The prototype for the F3B-1 fighter was the XF3B-1 (Model 74), but after Navy tests, the Model 74 was sent back to the factory and rebuilt as the F3B-1 (Model 77), with completely redesigned landing gear, wings, and tail unit. It could be used either with landing gear or with a single float. The F3B-1's ailerons and tail surfaces used an entirely new method of semimonocoque, all-metal construction in which added stiffness was provided by a corrugated covering. In this type of construction, a metal skin is stretched over a light frame. Semimonocoque construction proved so satisfactory that it was used for all subsequent Boeing biplane fighters. In all other respects, the F3B-1 was a conventional design with a metal tubular frame, built-up wood wing spars and plywood ribs, and a fabric covering.