Allison's Flexible Kite (United States Patent and Trademark Office number 2,737,360)
William M. Allison was born in Canada and moved to the U.S.A. state of Dayton, Ohio in the early 1930's.
At the age of 13 he built model planes that displayed fine detail and craftsmanship for a boy his age, according to kite expert Tal Streeter who has researched the early years of Allison for his book ?Great Kites of the Western World? .
As an adult he worked for the Westinghouse refrigerator factory in Dayton as a mechanic.
Allison enjoyed flying kites and helping others in the art of fine tuning and kite flying. He enjoyed experimenting with designs of his own.
Sometime in the early 1950's an idea came to him that maybe a kite could conform to the flow of wind and still obtain lift. As a result he developed a flexible kite, which Allison referred to as a polymorphic kite when describing how the kite conform to the fluctuations of the air stream.
It is unknown what influenced Allison's invention, it may have been a windsock or a sail boat spinnaker but according to his patent application on September 8th 1950 the kite was an instant invention. Allison's invention was basically a semi-rigid canopy kite " built from any light material, relatively impervious to the passage of air, for example paper." (ref from patent number 2,737,360). The reference to paper points to the fact that when Allison designed the flexible kite in early 1950, Polyethylene of the linear low density type (film) was not available until the very late 1950's and early 1960's. Another indication that the original design was made of paper is found in his patent (2,737,360) "The marginal area of the air foil panel is folded back and bonded to the surface panel for reinforced perimeter". Allison's original design was flown with the spines (longitudinal or brace members) on the back of the kite. His idea was to have a smooth passage of wind over the lifting surface of the kite. The patent text makes reference to this. "Slight resistance to the air flow, being the thin edge of panel, the tethers (bridle) and the small ends of brace members" (Spines). The Illustrated drawing of his patent shows how the kite appears in flight with the braces on the back. It's shape was similar to a windsock cut in half (along it's length) and shortened, the canopy is only supported in it's longitudinal plan by 3 braces (spines), tapering towards the trailing edge. The braces (spines) are not linked, and the kite can be rolled lengthwise and easily stored without having to dismantled the frame. The bridle which are part of the lateral extremities of the kite and form keels that help the stability and guide the wind over the main surface of the kite. The kite is tailless and requires a long bridle from the keels to maintain it's shape when in flight. Allison applied for a patent not long after perfecting his kite (1950). The patent office withheld approval of his invention for 6 years. The patent appeared to conflict with another patent issued to Francis Rogallo of the U.S.A. In 1948. Rogallo, an aeronautical engineer also invented a Flexible kite. filed 1948 and issued in 1951. The wording 'flexible kite' had the United States Patent examiners look further into Allison's application and the examiner made reference to,
Wickersham :Patent 1,617,976
Van Ittersum :Patant 2,107,808
Wheelwright :Patent 2,386,762
Bach :Patent 2,463,135
Rogallo :Patent 2,546,078
Allison's patent was approved on March 6th 1956. The kite languished in this form with the possibility of the use of plastic film for the sail, from 1956 until 1962.
Web Page by Tom Lehane (update 2013)
Francis Rogallo Patent 2,546,078 issued 1951.
The patent filed in 1948 and issued in 1951 was the reason Allison was not given approvel for his flexible kite for six years as there was a possible conflict with Rogallo's flexible kite.