Here’s an interesting fact of the day. Alexander Graham Bell, the man credited with the discovery of the modern telephone device, was absolutely gaga about heavy lifting Tetrahedral style kites. Indeed, he spent the last part of his life feverishly working on kite design and launches at in his laboratory in Baddeck, Nova Scotia. Bell began building kites in 1899. He was led to experiment with them because of his interest in the flying machine problem. Orville and Wilbur Wright’s accomplishment at Kitty Hawk was still several years off, and the idea of lifting a manned heavier than air contraption was most decidedly not only on their minds. Bell’s belief (shared by a large cadre of men) was that a successful kite will also make a successful flying machine. A kite that will support a man and an engine in a ten mile breeze will probably also support the man and engine when driven by a motor at the rate of ten miles an hour. This proposition had not been actually proved at the time, and it was a driving preoccupation with Bell.
Bell’s earliest involvement with kite-building and heavy lifting designs arose from a preoccupation with the Box Kits of Lawrence Hargrave:
Hargrave was an inventor and early aeronautical engineer from Australia, who had been designing box style kites since 1892. The problem with his designs was that they worked very well in smaller sizes but rapidly lost efficiency the bigger you made them. Bell connected greater lifting area to greater wing size, and his designs sought to arrive at the efficiency point where lifting was not compromised by the weight of a larger sized wing. To accomplish this, Bell designed some of the most beautiful aerial contraptions ever– tetrahedral kite designs.
Tetrahedrons are a sided polygon, connected in a pyramid shaped framework which is an inherently strong structure. A tetrahedral kite is formed when two sides of the four sided figure are joined, then a number of these are joined together into a large tetrahedral kite.
As you can see, the kite designs were in a number of shapes and sizes, and gradually larger with more lifting ability.
Bell was able to prove that you can create a large kite, of any size desired, without any increase in the weight to sail area. Extra bracing in larger kite structures is not really required as the tetrahedral cell braces itself. In theory the more cells you add to a structure the stronger it becomes. Bell’s tetrahedral cells were made separately and are were 10 inches on a side. They were made from spruce rods, and covered with bright red silk. Each cell weighed about an ounce, and were joined with metal fittings. The towns people of the nearby small town Baddeck, in Nova Scotia, Canada, enlisted to make tetrahedrons, providing employment for many people.
The apogee of Bell’s work with lifting kites was probably the Cygnet (above). This was a gigantic unholy monster of a kite, with 3,393 cells assembled by Bell’s loyal Nova Scotian citizenry. It was so large and unwieldy that it was difficult to launch from land. So Bell and his associates built a small steam ship to launch her from and performed launches from a local lake.
The Cygnet I was launched on 6 December 1907, a certain Thomas Selfridge,* already getting a name in early aeronautical circles, piloted the kite as it was towed into the air behind a motorboat, eventually reaching a height of 168 ft. before crashing. This was the first recorded heavier-than-air flight in Canada. The kite definitely could hold a person in the air, but further experiments with the design demonstrated many limitations.; the most obvious being the great difficulty in steering such a large rigid structure in the air. Further experiments with a powered version of the Cygnet, the AEA Cygnet and the Cygnet III, were judged unsatisfactory — the kite could lift a man, but steered around in the air with only great difficulty.
Bell continued with the notion of powered heavier than air aircraft even in the wake of the Wright Brothers until 1909, with the launch of his last experiment, the heavier than air craft Silver Dart, which was more of an early airplane than an actual kite.
Conclusions: Lifting kits were hardly a failure from the perspective of design, but they ultimately couldn’t provide the military functional requirement to have a steerable aircraft that could carry significant loads up into the air and land again. Bell was a pioneer in the effort, contributing as much or more to the study of aeronautics as he did to audio technology.. yet he is hardly a footnote in the science of flight today, when compared to his other great contribution, the telephone.
* Lt. Selfridge had also become the first person killed in a powered heavier-than-air flight in a crash of the Wright Flyer at Fort Myer, Virginia, on September 17, 1908.