If you saw the Sanders Sea Fury portion of the Airshow at Oshkosh the
Wingtip Vortex was very graphic.  

My wife and I also attended a Fund Raiser Air Show at the Sanders
Aircraft Facility on a Private Strip about a month before OSH. The
spectators were about 100 feet from the runway with a light crosswind
blowing toward us.  The Sea Fury had the very dense smoke generators on
the wingtips so vortices were easily seen for minutes after each pass.

You would not believe how long these lasted and how strong they felt
when they drifted back to the crowd.  And this was at low angle of
attack and a not so large aircraft.  Seeing or feeling this it will make
a believer out of you.

Steve Colwell