Estimating Wind Direction And Speed
Estimating Wind DirectionA simple method is to wet a finger and hold it up; the side which feels cold first is the windward side. Another way is to observe the direction in which low cloud or smoke are moving. If these are not present, as an alternative, a handkerchief may be held up to flutter in the wind. By these means the operator can judge the kite's line of flight, and so will be able to guard against any possible obstructions, such as trees or overhead wires. Estimating wind direction is also useful in making forecasts and flight records, which are described below. In these cases a weather-cock and a pocket compass are the best guides. If there is no local weather-cock, the reader might be interested in the making of a simple type, as shown in Chapter 7. On-the-spot wind checks are carried out with a compass, and it is used in conjunction with the tests mentioned in the first paragraph. When the compass is held horizontally in the hand the needle points to the magnetic north, which is not the exact geographical north. The slight variation must be ascertained in any given place in order to find the true north. For example, in England the compass points about 8 degrees west of geographical north.
Estimating Wind SpeedThe Amended Beaufort Wind Scale, printed at the end of the chapter, is valuable for this purpose; as also is an anemometer. The Wind Scale was formulated in 1805 by Admiral Sir Francis Beaufort for measuring the velocity of the wind and since then has been periodically revised. An anemometer is an instrument for registering the speed of wind. Instructions for making and using a simple type are given in Chapter 7.
Estimates of wind speed are important for two reasons. In the first place, speed and strain are closely connected. For example, if wind speed is 5 m.p.h. and it increases to 10 m.p.h. then its strength intensifies and the strain on the kite increases. The strain becomes more pronounced as the kite climbs higher. Consequently, there is a stronger pull on the kite line. The larger the kite the more do these considerations have to be borne in mind. In the second place, wind speed is a factor to be noted when making weather forecasts and flight records, which are now suggested.