"Reverse" keel design??

Discussion in 'Sailboats' started by SeaJay, Sep 11, 2007.

  1. SeaJay
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    SeaJay Senior Member

  2. tspeer
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    tspeer Senior Member

    Don't believe everything you read on the internet.
     
  3. SeaJay
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    SeaJay Senior Member

    Tom - I'm highly skeptical of this claim but was wondering if there was any hydrodynamic principal to support it...something that I was unaware of. (me and apparently everybody else in the world)

    Regards,

    Doug
     

  4. jehardiman
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    jehardiman Senior Member

    In one sense, yes, there is less pressure drag by having a smaller entry half angle for a 2D foil and placing the point of maximum section well aft. It is a well know fact that NACA 00XX shapes have less hydrodynamic drag towed "backwards" than "forwards" at operational Reynolds numbers. But this is for locked, fixed zero AOA, straight line, ONLY.

    Otherwise, lift/drag and stall performance are poorer than a more "conventional" foil shape. Extreme sweep effects will tend to smear the data when different shapes are compared (due to the sweep making the apparent t/c << 0.1 which effectively makes all shapes flat plates from a hydro point of view), but data shows the advantage is still with a more conventional shape. See PNA Chpt. IX, FDD Chpt.6, and FDL Chpt 8.
     
    Last edited: Sep 12, 2007
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