Doug,
Ice Boats sail faster than the wind and they're apparent wind is always
behind them when they are in a groove. They are always sailing downwind.
The wind doesn't shift foreward it shift aft.

This doesn't happen with a displacement hull but if you get the Displ.
hull going you do get an increase in the Apparent Wind,
which will exceed the speed of the true wind. If you don't have to go to
far off course to build this higher apparent wind, you can get to the
Leeward Mark quicker. Even the America's Cupper, with Spinn. steer off
line and Gybe to the opposite Broad reach going downwind. Its faster.