Extra fins on rudder blade...??

Discussion in 'Hydrodynamics and Aerodynamics' started by Vronsky, Jul 26, 2016.

  1. Munter
    Joined: Jul 2007
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    Munter Amateur

    The misalignment between the hull and the plate looks like a source of drag to me. I think the plate is probably a misguided attempt to increase the effectiveness of the rudder.
     
  2. JSL
    Joined: Nov 2012
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    JSL Senior Member

    Yes, they are probably less..... I should have checked an actual drawing
     
  3. Squidly-Diddly
    Joined: Sep 2007
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    Squidly-Diddly Senior Member

    How can a combo:

    anti-vent,

    anti-roostertail,

    stiffener,

    and last but not least Swim-Step....

    be a "bad idea"? :D
    :idea:
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    I'd be pretty confident it wasn't a professionally fitted device.
     
  5. TeddyDiver
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    TeddyDiver Gollywobbler

    Becouse people use the cruising speed they are used to, turn the throttle until the log says 7kn without thinking more. Becouse of the fouled bottom they have more thrust..

    BR Teddy
     
  6. DMacPherson
    Joined: Mar 2005
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    DMacPherson Senior Member

    Is there any chance it is nothing more than a standing platform for some sort of work that needs to be done over the stern?
     
  7. JamesG123
    Joined: Mar 2015
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    JamesG123 Senior Member

    Probably not since the rudder is largely overhung by the stern. It would be quite awkward to stand on that.

    I'll go with a ventilation shield/duct.
     
  8. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    May be it is a place to stand on when cleaning the transom.
     

  9. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    "Hullspeed of this 21' displacement mobo is around 6 knots:"

    Doubtful, double enders sink their stern far more than conventional sterns , so hull speed is always lower.

    My guess would be surface area to help prevent the stern from sinking under power.
     
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