With no environmental forces on the DEEP DRILLER, the average of the starboard drafts is 59.0 feet, and the average of the port drafts is 61.0 feet. KGT is 52.84 feet. What is the value of TCG?
• Difference between port and starboard drafts indicates the direction and angle of list • Relationship between TCG (transverse center of gravity), metacentric height/KGT, and the angle of heel • How the sign convention for TCG (port vs starboard) is tied to which side is drafting deeper
• First, decide which side the vessel is heeled toward based on the given port and starboard drafts. What does that tell you about the direction (sign) of TCG? • Think about how a small list angle relates to the difference between port and starboard drafts. How can you estimate the angle of heel from those drafts? • Once you have the direction of list and the approximate angle, how does that angle combine with KGT to give the off-center distance of G (the TCG)?
• Be clear on which side is deeper and which is shallower and how that links to the sign of TCG • Confirm you’re using the relationship between heel angle, transverse metacentric height (or KGT), and TCG, not a longitudinal stability formula • Before choosing, compare the magnitude of your computed TCG with the answer choices: for a small difference in drafts, should TCG be large (feet) or small (fractions of a foot)?
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