Your vessel's drafts are: FWD 23'-10", AFT 26'-00". The LCG of the forepeak is 200 feet forward of amidships. How many tons of ballast must be pumped into the forepeak in order to have a drag of 1 foot? (Use the reference material in Section 1, the blue pages, of the Stability Data Reference Book)
• Trim and moments: How adding weight forward affects trim and draft difference between bow and stern • Moment to Change Trim 1 Inch (MT1" or MCT 1') from the Stability Data Reference Book tables and how to use it • Using LCF/LCG distances (Longitudinal Center of Flotation / Longitudinal Center of Gravity) to compute trimming moments
• From the current drafts, determine the vessels present trim (drag) and the trim you want to end up with. How much total change in trim (in feet or inches) is required? • Once you know the total trim change, how do you use the ships MCT value from the blue pages to find the trimming moment needed? • The ballast goes into a tank 200 feet forward of amidships. How do you turn that trimming moment into a required weight, using its distance from the LCF or from amidships?
• Be sure you are using MCT at the correct displacement taken from the Stability Data Reference Book for a vessel at drafts close to the mean draft of the problem. • Convert all trim changes into the same unit (all inches or all feet) before using MCT. • When you compute required weight, confirm: Weight (tons) = Trimming Moment (ft-tons) ÷ Lever (ft), and that you used the correct lever for the forepeak LCG.
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