The COASTAL DRILLER at a draft of 10.5 feet, transfers a portion of the on board liquids from full drill water tank #23 to empty drill water tank #24. What is the change in the free surface correction?
• Free surface effect and how it changes when liquids are moved between tanks • Difference between a full tank, a partially filled tank, and an empty tank for free surface correction • How the vessel’s draft and tank geometry tables are used to find the numerical free surface correction
• Think about whether a completely full tank has any free surface effect, and whether an empty tank has any free surface effect • After transferring liquid from a full tank to an empty tank, what is the new condition of each tank with respect to free surface? • Should the total free surface correction increase, decrease, or stay the same after creating one or two slack (partially filled) tanks instead of a full and an empty tank?
• Verify from your stability booklet or exam tables which tanks are slack (partially filled) before and after the transfer • Check the free surface moments (FSM) or free surface correction values for each relevant tank at the given draft of 10.5 feet • Be sure to use the difference between the initial total correction and the new total correction, not just a single tank’s value
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