At 1756 you determined your vessel's position to be 41°10.4'N, 71°59.2'W. From this position, you wish to change course to head for a point 5 miles west of Block Island North Light. With a reported set of 050°T, a drift of 2.0 knots and turning RPMs for 14 knots, which course should you steer to make good your desired course?
• Current triangle / current sailing: combining ship’s speed and set & drift to find course to steer • Converting set and drift (050°T at 2.0 knots) and ship’s speed (14 knots) into vectors • Relationship between desired track (to a point 5 miles west of Block Island North Light) and the course to steer to offset current
• First, sketch or visualize the track line from your known position to the destination point. What direction (true course) does that track run before applying current? • How does a current setting 050°T with 2 knots affect a vessel moving at 14 knots? Which way will it push you relative to your desired track? • When you construct the current triangle, on which side of the desired course line will your course to steer lie, and will it be a larger or smaller angle than the track?
• Be sure your speed through the water (14 knots) is separate from the speed over ground that results from current. • Verify that you are using true bearings consistently (no magnetic/compass conversions in this problem). • Check that your constructed triangle makes sense: the resultant (track made good) should align with the line from your starting fix to the destination point.
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