Your position is 3 miles due east of Montauk Point Light. What is the course to steer to arrive one mile due south of Block Island Southeast Point Light, if you are turning for 8.6 knots, the current is 130° at 1.2 knots, and a northerly wind causes 3° of leeway?
• Set and drift of current on a course line • Effect of leeway from a northerly wind on your heading • Plotting from an assumed DR (dead reckoning) track to make good a required track over the ground
• First, on the chart, locate your starting point and required destination point and draw the straight-line track you want to make good over the ground. What is the true course of that line? • Next, compute the current vector (direction and speed) and the ship’s speed through the water. How does the current vector combine with your ship’s speed vector to change your course made good? • Finally, think about a northerly wind: does it push you to the right or left of your heading, and in which direction must you aim your bow to compensate for 3° of leeway?
• Be sure you distinguish between course to make good (CMG) and course to steer (CTS) – they are not the same when current and leeway are present. • Double-check that the current direction (130°) is the direction toward which the current is setting, not from which it comes. • After you find the heading needed to counteract current, remember to add or subtract the 3° of leeway in the correct direction based on a wind from the north.
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