Converting the Dihedral Angle to a Measurement
In most cases you can disregard this section
because the amount of
dihedral is usually given as a readytouse measurement.
However, if the dihedral is given as an angle you will need to convert
the angle into a number you can use.
This article discusses how to convert angles to measurements. It does
not cover how to determine the correct dihedral angle for your design.
In these examples, the Sine function is the most
appropriate. See the
Trigonometry page for more details.
The Sine of an angle = the length of the opposite
side of the triangle divided by the hypotenuse of the triangle. You will
either need a table that gives the values of Sine for various angles or a
calculator that can determine the Sine of an angle.
For example, let's say you have a 60" wing that has 5° of dihedral. The
dihedral is per wing panel, not the total amount. In other words, the
included angle between the wing panels is 170° (a straight wing having no
dihedral is 180°).
Sketch a small diagram to help you out. The
hypotenuse of the triangle is half the wingspan (30" in this case).
Sine Ø = Dihedral ÷ Half Wing Span
For this example:
Wingspan = 60" (note that we will be using half
the wingspan)
Dihedral angle = 5°
Dihedral measurement = Unknown
1) find the Sine of the angle:
Ø = 5°
Sine 5° = 0.087156
2) Plug in the answer above to find
the opposite side of the triangle.
0.087156 = Dihedral ÷ 30"
Dihedral = 30" x 0.087156
Dihedral = 2.6" (under each tip)
