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Old Feb 29, 2004, 08:06 AM
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Punta Gorda, FL
Joined Apr 2002
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The vector of the air velocity can be resolved into a component at right angles to the 25% chord line and a spanwise vector. Neglecting frictional drag, the lift and drag are produced by the velocity perpendicular to the 25% chord line and the airfoil should be oriented accordingly. The spanwise vector does nothing but produce some small frictional drag. Since the effective velocity vectors are not parallel to each other, where the 25% chord lines meet at the center of the wing, there may be a middle effect which decreases lift and increases drag in that region. The Horton brothers designs added a bat tail at the wing center in an attempt to curve the 25% chord line from one panel to the other across the centerline in an attempt to reduce the middle effect . The Swiss SB-13 curved the leading and trailing edges in planform to attempt the same reduction in middle effect.
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