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in the center of gravity of the ship moving from (G) to (G5) (see Figure C-3). This movement reduces the original righting lever, GZ, and the resultant height of the ship's GM. The ship therefore becomes less transversely stable.
Should the ship, for whatever reason, continue to heel, the position of (G5) will continue to move due to the movement of the center of gravity of the affected ballast tanks, thereby reducing the vessel's GM and the resulting GZ. If the deck edge becomes immersed, the center of buoyancy (B) will move inboard, the effect of which will again reduce GM and the resultant righting moment, GZ. The effect of this change will make the vessel become very "tender," and it will "flop" from side to side.
If more tanks are made slack or there is a cargo shift due to the excessive angle of heel, it is possible for (B) and (G5) to reverse positions. Should this occur, GZ will be converted from a righting lever into a coupled turning force, which could cause the ship to capsize. This condition is known as negative GM (see Figure C-4).