Go fly a kite

Waimarino Bulletin, Volume 4, Issue 36, 24 February 1987, Page 7

Go fly a kite

Before attempting to fly any kite, a person should try to understand the basic aerodynamic principles that enable a heavier-than-air object to stay aloft. Although kites have been flown for several thousand years, it was not until the 19th century that anyone seriously studied how kites fly. The basic principles are really quite simple. An airplane flies by displaeing the air as it moves along. Kites, however, are tethered — that is, they are held in place by the kiteflying line. Air blown against the kite's coVer is blocked by the cover and, therefore, forced to move around the kite. If the kite is held at the proper angle to the wind, more air is deflected down around the kite than is forced up and over the kite. This downward deflection of the air flowing around the kite lifts the kite upward, overcoming the force of gravity. Other factors act on the kite simultaneously. The flat plane of a kite breaks the wind up into swirls of air turbulence. These turbulence swirls slow the air passing around the kite, reducing the lift caused by the downward deflection of air and increasing the drag. Drag pulls the kite backwards. The kite line, however, prevents the kite from moving backwards, and the net effect of these forces —

gravity, lift and drag — is to move the kite upwards. Getting any kite — from the most basic to the most complex — to'fly is a matter of achieving a successful lift-to-drag ratio; that is, the lift must exceed the drag. Naturally, the kite has to be constructed properly and maintained in perfect balance. Assuming that these prerequisites are fulfilled, obtaining the correct lift-to-drag ratio depends on angling the kite to the wind properly, a task which is accomplished by a carefully constructed bridle. Kites with dihedral (two-planed) angles or side surfaces are easier to keep balanced and angled properly. Flat-surface kites, although helped by the curve depressions in their coverings, need tails to react to air turbulence from behind and to provide the necessary stability. The table makes it easy to judge wind velocity and to select the nroDer kite to flv.

With these aerodynamic principles in mind, consider some of the other conditions necessary for successful kiteflying. The first is the weather. A steady breeze of five to 25 knots is generally considered good kite-flying weather. Different types of

The next consideration in effective kite-flying is to select the right place to launch the kite and keep it aloft. A large park or open field — a place where there are no trees or buildings to block the wind or to cause air turbulence — is ideal.