= Camber
{disambiguate=aerodynamics}
{wiki}
= Airfoil camber
{synonym}
<Camber (aerodynamics)> describes the departure of an <airfoil mean camber line> from the straight <airfoil chord>. A common scalar measure is the largest normal distance from that line to the chord, often divided by chord <length>. Its sign, position and full chordwise distribution matter when specifying a profile. A <symmetric airfoil> has zero <airfoil camber> under the corresponding midpoint convention.<Wing Geometry by NASA Glenn Research Center>[Airfoil Geometry, distinction between chord line, mean line, camber and thickness]{ref}
For an original camber-line model, let $\xi=x/c$ and choose
$$
\frac{y_c}{c}=4m\xi(1-\xi),\qquad 0\le\xi\le1.
$$
Its derivative is $dy_c/dx=4m(1-2\xi)$, so the maximum is at $\xi=1/2$, with $y_c/c=m$. With $m=0.03$ and $c=0.4\,\mathrm m$, the maximum displacement is $12\,\mathrm{mm}$. Doubling all lengths doubles this displacement while preserving the three-percent camber. This full-chord parabola is a stipulated example, not the piecewise mean line of <NACA 2412>.
Camber height is not itself <curvature>. In this example $y_c''=-8m/c$, so the midpoint <curvature> magnitude is $8|m|/c$ because the slope there vanishes. Uniform geometric scaling preserves the camber-to-chord ratio while changing curvature inversely with scale. Nor does the maximum height alone determine the mean-line slopes at other stations.
In <thin airfoil theory>, the mean-line shape shifts the <zero-lift angle of attack>; finite positive <lift> can occur at zero incidence. Determining that shift requires the mean-line distribution, rather than substituting a camber percentage for an angle. The independent shape choices in the early NACA programme were tested by measuring aerodynamic characteristics while systematically varying thickness and mean-line form.<The Characteristics of 78 Related Airfoil Sections from Tests in the Variable-Density Wind Tunnel by Eastman N. Jacobs and others>[Summary and profile derivation]{ref}
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