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5561[ksurf] Re: KitePhysics 102

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  • Dave Culp
    Sep 30, 1999
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      >The attached sketch doesn't reflect the speed polar of some
      >craft in particular, and is actually a bit of an
      >exageration, but it illustrates the idea. By the way, it's
      >not there for your edification, as I'm sure you know what
      >I'm talking about, but for anyone who hasn't been following
      >this carefully (and I wouldn't have attached it were it not
      >quite small).

      I know you know what you are talking about, Ken, but your drawing is inaccurate. If one draws the remaining two "bounding lines," from the ends of the vectors shown, they must define a parallelogram, but your drawing doesn't. As drawn, the vector geometry won't work.

      While it's true that apparent wind is greatest, for very high Vb/Vt sailcraft, on broad reaching courses, this is only due to the great craft speed, as you mention. However, the apparent wind will almost always be *less* than craft speed, on any course much over 100 degrees true, and certainly on the craft's fastest course, which will be nearer 115-120 degrees. This is true of all sailcraft, fast or slow.

      FWIW, for a given, fixed craft speed, apparent wind will be highest on close reaching (windward) courses, not broad reaching.

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