🔍 Key Concepts

• Longitudinal moments and how moving a liquid between two tanks affects total moment about the longitudinal reference point (often midships or aft perpendicular) • How to compute the moment of a weight: (weight) × (longitudinal distance from the reference) • The sign convention for increase vs. decrease in longitudinal moments when shifting weight forward vs. aft

💭 Think About

• Identify which tank (23 or 6) is farther forward or aft on the vessel and decide whether moving water between them moves weight forward or aft overall • Convert the 2.0 feet of drill water in the tank to a weight using the tank capacity data (volume per foot of sounding × density of drill water) • Compute the change in longitudinal moment as weight × distance shifted between the two tank LCGs (longitudinal centers of gravity) and then decide whether that change is an increase or a decrease based on the sign convention in the stability booklet

✅ Before You Answer

• Confirm the exact longitudinal position (LCG) of tank 23 and tank 6 from the Coastal Driller data table • Verify the volume per foot of sounding (or capacity curve) for each drill water tank so you get the correct weight for 2.0 feet of drill water • Double-check the direction of shift (forward or aft) and how that direction is treated in the vessel’s sign convention for longitudinal moments (forward positive or aft positive) before selecting increase vs. decrease