Here is the method that I have used to create airfoil base shapes
using AutoCAD R14.  The data I am using comes from Michael Selig's
collection of airfoils on his web site.  The idea is to create a
'script' file that is run within Autocad that performs the function of
automatically plotting a set of coordinates (the data).  This file
contains a couple of simple instructions followed by the data.  The
script file is then loaded into Autocad and run.  The result is an
airfoil with unity chord created using the PLINE command.  It is
simply scaled to whatever size you need.  Included are the files
Clarky.dat, Clarky.scr and Clarky.dwg which you can examine and work
with.  I have used the data for a Clark Y as an example and you should
try to run it yourself.  The data is as downloaded and was processed
as follows:

1)  Format the data

The data needs to be in a format that Autocad can recognize, i.e. two
columns of X and Y coordinates separated with a comma.  You can format
the '.dat' file manually if you have the time.  I achieved the
transformation by using Excel to remove the unwanted spaces/tabs and
insert the comas.  Import the file as text into Excel.  It will ask
how the file is delimited.  I chose comas/tabs as the delimiting
method as this is the nature of the data from the website.  Remove any
header information (like 'Clark Y Airfoil').  Once the data is in the
spreadsheet as two nice columns, I export it as a text file, coma
delimited.  The formatting is done and you can open the data in a word
processor (notepad works well) to continue.

2)  Add the script commands

There are really only two commands that are necessary.  'Osnap none'
which turns off any snap settings.  This is necessary because of the
way plotting can be affected by your existing snap settings.  Just try
it without this command and your snap to endpoint set as a default and
you will see what I mean.  The command that does the work is 'Pline'
which just plots the data that follows it until it runs out of data to
plot.  Both of these commands appear at the top of the file just ahead
of the data.  There should be no other text or empty lines before or
after these commands (other than the data).

3) Save the file as a script file 

Save your newly created script file as text with the extension .scr
which Autocad will recognize.  Open Autocad and select 'Run script...'
from the tools menu.  Select the file you just created and you should
get an airfoil plotted at the origin of your drawing.  Zoom to extents
and admire your 'work'.

Lloyd MacLean
5/10/02