Kite equilibrium and bridle length

Abstract

Kite design has recently seen a revival, with sports such as kite buggying and kite surfing becoming significant businesses in some countries. Since the aerodynamics of kites has not been explored in much depth this paper sets out to explain a major behaviour of kites, predicting where they will settle during flight. The analysis is confined to a vertical plane containing the kite string. It examines the basic forces for single-line or two-line kites and shows how the line azimuth angle(s) and equilibrium settling point(s) can be derived from the aerodynamic properties of the kite, from the kite mass and from the bridle lengths. It is noted that while several equilibrium points are predicted not all are stable equilibrium points. Wind tunnel tests with a specially built rigid model are described and these are shown to confirm theoretical predictions.