Bell's tetrahedral kites
Tinkering with geometry to conquer the skies
Alex Q. Arbuckle
1902-1908
In 1899, Alexander Graham Bell, famous for inventing the telephone, began experimenting with kites in search of insights into the possibility of powered flight. Inspired by the box kite designs of Australian Laurence Hargrave, Bell began multiplying the lift-providing cells, creating compound structures of multiple kites. The basic problem of creating flying objects is that as a body’s surface area is squared, its weight is cubed, limiting the maximum size and lifting capability.Over the course of years experimenting at his Nova Scotia laboratory, Bell discovered that a tetrahedron — a three-dimensional prism of four triangular sides — could be useful.
Bell built tetrahedral cells with 10-inch spruce rods, with two sides of each pyramidal polygon covered in crimson silk, weighing about an ounce in total.Creating compound assemblies of these pyramid-shaped cells, with shared joints and spars, allowed Bell to scale up his designs without increasing the weight-to-surface area ratio.Bell’s largest tetrahedral design, the “Cygnet,” was composed of 3,393 cells. It successfully flew and carried a human passenger when towed behind a steamship, but was destroyed on landing.That passenger, U.S. Army Lt. Thomas E. Selfridge, would later become the first person to die in a powered airplane flight as a passenger on a Wright Brothers invention.
The tetrahedral principle enables us to construct out of light materials solid frameworks of almost any desired form, and the resulting structures are admirably adapted for the support of aero-surfaces of any desired kind, size, or shape. - Alexander Graham Bell, National Geographic, 1903
