MS-DOS/VGA program to draw and print NACA 4-digit foils, written by
Bruce Winterbon
R.R. 1, Deep River
Ontario, Canada
K0J 1P0
e-mail: bk850@freenet.carleton.ca
This program is based on my program BOAT for the design of stripper canoes. I received the algorithm for construction of the NACA foils from Nick Schade, in the form of some Pascal code, and have incorporated that into this program. The program is freeware: it may be freely distributed, and no charge shall be made for the program save for a reasonable nominal fee for handling and the cost of materials. s
All the program does is allow you to create images of these foils, one at a time , of any desired size, and print those images, full size, on your printer. The printing should be able to be done on almost any printer capable of printing graphics, but I have been able to test the printing only on an Epson-(semi)compatible 9-pin dot-matrix printer and a HP DeskJet 500. n
If you have suggestions for improvements, or if you find bugs, write or e-mail to me at the addresses above.
The program needs a mouse to run. Also it requires at least EGA or VGA graphics. It runs from DOS; it doesn't need Windows. (Windows slows programs down.) It could probably be run from a floppy disk, but it would be painfully slow -- it should be installed on a hard disk. The "standard" version of the program, the one archived at an FTP site, will run on an 8086 or higher CPU, with no numeric coprocessor ('87 chip). If you have an 80286 or higher CPU, I can provide either "real mode" or "protected mode" versions that take advantage of it. Real mode uses only the standard 640K of memory, and protected mode uses extended memory. Also, if you have a numeric coprocessor I can provide a version that uses it, and will therefore run faster than the no-coprocessor version. If you have a 486: the 486SX does not include a coprocessor but the 486DX and 486DX2 processors do have built-in coprocessors.
In text mode, the screen is 80 characters by 25 lines; in graphics, 640 by 480 pixels. If you NEED something different, I'll try to help.
Besides the program FOILS.EXE, the files FOILS.HLP, FOILS.TVR, EGAVGA.BGI, and SIMP.CHR are necessary to run the program. The protected-mode version also needs the files DPMI16BI.OVL and RTM.EXE. The program creates data files with the default name FOILS.DTA. All of these files should be in the same directory. If you change the name of the program, then all of the files on the disk with names FOILS.* should be changed correspondingly. "
The program can be run by typing
FOILS
FOILS datafile
where "datafile" is the name of a data file, or the path to one. If the extension of the data file is .DTA, it needn't be specified. What you have typed is called the "command line", and the portion of the command line is called the parameter or parameter list. ^
In the first case (no command line parameter), when the program starts it looks in the directory the program is in for a file with the extension .DTA and the same name as the program: if the program file is FOILS.EXE, it will look for a file FOILS.DTA to be read as a data file. If "datafile" is given it looks for that file to read as a data file.
If it doesn't find the file it gives a warning message. When one is installing the program, this file will not exist, and the message warning one of that is proper. j
There is no printed manual. The help text is intended to take the place of such a manual. Use the help text. While you may be able to figure out what each function is supposed to do, there may be some features that you might not find by accident. There is some redundancy in the help text (the same information in diferent places) but probably not yet enough.
Some of the features (File, Change Directory, and Text Colours dialogs) are inherited from the Borland Pascal environment. The help text for those features is also inherited, with some modifictions.
I have tried to make as much as possible editable. One can alter display colours, printer control codes, units of measurement, and so on. All of these things, as well as fitting parameters, are saved automatically as part of the data file. +
One can work in English or metric units. =
The foil patterns are drawn full size on the printer paper. If foils are more than 8 inches (20 cm) deep, the patterns will require piecing. A line is drawn across the page where piecing is necessary. If the paper is not continuous-feed, marks are drawn at the corners of each sheet to help put the sheets together. #
The program is controlled through the menu bar at the top of the screen. The
menu is opened by pressing "Alt"+"Space" (together). The other two menus are opened by pressing "Alt"+"Z", where "Z" is the highlighted letter of the menu. For example, the "File" menu is pulled down by "Alt"+"F". Also "F10" activates the menus, and one can shift among them with the left-arrow and right-arrow keys, or open them with the up and down arrows. The menus may also be opened by clicking on them with the mouse. They may be closed by pressing "Esc". See
****File****Draw
When a menu is selected, the "focussed" item in the menu will be indicated by a different colour. Focus may be changed with the up and down arrow keys. Left and right arrow keys switch between menus. To select a menu item
i) highlight it with the arrow keys, then press "Enter";
ii) type the highlighted letter; or
iii) click on it with the mouse.
