sentences:  Data and concept documentation was given to the Navy in 1939, with wind tunnel tests on full-scale models being completed in 1940-1941.The original prototype, designated the V-173 ("Flying Pancake"), was built of wood and canvas and featured a conventional, fully symmetrical aerofoil section (NACA 0015).Designed as a "proof-of-concept" prototype, the initial configuration V-173 was built as a lightweight test model powered by two 80 hp (60 kW) Continental A-80 engines turning F4U Corsair propellers.