🔍 Key Concepts
• Effect of a set and drift current on a vessel’s actual speed over the ground
• Using vector addition of ship’s speed through the water and current to find resultant speed
• Interpreting courses and directions on a current diagram (true north, angles, scales)
💭 Think About
• How would you draw the ship’s motion and the current as vectors from the same point, and in what directions would they point on your plotting sheet?
• Once both vectors are drawn to scale, how do you find the resultant vector, and what does the length of that vector represent?
• Is the current helping your vessel (generally from behind), opposing it (generally from ahead), or mostly from the side, and how would each case affect your speed made good compared with 9.5 knots?
✅ Before You Answer
• Convert both speeds to the same scale on your plot (e.g., 1 knot = 1 unit on your diagram) before adding vectors.
• Carefully mark 000°T (straight up) for the vessel’s course and 082°T (slightly above the east line) for the current direction so the angle between them is correct.
• After drawing the resultant, compare its length to the original 9.5‑knot vector to judge if the speed made good should be slightly higher, slightly lower, or nearly the same before picking from the choices.