WE SHOULD HAVE INVENTED THE ROTOR POWERED SHIP

WE SHOULD HAVE EXPECTED the rotor ship to be an American invention, says Dr. Edwin E. Slosson in Science Service’s Daily Science News Bulletin (Washington) ; first, because the principle involved is the same as our pitchers employ in putting the curve on a baseball; and, second, because this force has been thoroughly studied in American laboratories of aero-dynamics. He goes on:

“A recent technical paper by Elliot G. Reid of the Langley Memorial Aeronautical Laboratory is devoted to’ tests on rotating cylinders’ and gives the formulas by which the force can be calculated and photographs showing how air currents behave in passing around a cylinder. If the cylinder is stationary, the wind divides and goes by equally on both sides, producing no effect except a push on the windward side. But if the cylinder is revolving the wind receives different treatment on the two sides. On the side of the cylinder where the rotary motion is in the same direction as the wind, the air is helped along and speeded up by the friction of the surface of the cylinder. Consequently, the air-pressure is reduced on this side and a sort of suction is formed. On the side of the cylinder that is turning against the wind, the opposite effect is produced by the friction. That is, the flow of the air current is impeded, the air is comprest and its pressure on the cylinder is increased. The net result of diminishing the pressure on one side and increasing it on the other is to produce a push acting on the cylinder at right-angles to the wind, and it is this force that propels the Flettner boat.

The power of this cross-wind force depends upon the velocity of the wind, the height and diameter of the cylinder and its speed of rotation. The greater these are the stronger is the power developed. The Langley Laboratory finds that this force appears suddenly when the speed of the surface of the rotating cylinder rises to half that of the wind, and that there-after the force increases steadily with the speed until the surface is moving twice as fast as the wind, or faster.

The experiments suggest that if the rotating shaft is made in the shape of a Greek cross instead of a smooth cylinder a greater cross-wind force may be produced, tho it requires more power for rotation. The National Advisory Committee for Aeronautics has been engaged for a year in the investigation of the possibility of equipping airplanes with rotating cylinders, so as to utilize this cross force to impart a lift to the machine instead of depending wholly on the angle of the winds. But neither our baseball fans nor our aviation experts have applied the principle to ship propulsion. So Anton Flettner has a free field, and it his invention works as well as the German papers claim, he may appear before long in one of our ports with the ten-thousand-ton sailless ship that he plans to construct for transatlantic trade. It will be as strange an apparition as the submarine that bobbed up at Baltimore loaded with German dyes and drugs during the war, and it will be much more welcome.”

Source: The Literary Digest for February 14, 1925

This entry was posted on Wednesday, March 26th, 2008 at 11:04 am and is filed under Boats, Engineering, Transport. You can follow any responses to this entry through the RSS 2.0 feed. Comments and pings are closed.

Leave a Reply

You must be logged in to post a comment.