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Vane propellers

 
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Old 01-12-2007, 12:36 PM
 
Join Date: Apr 2006
Posts: 841
Default Vane propellers

Someone asked about vane drives. I found my copy of a paper on the subject, while looking for something else, naturally. The paper is titled The Design and Construction of Small Craft, by R. Munro Smith, A.M.I.N.A., published by the Technical Section, Associates of Engineering and Shipbuilding Draughtsmen, 96 St. George's Square, Westminster, London, 1924

As I explained, in part, the propellers were three-bladed, crude triangles. The shafts were above the waterline and only the vanes at the bottom impinged against the water. The propellers were 11 feet in diameter and had a pitch of 16 feet. The design rotary speed was 66 rpm. The area of water acted upon at full speed was 59.28 sq ft. Shaft horsepower was 116.

Comments were as follows: The vane wheels do not require immersed struts or supports. Every portion of the immersed blade is acting efficiently during its passage through the water. High propulsive efficiency in relation to all o0ther known methods of propulsion. Great maneuvering powers. Effective variation of water acted upon with variations of draft. Higher revolutions per minute than paddlewheels and less weight of machinery. Compared to sidewheelers, overall width is reduced. The vanes are stronger than paddlewheels.

I do not know why such a wonderful system failed to be adopted, but I suspect that using only part of the wheels in the water represented about a 60% loss in efficiency compared to a fully immersed propeller. Other devices, such as the tunnel stern and the Kort nozzle did utilize all of the wheel blade area to do work. In any event, this experimental boat was probably the only one ever built.
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