Your vessel's drafts are: FWD 22'-04", AFT 23'-06"; and the KG is 22.4 feet. Use the selected stability curves in the blue pages of the Stability Data Reference Book to determine the righting arm at 19° inclination if the center of gravity is 1.3 feet off center.
• Cross curves of stability (GZ curves) in the Stability Data Reference Book • Effect of off-center KG on the righting arm at a given heel angle • How to read the blue pages stability curves for a specific displacement and angle
• First, think about how to find the basic righting arm (GZ) at 19° for the ship’s actual displacement and KG shown on the blue curves, before you worry about the off-center shift. • Ask yourself: how does a transverse shift of G (1.3 ft off centerline) modify the righting arm at a given heel angle? Does it increase or decrease the effective GZ? • Consider the geometry: what is the horizontal separation between the shifted G and the buoyancy line at 19° heel, and how does that relate to the sine or cosine of the heel angle?
• From the blue pages, be sure you are using the correct displacement curve that matches the drafts given (FWD and AFT) and their corresponding displacement in the reference book. • Confirm you have the correct GZ at 19° for a centerline KG of 22.4 ft before applying any correction for the 1.3-ft off-center shift. • When applying the off-center G correction, carefully check the trigonometric function and units (feet vs degrees) so the adjusted righting arm makes physical sense.
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