A few of the menu items (e.g., read or save a file) can be selected with the function keys. `
When a menu has been selected, typing a letter selects a menu item, "Alt"+letter another menu.
The status line at the bottom of the screen shows some menu functions available directly from the keyboard, and also shows help prompts. The menu functions may be invoked by pressing the indicated keys or by mouse clicks on the appropriate part of the status line. f
Most of the menu functions create standard text
screens or standard graphics
screens. Some use both. d
Highlighted terms (as above) in the help text refer to other help topics. They may be selected by double-clicking on them with the mouse. If the background of the highlighted term is also highlighted, that item is "focussed". Focus may be changed by single mouse clicks, or by pressing "Tab" and "Shift"+"Tab". A focussed item may be selected by "Enter".
The help screen may be moved by clicking on its top line and dragging it. It may be enlarged to full screen or returned to its previous size by clicking on the little box ("icon") in the top right corner. Its size may also be changed by clicking on and dragging its lower right corner. One may move about within the text with the scroll bars in the usual way. The help screen can be closed by clicking on the icon in the its top left corner, or by pressing "Esc".
Dialog Boxes
One interacts with the program through the main menu, text screens, and graphics screens. The text screens are called dialog boxes. "Enter", "Esc", and clicking on the icon in the top left corner exit from the text screens. "Esc" and the mouse click on the icon cause the work done in them to be discarded. If the "Cancel" box is focussed, "Enter" causes cancellation. If a text input line is focussed, then "Enter" merely shifts focus instead of exiting from the screen. {
When in a dialog box, one can't invoke the main menu, even though it is still visible. One can get help by pressing "F1".
A text dialog box may contain "radio buttons", precisely one of which can be selected. These are indicated by parentheses, ( ), and the button with the dot in it, (
), is the selected one. It may also have "check boxes" (indicated by brackets,[ ]), any number (including 0) of which may be selected ([x]). One can move from one item to another with the mouse or with the "Tab" and "Shift"+"Tab" keys.
(Return to Introduction "
File
Print
patterns**Draw
Units
About
This screen gives copyright information, date of compilation, and (graphics and processor) target of this copy of the program. i
This program is freeware. It may not be sold, except for a nominal sum to cover handling and materials. }
The program uses some of the code developed for my boat-design program, which in turn was written to aid in the design of stripper canoes. A demo copy of the boat-design program, BOAT, is available by FTP. It contains all of the features of the full program except that it can not read nor write data files, so that each time one starts the program, one is starting from scratch. 0
The full BOAT program may be obtained from me:
Bruce Winterbon
R.R. 1, Deep River
Ontario, Canada
K0J 1P0
e-mail: bk850@freenet.carleton.ca
The current price is US$75.
(Return to Introduction?)
File (Alt-F)
The File menu includes choices for saving and reading data files, changing directories, printing station patterns and tables of station coordinates, changing the screen appearance, and exiting the program: z
Save**SaveAs**Read**Change
printer**Print
Patterns
Text
Colours**Graphics
Colours
Check
aspect
ratio**Exit
There are prompts to save a data file before exiting from the program and before reading another data file. Also there are prompts when saving if a file of the same name exists.
(Return to Introduction?)
File
Save (F2)
The Save command allows one to save the foil parameters to a disk file. The "environment", i.e., the fitting parameters, screen colours, etc., is automatically saved as part of the design. The file will be saved with its present name. The duplicate-file-name warning box will appear to remind one that the file already exists, and the previous version can be saved with a similar name. Y
If you wish to save the data under a new name, select the File
As command instead.
(Return to File?)
