🔍 Key Concepts

• Moment = Weight × Distance from reference (LCG) for longitudinal moment calculations • Effect of discharging liquid from a tank on the vessel’s total weight and longitudinal moment • How to use tank sounding/percentage full tables on the Coastal Driller stability data sheet to find weight of liquid for a given depth change

💭 Think About

• First, think about whether discharging drill water will make the total longitudinal moment increase or decrease. What sign (positive or negative) should you expect? • How do you find the weight of 2.5 feet of drill water removed from tank 23 using the stability booklet or tank table? • Once you know the weight change, how do you combine it with the tank’s longitudinal position (LCG) to compute the change in longitudinal moment?

✅ Before You Answer

• Confirm the LCG (longitudinal center of gravity) or longitudinal position used for drill water tank 23 on the Coastal Driller plan or tank table • Verify the weight of 2.5 feet of drill water, not the total tank capacity, using the correct density and tank calibration • Check that the sign of your final moment change reflects that the weight is being removed (discharged), not added (loaded)