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National Advisory Committee for Aeronautics, Report - Model Tests with a Systematic Series of 27 Wing Sections at Full Reynolds Number

This report contains the results of the investigation of the first systematic series of wing
sections, 27 all together,madein the variable density wind tunnel of the National Advisory
Committee for Aeronautics at about 20 atmospheres pressure. It was desired to obtain infor-
mation about those aerodynamical properties of the wing sections which can not be computed.
These are the drag at several angles of attack, and the two values of the lift coefficient when
(a) the lift coefficient has its maximum and (b) when the air forces change irregularly, com-
monly known as the “burblepoint.” Without additional work, there was also obtained a
check on the aerodynamic properties open to computation, namely, the lift and the moment.

In this first systematic series, the measurements were confined to one tank pressure,
about 20 atmospheres. This gives approximately a full size Reynolds Number, for the model
scale is about one-tenth, the velocity about one-half of the actual velocity.

The investigation was confined to such wing sections as have a very small travel of the center
of pressure. The rate of the travel of the center of pressure is certainly an aerodynamic prop-
erty of great practical importance,‘afi'ecting the usefulness of the section for design purposes;
it is not wise to compare the performance of several wing sections without taking the different
rates of travel of the center of pressure, ii any, into account. 'Within the useful range of the
angle of attack, the wing osections described 1n this report have their center of pressure at about
25 per cent of the chord. Their rate of travel of the center of pressure is accordingly small.
and the comparison of their performance 18 all that remains to be done. Wing sections with
a larger rate of travel of the center of pressure may be taken up in a later research.