Unusual Rudder Design, but is it any goodl?

Discussion in 'Boat Design' started by CaptainAB, Jul 29, 2008.

  1. CaptainAB
    Joined: Jul 2006
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    Location: South Australia

    CaptainAB Always Learning

    I took the attached photograph of a 40' shallow draft river boat whilst it was on the slip. It has a design of rudder I've not seen before.

    Does anybody know anything about it? Does it have any special benefits maybe for low speed work or perhaps in very shallow water?



    Attached Files:

  2. Gilbert
    Joined: Aug 2004
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    Location: Cathlamet, WA

    Gilbert Senior Member

    I will go out on a limb here and do a little guessing, but I think my guess will have some merit.
    The central plate should have been adequate for most boats to get good control and maneuverability, although the horizontal plates that the port and starboard vertical plates are mounted on would have been better if they were on the top and bottom of the central plate.
    However, the fact that the propellor is in a tunnel made the single plate less effective than if it were not in a tunnel. Apparently this is a vessel that requires exceptional maneuverability and so the port and starboard vertical plates were added to try to improve maneuverability. It must have made some improvement or they probably would have removed them. Having had no experience with a rudder like this, I can't really give you a good answer as to how effective it is.
    You might try talking to the crew.
  3. Petros
    Joined: Oct 2007
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    Petros Senior Member

    I would also guess this is an attempt to get more rudder authority without making the rudder profile any larger. It might also have the effect of vectoring the prop wash.
  4. Fanie
    Joined: Oct 2007
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    Location: Colonial "Sick Africa"

    Fanie Fanie

    Yes, almost like an open frame jet drive.

  5. MikeJohns
    Joined: Aug 2004
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    Location: Australia

    MikeJohns Senior Member

    I have to laugh sometimes, when it comes to rudders we see all types of experimentation. Nearly always detrimental wrt drag.

    There is nothing to recommend the configuration shown, the drag penalty is very high for a number of reasons.

    They would be significantly better off (far less drag and much more lift) using a semi balanced foil shaped articulated rudder.
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