Your ETA at Chesapeake Bay Bridge and Tunnel between trestles B + C is 2300. If your engine speed is 9.8 knots, what will be your approximate speed over the ground, at that time, allowing for the predicted current?
• Difference between speed through the water (engine speed) and speed over the ground (SOG) when current is present • How favorable current (with you) and adverse current (against you) change SOG compared to engine speed • Using predicted set and drift of the current at 2300 for the Chesapeake Bay Bridge Tunnel area from a current table or exam current diagram
• Is the current at 2300 acting more with your course, more against it, or mostly from the side? How would that affect your speed over the ground compared to 9.8 knots? • Look at the drift value at 2300. If the current is mostly in the same direction as your course, would you add or subtract that drift from 9.8 knots to approximate SOG? • Compare each answer choice to 9.8 knots. Which options represent a strong helping current, a strong opposing current, or only a small effect? Which one best matches the predicted current at that time?
• Confirm from the exam current diagram whether the current at 2300 is favoring or opposing your course between trestles B and C • Check the magnitude of the current (knots) at 2300 and compare it to how far each answer choice is from 9.8 knots • Make sure you are using speed over the ground, not confusing it with speed through the water or average speed over the entire trip
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