File
Save As (Shift+F2)
The Save As command allows one to save the data with a new file name. It displays a File
dialog
box, within which you can select the name of an existing file, or enter a new file name. If you select the name of an existing file, the duplicate-file-name warning box will appear to allow you to change the name of the old file.
(Return to File**File
Save?)
File
Read (F3)
The Read command displays a File dialog box. In this dialog box you select the data file you want to read. When the program is started it looks for a data file FOILS.DTA in the same directory as the program file, FOILS.EXE. If the program name has been changed it will look for a .DTA file with the same name as the program.
(Return to File?)
File Dialog Box
The File dialog box contains an input box, a file
list, a file information panel, the standard cancel button, one other action button (Open), plus a history list that's attached to the Name
inputbox.
If one is to write to the selected file, and the file name chosen is that of an existing file, the duplicate-file-name warning box will appear. $
(Return to File
As**File
Read !
File
printer?)
File Name Input Box
The Name input box is where you enter the name of the file to load, or the file-name mask to use as a filter for the Files list box (for example, *.*). The history list is opened by clicking on the down arrow or pressing the down-arrow key. $
(Return to File
As**File
Read
File
dialog
box?)
Files List Box
The Files list box lists the names of files in the current directory that match the file-name mask in the Name input box, plus the parent directory and all subdirectories.
File Information Panel
The File information panel (at the bottom) shows the path name, file name, date, time, and size of the selected file. None of the items on this information panel is selectable. $
(Return to File
As**File
Read
File
dialog
box?)
File Open Button
The Open button directs the program to read from or write to the selected file. $
(Return to File
As**File
Read
File
dialog
box?)
File
Change Directory
Change Directory brings up the Change Directory dialog box, in which you can change the directory in which to look for data files. This dialog box consists of an input box, a list box, the standard OK and Help buttons, and two other buttons (Chdir and Revert). R
The Directory Name input box is where you type in the path of the new directory. p
The Directory Tree list box enables you to navigate directories by using the selecting bar and pressing Enter. W
If you're using the keyboard, press "Enter" to make the selected directory be the current directory, then choose OK (Alt+K) to exit the dialog box. If the selection bar is on one of a list of subdirectories, pressing "Enter" closes the rest of the list. If it is on a directory with subdirectories, "Enter" opens the list of subdirectories. c
The Chdir button changes the current directory once you've selected or typed in a directory name. ~
The Revert button is the same as "Cancel": you return to the directory in use when the Change Directory function was called.
(Return to File?)
File
Set up printer
On the left one selects both the type of printer and, depending on the type, the resolution or paper size one wants. The R, H, or P on the left indicates whether the printer is operating as a raster device, uses HPGL graphics commands, or uses PostScript graphics commands. For example, an HP LaserJet can be used in either raster mode (third choice) or HPGL mode (the next-to-last choice). :
Most printers can be made to emulate (i.e., to act like) at least one of the printers in this list. Many 24-pin printers can emulate 9-pin printers. Not all printers offer a choice of resolutions: check your printer manual. Although some colour printers can be used, the drawings will be in black and white only.
It takes longer to print at higher resolutions, so for patterns it is usually better to use the lowest resolution available, but for other graphics printing a higher resolution is better. m
The printer port may be selected (LPT1, also called PRN, is the usual port) or the output may be directed to a file for later printing. If writing to a file is chosen, the file name may be entered from a File
dialog
box. NUL is a "null" printer: the program does all its work but doesn't actually send anything to a printer. This is useful to preview your output. b
The plot orientation is either "portrait", the usual way, or "landscape", sideways on the paper.
If printing a graphics screen rather than a pattern, one can send a form feed command (skip to top of next page) before printing. =
A second dialog box selects certain printer
parameters.
Return to File
Print
patterns?
Select printer parameters
Particularly with the so-called Epson-compatible 9-pin printers, compatibility is not perfect, and different printers have different resolution, page size, etc. These parameters may be changed here. Try the parameters that are given, and if things aren't quite right then use your printer manual, and experiment.
