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What are the aerodynamic advantages and disadvantages of the Weltensegler Wing?

Would this kind of wing configuration come to help for a glider? Is there any difference between them and gull wings? What are the aerodynamic advantages of gull wings?

Weltensegler Aircraft

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The inspiration for the Weltensegler wing were birds. The reason for their wing shape is structural, however, not aerodynamic. Your photo shows the 1922 version, called "Baden-Baden Stolz", which was a follow-on to the original and more ambitious version of 1921. The 3-side-view below shows the planform (picture source). However, this airplane never flew, which probably saved the life of its pilot. While pitch and limited roll control was possible with the elevons on the outer wings, no consideration was given to directional control.

Weltensegler 3-side view

The 1921 version was controlled by warping of the outer wings, the washout of which was controlled with pulleys and springs. The idea was that this would help to adjust the wing shape to flight speed. The picture below shows the first and last flight, which is historically significant as the first glider flight in which a considerable gain in height was achieved. However, it ended in a spiral dive which killed its pilot (picture source).

Weltensegler 1921 in flight

Weltensegler is actually the name of the company which was founded by Friedrich Wenk. Alexander Lippisch was one of his employees.

The configuration cannot be recommended for a glider. It is much better to have a straight inner wing and dihedraled outer wings, as explained in this answer. The anhedral of the outer wings of the Weltensegler wings will produce a downforce on the windward wing, rolling it into the wind which is the opposite of what is needed for coordinated flight. Other configurations using an "M"-shaped wing did so for different reasons and use rudders and much more anhedral on the outer wing panels.

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  • $\begingroup$ Peter, generally while gliding, don't gulls have a drooped wingtip configuration? How does it help them? $\endgroup$ – Risshi Jain Mar 29 '17 at 13:31
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    $\begingroup$ @RisshiJain: I think it helps them to keep the wings outstretched without much effort. The tension part on the lower side of the wing will be more stable because it will pull the lower wing contour outward. Once the wing flips into a polyhedral shape, bones and tendons will have trouble to stay in place. $\endgroup$ – Peter Kämpf Mar 29 '17 at 16:27
  • $\begingroup$ Having an anhedral in the main wing will cause it to be very laterally unstable. Most planes nowadays have a few degrees of dihedral to keep the plane stable in case of a gust of wind coming from the side. Also, this plane had no vertical stabilizer. $\endgroup$ – alex Mar 30 '17 at 8:17
  • $\begingroup$ @alex: Note the distinctive washout in the outer panels: The Weltensegler gliders had a bell-shaped lift distribution long before the Hortens were around, and as such did not strictly need a vertical. But some sort of drag device on the outer wings would had been handy to avoid the spiral dive. $\endgroup$ – Peter Kämpf Mar 30 '17 at 14:04
  • $\begingroup$ @Peter Kampf: That's exactly what I was thinking. That may have saved the pilot's life if one had been outfitted. $\endgroup$ – alex Mar 31 '17 at 6:36

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