Windsurfing 101 ... Sails Part 2 - How The Wind Works

How the Wind Works

Basically, wind is a direct result of horizontal differences in air pressure. Air flows from areas of high pressure to low pressure.

For instance, we are sure that you have experienced opening a can of coffee that has been vacuum packed. The noise that you hear (a pop-pssst type of sound) is caused by air rushing from the area of higher pressure from inside the can to the area of lower pressure outside the can.

Obviously, there is more to wind than that but it gives you a basic idea of pressure differences. These pressure differences are a very important factor when it comes to how a sail actually works in the wind.


Wind Directions

Sideshore winds - usually ideal The wind blowing sideshore (from left to right or right to left across the launch area) is the ideal orientation for most forms of windsurfing and it's normally fairly easy to get back to where you started from (as long as you know how to turn around ! ).

Onshore Winds - not always ideal Light onshore winds are usually OK for beginners, as they allow you to sail parallel to the shoreline in fairly shallow water. In coastal areas, if the wind isn't too strong then there shouldn't be much shorebreak surf, but stronger onshore winds will rapidly build up waves.

Offshore Winds - not good ! An offshore wind is generally gusty and fluky close inshore, and gets progressively stronger the further out you go. So the principle danger is being blown away from the shore, and then not able to get back. This is particularly pertinent for the beginner, who will find it all getting more and more difficult, and thus spend more and more time in the water, getting blown where they don't want to go at an ever increasing speed.

Obviously, offshore winds are not so much of an issue on inland waters - the worst that can happen is that you get blown to the other side of the lake/reservoir. Still, even inland it's an unnerving and inconvenient experience, and as far as the beginner is concerned offshore winds are to be avoided at all costs.


How A Sail Works In The Wind

1) When the wind blows on a correctly trimmed sail the air flow separates and passes on either side of the sail.

2) On the leeward side, the wind is accelerated by the built-in curve of the sail. This results in an area of low-pressure.

3) On the Windward side. An area of high-pressure is created, thus creating an imbalance in air pressure.

4) This difference in air pressure actually pulls the sail into the wind.