Basically aspect ratio is the ratio of a wing’s length to its breadth. Generally speaking if the aspect ratio is larger then the wing or kite is more efficient (take a look a high performance gliders for example). However we cannot keep increasing the aspect ratio of a kite since it is not a rigid flying body and it is supported on its bridle lines (which keep it in shape). If the aspect ratio is too large, the drag on the tips increases and the kite assumes a rather unsightly banana shape in the air. Similarly it begins to move around a lot (oscillates). We see many kite designs based on an optimum aspect ratio of between 3 and 4. The Skytiger Hi –series kites are good examples and are faster and more efficient than the standard Skytigers. Good examples of low aspect ratio kites are NASA wings and the Wipika marine wing, however both of these kites have their own relatively unique features – the NASA wings are simple, cheap and can be made very easily, the Wipika however is still probably the best kite for consistently relaunching off water !!
Recommended reading – Stunt Kites II by Servaas van der Horst & Nop Velthuizen ISBN 90-6868-085-4 (a must for every kite enthusiast).