sweepback and spanwise flow

[lunatic]

I must thank Boat Design Forums for a good explanation of leading edge vortex drag, the backside problem inhibiting windward performance. In attempting to maximize offwind performance I have been sailing with spanwise flow into a top and bottom LEV resulting in 2 trailing vortices; without cordwise flow is there any downwash or circulation? Some spanwise flow should exist the sweepback common in many traditional rigs, sailboards, head sails set on forestays, even some high AR sailplanes are swept back, and nature has many examples. Seems this would rotate the driving force up,not forward and add to tip vortex. Is there any benefit in sweepback with low speed flow?