Your vessel's drafts are: FWD 19'-09", AFT 20'-09"; and the KG is 24.6 feet. Use the selected stability curves in the blue pages of the Stability Data Reference Book to determine the remaining righting arm at 15° inclination if the center of gravity is 0.5 foot off the centerline.
• Stability curves in the blue pages – locate the curve for the correct displacement and KG and read the GZ at 15° • Effect of off-center KG – horizontal shift of G from centerline reduces the effective righting arm at a given heel angle • Relationship between GZ, GM, and transverse shift of G for small angles of heel
• First, if the KG were exactly on the centerline, what would the righting arm (GZ) be at 15° according to the selected curve? • Next, think about how a 0.5-foot shift of G to one side changes the geometry: does it increase or decrease the righting arm on the heeled side? • For small angles, how can you estimate the reduction in GZ caused by a known transverse shift of G, and then apply that to the 15° value you read from the curve?
• Confirm you are using the correct stability curve for the vessel’s draft and KG = 24.6 ft • Make sure you read the GZ value at 15° from the curve before adjusting for off-center G • Verify whether the heel direction makes the off-center G act to help or oppose the righting moment at 15°, and adjust the GZ value accordingly
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