The shape and location of the lift and drag polar of the airfoil is the key to airplane performance. The images below show, how the cd-cl polar changes, when the camber line gets reflexed.
Lift vs. drag coefficients for different amounts of reflex.
Now we have a problem: while we add reflex to the camber line, in order to shift the moment coefficient towards the positive values, we shift the lift vs. drag polar down. This means, that we actually reduce the lift at a certain angle of attack and, what's even worse, we also reduce the maximum lift coefficient. A reduced maximum lift coefficient leads to higher stall and landing speeds, which is not exactly our aim. Of course the aerodynamicist already knows a remedy against low lift: he increases the amount of the maximum camber. Indeed, this increases the lift, but also reduces the positive moment coefficient.
Last modification of this page: 08.09.03
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