Some raster-type printers may require a "set-up string" of characters before acting properly. The appropriate string can be entered here. I have put the mode-switching commands for HP raster printers in this set-up string instead of hiding it in the program. You shouldn't need to change it. Any control characters in the string, those with ASCII codes less than 32 or greater than 128, are represented as "#n ", where n is the ASCII code. (Note the space after the number.) For example, "ESC" is "#27 ", and "ESC X" (with no spaces) appears as "#27 X", with a space after the number; this space is interpreted as part of the control character. To insert the character "#" use "##". 5
The code selecting the graphics mode of the Epson-compatible printers may be changed here. I have conflicting information on printer commands and resolutions for these printers. Manufacturers appear to differ on what the standard is. You may have some fiddling to do to get things working right. Each resolution for the dot-matrix printers corresponds to a different graphics command, ESC x n1 n2, where n1 and n2 specify the number of points to be plotted, and x represents the varying part of the command. The graphics data are sent to the printer in a different way for 9-pin and 24-pin modes, and the highest resolution for each is in yet another order: that's four different ways of arranging the data. If you use a graphics code that corresponds to a different ordering of graphics data, the plot will be garbage. }
9-pin printers typically have codes like ESC K n1 n2, and 24-pin printers usually recognize these codes and also have codes like ESC * m n1 n2, where m is an integer. m=0 corresponds to K. The number m is sent as a character, not as ASCII code, so that m=0 would have to be sent as #0 rather than 0, and m=33 would be sent as #33 or as an exclamation point, !, which has code 33. 7
Use the "Test" button (see below) to sort things out. .
Epson 9-pin printers go much faster in text mode than in graphics mode, so the program scans each line of graphics and replaces graphics blanks by text blanks whereever possible. If it isn't working on your printer, perhaps the width of a character in pixels is nonstandard. That may be changed here.
Some printers have different print-quality modes. The mode may be selected here for DeskJet printers, or in the set-up string for others. 3
When printing with HP raster printers, the amount of data to be sent to the printer can be a bottleneck. These printers support various schemes of compressing graphics data, and one of them, run-length encoding, is used here. If it works all right, use it; if it seems to be causing problems, turn it off.
Also if the printer is connected to a serial port the connection may be non-standard; quantities describing this connection may be changed here. Don't make changes unless you know what you are doing.
If you do make changes, and they don't work, you can return to the standard values by choosing the "Default" button. This changes the values, but does not exit from this dialog box.
The "Test" button prints (on the printer) a box of the size specified by the "resolution" and "print area" boxes. It returns you to this dialog box after printing. Print the box, compare its size with what was specified, and adjust accordingly. To start with, you'll probably want to find out how many points you print across the page. Set the vertical resolution to a small number of dots, 10, say, and select "Test". If the box extends off the screen, reduce the horizontal resolution and try again. Once you have a line that's too long and one that's too short you can measure the two to determine how many points are printed on one line. Now enlarge the vertical resolution. If you are using separate sheets of paper you'll need to go through the same procedure. If you can print on continuous-feed paper you can just measure the box once and calculate how long it should be to fit on one page.
Once the resolution is correct, measure the box and correct the size in inches or mm, or your patterns will not be printed the right size.
The corrected settings will be saved with your data file, but it would be a good idea to write them down somewhere in case something happens to the data file.
Return to printer
selection?
Labels on patterns
The program writes a four-line label on each pattern as it prints it, so that the patterns can be identified later. All lines can be changed. The first line is the foil code, the second the file name, and the third is the date. The fourth is blank.
The size and position of the label can be changed, and one can choose to have the program pause after each stage of the printing process. This is handy if one is printing to the NUL device to see what the output will look like. 1
Finally one is ready to print
graphics
box.
Return to File
Print
patterns?
Graphics printing
When the graphics box is being printed, the printing can be stopped by pressing "ESC".
