kite

kite, oldest known heavier-than-air craft designed to gain lift from the wind while being flown from the end of a flying line, or tether.

Over the millennia, kites have been used to ward off evil, deliver messages, represent the gods, raise banners, discover natural phenomena, propel craft, drop propaganda leaflets, catch fish, spy on enemies, send radio signals, measure the weather, photograph the Earth, and lift passengers skyward. Modern kites are flown mostly for pleasure and sport, in addition to being a folk form of artistic expression. The kite was the ancestral aircraft that launched manned flight.

History

Europe and the West

Kite flying began much later in Europe than in Asia. While unambiguous drawings of kites first appeared in print in Holland and England in the 17th century, pennon-type kites that evolved from military banners dating back to Roman times and earlier were flown during the Middle Ages.

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During the 18th century tailless bowed kites were still unknown in Europe. Flying flat arch- or pear-shaped kites with tails had become a popular pastime, mostly among children. The first recorded scientific application of a kite took place in 1749 when Alexander Wilson of Scotland used a kite train (two or more kites flown from a common line) as a meteorologic device for measuring temperature variations at different altitudes.

Three years later, in June 1752, in what is the most famous of kite experiments, the American inventor and statesman Benjamin Franklin, with the aid of his son, lofted a flat kite fitted with a pointed wire and silk sail during a thunderstorm. Somehow both father and son avoided electrocution as a metal key attached to the flying line became electrified. Franklin proved that lightning was the natural phenomenon called electricity, not the wrath of the gods. One immediate and practical outcome of the experiment was Franklin’s invention of the lightning rod.

The first manned flights

Although kites had been used as man lifters since ancient times, the kite’s greatest technological contribution was in the development of the airplane. In the 19th century the British scientist Sir George Cayley, known as the father of aeronautics, used modified arch-type kites to make “flying machines,” which in 1853 led to the first recorded manned flight in a glider. Cayley’s comprehension of both thrust and lift was the leap in understanding that would ultimately quell the ancient and faulty obsession with flapping wings as a means for manned flight. Other visionaries built man-lifting kites, many of which were rudimentary biplane gliders. Otto Lilienthal of Germany experimented with “aeroplane” kites in the 1890s and became the first man to soar in one of his kites in true hang-gliding fashion.

Around 1900 Orville and Wilbur Wright, self-taught aeronautical engineers who ran a bicycle shop in Ohio, began testing their biplane designs as kites. It was the Wright brothers who first focused on control—the missing ingredient for manned flight that had baffled other aviation pioneers. The brothers constructed a special box kite and braced the wings with wires in such a way that they could be twisted in opposite directions to make the kite bank and turn. They called the principle “wing warping,” and it was the breakthrough that had eluded the great inventors who had worked on flight—from Leonardo da Vinci to Alexander Graham Bell.

With the invention of the airplane, the kite fell from favour among adults. Except for occasional meteorologic survey work, which continues to the present, the kite’s status changed from a serious scientific instrument to a child’s toy once again.

Kite structure

The form and size of kites are remarkably varied. Some kites can fly in the lightest breeze, while other designs require steady winds. Kites can be made of two sticks covered with a sail material or be constructed in a configuration requiring a complex framework. Until recently, the materials for constructing kites—bamboo or wood, fabric or paper, and string—had remained essentially unchanged for more than 2,000 years. Today, kites are often built with synthetic materials.

There are eight generic kite types. The flat, bowed, box, sled, and delta require a rigid framework fitted with a sail material, as does the compound, which is formed by integrating two or more of the above types to form one kite. A radical departure in design, the parafoil, a soft airplane-wing shape with no rigid members, used by the skydiver as a parachute, assumes its efficient flying profile entirely from the wind’s inflating the air channels along the leading edge. Another deviation in form is the rotor, a kinetic kite that manifests lift and the Magnus effect through a horizontal spinning vane sandwiched between two cylinders—a rigid frame and sail in one.

Although tailless kites had been common in Asia for centuries, it was not until 1893 that William A. Eddy, an American journalist with an interest in meteorology and kite aerial photography, made a significant contribution to kite development in the West by introducing his now-familiar tailless, elongated diamond-shaped design. The Eddy kite, an adaptation of the ancient Javanese bowed kite known as the Malay in the West, was a reliable and popular flier that ignited a renewed interest in kite flying and was briefly used by the United States Weather Bureau. In Australia that same year, British-born explorer and inventor Lawrence Hargrave contrived the box kite, or cellular kite, as a by-product of his research to develop a stable three-dimensional lifting surface for powered manned flight. Exceptionally steady in high winds, Hargrave box kites flown in train, using flying line of piano wire, soon replaced the Eddy kite and were used for meteorologic work well into the 1920s.