Understanding the speed of the wind while sailing is a very useful skill that that can help you make a number of essential decisions including:
o Which sails to put up and use
o When to reef the sail
o The best point of sail given the current conditions
o How to set your sails for optimal performance and power
Many boats are now equipped with wind and speed indicators that automatically calculate the wind speed for you. However, if you don’t happen to have one handy, there are a number of indicators you can use to help determine the current wind speed.
Flags are an excellent source of wind direction and speed; however they can only tell you the speed up to a certain point. The following indicators can be applied to flags to determine wind speed:
1. Flag Flips Open Occasionally: 1-3 knots
2. Flag is Partially Extended: 4-6 knots
3. Flag is Fully Extended: 7-10 knots or more
Wind Socks are used by pilots to determine wind speed and direction and are very common on tops of buildings where a helicopter could land. They are also limited in their use since they max out at a certain wind speed. The general rule of thumb for wind socks is the following:
1. Oriented Toward the Wind (Not Extended): 3 knots
2. Half Way Extended: 7.5 knots
3. Fully Extended: 15 knots or more
Waves are a great source of information regarding wind speed when there are no land based indicators. One excellent measure is the Beaufort Wind Scale which was created in 1805 by Admiral Sir Francis Beaufort of the British Royal Navy. This scale identifies the speed of the wind based on how a wave looks and acts. A number is usually given to each level as a short hand method for identifying the wind conditions.
1. Light Air; Ripples Appear: 1-3 knots (Beaufort Level 1)
2. Light Breeze; Small Wavelets; No Whitecaps: 4-6 knots (Beaufort Level 2)
3. Gentle Breeze; Large Wavelets; White Caps Form: 7-10 knots (Beaufort Level 3)
4. Moderate Breeze; 1-4 ft Waves; Numerous Whitecaps: 11-16 knots (Beaufort Level 4)
5. Fresh Breeze; 4-8 ft Waves; Whitecaps and Spray: 17-21 knots (Beaufort Level 5)
6. Strong Breeze; 8-12 ft Waves; Whitecaps and Spray: 22-27 knots (Beaufort Level 6)
The Beaufort scale continues until it reaches Hurricane winds at level 12. The scale can also be associated with land based effects such as trees bending or breaking.
The ability to determine wind speed will help you sail effectively, efficiently, and safely. With knowledge of the current wind speed a sailor can decide if they need to put up a Genoa or a storm jib. In addition, understanding the speed and character of the wind will help determine how fast you are moving and how long it will take to get from point A to point B.