AQM-91A wing and tail profiles

Results

To start with the results: here are plots of the three profiles. The derivation and resulting coordinates are shown below.

NACA 6-series design method

The NACA 6-series airfoils were developed by means of conformal transformations, as described in NASA TM-4741 - Computer program to obtain ordinates for NACA airfoils and others references. I decided not to pursue this scientific way, but to use practical engineering approach instead, since this was more than adequate for the purpose. The webpage Thickness Function for NACA 6-Series Airfoils offers yet another method, but I did not use it either.

NACA 64A thickness distributions

The coordinates for the (symmetrical) 64A006, 64A008 and 64A010 are taken from Abbott & Von Doenhoff, pages 354 to 356. Note that the footer on page 356 is not correct: it says 'NACA 64₃-018 Basic Thickness Distribution' but it is NACA 64A010. The NACA 6A-series airfoils have basically straight upper and lower lines aft of 80% chord, mostly for manufacturing reasons.

I checked whether the thickness distributions are simply scaled up, but the thickness ratios shows that there are small differences. The ratios also showed a peculiar ratio for 7.5 percent chord. A check in TN-1368 showed that the number 2.905 should be 2.805. The 64A007 data is linearly interpolated from 64A006 and 64A008, and thus the first result is found.

The NACA 64A camber line

I was puzzled by the question what camber line was used for the 64A family. Abbott & Von Doenhoff page 121 says: "When the mean-line designation is not given, it is understood that the uniform-load mean line (a=1.0) has been used". But the coordinates that I calculated with a = 1.0 did not match the NACA 64A210 and 64A410 data listed on pages 430 and 431. I then found the following in NACA TN-1368, page 2: 'A special mean line, designated the a = 0.8 (modified) mean line, has also been designed to maintain straight sides on the cambered sections". This indeed gave me matching coordinate data. One question remains for me: the a = 0.8 (modified) mean line is not perfectly straight for the last 20% chord, which is the whole idea behind the 6A series. The data below for the a = 0.8, a = 0.8 (modified) and a = 1.0 camber lines is taken from Abbott & Von Doenhoff, pages p402, 403 and 405. They represent the camber line for a design C_L = 1, and are to be scaled according to the actual design C_L.

NACA 64A410 check calculation

To check my method, I had just one reference profile: the NACA 64A410 coordinates as listed on page 431 of Abbott & Von Doenhoff. I calculated 'my' 64A410 profile coordinates using the NACA 64A010 thickness distribution, combined with the a = 0.8 (modified) camber line scaled down to 40%, using the equations on page 113 of Abbott & Von Doenhoff.

I'm happy to report that the differences were very small. They are most likely rounding errors, slide rule vs computer. The large differences for 7.5% chord are again the result of the 2.805 vs 2.905 error, as reported above.

NACA 64A306 calculation

Now the method has been verified, NACA 64A306 profile coordinates were calculated using the NACA 64A006 thickness distribution, combined with the a = 0.8 (modified) camber line scaled down to 30%.

NACA 64A310 calculation

NACA 64A310 profile coordinates were calculated using the NACA 64A010 thickness distribution, combined with the a = 0.8 (modified) camber line scaled down to 30%.