 NACA 2412

NACA 2412 is a NACA four-digit airfoil with maximum airfoil camber two percent of the airfoil chord, located at forty percent chord, and nominal maximum airfoil thickness-to-chord ratio twelve percent. It combines a nonzero airfoil mean camber line with the same nominal thickness parameter as NACA 0012.^[ref]

The construction is developed in NACA four-digit airfoil. A new calculation away from the maximum-camber station illustrates its normal offsets. At $x/c=0.2$, the mean line gives $y_c/c=0.015$ and $d{y}_c/dx=0.05$. The finite-edge thickness polynomial gives $y_t/c\approx 0.05737543$. With $\theta =\arctan (0.05)$, the normalized surface coordinates areTheir midpoint is exactly the construction point $(0.2,0.015)$ before numerical rounding. Their horizontal coordinates differ because thickness is placed along the local normal vector. Simply adding and subtracting $y_t$ vertically would produce a different geometry at this sloping station.

For a $0.50\mathrm{m}$ chord, these paired points are separated by $2y_t\approx 57.3754\mathrm{mm}$. This local normal separation is smaller than the nominal $60\mathrm{mm}$ maximum thickness. Airfoil thickness convention explains why a projected or same-horizontal-station measurement must be distinguished from this paired normal distance.

The two-percent camber is not a two-degree incidence or a prescribed lift coefficient. Its aerodynamic effect depends on the mean-line slopes and the flow. A wind tunnel comparison with NACA 0012 can hold nominal thickness and Reynolds number fixed while observing the change due to airfoil camber. Such comparisons follow the systematic separation of thickness and mean-line form in the original NACA investigation.^[ref]