gmm@bunker.UUCP (Gregory M. Mandas) (09/25/84)
[] > From ittvax!decvax!harpo!whuxle!spuxll!eisx!jeb Mon Sep 24 14:59:31 1984 > Subject: Swept-forward wings > Newsgroups: net.aviation > > Several varieties of two-place sailplanes have swept forward > wings, and it doesn't seem to affect the way they fly. I have > flown a Blanik fairly often, and didn't notice anything odd. > Most of the two-placers that sweep the wings forward have tandem > seating with wings mounted mid-fuselage or shoulder height. > They want the leading edge to meet the fuselage far enough back > that the back-seat passenger (instructor) can still see over > the edge of the wing. But putting a straight wing at that > location will put the center of lift too far back, so they sweep > the wing forward. I believe the placement of the wing is due to the forward sweep, not the other way around. I understand they sweep wings forward to reduce induced drag created by the wing tip vortices. The forward sweep causes the vortices to travel toward the root instead of the tip. The turbulence dissipate along the fuselage reducing drag. > > I believe that swept-back wings contribute something to dynamic > stability around the yaw axis: if the plane yaws to the right, > the left wing presents more frontal area to the relative wind, > producing more drag and tending to correct the yaw. This effect > may be fairly slight, I'm not sure. Isn't the swept wing meant > mostly to deal with high-speed (and supersonic) flight? > I also heard that the swept back wings create havoc on cross wind landings when cross controlling. As you present the high wing, in the slip, the frontal area is increased and the low wing's frontal area is reduced. This simultaneous increased and decreased lift situation would tend to roll the plane towards the low wing. Aileron rolls anyone. > Jim Beckman AT&T-ISL, South Plainfield, NJ eisx!jeb Greg Mandas ittvax!bunker!gmm