A Quick Tutorial

This is just a quick step-by-step tour of MacFoil, to introduce you to the various features of the program. The links sprinkled throughout will take you to the details about the feature under discussion.

(It's assumed throughout that you're working in inches: if you normally work in another unit, you should set your program preferences to reflect that. Also, the graphics here are just screenshots of a small (8 inch chord) airfoil, so they'll fit comfortably on the page. Because of that, some of the small details aren't visible. In the program, you can increase the chord to see the finer stuff, and when you print at high resolution, of course, the details appear in all their glory, even on small airfoils.)

Start MacFoil, and create a new, empty plot by selecting "New" from the File menu.

Now we need to import some airfoil data, so click the "Airfoil..." button in the top left corner of the window, and find and open the Clark-Y airfoil file that came with MacFoil. It will immediately draw, looking like this:

Try clicking the various checkboxes at the bottom of the window. These control various plotting options.

Let's add sheeting to the airfoil. Hit the Tab key to move the selection to the Sheeting field, or click in the Sheeting field to select it. Enter a number in the Sheeting field by typing "1/16", then hit Tab again to redraw.

(Note that the plot redraws after you change a field and then move the selection elsewhere. In other words, it won't redraw until you "commit" the value you typed. Alternatively, you can hit the Plot button at any time to redraw with the currently entered data.)

Add a spar by first tabbing to the spar 1 Position field. Type "31%" in the field, and hit Tab. Note that a single vertical line is drawn in the foil, at 31% of the chord. Type "1/4" in the Width field, hit Tab, and there are 2 vertical lines, 1/4" apart, centered at 31% of the chord. Finally, type "1/4" in the Depth field, and you will have a square spar notch on the upper surface of the foil. Try checking and unchecking the box next to the spar: you'll see the spar rotated to be flush with the foil if the box is checked, otherwise its sides will be vertical.

Add a second spar directly under the first one. Type "31%" for Position, "1/4" for Width, and "-1/4" for Depth. Note that a negative Depth means to measure from the bottom surface of the airfoil.

Finally, lets add a reference line to show where our 1" trailing edge stock will meet the wing. Simply type "-1" into the spar 3 Position field and hit Tab or the Plot button: negative numbers in the Position field are measured from the trailing edge. Note that the 1 inch is measured from trailing edge of the original foil, NOT the inset (sheeted) foil.

Modify the airfoil to make it a little thinner by clicking the "Modify..." button in the upper right. Enter "9.5%" for the thickness, and leave the camber alone. Click OK, and see how the airfoil has thinned.

Lets compare the two airfoils. Click the "Overlay..." checkbox and choose Clark-Y again. See how the original (drawn in red) is uniformly thicker than ours, and how the camber lines are the same (remember we didn't change the camber). Click the "Overlay..." checkbox again to get rid of the original foil.

Click the "Template Seup..." button to bring up the Foam Template Setup dialog. You can move this dialog, if needed, to get a clear view of your plot while entering the template info. Type "1/2" in the "Template height" field and hit the Tab key. The template bottom will be drawn, 1/2" below the chord line. Type "1.5" in the "Foam block height" field, and an outline of the foam block will be drawn over the top.

Tab to the "Wire kerf" field, and enter "0.05", then watch the lower leading edge of the foil as you hit Tab again. It's subtle and hard to see, but the lower surface of the foil, especially at the leading edge, is adjusted to compensate for the foam removed by cutting.

Tab to the "# Station lines" field and enter "10", then hit Tab, and numbered station lines will be drawn across the foil. These are for monitoring your cutting progress, particularly helpful when cutting tapered cores.

Tab to the "LE Ramp Length" field and type "1/4", then hit Tab and enter "1/4" in the "LE Intersection" field, and hit Tab again to commit the value and redraw. We now have lead-in ramps for the cutting wire, that intersect the airfoil 1/4" in from the leading edge. Click the "Angle LE Ramps" checkbox to angle the ramps so the transition angle to the airfoil is less steep.

Type "1/4" in the "TE Ramp Length" field to create a 1/4" long lead-out ramp. You can choose from the three radio buttons to make the lead-out ramp follow the upper surface of the airfoil, the camber line, or the lower surface.

Click "OK" to dismiss the template dialog, and you should have this:

Type "2" into the "Washout" field and hit Tab to rotate the template 2 degrees: now you will have 2 degrees of washout built in to the template:

Export the plot to DXF by selecting Export->DXF from the File menu. The plot information (minus any text) will be saved as a DXF file, suitable for importing into your favorite CAD program, perhaps to set up toolpaths for a CNC cutter. You can also export as EPS (for illustration programs like Adobe Illustrator) or PICT (native graphics format for the Macintosh).

That's it for this quick tour: for more details on any of these steps, explore the various sections of the Help files.