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National Advisory Committee for Aeronautics, Technical Notes - Aerodynamic Characteristics at Reynolds Numbers of Three Airfoil Section Formed by Cutting off Various Amounts from the Rear Portion of the NACA 0012 Airfoil Section

An investigation has been made of the two-dimensional aerodynamic
characteristics of three airfoil sections formed by removing 1.5, 4.0,
and 12.5 percent of the original chord from the trailing edge of the
NACA 0012 airfoil section. The tests consisted of measurements of
section lif , drag, and pitching-moment coefficients at Reynolds numbers
of 3.0 X 10 and 6.0 X 106 for the airfoil sections both in the smooth
condition and with roughened leading edges. The characteristics of the
airfoil section obtained by cutting off 1.5 percent chord were also
determined with a spanwise row of rivet heads On each surface near the
trailing edge.

The results indicate that, when the trailing edge is thickened by
removing portions from the rear of the NACA 0012 section, the drag
coefficient for most lift coefficients becomes higher, the maximum lift
coefficient varies by a relatively small amount for the smooth airfoil
-and progressively increases for the rough leading-edge condition, and
the aerodynamic-center position consistently moves rearward. Applying
rivet heads to the section formed by cutting away 1.5 percent chord
altered the aerodynamic characteristics to a degree which, in most cases,
was barely perceptible.

The use of airfoil sections having relatively thick trailing edges
is frequently expedient in the structural design of helicopter blades
and is sometimes considered desirable for those portions of airplane
wings containing control surfaces. A method sometimes employed to
obtain an airfoil having a thick trailing edge consists of removing a
sufficient amount from the rear of an existing conventional airfoil
section to result in the desired trailing-edge thickness. The effects
upon the section aerodynamic characteristics of such a modification,
however, have not been extensively investigated. The investigation
reported in the present paper was made in an attempt to evaluate the
effects upon the aerodynamic characteristics of the NACA 0012 airfoil
section of removing various amounts from the rear portion of the airfoil.