                                 AIRFOIL
                               Version 2.01
                   Copywrite (c) 1992 All Rights Reserved

The purpose of this program is to provide the user with a means to enter,
modify, and plot various airfoil curves.  It has been created with the R/C
enthusiast in mind as an inexpensive software tool.  Others interested in
aerodynamics may find it beneficial.  This software has not been copy
protected to enable the owner ease of personal backups or installation to
a hard disk.  Owners may maintain as many copies as desired, but it should
never be possible for more than one user to be able to use this software from
copies of one original.  Your cooperation will enable the maintenance and
improvements of this software.  Refer any questions/improvements to:


                                                Jeff Christensen
                                                2311 E. 2400 N.
                                                Layton, UT  84040
                                                (801) 546-3631

You may desire to delete this file from your working disk after obtaining
a hardcopy to free up more space for addtional curve data files.



1. INTRODUCTION

The purpose of this section is to define terminology used throughout this
document and give basic generalities about aerodynamics.  For further
detailed references of aerodynamics, see the end of this document and consult
your local library.

An airfoil is the cross-section of a lifting surface (eg. wing, rotor,
propeller, etc.).  The airfoil shape is actually comprised of two curves, the
upper surface and lower surface curves.  The chord of an airfoil is the linear
distance from the leading edge to the trailing edge of the airfoil.  The
camber of an airfoil is the curve which is midway between the upper and lower
surface curves; the median line.  Finally, the thickness of an airfoil is the
distance from the camber curve to either surface curve (since the camber is in
the center of the upper and lower surface curves, the distance is equivalent).
These curves are usually specified in percentages of the chord to enable ease
of plotting to any specific chord length.

Airfoils should be modified by changing their camber or thickness curves
seperately as opposed to modifying either surface of the airfoil itself.  The
latter practice will cause the camber and thickness curves to change
simultaneously giving unpredictable results.  In general, increasing the
camber will increase the coefficient of lift for a given angle of attack thus
reducing the required airspeed.  This comes with a cost of higher profile
drag.  Less camber reduces this profile drag enabling higher speeds for racing
or penetration considerations.

This software enables the user to modify the curves he desires to create the
airfoil he desires.  Mixing and matching camber and thickness curves of
different airfoils is also provided.  Curves for this package are entered
with the X chord percentage parallel to the chord and the Y chord percentage
being perpendicular to the chord.  All percentages are assumed in the
0.0 - 100.0 (eg. 50% = 50.0, 75.2% = 75.2, 0.5% = 0.5, etc.) range with the
leading edge usually at the 0.0 range and trailing edge at the 100.0 range.


2. GETTING STARTED

This program maintains a data base of airfoil curves which the individual
user will augment according to his needs.  For this reason, it is highly
recommended that frequent backups are made of your work.  Remember anything
you create will likely not be able to be restored by the author in case of
some data loss.  Further, since you are storing data to the disk and the
program must be able to write to the disk, the disk should not be write
protected.  This holds true even if no new data is to be entered to the
disk.

First, perhaps the most difficult part is to setup the appropriate escape
sequences for your individual printer.  This will only need to be done one
time for the specific printer.  Start by making a back-up of the original
disk (remember the importance of backing up).  The file, MYPRT.SUP, is what
the program uses to read the printer escape sequences.  The first line of
numbers are the decimal ASCII values (eg. 27 equates to ESC, 65 -> 'A',etc.)
required to place your printer into 960 dots per 8" line with no line spacing.
The second line is the decimal ASCII values required to place your printer
into text mode.  This MYPRT.SUP is originally setup for an EPSON FX-80.
Your printer may not be that much different (if at all).  The author is not
aware of all escape sequences for all printers, however as users inform the
author of the escape sequences for specfic printers, they will be made
available.  Refer all questions to the address/phone above.

>> To begin the program, type AIRFOIL from the DOS prompt. <<


3. OPERATION/CURVE CONTROL

The upper left screen is the command control window for the software.  It is
comprised of two fields, the operation and curve fields.  The operation is
the function to be preformed on the selected curve.

The operation may be selected in two ways.  The first is by using the up and
down cursor control keys.  One cursor will take you through the list of
options in one direction, while the other will reverse that direction.  Once
the desired operation is selected, pressing the Enter key <CR> will cause
that operation to become active.  You will then, in most cases, have the
option of selecting which curves (airfoil, camber, or thickness) the active
operation will use.  After the desired curve is selected, pressing the Enter
key will begin the function.  To abort a function, press the 'Q' key to
return to the operation selection mode.

