shouldn't optimized designs be "salt" OR "fresh" water?

Discussion in 'Boat Design' started by Squidly-Diddly, Sep 11, 2009.

  1. Squidly-Diddly
    Joined: Sep 2007
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    Squidly-Diddly Senior Member

    shouldn't optimized designs be "salt" OR "fresh" water due the substantial differences in density? It seem quite noticeable in a kayak or rowing scull.

    Do nautical CAD programs make calculations for both, and what tends to happen when the numbers get re-crunched?

    In related news, I don't see a lot of 'air' in those sails on Peru's Lake Titicaca at 12,500 ft.

    [​IMG]
     
  2. messabout
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    messabout Senior Member

    There is a density differetial but it is not a big one, only two and one half percent. I am pretty sure that the skippers of big vessels like tankers or bulkers take account of the difference. A ship entering the St. Lawrence seaway from the east would begin to draw more water as they progressed toward some great lakes destination. A dinghy or other small boat would not notice much difference I suspect.

    I take your remarks about kayaks in fresh versus salt water as a point of interest. A kayak that displaced...say 240 pounds would have a tiny bit more wetted surface in fresh water than in salt. The difference would be insignifigant at 165 cubic inches of displaced volume. Most kayaks would have a surface difference of about one half square foot of surface. The boat would feel a difference of 6 pounds of weight more or less. An expert paddler would feel the difference. Klutz paddlers, like me, probably would not
     
  3. DMacPherson
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    DMacPherson Senior Member

  4. rwatson
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    rwatson Senior Member


  5. DMacPherson
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    DMacPherson Senior Member

    See page 2 of the PDF.

    Don MacPherson
     
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