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Longline Control & XC Shuttling of Sweeping Kites

Directing sweeping kites by pulling lines from the ground is the simplest cheapest control actuation method. At distances of a few hundred meters where common direct multiline kite control is too mushy AWECS designers have been forced to resort to radio-controlled pods with batteries and servos. This adds flying weight, capital/operating/maintenance costs, and failure modes (dead batteries, communications gaps, worn-out servos, etc.). A related problem is how to shuttle a kite XC crosswind on tracks or cableways where control lines must somehow keep up the chase. This post describes methods extending direct multiline control to higher altitudes and crosswind shuttling.

Driving a string pulley loop set crosswind between two anchors is a powerful way to tap a shuttling powerkite. A stock generator with a pulley-wheel can be so driven but a direct kite control method of a shuttling kite has been elusive. A pair of string pulley loops moving in tandem can do the job. The "upwind loop" is connected to the forward lines (A, B) brought together aloft as a bridle junction. The downwind loop is connected to a pulley/control-bar thingy at the bridle junction to toggle brake lines (D) left or right, retarding or advancing the loop relative to its partner. Both loops drive the generator shaft at one end of travel while a pulley pair at the other end varies the moving loops relative to each other. To operate use either cross-linked heddle pulleys with reins or a pulley T-bar moved by a joystick or steering wheel. Photos and sketches are pending, so have fun imagining thingies and layouts.

A general principle for controlling long-line kites is to use the thinnest low-stretch lines (esp. UHMWPE) for control lines. Catenary mush is minimized and can be reduced further by a small tensioning drogue on a pulley self-flying partway up the line. Such tensioning robs a bit of raw performance, but less than a control pod up to considerable distance. Tensioning reduces control lag so much that crisp control over many hundreds of meters is enabled.

Misc. Tips:  The use of reins to a control bar, such as control draft animals, allows personnel to stay "out of the bite" of dangerous ground tackle. Another bar-trick is to "float" a control bar to the brake lines unconnected to the main anchor "working line" to fore-lines, but you must stay near that anchor point.

FairIP/CoopIP                       ~Dave Santos             July 15,2010        M1813

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