1047

Item 1047

OTHER: Aerodynamics - Airfoil - Characteristics

Notations:

Angle of Attack (α)

Coefficients:

Coefficient of Lift (c_l)

Coefficient of Drag (c_d)

Coefficient of Moment (c_m)

Coefficient of Normal Force (c_n)

Coefficient of Chordwise Force(c_c)

c_n = c_l * cos(α) + c_d * sin(α)

c_c = c_d * cos(α) + c_l * sin(α)

Notes:

Aerodynamic Center (AC)

Center of Pressure (x_cp)

Addition information: Center of Pressure or Aerodynamic Center? ~ by Prouty, Vertiflite2002 Directory p.28.

Center of Pressure Position:

x_cp /c = c_mac /c_l

NACA Four-digit Wing Sections:

First digit [m]:- The maximum value of the mean-line ordinate [y_c]; in percent of the chord.

Second digit [p]:- The distance from the leading edge to the location of maximum camber; in tenths of the chord.

Third & forth digit [t]:- Thickness at thickest location; as a percentage of chord.

NACA 6-series Airfoils:

First digit []:- Represents the series name.

Second digit []:- Indicates the location of the airfoil's maximum thickness (or minimum pressure) in tenths of chord (or length). In this case, the value 4 tells us that the airfoil is at its maximum thickness 40% back (or 0.4 chord) from the leading edge.

The first digit after the dash is called the design lift coefficient, which is provided in tenths. What this means is that the airfoil was designed for maximum efficiency at a lift coefficient of approximately 0.2. At this operating condition, drag is minimized.

The final two digits are the maximum airfoil thickness in percentage. Thus, this airfoil has a thickness-to-length ratio of 15% at the maximum point, which we already know is 40% back from the leading edge.

Now there are some slight differences between the class of airfoil we just discussed and and those you list in your question. First, you'll notice the capital A that appears in place of the dash (-). This indicates a modification to the basic geometry that eliminates much of the "cusped" shape on the lower surface towards the trailing edge of the airfoil. The purpose of this was entirely practical. Although the highly curved shapes were the result of the conformal mapping process, such shapes were impractical to build from an aircraft manufacturer's viewpoint. Therefore, the letter A simply indicates that the curved shape has been replaced by a flat surface from about 80% chord to the trailing edge. The other difference in the airfoil names is the decimal followed by two digits. All this indicates is a slight adjstment to the maximum thickness of the basic shape. While the 64A210 is 10% thick, the 64A210.68 is 10.68% thick and the entire thickness distribution along the airfoil length is scaled up to reflect this.

The VR-7 is a modified 62-512.

Back to top | SynchroLite Home Page | UniCopter Home Page

Last Revised: February 20, 2005