Author Topic: How to calculate relative wind for a ship  (Read 310 times)

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Offline SB

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How to calculate relative wind for a ship
« on: June 13, 2017, 06:44:17 PM »
I wonder if anyone can help.
 
I am trying to find an easy way to work out the relative wind direction and speed when one knows the ship course and speed and the forecast/actual wind sped and direction, preferably to do this in an excel format.  Can anyone help?

Many thanks

SB


Offline SB

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Re: How to calculate relative wind for a ship
« Reply #2 on: June 14, 2017, 06:28:46 AM »
Thanks.  This is where I have got to but the formula(s) below do not work when the true wind speed is greater than the ship speed. Can anyone show me what I am doing wrong and how to correct this?  Many thanks.

       E                               F                   G                     H                            I                     J
Ship Speed (kts)   Track    Wind Direction    Wind Speed (kts)   Relative Wind Speed   Relative Wind Sp
    20                            130                  260                   18                           174                            26
    22                            168                  260                   24                           #NUM!                   #NUM!
   19                            288                  260                   15                           266                            4
   10                            341                  260                   10                           260                            0

I=F6+DEGREES(ASIN(H6/E6*SIN(RADIANS(F6-G6+180))))

J=(E6*COS(RADIANS(F6-I6)))+(H6*COS(RADIANS(F6-G6+180)))

 

anything