We couldn’t tack to port, so we continued, our only hope being the possibility that the back would return before we reached the port layline. It did, and we tacked. For a moment, I thought we’d have him. But no, the wind gradually veered to its median position, and, near the mark, he crossed two boatlengths ahead. And there went the Summer Series. Now, if I’d hit those shifts in a different sequence—if I’d used a different jib and had been faster, if I’d been faster downwind—if, if, if. And the biggest if was: if the beats had only been longer. On short, half-mile legs, there’s typically time for but one shift of an oscillating series, and that one shift becomes a persistent shift. If (at the average speed of a racing sailboat, five knots) it takes about eight to nine minutes to sail a half-mile beat, and if oscillating shifts occur about once every five to eight minutes, it’s unlikely that more than one shift will occur during a beat. If the shift extant at the start persists for two or more minutes after the start, then the first shift of the beat is almost certain to be the only shift.