Alexander Graham Bell's Tetrahedral Kites

Alexander Graham Bell is best remembered for inventing the telephone, but the great Scottish inventor’s interests weren’t limited to just one field. Aside from his priceless contributions in the field of acoustics and telegraphy, Bell is also credited with the invention of the metal detector, the audiometer (an instrument used to detect hearing problems), and a device to locate icebergs. Bell and his associates investigated the possibility of impressing a magnetic field on a physical device as a means of recording sound—the basic principle behind tape recorder and hard disc—but could not develop a workable prototype. Bell also had a great passion for aeronautics.

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July 7, 1908. Alexander Graham Bell (right) and his assistants observe the flight of a circular tetrahedral kite.

Bell became obsessed with flight and began studying the possibility of building a kite large and stable enough to carry a man. His first innovation was the box kite, which he built by joining the sides of several triangular kites together to create a box-like structure. Bell realized that by sharing joints and spars, he was able to greatly increase the surface area of his kites with little increase in weight. Then he combined several box-like cells to create large pyramidal structure with three triangular sides and a triangular base. This geometric form, known as a tetrahedral, is one of nature's most stable structures. Although it looks pretty complicated, tetrahedral kites are very easy to fly.

Bell believed that the future of flight lied in kites and not in airplanes, which the Wright brothers had demonstrated. He was convinced that his tetrahedral cell structure was more stable than the Wright brothers’ machine.

In 1907, Bell collected a group of a young men interested in aviation and established the Aerial Experimental Association (AEA), whose purpose was to build a practical powered airplane. The same year, the AEA built the largest tetrahedral kite, named the Cygnet, meaning “little swan” in French. It was composed of over 3,393 cells, was 40 feet long and weighed 91 kg. It successfully flew carrying a human passenger 168 feet above water when towed behind a steamship. Unfortunately, it crashed and tore to pieces on landing.

In the meantime, Bell’s own colleagues—the other members of the AEA— became more interested in producing conventional aircraft, and subsequently a series of airplanes were designed. One of these planes, named the “June Bug”, won the Scientific American Trophy in an exhibition in 1908. Its pilot, Glenn Curtiss, who would later establish a large and successful aeronautical manufacturing company, flew 5,360 feet in just under 2 minutes. By the end of that year, the AEA flew over 150 flights without mishap.

The AEA was financed entirely by Alexander Graham Bell’s wife, Mabel Bell. When the funds ran out, the association was disbanded. In less than two years of its existence, the AEA made many innovative contribution to airplane design such as cockpit enclosures and tail rudders. One of Bell’s invention was the aileron, that is now a standard component on all aircraft.

Despite the gradual disinterest in kites and the growing success of the American brothers’ airplanes, Bell made two more massive tetrahedral kites, named Cygnet II, and III, but neither one was successful. His Cygnet III with a 70-horsepower motor was reported to have flown only one foot. Bell eventually abandoned his experiments in 1912.

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