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To provide a camber line with a very far forward location of the maximum camber, the 3-digit camber line was developed and reported in NACA Report 537. The first digit of the 3-digit camber line designation is defined as two thirds of the design lift coefficient (in tenths); the second digit, as twice the longitudinal location of the maximum camber (in tenths of chord); and the third digit of zero indicates a non-reflexed trailing edge. A 210 camber line has a design lift coefficient of 0.3 with the maximum camber occurring at 0.05 chord and no reflex at the trailing edge.

The camber line is made up of two equations so that the second derivative decreases linearly to zero at a point r slightly aft of the maximum camber position and remains zero from this point to the trailing edge.

y'' = k*(x-r) if x < r and
y'' = 0 if x ≥ r
y(0)=0 and y(1)=0 where x is fraction of chord.

These differential equations may be integrated to show that

y=(k/6)*(x**3 -3*r*x**2 +r**2*(3-r)*x) if x < r and
y=(k*r**3/6)*(1-x) if x ≥ r

This camber line family was reported in NACA Report 537 and the following values of k and r for selected values of m were given as:

Camber-line
designation
mrk
2100.050.0580361.400
2200.100.126051.640
2300.150.202515.957
2400.200.29006.643
2500.250.39103.230

Note: k is written as k1 in both NASA 4741 and Abbott and von Doenhoff. The notation in 4741 and AVD differ again. The variable r used here agrees with 4741, but is called m by AVD. Also note that m is not actually used in the equations.

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