The reasoning--though incomplete--is based on the Bernoulli effect, which correctly correlates the increased speed with which air moves over a surface and the lowered air pressure measured at that surface. [...]A few years later I carried out a calculation according to a naive interpretation of the common explanation of how a wing works. Using data from a model airplane I found that the calculated lift was only 2% of that needed to fly the model.
The calculation in the bottom is incorrect. It assumes that the top of the wing is greater, so the speed of the air is greater, so the pressure on the top of the wing is smaller. The problem is that then it multiplies the difference of pressure by the surface of the wing, but it doesn't consider that the top of the wing is greater. (There is another problem, the surface is curved, so you must consider the direction of the forces in order to add them.) When you take into account this, the "lift" you get from this calculation is not the 2%, it's exactly 0% (as 0% because there is a mathematical theorem that says that it's 0%).
But there is a detail that I don't like in that explanation. You need the viscosity to get the vortex when the plane starts. You don't need the viscosity to fly. You can fly without viscosity, but you can't "take of" without viscosity. (Well, you need also the viscosity to change correct the circulation of the vortex when you change the speed, o the correct misquotes is "You can fly at constant velocity without viscosity.".)
Comments
The calculation in the bottom is incorrect. It assumes that the top of the wing is greater, so the speed of the air is greater, so the pressure on the top of the wing is smaller. The problem is that then it multiplies the difference of pressure by the surface of the wing, but it doesn't consider that the top of the wing is greater. (There is another problem, the surface is curved, so you must consider the direction of the forces in order to add them.) When you take into account this, the "lift" you get from this calculation is not the 2%, it's exactly 0% (as 0% because there is a mathematical theorem that says that it's 0%).
There is a more detailed and correct explanation in http://physics.stackexchange.com/questions/46131/does-a-wing... . The secret sauce that makes the planes fly is the vortex around the wing.
But there is a detail that I don't like in that explanation. You need the viscosity to get the vortex when the plane starts. You don't need the viscosity to fly. You can fly without viscosity, but you can't "take of" without viscosity. (Well, you need also the viscosity to change correct the circulation of the vortex when you change the speed, o the correct misquotes is "You can fly at constant velocity without viscosity.".)