Apparent Wind and Kiteboarding
The principles of lift generated by apparent wind acting on a windsurfing sail apply in the same way to a kite used in kiteboarding. The action of pulling down on the control bar has the same effect on the kite as sheeting in a windsurfing sail. It increases the angle of attack of the apparent wind on the kite and thus increases its lift. Similarly, to ease the power off, the bar is pushed up to reduce the angle of attack. A kiteboarder has the added advantage that, in light winds, even though he may not be moving quickly over the water on his board, he can make the kite move much faster through the air. To do this the kite is not held at a fixed height, but is moved up and down in a manoeuvre that is referred to as sineing or signing. Because the kite is moving very rapidly through the air, the apparent wind is much faster and the kite can generate a lot more power. The kite is sometimes said to execute a figure eight pattern in the air. However, this is only applicable if the kiter is stationary. Under normal circumstances, the kiter is moving on his board over the water and the kite is also moving with him in the same general direction. If it was possible to attach a smoke canister to the trailing edge of the kite, the pattern traced out in the air would be similar to that shown in the diagram below. Those who have studied mathematics will see a similarity between this pattern and the plot of the mathematical function sine(x) which is called a sine wave. The expression “to sine the kite” most likely originated from this association with the mathematical function.
Understanding Apparent Wind
Copyright © 2008 Denis Wee. All rights reserved.