To answer your question Mary, yes, on a much smaller scale it does happen off the back and tip of a mast/sail. The reason you can actually see the vortex when seated by a window in an aircraft is the much greater difference in pressure from the bottom to the top of the wing, which causes a lowering of temperature in the vortex to the dew point, forming fog, as the compressed air on the underside of the wing expands and cools going over the top. If the air is humid (like in Florida, all the time) you can see the vortex as fog. (if you sit near the front of the engine you can also see fog inside the engine cowling as take off power is applied, due to the reduced pressure inside the intake during engine acceleration) You can also see this as two streaming trails of fog off the wingtips if you sit at the approach end of any runway where big jets land in humid air.

The vortex's are much bigger when the wing is at a high angle of attack and "dirty" (flaps down, for take off or landing) as the wing is creating the most lift then. You don't see them at cruise as the wing is "clean" flaps up, fast and low angle of attack in dryer upper air. The vortex is still there but you can't see it in the dry air.

I have often thought of putting an end plate up there at the top of the sail but as the boat heals over, I think the end plate might become more drag than lift. If you were to capsize, it might also be more of a hindrance to righting. If you could keep the boat sailing with the mast straight up all the time, in theory, it would help reduce the tip vortex drag...in theory.

It is nearly impossible to measure how much it would help a sail boat, as the boat bobbs up and down over waves, which negatively effects the flow, in addition to the healing.

I think development of a soft-hard wing sail could yeild results. By this I mean a mylar/dacron wing sail with removeable battens/ribs, that looks like a hard wing, ala C cats, but then could be collapsed like an accordian back on the beach, for storage. The mast would be enclosed by the wing which would be raised around the mast, using the mast for support as a normal airplane wing uses the spar to support the ribs.

This wing sail plus boards/foils that lift the hulls clear, and the T foil rudders I think would make the next big advance in sailboat speed. We still have to figure out how to make the hulls get over the waves that come with big wind though...the Moth sailing up in the air looks cool, but can it be done consistantly in rough seas?