Use the material in Section 1, the blue pages, of the Stability Data Reference Book. If the KG is 24.2 feet, and the drafts are: FWD 23'-04", AFT 24'-05"; at what angle will the vessel lose positive stability?
• Using forward and aft drafts to find the vessel’s displacement in the hydrostatic data (Section 1 blue pages) • Relating KG and the cross curves/righting arm (GZ) curves to find the angle of vanishing stability • Understanding that the vessel loses positive stability when GZ returns to zero at large angles
• From the given drafts, how do you determine the vessel’s displacement using the tables/curves in Section 1? • Once you know the displacement, which specific curve or table in the blue pages lets you relate KG = 24.2 ft to the angle where GZ becomes zero again at large heel? • On the chosen curve, how can you visually identify the first non-zero GZ and then the angle where GZ crosses back through zero as the ship heels further?
• Be sure you are using the correct displacement line that matches the drafts given (interpolate if needed). • Confirm you are reading the curve that corresponds to the actual KG = 24.2 ft, not a different KG or GM. • Verify that the angle you select is where positive righting arm (GZ) just disappears (crosses zero again after its maximum), not where it first becomes positive.
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