Stability


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Kyle Hauser

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Sep 26, 2005
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What do you think the Titanic's stability was steaming normal speed in calm water would have been compared to a modern cruise ship?
 
Jul 9, 2000
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From what I understand, an Olympic class liner was a decidedly more stable seaboat then just about any one of their contemporaries. One of the reasons for this is that the design avoided throwing in a lot of topweight where it served no useful purpose.

You'll notice that a lot of modern cruise ship's appear to have a substantial amount of topweight, and to avoid getting bitten by that, they use lighter materials, fin stabilizers, and they typically operate in much calmer waters then what you tend to see on the North Atlantic run. Take away those stabilizers and I suspect that a modern cruise ship wouldn't compare very well to an Olympic class liner.
 
Aug 10, 2002
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Kyle:
The true amount of stability a vessel has is indicated by her Righting Moment. This is the perpendicular distance between the force arm down through the Center of Gravity (G) and the force arm up through the Center of Buoyancy (B) (known as the Righting Arm) times her displacement. You need to find the value of GZ the righting arm for a given angle of inclination at a certain displacement. This is found on her Cross Curves of Stability, drawn up by her designer. Then multiply that GZ times the displacement, to get her Righting Moment. Since in the short term displacement doesn't change we say that GZ is an indicator of the amount of stability a ship has at any angle of list.
The most commonly calculated indicator of stability is the Metacentric Height (GM), but it is only valid for small angles of inclination, say out to about 10 degrees list.
Generally, we find that a ship increases her displacement her Righting Moment increases.
Regards,
Charlie Weeks
 
Mar 22, 2003
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Hi everyone:

Just wanted to let you folks know that a new research article by me has been posted on the TRMA website called: "A Matter of Stability and Trim." This article derives the height above keel for Titanic's Center of Buoyancy (KB), Center of Gravity (KG), and Metacenter (KM) for the night of April 14, 1912, before the accident took place. Also derived are the ship's Metacentric Radius (BM), Initial Righting Arm (GZ) and Righting Moment (WxGZ) as a function of heeling angle in degrees. In addition, the location of the ship's Longitudinal Center of Floatation (LCF) is also derived. These parameters, along with the ship's displacement (W), draft (T), and Metacentric height (GM) on the night of April 14 are also presented and discussed. Knowledge of these parameters are a must for anyone wanting to build an accurate floating model that has the same stability and trim characteristics as the real ship, or for someone interested in analyzing other aspects dealing with its initial stability or trim conditions.

The direct link to the article is: A MATTER OF STABILITY AND TRIM.
 
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Way to go Sam! Since the data from the Titanic's inclining experiments is long lost, there's been a need for this information for a very long time now. I'll be reading over this with a great deal of interest.
 
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