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FOILGEN: This program is used for airfoil geometry generation. For airfoils with analytically defined ordinates, this program produces airfoil definition data sets in common file format. This includes NACA 4-digit, 4-digit modified and 5-digit airfoils. In addition, the NACA 6 and 6A camber lines are available. The user can combine any combination of thickness and camber lines available within these shapes. This provides a wide range of airfoil definitions. The program runs interactively.
LADSON: This is the NASA program that provides a reasonable approximation to the NACA 6 and 6A series airfoils. It was written by Charles Ladson and Cuyler Brooks (Ladson and Brooks, 1974). Originally it ran on the NASA CDC computer. It has been ported to run on a personal computer (Macintosh). Only minor modifications were made to produce a program to generate a set of ordinates in a standard file format.
The program is only an approximation to the ordinates because there is no simple algebraic formula available to describe the thickness distribution. I spoke briefly to Charles Ladson some years ago, and he said that he thought it would be impossible to generate a more accurate program. When he was doing this work he investigated the availability of more detailed notes on these airfoils and discovered that all the records have been destroyed. The only information available is that contained in the actual NACA reports. However, this program is much more accurate than attempts to simulate the 6 and 6A series thickness envelope by using a modified NACA 4-digit airfoil formula. The program was developed to handle thicknesses from 6 to 15 percent
One other possible problem is the value at the trailing edge. Originally further processing was required to find the value. The program was modified to linearly extrapolate the values near the trailing edge to get the final values. This
was the approach recommended by Ladson. This is done in the new routine added to generate the file of points, stdout. The user should check this approximation if the results appear to be in error at the trailing edge.
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Note: A recent note on the sci.aeronautics newsgroup provided some useful comments related to these programs. Mike Logan, NASA Langley (mlgan@avd47.larc.nasa.gov) relayed the results of a study made at another school. In that study, Mike's
Quickmod code was judged to be better than FLOFT/WLOFT for developing aircraft geometry. AutoCAD was judged second, followed by Raymer's RDS code, DesignCAD and finally FLOFT/WLOFT. For an individual doing a particular job, each of these methods should be
evaluated to decide which one is most appropriate.
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