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spence -> RE: Kirishima (11/24/2015 11:22:27 PM)
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Just in case folks didn't take Naval Architecture 101 the "G" in "GM" stands for Center of Gravity or the point at which the weight of the ship acts downward. The "M" in GM stands for the Center of Flotation and can be visualized as the point where the upward force of flotation acts upward. Both are located on the centerline of the hull (as viewed in cross section) The distance between them is called the Metacentric Height and is a measure of the stability of a ship. The larger the distance between the two the greater the overall stability of the ship if the M point is above the G point.
If the M is above the G then the ship floats in all conditions of heel or list because the vectors symbolizing both the flotation and weight act to "twist" the hull towards an upright position.
As a ship fills with water both the Center of Gravity and Center of Flotation "move" lower within the hull but the Center of Flotation moves more. Filled with enough water the Center of Flotation becomes lower than the Center of Gravity. In a perfectly upright position this won't capsize a ship but if a ship takes on a list then the twisting action of the offset (vectors) of the Center of Gravity and Center of Flotation act to make the hull continue rolling over. An additional problem for damage control personnel is that as flooding occurs in "random compartments" both the G and the M move but in a not quite completely known amount or direction. What the DCA knows is only that they have moved some amount and that the distance between the G and the M has decreased: thus the stability has decreased. Since both the G and the M are located on the centerline of the hull the very fact of the list may act to place the M (Center of Flotation) lower in the hull than the G (Center of Gravity) which will cause a twist towards "upside-downess".
They also mention that several of the large caliber hits opened large second deck compartments to the sea. Water sloshing from side to side within the hull would tend to exaccerbate a list. Counter-flooding to correct a list would cause water leaning one way to slosh back towards the other side causing an even bigger list in the opposite direction. Might help to explain the sudden capsizing in the opposite direction from the original list.
Took that course 40 years ago....
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