Coastal Skipper and Yachtmaster Quiz · Chartwork and passage planning
A marina sill dries 1.2 m. You draw 1.8 m and want 1.0 m under the keel. Reading this curve, between what times can you cross the sill?
A graph of height of tide against time, on a grid with a line for every metre and every hour. The curve rises smoothly from low water of 1.0 m at 0600 to high water of 5.0 m at 1200 and falls again to 1.0 m at 1800. Read off the curve: 2.0 m at 0800, 4.0 m at 1000, 4.0 m at 1400 and 2.0 m at 1600. Caption: sill dries 1.2 m, draught 1.8 m, clearance wanted 1.0 m.
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1000 to 1400. First find the height of tide you need: 1.2 m to cover the sill, plus 1.8 m of draught, plus 1.0 m of clearance, which is 4.0 m. The curve rises through 4.0 m at 1000 and falls back through it at 1400, so that is your window.
