In spite of the benefits from an increase in aspect ratio, it was found that definite limitations were defined by structural and drag considerations. The higher the aspect ratio, the greater the lift. It is also known that the larger the wingspan, as compared to the chord, the greater the lift obtained. Wing flaps cause an ordinary wing to approximate this same condition by increasing the upper camber and by creating a negative lower camber. Thus, high-lift wings have a large positive camber on the upper surface and a slightly negative camber on the lower surface. Camber is positive when departure from the chord line is outward and negative when it is inward. Upper camber refers to the upper surface, lower camber to the lower surface, and mean camber to the mean line of the section. Camber refers to the curvature of an airfoil above and below the chord line surface. The amount of lift produced by an airfoil increases with an increase in wing camber. High-lift wings and high-lift devices for wings have been developed by shaping the airfoils to produce the desired effect. Research has shown that the most efficient airfoils for general use have the maximum thickness occurring about one-third of the way back from the leading edge of the wing. The shape of the airfoil is the factor that determines the AOA at which the wing is most efficient it also determines the degree of efficiency. At this angle, the wing has reached its maximum efficiency. This ratio varies with the AOA but reaches a definite maximum value for a particular AOA. The efficiency of a wing is measured in terms of the lift to drag ratio (L/D).
#AIRFOIL SHAPES SKIN#
The best wing is a compromise between these two extremes to hold both turbulence and skin friction to a minimum. A wing with a low fineness ratio produces a large amount of turbulence. A wing with a high fineness ratio produces a large amount of skin friction. If the wing has a high fineness ratio, it is a very thin wing. Turbulence and skin friction are controlled mainly by the fineness ratio, which is defined as the ratio of the chord of the airfoil to the maximum thickness. The shape of the airfoil determines the amount of turbulence or skin friction that it produces, consequently affecting the efficiency of the wing. The resulting aerodynamic properties of the wing are determined by the action of each section along the span. A wing may have various airfoil sections from root to tip, with taper, twist, and sweepback. Shape of the AirfoilIndividual airfoil section properties differ from those properties of the wing or aircraft as a whole because of the effect of the wing planform.
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