Graphics can take many different forms in the PC world. To handle all of these varieties, and the different one that will appear next week, Borland (this program was written in Borland Pascal) has chosen to have graphics functions in the language write through the so-called Borland Graphics Interface, or BGI, to the graphics device. The file EGAVGA.BGI is the Borland-supplied "device driver" that allows drawing graphics on the screen. G
Borland leaves other drivers for other software companies to supply. The printer drivers I have used here to print the graphics box were written by Quinn-Curtis (and modified by me: my printer is not quite compatible with the Epson 9-pin "standard", and also I wanted to see on the screen what was being sent to the printer.) +
Return to print
patterns**Pattern
labels?
File
Print patterns
One reason for writing the original boat-design program was to have it construct patterns on a printer.
Use File
printer first, to choose printer and resolution. Low resolution is usually adequate for printing patterns, and it is faster.
Next one selects
labels to appear on each printed pattern. Then the graphics
printing starts. When the printer is printing graphics, the screen
displays progress. R
Most printers print only an approximately 8-inch-wide strip, so full-sized patterns will almost always have to be pieced. A line is drawn across the paper where it must be pieced so that it is easy to assemble the pieces. If the printer uses separate sheets of paper instead of a continuous roll, the corners of the printing area will be marked to aid reassembly. Index marks are drawn at the left and right edges of the paper to aid further in alignment. Other index marks are put on the curves at the sheerline. When the program is printing graphics, it displays a box showing the progress. 8
Printing can be stopped at any time by pressing "Esc".
(Return to File ?)
Screen display of graphics printing
To print graphics, the program first writes the graphics commands to a file called a graphics metafile, then reads back the metafile. If the printer is a raster device (a dot-matrix or an inkjet printer, for example), the program uses the metafile to construct an image in memory (a bitmap) of the page to be printed, then sends that bitmap to the printer. If instead the printer can act on HPGL or Postscript graphics commands, when the program reads the metafile it sends the appropriate commands directly to the printer.
While all this is going on, the program is displaying progress. The graphics screen shows an image of the page to be printed, squashed or stretched to fit the screen. Lines are drawn on the screen as the appropriate commands are read to and from the metafile, and the bitmap image is written to the screen as it is sent to the printer. Because the number of dots on the screen and on the printed page are different, the screen image will not be as clear as the printer output.
Return to File
Print
patterns?
File
Text colours
This function calls the Colours dialog box, which allows you to change the colours of the text screens: the main menu, the desktop, and the dialog boxes.
The Colours dialog box consists of two list boxes, a text display area, the standard OK, Cancel, and Help buttons, and one of the following:
On colour and black-and-white systems, it
also contains two color palettes.
On monochrome systems, it contains a set
of radio buttons instead of the palettes.
The Group list box contains the names of the different regions of the program that you can customize: desktop, menus, and dialogs. z
When you select a group from the Group list, the Item list box displays the names of the different views in that region. j
On colour and black-and-white systems, you use the Foreground and Background palettes to modify colours. l
On monochrome systems, you use the Colors set of radio buttons systems to modify the character attributes. l
On all systems, the display text (above the Cancel button) shows the current colour or attribute settings. b
Changes do not take effect on the desktop until you close the Colours dialog box by choosing OK.
(Return to File?)
File
Graphics colours
Refer to the graphics help screen for general help.
This function allows you to change the colours of the graphics screens. The screen contains the features of the graphics screens so one can immediately see the results of the changes. Portions of the graphics box may be enlarged by outlining them with the mouse, just as in the other graphics screens. Colours are specified by their numbers in the palette, and the palette is shown.
Some of the features which can be changed in this function are not used in the FOILS program. It was easier to leave them in than to change everything.
(Return to File?)
File
Check aspect ratio
This module lets you adjust horizontal and vertical scales so that if the program were to draw a circle on the screen it would appear as a circle, not squashed into an ellipse. When one is viewing graphics screens one can choose whether to maintain the corect aspect ratio or to allow horizontal and vertical scales to vary independently.
(Return to File?)
File
Exit (Alt-X)
The Exit command terminates this program and returns you to DOS. If the hull or environment was changed since the file was last saved, a warning message will allow you to save the current version.
(Return to File?)
