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Wind. Wind Terms True Wind Relative Wind Apparent Wind Plotting Wind. Wind Problems True Wind Desired Winds. Lesson Overview. True Wind. True direction and speed of wind in relationship with the earth. Ship’s heading and speed does not affect true wind (obviously.). Relative Wind.
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Wind Terms True Wind Relative Wind Apparent Wind Plotting Wind Wind Problems True Wind Desired Winds Lesson Overview
True Wind • True direction and speed of wind in relationship with the earth. • Ship’s heading and speed does not affect true wind (obviously.)
Relative Wind • Relative direction and speed of true wind in relationship to your ship. • You will always know relative wind. • Ship’s anemometer will provide this info.
Apparent Wind • True direction and speed of true wind in relationship to your ship. • Apparent wind is always on the same side of the ship as true wind. (i.e. it will never “cross your bow.”) • As ship’s speed increases, apparent wind moves forward towards the bow.
Wind vector Plotted in the 135° direction. Plotting Wind • Always referred to as direction FROM which the wind is coming. • Plotted in the opposite direction, e.g. plotted as where is wind going? True Wind 315° 15kts
Working Wind Problems • No relative plot. • Remember wind comes from somewhere. Plot where it is going. • Convert relative wind to apparent wind.
Wind Vectors • er vector • ship’s course and speed • rw vector • apparent wind direction and speed • ew vector • true wind direction and speed
Setup • Information you NEED to know: • Your course and speed (er vector) • Apparent wind direction and speed (rw vector)
e r Determining True Wind 1. Plot your course and speed. 270° 15kts
e r Determining True Wind 2. Convert relative wind to apparent wind. Relative Wind 045°R 15kts 45° r Apparent Wind 315°T 15kts w
r w Determining True Wind 3. Move apparent wind vector to end of er vector.
e r w Determining True Wind 4. Draw the ew vector from the center to the end of the rw vector. True Wind going to 202°T 11.5kts True Wind 022°T 11.5kts
Computing Desired Winds • Information you NEED to know: • Where do you want the wind? • True Wind
e w Computing Desired Wind 1. Compute True Wind. True Wind 022°T 11.5kts
e w Computing Desired Wind 2. Plot a sample course of 000°.
W e R w Computing Desired Wind 3. Plot desired winds. (RW) Desired Winds 30° to port, 20kts (330°R, 20kts)
11.5kt arc W e R w Computing Desired Wind 3. From the end of the RW line, swing an arc equal to the speed of true wind. Desired Winds 330°R, 20kts E2 True Wind 022°T 11.5kts E1
W e R w Computing Desired Wind 4. Connect E1W and E2W. Desired Winds 330°R, 20kts E2 True Wind 022°T 11.5kts E1
W e R w Computing Desired Wind 5. Measure angle between 000° & E1W. Measure speed between E1R. Desired Winds 330°R, 20kts 57° to Port True Wind 022°T 11.5kts E1 10kts
W e R w Computing Desired Wind 5. Add angle to true wind to get ship’s course. 022 Desired Winds 330°R, 20kts 57° to Port +57 079 True Wind 022°T 11.5kts E1 Add port Subtract starboard 10kts Ship’s course and speed 079°, 10kts
W e R w Computing Desired Wind 6. Do the same for E2W. 022 122° to Port Desired Winds 330°R, 20kts +122 E2 144 True Wind 022°T 11.5kts 23.5kts Ship’s course and speed 144°, 23.5kts
W e R w Computing Desired Wind E2 E1 Desired Winds 330°R, 20kts 079° 10kts r1 True Wind 022°T 11.5kts 144° 23.5kts r2
