🔍 Key Concepts

• Understanding how to read a sounding and convert it to volume added when filling a tank with seawater • Using the tank’s sounding table or capacity curve to find weight added per inch or per foot of sounding change • Calculating vertical moment as weight × vertical distance (VCG change or KG reference)

💭 Think About

• How do you go from a sounding in feet to the weight of ballast added when you fill the tank from its current level to full? • Once you know the added weight of ballast, what vertical distance should you be multiplying by to find the vertical moment for that added ballast? • Which answer choices are reasonable given the approximate size of a drillship tank and typical ballast weights?

✅ Before You Answer

• Make sure you are using added ballast only (difference between final and initial condition), not the full tank contents • Confirm you are using the correct vertical arm (distance from the reference point to the tank’s center of gravity) for the ballast added • Double-check that your units are consistent: weight in long tons and distance in feet, so moment is in ft-long tons