Guys, I left the semantics based posts on page one since they came before the request to move on. Let's not dwell on this whole "suck" and "vacuum" thing. As I said earlier move on to some aerodynamics or this'll simply get closed.
Originally Posted by alasdair
Just to introduce a little perspective, an average model with a wiingloading of 20 oz/sq.ft would be supported by a pressure rise averaging say 0.02% over the underside, and a pressure reduction averaging 0.04% over the top surface. That is hardly pulling a vacuum, just a slight perturbation of the standard atmospheric pressure of 14.7 psi
I ran this same sort of calculation on a 747 one time. With all the square inches of that massive wing and despite the gross takeoff weight it came down to an average difference between the lower and upper surface of a hair over 1psi to achieve flight. And as Alasdair suggests our models only need a few oz/sq inch even for the biggest and heaviest.
One of my free flight rubber models has 150 sq inches of area and weighs 5 oz ready to fly with the motor all wound up. So that's only 5/150= 0.033 oz/sq-in difference over the wing's area to fly.