Weathervane

A weathervane is an instrument that shows which direction the wind is flowing. A weathervane is usually attached to the roof of a house or some other elevated object so that it has direct access to the wind. Weathervanes can come in various sizes and shapes. Many are used as decoration ornaments on a house.

There are two design principles that a weathervane must follow.

The weathervane must have equal mass on both sides so that it is balanced in the center.
The weathervane must have unequal areas so that the smallest area, usually the arrow, points to the direction of the wind.

The equal mass principle allows the weathervane to rotate freely and the unequal area principle enables the smaller end of the weathervane to point to the direction of the wind.

Weathervanes can be used for ornamental purposes or for more accurate measurement purposes. Ornamental weathervanes typically have a rooster, called a rooster weathervane, or some other kind of animal as a figure. These weathervanes may also have directional markers to help identify the direction of the wind. Sometimes the ornamental weathervanes may not be as accurate for very light winds because the weight may not be evenly distributed.

Professional weathervanes are usually less fancy and feature simple, yet functional designs. Sometimes a device called an anemometer which measures the speed of the wind may be attached to the weathervane as well.

As a smarter consumer make sure you first determine if you need the weathervane for ornamental or accuracy purposes. Also, figure out where you want to mount the weathervane as it might require additional installation materials. The Internet is a good resource to find pictures of weathervanes as well as purchase directly. Make sure to find out the degree of accuracy of the weathervane before you buy.