Date:	Mon, 18 Jul 1994 06:43:57 -1000
From:	gast3@digi.de
Message-Id: <199407181643.AA02308@digi.DIGI.DE>
Organization: Division of Applied Sciences, Harvard University
Subject: rev venting


DO NOT respond to gast3@digi.de
Respond to john@multinet.de

The following was extracted from Revolution Patent of 14 October, 1988
International Publication Number: WO 90/02917  19 April, 1990

  The purpose of the venting is to vent airflow during reverse flight
and during tight-turning-radius maneuvers. In reverse flight, the
relative air motion, is from the aft portion of the sail toward the
leading edge. In absense of the venting screen, under the reverse 
flight conditions, an air pocket is formed in the sail at the
leading edge which acts as an air-breaking mechanism, which causes 
the airflow to backup.  By venting the leading edge area of the 
induced air pocket, the air-breaking action is significantly reduced
by allowing a large portion of the airflow to continue through the
restrictive leading edge area. This in turn greatly improves the
reverse flight characteristics of the device.

  Secondly, this venting improves the turning characteristics of the
kite. A turn is produced when the leading wing of the sail flies 
faster relative to the trailing wing of the sail. This occurs when 
the leading wing portion experiences greater lift than the trailing 
wing portion. By reducing the trailing wing air speed to zero, the 
trailing wingtip becomes the center of rotation. On presently available
flying devices, the above conditions represent the tightest turn radius
possible. In other words, the minimum turn radius attainable in
presently available stuntkites is a radius of one wing span.
By venting the sail, the turn can be optimized by zeroing and the 
reversing the flight direction of the trailing wing. The turn radius 
is reduced to one-half of one wingspan, producing a controlled
propeller-like spinning action, heretofore unheard of in the
prior art.

Claim 7.
  The kite of claim 1, wherein said sail further comprises a vented 
screen portion located adjacent the leading edge of said sail.


I have built two revolution-like kites from icarex, one with and
one without venting. The non-vented version while inverted, is unstable 
and hardly flies backwards. I don't even fly it anymore.


Over-the-Rainbow,

John Mitchell
Munich, Germany
john@multinet.de


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