Your vessel's drafts are: FWD 17'-05", AFT 20'-01"; and the KG is 25.6 feet. What is the righting moment when the vessel is inclined to 45°? (Use the reference material in Section 1, the blue pages, of the Stability Data Reference Book)
• Use the Hydrostatic Curves/KN curves from Section 1 (blue pages) for the vessel at the correct draft condition • Relationship: Righting moment = Displacement × GZ (or KN-based equivalent, depending on the data given) • Effect of actual KG (25.6 ft) when using KN or cross-curves to obtain GZ at 45°
• What table or curve in the blue pages lets you account for both the ship’s drafts and the angle of heel (45°)? • Once you know the vessel’s displacement at the given drafts, how do you combine it with the lever arm at 45° to get a moment in foot-tons? • How does the given KG modify the lever you read from the curves so you obtain the true GZ at 45°?
• Be sure you are using the correct displacement for the listed drafts (don’t assume even keel if it isn’t). • Confirm whether the curves you’re using are KN curves or GZ curves, and apply the correct formula to adjust for KG if needed. • After calculating, verify that your result’s units are foot-tons, and that its magnitude is consistent with the ship’s displacement and a reasonable GZ at 45°.
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