Chart Navigation & Plotting · Speed-Time-Distance — Distance Made Good with Current
You steer to make good a track at a planned 10 knots speed of advance, but a 2-knot fair (following) current is along your track. Your speed through the water can therefore be:
- A12 knots to make good 10 knots
- B8 knots, while still making good 10 knots over the ground✓ Correct
- C10 knots regardless of current
- D20 knots
Explanation
A fair current adds to your speed over the ground. To make good 10 knots SOA with a 2-knot following current, you need only 8 knots through the water (8 + 2 = 10). A head current would require a greater speed through the water than the SOA.
Authority: Bowditch (Pub. No. 9), Current Sailing
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