π Key Concepts
β’ Load line zones and marks: how Tropical, Summer, and Winter freeboards compare on the same ship
β’ Change of draft from consumption: using TPI to find how many inches the ship rises as fuel, water, and stores are used
β’ Dock water vs salt water: using the hydrometer reading and the given fresh water allowance to correct the loading condition
π Think About
β’ Track the voyage day by day: what load line applies at the start, after 6 days, and after 9 days? At each point, what is the maximum allowed draft (minimum freeboard)?
β’ Calculate the total weight of fuel, water, and stores consumed before entering the winter zone, then convert that to inches of change of draft using TPI.
β’ Use the hydrometer reading of 1.020 and the 5-inch fresh water allowance to find how many inches of extra sinkage you have in the loading water compared to salt water, and adjust your starting freeboard accordingly.
β
Before You Answer
β’ Be sure you are using freeboard values from the deck line given in the table (61" T, 66" S, 71" W) and the fact that T is 5 inches above S and W is 5 inches below S.
β’ Confirm the total consumption before entering the winter zone: days Γ 28 tons/day, then divide by 46 tons per inch (TPI) to get inches of change of draft.
β’ Before picking an answer, verify you have applied both corrections: (1) rise due to consumption of weights, and (2) salt-water correction from hydrometer 1.020 using the 5-inch fresh water allowance.