(Image credit: Vintage Aviation News)
In the 1930s, Italian engineer Luigi Stipa had ideas about fluid motion and developed the “intubed propeller”. Stipa’s main idea was to place the engine and propeller inside a fuselage that acted as a tapered duct, or venturi tube. To prove the concept, the Stipa-Caproni was developed in 1932 by the Caproni aviation company as a test of new technology. The design compressed the airflow from the propeller and the engine’s exhaust before releasing it at the back of the aircraft. The approach used Bernoulli’s principle to improve the efficiency of the propeller. It was similar to how turbofan engines work, but Stipa used a piston engine instead of a gas turbine. Later, Stipa believed that German rocket and jet technology, particularly the V-1 flying bomb, was using his patented invention without giving him credit. However, his ducted-fan design had little mechanical similarity to turbojet engines and had nothing in common with the pulsejet used in the V-1. Stipa worked for years on a mathematical study while at the Engineering Division of the Italian Air Force. He found that the inner surface of a venturi tube needed to be shaped like an airfoil for maximum efficiency. He also computed the ideal shape of the propeller, the ideal distance from the tube’s leading edge to the propeller, and the most efficient rate of revolution. After his research, he asked the Italian Fascist government to build a prototype aircraft. The government at that time wanted to showcase Italy’s achievements in aviation, so in 1932 it commissioned Caproni to build the aircraft. The Stipa-Caproni, also known as the Caproni Stipa, was a mid-wing monoplane mainly made of wood. Its fuselage was a short, fat tube that opened at both ends, creating a tapered duct. Twin cockpits were mounted in a hump on top of the fuselage. The wings were elliptical, and the main beams ran through the duct, with the engine inside it.Design of Stipa-Caproni
The Cancellation
