The inspiration, the philosophy, and the story behind the Jart can be found on the Jart World Web page. Well worth a visit!

Thursday, November 15, 2007

An Airfoil Plotter for AutoCAD

In the February 2005 R/C Soaring Digest I discovered an airfoil plotting program written for AutoCAD users.
Above is a screen shot of my AutoCAD at work. The Airfoil selection dialog box is open and my Jart drawing is in the background.

It sounded very interesting and as I use AutoCAD I thought that I would give it a try. I am no computer boff but I managed to get it all working without any problems. I just followed the instructions and installed the program and am extremely happy with the results.

No more manually inputting coordinates. It is done automatically for me. Phew!
I even went so far as to create my own button for Airfoils, so I don't even have to type anything. It's just a click away.

Below is the article as it appeared in the R/C Soaring Digest, with links to where you can download the program. If you use AutoCAD and want to draw airfoils then this program is an absolute must for you.


An Airfoil Plotter for AutoCAD
by Dennis Mead

R/C Soaring Digest - February 2005

I have an airfoil plotting program written for AutoCAD users who design their own planes using that program.
This is a routine written entirely in Autolisp, so it runs within AutoCAD without depending on any external resources. It can be installed or removed almost as easily as moving or deleting a folder. No fancy installation/removal steps are needed.
When designing a model plane in AutoCAD, the routine can call up and draw airfoils directly into the drawing without having to use any other programs or intermediate steps. After the program is loaded, just type the word “airfoil” any time you desire and the routine is running. An airfoil can be selected and drawn to any length of chord and thickness desired. All that is needed is the airfoils’ X & Y coordinate data. The data files may have any extension: .dat, .cor, .vec, and even .txt.Very fast, very simple.
For more info, see the “Airfoil.readme.txt” file. Airfoil.lsp is also a text file so it may be scrutinized easily if you wish.
The original program was downloaded from the web back in 1995 and was deficient in several ways. I re-wrote some of the code and added to it in order to make it work easily. The original author is noted at the beginning of the file, but so far all efforts to find him have been futile. I assume that since the original program has been in the public domain for quite some time, that the original author won't mind the improvements.
The “AIRFOILS.exe” file contains the program, the “readme” file, and also several folders of airfoil data. The airfoil data files were gleaned from a number of web-based resources.

Inconveniences: Some airfoil coordinate data is tab delimited. For some reason, Autolisp cannot recognize the “tab” character, so it is not possible for the routine to sort this out. Rather than having to manually edit out tabs in the data files, I have included a handy utility which can take a whole batch of files and convert all of the tab characters in all of the files into spaces and then place these converted files into a new folder. This utility was written by a friend of mine for one of his projects and he kindly modified it for our use here. This takes care of the only real quirk in using Airfoil.lsp.
Other data requirements are easy to check and correct. See the “Airfoil.readme.txt” file.
The “Tab_2_Space.exe” utility takes a whole batch (folder full of) of airfoil data which is tab delimited and replaces all of the tabs with spaces. This is needed sometimes because Autolisp does not have the ability to recognize the tab character in data files. Most all airfoil data is space delimited, so 99% of the time, the utility is not needed... but it's nice to have because it saves so much time and the possibility of making errors when editing data by hand.

For Macintosh OS, too:
The Autolisp routines and data files will work on a Macintosh if someone happens to be running AutoCAD Release12 (the last version for the Mac). The only thing that you Mac users may not be able to run is the “Tab_2_Space.exe” utility... unless you have one of the Mac programs that simulate a PC. An alternative to “Tab_2_Space.exe” is a small text processor, Tex-Edit Plus, which can rapidly exchange the “tab” character for a “space” character and quickly go
through a series of text files.

Final notes:
You will find all instructions/descriptions in the “readme” files as well as in the header of the Airfoil.lsp file. Some of the readme files may not exactly reflect Macintosh AutoCAD usage.

I hope RC Soaring Digest readers will find this program useful. Now off to design that next model! We have to keep proliferating graceful flying objects y'know.
AIRFOILS.exe (PC) includes the routine, readme file, Tab_2_Space.exe utility, and folders of airfoil coordinates.

AIRFOILS (Macintosh) includes the routine, readme file, and folders of airfoil coordinates.

Tex-Edit Plus can be found at

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