Your vessel is on course 270°T, speed 10...

Your vessel is on course 270°T, speed 10 knots. The apparent wind is from 10° off the port bow, speed 30 knots. From which direction is the true wind?

🔍 Key Concepts

• Relative (apparent) wind vs. true wind – how the vessel’s motion changes the wind you feel on board • Vector addition – how to combine the ship’s motion vector and apparent wind vector to get the true wind vector • Courses and bearings in True (°T) – relating directions to the bow (port/starboard, ahead) back to true bearings

💭 Think About

• Sketch the vessel’s course as an arrow pointing 270°T and show the apparent wind coming from 10° off the port bow. Which true direction (°T) does that line point back to? • Remember that apparent wind is what you feel on a moving vessel. To get true wind, how do you combine (add or subtract) the ship’s velocity vector and the true wind vector? Set up a simple vector diagram. • Compare the speed of the ship (10 knots) and apparent wind (30 knots). In your vector triangle, where should the longest side be, and how does that affect the true wind direction relative to the bow?

✅ Before You Answer

• Be clear which way the port bow is relative to the vessel’s heading of 270°T (port is to the left when looking forward). • Verify that you are using the correct vector relationship: Ship’s motion + True wind = Apparent wind (not the other way around). • After you find a possible true wind direction, check that when you combine it with the vessel’s motion (10 knots on 270°T), the resulting apparent wind would indeed be about 10° off the port bow at 30 knots.

🔍 Key Concepts

💭 Think About

✅ Before You Answer