And why is wind data so important? Each sailor must know which direction the wind is blowing in order to be able to perform even the simplest maneuvers and calculate routes. The wind can make the difference between a great trip and a terrible one.

The Wind Triangle

The calculation of wind direction can be easily explained through the “Wind Triangle”, which shows the relationship between the speed of the boat, the Apparent Wind (the wind you notice while sailing), the Real Wind (the wind in relation to the surface of the water) and the heading of the compass.

True Wind Direction

The True Wind Direction is the direction of the wind according to the compass in relation to the water. It is measured from the boat, which can be facing any direction and with a little luck sailing at good speed. Thus, to obtain an accurate reading, the wind direction must be calculated using multiple sensors and not just one. Simply put: Real Wind = Boat Speed ​​+ Apparent Wind.

Angles vs. Addresses

It is necessary to make an important distinction when we talk about instruments, and in general sailing: Normally we refer to a value relative to the boat as an Angle (for example, the Apparent Wind Angle is 35 degrees starboard of the bow) . A value relative to an external point such as water or another point on Earth is a Direction (for example, the True Wind Direction is 315 degrees magnetic).

Unfortunately it is quite common to see True Wind Direction used to actually refer to True Wind Angle – even by instrumentation manufacturers who should know better on this topic. When using your instruments you should always know the difference between angles and direction.

Advanced wind calculations

Using Heading and True Wind Angle data to calculate True Wind Direction is a sufficiently accurate formula to monitor wind shifts. However, this does not take into consideration how the boat is traveling through the water.

When you sail heeled into the wind, the leeway effect (when the boat moves on the water sideways) will come into play. If you add the angle of leeway to the heading of the ship you will get the Course. Advanced instrumentation systems calculate wind using Course and not Heading.

The Course is the direction in which you navigate through the water. You should not confuse it with the COG, which is the Course Over the Ground.

And that's the end of our advice for this week, but don't miss the next chapter where we will delve a little deeper into the topic of “Showing the data”, see you soon.