A patent filed on July 15th 1975 by Peter J. Pearce and Toby J.Cowan and granted on April 19th 1977.
Patent number 4,018,408, consisted of two arched sails.
Each sail is separated, forward and aft similar to a box kite arrangement only the forward sail has a larger area than the rear or aft sail. Their concave shape face downward in flight like a flexible sail of a Sled kite.
Pearce and Cowan made reference to Allison's kite in their Patent application filed on July 15th 1975 (596,015) stating that it had a concave surface facing downward and that the sail is flexible.
Their kite includes two sails attached to a rigid frame.
The sails form a parabolic arched surface and form a shape of a trough with their open, concave shape facing downward in flight.
A kite designed by A.B. Wilder in 1924 (Patent No 1,490,356) and reference cited by the examiner of the Arch Kite patent. A.B. Wilder almost had the concave kite concept, only his invention was flown with the curved surface facing down. (See drawing above). The kite also incorporated a paper webbing between it's curved bowed members which the patent referred to as a top plane or wing.