Download the Plane Maker Manual - X-Plane

30 3. SHAPING THE BODY OF AN AIRCRAFT
of each piece. The Plane Maker-calculated value for the chord length is multiplied by the ratio you
set here to get the actual width of this piece.
For instance, if Plane Maker saw that the chord length should be 5 feet at the center of a
given piece, and you used a chord ratio of 2, the center would end up with a 10-foot chord length.
Likewise, if you had chosen a ratio of 0.5, it would end up with a chord length of 2.5 feet.
Finally, the “chord offset” setting, seen in Figure 3.25, determines how far forward or back a
given piece gets shifted. Positive values will push the wing section behind the reference point, while
negative values will push it forward of the reference point. This is specified as a ratio of the Plane
Maker-calculated chord length. Thus, with a calculated chord length of 5 feet, and a chord offset
of 0.5, a given piece will be pushed farther behind the reference point by 2.5 feet.
Use the above settings to customize the fine details of a wing section’s size and shape.
Setting a Wing’s Airfoils
Creating a wing in the standard Wings dialog box specifies only the wing’s size, location, and the
direction it’s pointing—it does not specify what shape the wing has. Is it thin along the trailing
edge and fat along the leading edge? Maybe it is fat along both edges, or maybe it is fat in the
middle and thin at the edges. To tell Plane Maker just what (cross-sectional) shape the wing has,
we need the Airfoil dialog box, which is launched from the Expert menu.
Each wing section can have four different airfoils set for it. These four airfoils come in two sets,
one for high Reynolds numbers and one for low Reynolds numbers. Each set has one airfoil for
the root and one for the tip. These airfoil shapes are then blended together linearly in the portion
between the root and tip, and the two sets (the low and high Reynolds number sets) are blended
together between the Reynolds numbers.
The airfoil shapes themselves must be created using the separate Airfoil Maker application,
which, like Plane Maker, is included in the X-Plane installation folder. X-Plane does not look at
the shape of the wing and then decide how much lift, drag, etc. the foil will put out—X-Plane is
not a computational fluid dynamics program. Instead, X-Plane uses pre-defined airfoils that list
the performance of any airfoil (lift, drag, moment) to predict how the plane will fly with that foil.
For information on using Airfoil Maker to create these airfoils with predefined performance, see the
Airfoil Maker supplement to the X-Plane Desktop manual.
To apply an airfoil shape to a wing after the wing has been created, open the Expert menu and
click Airfoils. In the Airfoils dialog box, go to the Wings tab. Here, you can set two versions of
both the root and the tip airfoil for each wing section. The foils on the left are for the root side of
the section, and the ones on the right are for the tip side, as seen in Figure 3.26. Plane Maker will
interpolate between the root and tip airfoil to create the shape of the middle of the wing section.
The top root-and-tip pair of foils in each wing’s box specifies the low Reynolds number version
of the foil; the bottom pair specifies the high Reynolds number version. Once again, X-Plane will
interpolate between these two when your Reynolds number is between the high and low values.
The following two pages may be useful in determining what airfoils to use in your wing (assuming
you’re modeling an aircraft that is already in production):
• The Incomplete Guide to Airfoil Usage
• StrategyWiki: Airfoils
To set an airfoil to be used on a particular wing, in a particular place (root or tip), and for a
particular Reynolds number (high or low), click the gray box to the left of that position on that
wing. A dialog box will appear for you to navigate to the airfoil file’s location. X-Plane’s default
airfoils are found in the X-Plane 10\Airfoils directory.