You are loading in a port subject to the winter load line mark and bound for a port subject to the tropical load line mark. You will enter the summer zone after steaming four days, and you will enter the tropical zone after twelve days. You will consume 38 tons of fuel, water, and stores per day. The hydrometer reading at the loading pier is 1.004, and the average TPI is 72. What is the minimum freeboard required at the start of the voyage?
• Load line zones and seasonal freeboards – how winter, summer, and tropical freeboards (95, 88, 81 inches) relate to each other and which one controls at different parts of the voyage. • Dock-water vs. salt-water correction – using the hydrometer reading 1.004 and the 6-inch fresh water allowance to find how much deeper the ship will float in the loading water compared to salt water. • Consumption of fuel/water/stores – using 38 tons/day and TPI 72 to find how many inches of draft (or freeboard) change occur during the 4 days in the winter zone and the next 8 days in the summer zone.
• Which load line (winter, summer, or tropical) actually limits you at departure, given that you start in a winter zone but will later be in summer and then tropical zones after burning off weight? • When you cross from winter to summer, will the ship be lighter or heavier than at departure, and how does that compare to the required summer freeboard? Do the same check for the summer-to-tropical boundary. • How do you convert total tons consumed between zone boundaries into inches of draft change using the TPI, and how does that affect freeboard at those times?
• Compute the dock-water allowance using the 6-inch fresh water allowance and the hydrometer 1.004; be sure you know whether to ADD or SUBTRACT this from the required winter freeboard at departure. • Calculate the change in draft (or freeboard) for 4 days and for 12 days of consumption using 38 tons/day and 72 TPI; verify the units (tons and tons per inch). • At each key point (departure in winter water, entry to summer, entry to tropical), check that the calculated freeboard is not less than the required seasonal freeboard for that zone before choosing an answer.
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