There are basically two types of sail materials used in hang glider sails: Woven Polyester Fabrics, and Composite Laminated Fabrics made of some combination of polyester film and polyester fibers.
Woven polyester sailcloth is a very tight weave of small diameter polyester fibers that has been stabilized by the hot-press impregnation of a polyester resin. The resin impregnation is required to provide resistance to distortion and stretch. This resistance is important in maintaining the aerodynamic shape of the sail. Woven polyester provides the best combination of light weight and durability in a sail with the best overall handling qualities.
Laminated sail materials using polyester film achieve superior performance by using a lower stretch material that is better at maintaining sail shape but is still relatively light in weight. The disadvantages of polyester film fabrics is that the reduced elasticity under load generally results in stiffer and less responsive handling, and polyester laminated fabrics are generally not as durable or long lasting as the woven fabrics.
In most hang gliders, the control is and has been achieved using a horizontal bar held by the pilot, also known as 'triangle control frame' (TCF), 'control bar' or 'base bar'. This bar is usually pulled to allow for greater speed. Either end of the control bar is attached to an upright, where both extend and are connected to the main body of the glider. This creates the shape of a triangle or A-Frame. In many of these configurations additional wheels or other equipment can be suspended from the bottom bar or rod ends.
Images showing a triangle control frame on Otto Lilienthal's 1892 hang glider prove that the technology of such frames has existed since the early design of gliders, but he did not mention it in his patents. A TCF shows also in Octave Chanute's designs. It was a major part of the now common design of hang gliders by George A. Spratt. The most simple A-frame that is cable-stayed was demonstrated in a Breslau gliding club hang gliding meet in a battened wing hang glider in the year 1908; hang glider historian Stephan Nitsch has collected instances also of the U control frame used in the first decade of the 1900s; the U is variant of the A-frame.