http://www.nasa.gov/centers/dryden/Features/AMA_Expo.html#.Us-1iPtlnqd

As one of the featured speakers at the event, Albion Bowers,
Associate Director for Research at NASA Dryden, will detail a student project at
the center that proved early German aerodynamicist Ludwig Prandtl's theory that
adverse yawing of an aircraft during a turn could be overcome via wingtip
aerodynamics alone, without use of vertical tails or rudders.

Bowers will discuss the history, research and uses of the sub-scale Prandtl-D
flying wing, a radio-controlled glider model designed, built and flown by the
aerospace engineering students that he mentored during the 2012 and 2013
Aeronautics Academy Internship at NASA Dryden.

Adverse yaw due to induced drag has always been one of the thorny problems of
flight. The students proved that not only could adverse yaw be overcome, but it
could be turned into proverse yaw just as birds achieve it, without relying on
rudders or complicated computerized flight controls to accomplish it.