Whoops, I should have said "winglet" rather than "canard." I was refering to the winglets used at the tips of wings to reduce drag that is induced by a wing tip vortex.
That's kind of what I thought you meant. Somebody just recently was telling me that Suicide sailors at one time were using endplates on the tops of their masts to reduce vortex drag at the top of the sail (or something like that). But it did not seem to do anything to improve performance, so they stopped using them.
