If you have a window seat on a jet next to the trailing edge of a wing, in certain atmospheric conditions you can see the vortices spinning down like ghostly whirling dervishes.
Heaven help me for asking this question of a bunch of engineers, but does this happen on a smaller scale off the trailing edge of a sail?
Here is an excerpt from an e-mail from a friend of mine, partially on this subject:
In the late 60s the A-cats and C's at Cabrillo Beach YC, Long Beach, CA, used "end plate" booms. Some used a wishbone down low with Dacron filling it in. Others used a normal, for the day, boom with Ocumme ply wings. We made sure that it was very slightly HIGHER at the clew. This was.....to compress the air and make the air lift. If the Park Avenue Boom thing angled down, we felt it would blanket part of the bottom of the sail.
The old Suicide class (ask Bill Roberts) was anything-goes in monohull, but with only 125 square feet of actual sail area, including mast. It became very efficient, using an A-cat style mast and wishbone main, 1950's and 60's materials, of course.
Tried was an end plate on the top of the mast.....for reducing tip vortex, although it was angled up on the front for the same reason the boom was angled down on the tack. The class ruled that they had to count the tip deflector as sail area, so it was quickly abandoned.(Most booms on dinghies are faster with the boom lower at the clew, It makes for leading edge foot, instead of trailing with its tip vortex and loss of pressure under the boom.)