Draw (Alt-D)
The editing or work of the program is done in the "Draw" menu. The first item in this menu uses a graphics
screen, and the second a text
screens. The sub-menus of the "Draw" menu are
Draw
foil**Units.
(Return to Introduction?)
Draw
Draw foil
All of the parameters of the foil may be changed within this function. The length is specified, and then one can give either the four-digit code, or the values of the parameters that make up that code. T
The four-digit NACA code is defined as follows. All lengths are given as percentages of the foil size. The first digit is the maximum camber, so it must be no greater than 9. The second is the position of this maximum camber, aft of the leading edge of the foil, but in tens of percent. The last two digits give the thickness of the foil.
Suppose the code is 1234. Then the maximum camber is 1%, it occurs 20% aft of the leading edge, and the foil thickness is 34%. g
I have chosen to generalize the foil a little bit, so that one can specify the position of the maximum camber to one percent, instead of 10%. Note that if you do not use a multiple of 10%, the code shown will not correctly descibe the foil. If you print such a foil pattern, you should note in the text printed on it that it is not a true NACA 4-digit foil.
The positions of the upper and lower surfaces of the foil will be calculated at all multiples of the step size along the length of the foil. If the step size is too small, the program will demand more memory than is available, and will crash.
If the camber is 0, the foil is symmetric. The two surfaces are given by + and - f, where f is a square-root term, to give a parabolic leading edge, plus a fourth-order polynomial. To camber the foil, the two surfaces are each raised by a simple piecewise quadratic function.
Draw
Units
Refer to the dialog
box help screen for general help.
One can use English or metric units in this program. In English units, all linear dimensions are stored in inches, but can be displayed as feet or inches; in metric units the data are stored in mm, and displayed in mm, cm, or m.
Longitudinal and transverse dimensions can be displayed differently: for example all lengths could be displayed in feet, and all widths in inches (or vice versa!). This too is inherited from the BOAT program. English and metric units can not be mixed, but a foil can be converted from one to the other. When one changes between feet and inches, or mm and cm, only conversion factors used in the displays are changed; when one changes between English and metric units, all dimensions are converted.
(Return to Draw?)
Graphics screens
Graphics functions are '
File
Graphics
colours**Draw
The graphics screens show two windows, called the graphics and index windows or boxes. The graphics box shows all or part of the drawing (i.e., a foil) that one is working on. The index box shows which portion of the whole drawing appears in the graphics box. When something less than the whole drawing is being displayed, it can be pushed partially outside the edges of the drawing so that there is more blank space at the edges. z
The mouse cursor can be moved a pixel at a time with the arrow keys, and eight pixels at a time with "Shift"+arrow keys. {
When the mouse cursor is in the graphics box, its coordinates in the drawing are shown on the right side of the top line.
One can choose whether horizontal and vertical scales are the same, or vary independently whenever one selects a subview. The ratio of horizontal and vertical is called the aspect ratio, and it can be either fixed or variable. s
When a graphics function is started, the whole view is shown. One can select part of this view with the mouse, as follows. Place the mouse cursor at one corner of the desired portion of the view, press and hold the left mouse button, and move the mouse cursor to the diagonally opposite corner. A box will outline the area of the new subview. When the mouse button is released, the graphics box will display the subview, and the index box will show what part of the whole view is being shown. If the box drawn is too small, the view does not change. This is too prevent accidents from pressing the mouse button inadvertently.
The right mouse button cancels any action started with the left button. Thus if for example one is drawing a box to outline a subview, as in the previous paragraph, and presses the right button before releasing the left, the view will not be changed. If the right button is pressed when the left button is up, while the cursor is in either the graphics box or the index box and not on a draggable point, the view reverts to full scale.
When the graphics box is showing a subview, one can outline another subview within the graphics box, and this can continue until the view is so small that there is an arithmetic overflow. (This will stop the program. Save your work often!) Or, if the mouse cursor is within the index box, then i) if the cursor, shown as a hand, is in the inner box of the index box that represents the portion of the view being displayed, that box can be moved with the mouse, using the left button, or ii) if the cursor is not in that inner box, it will be shown as a cross, and a subview can be outlined as if in the graphics box. Again the right button cancels the action.
