Spencer and ex Sikorsky engineer Vincent A. Larsen designed the single engine SL-12C amphibian in 1969. It was a two-place, high wing monoplane. The main wheels located in rearward-retracting wing floats; motor in hull drove the prop on a shaft above the fuselage.
First flying in May 1939 registered NX20621, piloted by Percy Spencer, flight tests exposed so many problems with the design and construction that the plane was dismantled after logging 10 hours, and the company reorganized as Colgate-Larsen.
Colgate-Larsen Aircraft Corporation succeeded Spencer-Larsen Aircraft Corporation around 1940, continuing its work at Amityville, Long Island, NY, on novel-design small four-seat amphibian flying-boat, the CL-15 (formerly SL-15).
Spencer leaves Spencer-Larsen in September 1940 and starts the work on his own S-12 Air Car amphibian design.
Engine: Menasco D-4, 150 hp
Wingspan: 40 ft
Length: 27 ft 10 in
All Aero 