You are loading in a port subject to the tropical load line mark and bound for a port subject to the winter load line mark. You will enter the summer zone after steaming one day, and you will enter the winter zone after a total of eight days. You will consume 36 tons of fuel, water, and stores per day. The hydrometer reading at the loading pier is 1.002, and the TPI is 47. What is the minimum freeboard required at the start of the voyage? Reference Table BL-0005 below.
• Seasonal load lines and freeboards: Tropical, Summer, and Winter values from Table BL-0005 • Dock water (hydrometer) correction using the given fresh water allowance and relative density 1.002 • Change in draft from consumption of fuel, water, and stores using TPI (tons per inch immersion)
• Work backwards from the strictest seasonal requirement you will face on the voyage. Which zone has the largest required freeboard? • Figure out how many inches of freeboard the vessel will gain between departure and entering the winter zone from (a) going from dock water to seawater and (b) burning 36 tons/day for 8 days. • Once you know how many inches of freeboard you will gain, subtract that from the winter freeboard requirement to find what freeboard you must start with at the loading pier.
• Compute the dock water allowance from the 10-inch fresh water allowance and hydrometer 1.002 (hint: it will be slightly less than 10 inches). • Confirm total weight burned: 36 tons/day × 8 days, then convert this to inches of freeboard change using TPI = 47 tons/inch. • After finding the starting freeboard, double-check that by day 1 (entering the summer zone) the freeboard is at least the summer value from the table.
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