At 2155: Montauk Point Light bears 249°T Watch Hill Point Light bears 335°T Block Island North Light bears 045° T At this time, you wish to change course to 288°T. The current has a set of 355°T and a drift of 2.0 knots. If your vessel is turning RPM's for 9 knots, what course must you steer in order to make your desired course good?
• Set and drift and how they affect your course made good versus your heading • Using a current triangle / vector triangle to combine ship’s speed through the water and current to get course made good • Difference between course steered (heading) and course made good (CMG)
• First, sketch a vector for your desired course and speed made good (9 knots on 288°T). How does the current vector (2 knots on 355°T) need to be applied to that? Think about tip‑to‑tail vector addition. • Ask yourself: are you correcting to the right or left of 288°T to counter a current setting almost due north? Which side of your bow is the current pushing you toward? • When you draw the current triangle, which angle represents the course to steer and which represents the course made good? Make sure you label them carefully so you don’t mix them up.
• Be sure you are using true directions for all vectors (no conversion to magnetic needed here). • Check that you’ve used speed through the water (9 knots) for the ship’s vector and 2 knots for the current, not the other way around. • Confirm that your final course to steer is reasonably close to 288°T but offset in the correct direction to counter the north‑setting current.
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