The Flying Machine (Ornihopter)

The Hang Glider is a modified version of Leonardo Da Vinci's invention: The Flying Machine.To accomplish the success of this prototype, Leonardo studied how bats flew. He carefully examined the exoskeleton of its wings. This would be the base of invention. Leonardo calls it "The Great Bird". The Flying Machine was designed as a bat. So the wings had to move. Going up and down and then stop to glide. This design was to sustain flight rather than to push forward based on human power and wind.  Unlike Da Vinci's invention the hang glider is a equilateral triangle that is used for the sole purpose of gliding. Da Vinci's invention was actually imitating a bat. There are many models made from his notes, But none will be as good as the original.

Carroll Gray. FLYING MACHINES (2003). Retrieved December 2,2011.
 From http://www.flyingmachines.org/davi.html