The second method of operation selection is by pressing the key of the first
character of the desired operation.  This will change the function to the
first operation that begins with that letter.  In the cases where more than
one operation begins with the same letter (Print and Plot, for instance)
striking the key will toggle between the two operations.  As before, pressing
the Enter key will switch to curve selection where appropriate.  The curves
may be selected in a similar manner by hitting 'A', 'C', or 'T' (airfoil,
camber, or thickness respectively).  Remember, as before, pressing Enter
will begin the operation on the curve while pressing 'Q' will return you to
operation seletion mode.


4. OPERATION SUMMARY

Now that control of the software has been explained, the only thing left to
explain is the various operations available and what curves these operations
work on.  The opertion will be listed first with the curves that it may
operate upon listed in parenthesises () following.

   4.1 Use - (Airfoil,Curve,Thick)

      This command is used to load any of the previously saved curves.  This
      causes the selected curve data to become active replacing the old data
      for this curve (see Save if the old data is to be stored).

       4.1.1 Airfoil curve
          When a airfoil curve is to be 'Use'd, the first window opened will
          be a list of all the available airfoil families (directories).  Use
          the cursor keys to position the cursor on the desired family and 
          press the Enter key.  A window will now be opened which is a list of
          all available airfoils within that family.  Using the cursor keys and
          pressing the Enter will load the selected airfoil.  Since an
          airfoil is comprised of a camber and thickness, all curves will be
          replaced with the new data.
       4.1.2 Camber curve
          If a camber is to be 'Use'd, a window will be opened that is a
          list of the available camber curves.  Use the cursor keys to
          position the cursor on the desired curve and press the Enter key.
          This will cause the selected camber data to replace the old camber
          data and cause the airfoil curve/data to be modified appropriately.
       4.1.3 Thick curve
          If a thick is to be 'Use'd, a window will be opened that is a
          list of the available thickness curves.  Use the cursor keys to
          position the cursor on the desired curve and press the Enter key.
          This will cause the selected thick data to replace the old thick
          data and cause the airfoil curve/data to be modified appropriately.

   4.2 Edit - (Airfoil,Camber,Thick)

      This command is used to enter numerical data for the selected curve.
      The editor works on a field basis.  The cursor keys will allow
      movement throughout the data without changing the existing data.  If
      a value is to be changed, type in the new value and press the Enter
      or Space key.  If one of the cursor keys are hit after a field has
      started to be modified, the old data will remained unchanged.  Enter-
      ing data for all curves are equivalent with the exception that the
      airfoil has two curves for its upper and lower surfaces.  (NOTE: the
      editor/software expects to have an equal number of points for the
      upper and lower surfaces.  If this is not always the case, enter the
      last point of the curve with the fewer points in the remaining
      positions.).

      Make sure to 'Enter' (or Space) the last value in before ending your
      edit session.  To end the edit session, press the 'Q' key.  The
      program will now prompt you for a name for your curve.  Enter up to 25
      characters (including spaces) and press Enter.  Modifying the airfoil
      data will cause the camber and thick curves to be updated
      appropriately.  If the camber or thick curves are 'Edit'ed only the
      airfoil data will be modified using the new edited curve and the other
      previous curve.

   4.3 New - (Airfoil,Camber,Thick)

      This command will clear all the data for the selected curve.

   4.4 Scale - (Airfoil,Camber,Thick)

      This command is used to scale all of the Y values for the selected
      curve (exception is selecting airfoil; see below).  The user will be
      prompted for the scale factor which all Y components of the curve will
      be multiplied by.  It then will modify the airfoil curve appropriately.

       4.4.1 Airfoil curve
          As mensioned previously, it is wiser to change the camber and/or
          thickness curve as opposed to the whole airfoil curve.  When you
          select Scale Airfoil, a warning will appear reminding the user of
          this.  If the user continues with this operation, instead of
          scaling the airfoil, the user entered value represents an offset
          value in a percentage of the chord that will be subtracted from
          the upper and lower surfaces.  Since this is changing the
          'distance' or thickness curve, the thick curve will be updated.
          The camber will remain the same.

