The alternate way of describing this airfoil is through percent of chord, for example: 4 percent camber, 40 percent chord with 15 percent thickness. Thus for the NACA 4425 the maximum camber is 0.04*c located at 0.4*c from the leading edge, and has a maximum thickness of 0.15*c. The last two digits (15) give the maximum thickness in hundredths of a chord. Using the NACA 4415 shown above in figure 2 as an example, the first digit (4), represents the maximum camber in hundredths of chord, the second digit (4) is the location where the maximum camber is located along the chord from the leading edge in tenths of a chord. The NACA “four-digit” airfoils were the first developed in the early 1930’s. NACA developed a large database and produced several naming conventions for different classifications using a numbering system. Airfoil shape design was a much customized art early on, however in 1930’s the National Advisory Committee for Aeronautics (NACA) performed an exhaustive amount of design and testing of various airfoil shapes. The Wright brothers experimented and tested their own shape designs as well. Phillips patented his first airfoil shapes. These cross-sections come in all variants of thickness, camber, and chord length. Changing the angle of attack also influence the behavior of an airfoil. The camber of the airfoil is the dominant characteristic which influences the lift, drag, and moment produced by the airfoil. The camber is then said to be zero since it is the maximum distance between the chord line and the mean camber line.
![thin airfoil theory thin airfoil theory](https://i.ytimg.com/vi/tiSzs6zVRhE/maxresdefault.jpg)
When the mean camber line and the chord line lie directly on top of each other the airfoil is symmetric. The distance then between the leading edge and trailing edge is simply the chord and it is denoted by the letter c. The chord line is a straight line drawn from the leading and trailing edges of the airfoil. The mean camber line is equidistant from the upper and lower cross section, essentially a dividing line where the thickness is equal above and below. Further investigating this cross-section, Figure 2, illustrates several design features.The most important design feature is the mean camber line, shown in figure as a dashed line spanning the length of the chord. When the vertical tail induces a rudder deflection the local flow is turned and results in a yawing motion.Īn airfoil is best visualized as the cross-section of a wing as shown in Figure 1. All control surfaces are in essence are airfoils. In aerospace applications airfoils are not only utilized on the wing. Other sources define airfoils to be any shape or surface designed to turn flow.
![thin airfoil theory thin airfoil theory](https://i.ytimg.com/vi/85J5D7hfD_s/maxresdefault.jpg)
NASA defines an airfoil to be a “streamlined surface designed in such a way that produces useful motion.” The useful motion being referred to in aerospace applications is lift or propulsion depending on where the airfoil is utilized.