© Hal Mayforth

Shifty Characters

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ROB: The crew gave me a collective clip around the ear and told me to talk to you about persistent shifts.

Doc: I’m betting you had a rough time on the water today.

ROB: You could say that! We were looking starry after the first beat. Went around the top in third and pulled one back on the run.

Doc: … and …

ROB: Well, we went left up the next beat, the breeze went right, and our place went out the back door.

Doc: … yes?

ROB: Well, we’d worked out that the left was favored before the start—and it worked on the first beat. So we did it again on the second—you know, persistent shift and favored side and all that. How did those other blokes work it out that the breeze would go the other way?

Doc: What sort of persistent shift was it?

ROB: You mean that “continuing” or “completed” stuff? I don’t know! I just figured that coming off the land it would bend left as we got closer to the shore—you know, Coriolis effect and all that stuff.

Doc: Hmm … Did you know there are three kinds of persistent shift—and you sail them quite differently?

ROB: This should be amusing. OK smart guy. Let me have it.

Doc: The first is the fixed persistent shift. That’s the one that usually occurs because of geography or some other fixed influence—particularly where the wind is being channeled or bent. It is as regular as a metronome. You always hit the same side (the way you would with a fixed current benefit). That’s how you treated the upwind of this race you were talking about. It’s a “work-out-which-side-is-favored-and-get-there-fast” sort of approach.

ROB: You are trying to tell me it wasn’t fixed then?

Doc: Was the shift there the second time you tried?

ROB: Point taken.