       4.4.2 Camber/Thick curve
          This will causes one of the two selected curves to be scaled by
          the entered scale factor as mensioned above.  The airfoil curve
          will be updated accordingly.

   4.5 Plot

      This will cause the airfoil shape to be sent to the printer.  The
      user will be requested to enter the number of ribs.  If this value
      is greater than one, a root chord (width) and tip chord will be
      requested (for one rib, only one chord is entered.  The thickness of
      the skin is then requested.  This is to allow for balsa sheeting or
      other construction methods.  The program will then print the rib(s) to
      their exact dimensions (see section 4.10 Setup command).  Entering a
      zero (0) for the number of ribs or chord length will abort this command.
      NOTE: The camber of the airfoil will also be printed within the airfoil.
      The small tic mark on the camber line represents the highest point on
      the camber line if one exists.

   4.6 Print - (Airfoil,Camber,Thick)

      This command will cause the selected curve data to be printed in
      numerical values.  The curve 'shape' will not be printed.

   4.7 Quit

      This is to exit the program.  The program will prompt the user to
      see if he is sure.  Answering with a 'Y' or 'y' will terminate the
      program.

   4.8 Erase - (Airfoil,Camber,Thick)

      This command will erase the selected saved file (see 4.9 Save below).

       4.8.1 Airfoil
          After seleting Erase Airfoil, a window will appear which lists the
          available family of airfoils.  Using the cursor control keys,
          position the cursor on the airfoil family containing the file to
          be erased.  Pressing the Enter key will open a second window list-
          ing the files within this family.  Once again use the cursor keys
          to select the file and press the Enter key.  The file will be
          erased.

       4.8.2 Camber/Thick
          Selecting Erase Camber (or Thick), a window will be opened listing
          the available camber (thick) data files.  Position the cursor on
          the file to be erased.  Pressing the Enter key will erase the
          selected file.

   4.9 Save - (Airfoil,Camber,Thick)

      This command will save the current data of the selected curve to disk.
      If a file already exists under the user entered filename, the software
      will prompt if you wish to over write the old file.  If not, the file
      will not be saved.  The user may retry under a different name.

       4.9.1 Airfoil
          Save Airfoil will first prompt the user for the airfoil family
          name.  If the family name is a new name, it will be added to the
          airfoil family list.  If not the old family list will become active.
          The user will then be prompted for a airfoil name (filename) that
          the existing airfoil data will be saved under.  As described above,
          it will notify the user if the name has already been used and allow
          the user ot select whether over-writing is to occur or to abort.

       4.9.2 Camber/Thick
          Save Camber (or Thick) will prompt the user for the filename the
          current camber (thick) data is to be stored under.  If the filename
          has been previously used, the user will have the option of over-
          writing the old file or to abort the save.

   4.10 Setup
      This command is used to determine the appropriate scaling for plotting
      airfoil curves to the printer.  Originally the program is configured to
      plot curves in units of inches (chord lengths are expressed in inches).
      Using this command, the units of measurement can be changed to any other
      desired units.  The command will plot a rectangle to the printer and
      then request the dimensions of the rectangle.  These dimensions should
      be expressed in the units the user wishes to enter chord lengths.

      This command also insures the user the capability of changing the aspect
      ratio of the plotting.  Some printers have different aspect ratios
      causing the airfoil shape to be inaccuratly plotted.  Using this command
      and entering the dimensions of the plotted rectangle in the desired
      units will insure a correct aspect ratio.

This completes the explaination of the various commands of AIRFOIL.

5. CONCLUSION

This program was designed to provide an inexpensive means of manipulating
and plotting airfoils.  Updates and improvements on this software will follow
upon the success of its use.  Recommendations for improvements and new
features will be appreciated.  For information or help, send a self addressed
stamped envelope or contact by telephone:
                                          Jeff Christensen
                                          2311 E. 2400 N.
                                          Layton, Utah  84040
                                          (801) 546-3631
Please provide your serial number and owner name.

6. REFERENCES

Books:
MARTIN SIMMONS  Model Aircraft Aerodynamics, Argus Books, 1978, 1987
AL DOIG  Sailplane And Soaring Manual, RCM Anthology Books
LENNON  R/C Model Design
SELIG, DONOVAN, FRAZER  Airfoils At Low Speeds; Soartech 8, Herk Stokley, 1989
                        1504 N. Horseshoe Circle, Virginia Beach,  VA.  23451
