The horizontal rotor kite is a very unusual kite. When seen in the skies at a kite festival it often provokes many comments from spectators. The horizontal rotor kite has been around for quite some time although its exact date of origin or verified inventor have not been determined. Rotor kites are usually quite small when compared to other kites found in the skies. Indeed, the rotor kite seems so much like a child's toy that the vast majority of serious kite hobbyists do not even own one.
The horizontal rotor kite achieves flight through a little known scientific principle, the 'Magnus effect'. Kite flyers are generally very knowledgeable about the principles of lift and the Bernoulli effect, but often are not as aware of the Magnus effect and how it provides lift to a horizontally spinning object.
Plans to build an original horizontal rotor kite can be taken from a patent drawing or from Anthony's Kite Site, one of the better kite plan web sites on the Internet. Using either balsa wood or styrofoam meat trays, a rotor kite can be constructed in reasonable time. It will certainly gather attention at most kite festivals since they are not typically seen in the sky.
Likely, the most famous incarnation of the rotor kite is the "Skyroplane" toy which was first marketed in the early 1950's. Sporting two rotating wings, the Skyroplane came in a boxed set complete with a wooden flying reel and flying line. My Skyroplane is still in its original box and is lovingly cared for although it is fifty years old and has enjoyed many hours of flight time. The Skyroplane is still available today and can be reasonably purchased through a number of on-line sources including Jensen Scientific.
Recently, however, the horizontal rotor kite has become a major news maker. A Canadian firm, Magenn Power Inc. of Kanata, ON, a suburb of Ottawa, announced in November 2005 that they will use tethered kite like devices in an innovative application of technology to create electrical energy.
I first came across this as a news story in the Thursday, December 29, 2005 issue of The Toronto Star newspaper (hard copy version - Section D: Business (pages D-1 and D-10). The article is quite lengthy and features some interesting diagrams provided by Magenn Inc.
The company's web site states:
"The Magenn Power Air Rotor System (MARS) is an innovative lighter-than-air tethered device that rotates about a horizontal axis in response to wind, efficiently generating clean renewable electrical energy at a lower cost than all competing systems. This electrical energy is transferred down the tether to a transformer at a ground station and then transferred to the electricity power grid. Helium (an inert non-reactive lighter than air gas) sustains the Air Rotor which ascends to an altitude for best winds and its rotation also causes the Magnus effect. This provides additional lift, keeps the device stabilized, keeps it positioned within a very controlled and restricted location, and causes it to pull up overhead rather than drift downwind on its tether."
The essential difference between a true rotor kite of the variety known to kite builders and the Magenn MARS device is the fact that the horizontal rotor chamber is filled with lighter than air gas to aid in lift. The rotation of the horizontal rotor will provide some additional lift and generate power in the traditional manner of a spinning generator.
Wow - the simple rotor kite goes very high tech!
Magenn states that a one kilowatt portable generator rotor will be available first and could be used to power camp sites in remote locations. Larger four kw rotor generators could be used to power cottages or in disaster recovery locations. Even larger 60 metre long rotor units could generate 1.6 megawatts of power to meet the needs of thirty typical homes. Gathered together into an energy kite farm, even larger amounts of power could be generated, according to the company.
This is a story that deserves some watching as events continue to develop.
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Notes:
- The Magnus effect was fully explained by physicist G. Magnus in 1852. "On the derivation of projectiles; and on a remarkable phenomenon of rotating bodies." G. Magnus, Memoirs of the Royal Academy, Berlin(1852). English translation in Scientific Memoirs, London (1853)., p. 210. Edited by John Tyndall and William Francis.
- Depending on the orientation of the axis of a rotating cylinder (horizontal or vertical) the Magnus effect will either provide lift (horizontal spin dirention) or forward motion (vertical spin direction).
- A detailed explanation of the Magnus effect can be found at: the Magnus Effect page -and- NASA's web page on the Lift of a Rotating Cylinder.
- While not specifically related to kites, the application of the Magnus effect by German scientist Anton Flettner in 1926 to move a ship with a vertical rotating columnar 'sail' is one of the most unusual applications of the Magnus principle. Use of the Magnus effect to power a ship was revived by Jacques Cousteau in 1985 with his famous "Alcyone". Both are interesting topics for additional reading.