The course consists of a starting line, between two marks, laid at right angles to the wind s direction. The spinnakers are set, and the duel continues downwind to the second mark that is laid in close proximity to the starting line 100-meters further up the course. The boats round the marks 2-3 times before the winner crosses the Finish line.
Umpires follow each race and make instant penalty decisions.
Furious tacking is likely to ensue with the latter trying to force a crew error to rob their aggressor of the advantage. The end of the first windward leg provides an opportunity for the trailing boat to seize the edge by creating an inside overlap within two lengths of the mark, forcing the lead to allow room which usually means relinquishing its place. On the downwind run the trailing boat has a chance to attack from behind, positioning itself so it's spinnaker casts a wind shadow over the leader. Often the winner is not determined until the final few boat lengths.