🔍 Key Concepts

• Free surface effect and how it changes when you create a new slack tank • How to use the table of free surface moments for the COASTAL DRILLER (for specific tanks and depths) • The difference between a tank that is full or empty (no free surface) versus partly filled (has free surface)

💭 Think About

• Ask yourself: Before the transfer, which tank(s) actually had a free surface, and after the transfer, which tank(s) have a free surface? • Think about whether the full tank’s free surface moment changes much when you remove only 2.0 feet of liquid from the top – is it still almost full, or now clearly slack? • Focus on the increase in free surface moments: should you be adding the new free surface in tank 6, subtracting any change in tank 23, or both?

✅ Before You Answer

• From the stability data, find the transverse free surface moment per foot of liquid depth for tank 6 and for tank 23 at the relevant fill condition • Be sure you are using the free surface value for the actual depth of liquid in each tank after the transfer, not the capacity value • Confirm whether you should compute change in FSM = FSM_after − FSM_before, and apply that only to the tanks whose condition (full/empty/slack) actually changed