Paul MacCready: What we really went back to is what birds have been doing for a hundred million years, so who thought of it first is a question. One of the blind alleys that we went up in this development of the Gossamer Condor was — I was picturing that because the flight was so slow and the turns were fairly large, you could just have a wing that always had the same shape and you could gently get around the turn. But when we were having huge problems with the turn and with other aspects of stability and control, I finally sat down and really did some calculations and realized the huge increase of angle of the tack you get in the one wing versus the other wing and that it was necessary — in order to maintain lift —well, a big change of speed, I should say — in order to maintain lift, you have to change the angle of the wing. You just plain have to twist the wing, and when you finally began twisting the wing, it suddenly began working pretty well. But there were a lot of other problems to the stability and control part — but the need to wing twist was important, and I should have figured that out ahead of time and incorporated it right into the very first vehicle. But because I have mental blinders like everybody else, I went off on what I thought was a simpler approach. I tried to do everything on this project as simply as possible, assuming that the simple answer would work. You knew it wouldn’t always, but that saves you a lot of time so when you get to a troublesome thing, you can then spend some time with it.

We figured that one out. Then, by some ingenious tests with a little model that only took an hour to build, pushed around in a swimming pool — just a couple of slabs of balsa wood — we got some final insights about what some computer programs were trying to tell us. The computer programs, a rather elegant technology, were correct, but they didn’t give you any insight. This swimming pool event did give us the insight, and we figured out how to complete all the stability and control problems and came up with a final version that worked.