I am trying to figure out how to calculate the boat velocity using wind speed and wind direction. I have tried to find sources online but this is the only useful site I managed to find: https://sites.google.com/site/yoavraz2/sailingboatspeedvs.windspeed Unfortunately it has been a while since I did maths and I'm struggling with understanding how the VB (boat velocity) in the examples on the website is calculated and was wondering if anyone could explain it at all? The results don't have to be 100% accurate so as long as a rough estimation of speed is achieved that's fine. The part I am most struggling with is how the VB is calculated using a - apparent wind as I though you needed the boat velocity (VB) to figure out a. Thank you in advance for any help.