I fear I may be doing this wrong.  Trying to leave a comment here  -spork- 

 From the start of this wiki page... 
 "Devices that are powered by sails (such as sailboats, iceboats and sand yachts) can sail (that is, advance over the surface) faster than the wind. Of course they cannot do that by using simple square sails that are set perpendicular to the wind." 

 Actually, I'm pretty sure it IS possible to sail faster than the wind with a square sail set perpendicular to the true wind.  However, the vehicle must be constrained to move at some angle to the wind.  Consider an ice-boat one a downwind course 110 degrees off the wind.  With a square sail and low enough drag, the ice-boat should maintain a *downwind* vmg of nearly wind speed with this configuration.  That will give it a true speed far greater than wind speed.