This was not the only problem-framing aspect of MacCready's success: while previous attempts built complex airframes intended to have a low drag coefficient, he recognized that the issue was power dissipation - if the speed was low enough, the drag coefficient was not so critical, and things like wire bracing were acceptable. His initial insight was that "if you triple the size of a hang-glider-size plane and triple its wingspan to 90 ft. while keeping its weight the same, the power needed to fly it goes down by a factor of 3, to about 0.4 horsepower." And that, he knew, was what a trained cyclist could pump out for several minutes at a stretch.<p><a href="http://content.time.com/time/magazine/article/0,9171,90512,00.html" rel="nofollow">http://content.time.com/time/magazine/article/0,9171,90512,0...</a>