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The Metacentre

The Metacentre (M) “M” is a point, generally on the centreline, at which the initial upward forces acting through B cut the upward forces acting through B¹ after the vessel has been inclined by an external force. For a vessel to be stable G must be below M. This...

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Centre of Gravity (Cof G) and Centre of Buoyancy

Box Shaped Vessel Centre of Gravity (C of G) In Fig 1, the C of G is the point at which the entire weight of a body may be considered as concentrated so that if supported at this point the body would be balanced. The location of a body’s centre of gravity may coincide...

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