There is also a parameter area (the upper left part of the screen); click in any of its boxes to change parameters. Or use "Tab" and "Shift"+"Tab" keys to move the mouse into this area and to move it forwards and backwards, respectively, from box to box. New values of numerical parameters are entered at the top left of the screen. When the cursor is in one of these boxes an explanatory prompt will appear at the bottom of the screen, and a slightly longer explanation can be obtained with the F1 (help) key.
Some of the numerical parameters are bounded: if you give one an unreasonable value, it may appear to accept that value, but when the program recalculates, the parameter value is changed to a reasonable value.
Grid lines can be drawn. They will appear in both graphics and index boxes. Select the horizontal and vertical spacings (of the vertical and horizontal lines, respectively) in the appropriate box of the parameter area. A spacing of 0 means that no grid lines should be drawn. t
Work can be saved, under the old file name (F2) or a different one (Shift+F2) wile working in the graphics screen.
(Return to Introduction**Draw? Or page up to the top of this help text for a list of the functions that use graphics screens.)
File backup
Creating a new file with the same name as an old one destroys the old file. If a file already exists with the name that will be used for the new file, this dialog box appears.
To change the name of the new file, select "Cancel", then repeat the steps by which the file name was chosen. If one used File
Save (F2) from the main menu then use File
as instead.
Otherwise, the old file may be overwritten, or its name changed, or, if appropriate, the new data may be written at the end of the old file by selecting the Append button. The new file name proposed for the old file is chosen by extending the old file name to eight characters by adding 0s, if necessary, and then incrementing the extended file name until an unused file name is found. For example, if the old file is called OLDFILE.DTA, the extended file name would be OLDFILE0.DTA. If a file with that name already existed, the name OLDFILE1.DTA would be tried. If all those choices through OLDFILE9.DTA already existed, the next choice would be OLDFIL00.DTA, and so on.
If you change the selected backup file name, then you must be sure the name you have chosen is not that of an existing file, for if such a file already exists, it will be overwritten without warning. 8
To save the old file with a new name, select "Backup". =
To save the new data and discard the old, select "Replace". D
To write the new data on the end of the old file, select "Append". $
(Return to File
Save**File
File
Dialog
Box?)
Grid lines
If the variable here is greater than 0, vertical lines are drawn uniformly spaced across the graphics box. For example, if the x units are feet and the variable is 1, then there will be lines at 0 feet, 1 foot,...
Grid lines
If the variable here is greater than 0, horizontal lines are drawn uniformly spaced across the graphics box. For example, if the y units are inches and the variable is 1, then there will be lines at 0 inches, 1 inch,...
Length of foil
Set the length of the foil, in real units (inches, feet, mm,...).
Step size
Positions of the upper and lower surfaces of the foil will be calculated at all multiples of the step size along the length of the foil. If the step size is too small, the program will demand more memory than is available, and will crash.
NACA code Suppose the code is 1234. The first digit is the maximum camber, in percentage of foil length, which is 1. The next is the position of maximum camber, in tens of percent. Here the point of maximum camber is 20% aft of the leading edge. The last two digits give the thickness of the foil, here 34%. d
Note that leading digits are not shown, so that a code of (for example) 0034 would be shown as 34.
Foil thickness As a percentage of the length of the foil. It determines the last two digits of the code.
Maximum camber As a percentage of the foil length. It determines the first digit of the code, so the maximum value is 9.
Position of maximum camber As a percentage of the foil length. It determines the second digit. Hence for a "true" 4-digit foil this parameter must be 10, 20, .... However this program allows use of values of 1 to 99, even though the code then does not describe the foil correctly.
Aspect ratio: fixed or variable?
The ratio of horizontal and vertical scales is called the aspect ratio. R
If the aspect ratio is fixed, the ratio of the horizontal and vertical dimensions will be held constant. If the horizontal and vertical dimensions can be measured in the same units (they are both lengths, instead of the vertical dimension being a number or an area, for example) then the horizontal and vertical scales will be the same.
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