Before I started flying a glider 30+ years ago, I read a lot about aerodynamics and understood that lift was created because the top surface of the wing was longer than the bottom. Because more air moved over the top of the wing it created less pressure on top of the wing, than the bottom. That difference in pressure essentially sucked the wing upward, pulling the plane airplane with it by creating lift. As I learned more about jet airplanes and flight at mach speeds, I understood that most of the ability to fly was created by thrust and not lift. If a jet had a airfoil like the Wright Brothers, it would continue lift more and more as the speed increased. The result would make the jet very difficult to fly at high speed. I also heard many, many times from people in the industry, that even a rock would fly if given enough thrust. Hey, I threw a lot of rocks so that made sense to me.

When I first I started flying RC with my trainer, I believed that lowering a trailing surface on a wing (be it flap or aileron), increased the lift (as the theory of dynamics indicated) due to the air rushing faster over the top of the wing than the bottom. This difference in air pressure caused less pressure on top the wing than the bottom and, essentially, it sucking the wing upward. That made good sense to me because the trainer wing definitely had more surface on top, than on the bottom of the wing. So it made sense then, that as the aileron was lowered, the pressure on top increased, and "lifted" one wing more than the other. That explained that wing. But as I looked at the other wing, I realized that changing the angle of the aileron did NOT increase the length of the lower surface enough to explain the opposite effect on it. So, I and began to suspect something else was involved here.

However, when I got my second airplane (fourstar 60, with symmetrical wing) I found that the surfaces were the same on both the top and on the bottom. This took me back to previous "jet" theory--that it is thrust that makes if fly more than lift generated by the wing. When the aileron was defected down, it changed the length of the surfaces very little. Granted, it changed it some, but not enough to explain the significant increase in roll rate. This essentially, blew my whole belief in the theory of aerodynamics as I knew it. But, I didn't care, the fourstar flew great, and I was having fun.

When I finally got my first airplane with flaps (Ultrastick 60) I couldn't wait to try them out. After getting used to flying the new plane a while, it was time to try the flaps. I was flying straight and level at least 100' feet up, at a moderate speed and flipped the flap switch. I was expecting the plane to lift straight up, and/or slow down, but instead, the nose went up at a 45º angle and climbed rapidly. I was so surprised, I immediately turned the flaps off, and leveled the plane. Subsequent tries revealed that the plane needed a lot of down elevator in order to maintain level flight. I was very confused for a while, but then I realized that the flaps hadn't really created any "lift" as I knew it, but the result was actually caused by "push" from the air under the wing pushing up on downward deflected surfaces. Since the flaps were relatively closer to the CG than the tail, it began to make some sense, but not a lot.

I realize the "theory of aerodynamics" was developed by people much smarter than I, but I don't think the theory has the same effect on model airplanes as it does on full scale aircraft. My suspicion is that, the relative density of the air in relation to large aircraft verses small aircraft causes a much different effect on the two. The air is relatively more dense to a small airplane, than it is to a jumbo jet. There may be some residual effect due to gravity (and some momentum and inertia thrown in), but I think it is mainly the relative density of the air that we use to fly RC. I guess that is why Newton stated his "Law of Gravity" in a vacuum, because in reality, an apple and a feather don't fall at the same rate in the air we fly in. But then I believe tornadoes don't suck the air, they actually blow it--but that would be for a whole different forum.

Sorry this was so long! Retorts are welcome--unless they are about tornadoes, then please P.M. me so we don't get the tread off on a tangent :-)