New Skerry Rudder Design Opinions Requested

Discussion in 'Boat Design' started by GalenP, May 8, 2017.

  1. GalenP
    Joined: Dec 2012
    Posts: 25
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    Location: Washington State

    GalenP Junior Member

    Hi all,

    I am building a new one piece non-kick-up rudder for my CLC Skerry. I always row to the beach, and don't seem to sail in super shallow water.

    The other change I am going to make is placing the gudgeons higher up. As they are now it is difficult to get the rudder attached while on the water because they are so low. And the lower gudgeon drags through the water which can't be great.

    I will be using a NACA foil section, not that it is really that necessary, but why not.

    [​IMG]

    Questions:
    1. The new design is a little deeper, about the same amount of surface area. It's center of effort will move slightly back. And it won't be tucked up against the keel as close. Do you see any problems with all of that?

    2. Do you see any issues with moving the gudgeons up higher? Balance issues as it is?

    Any other suggestions are welcome on the design. I am also switching to a tiller handle, vs the push-pull tiller.

    Thanks for your help!

    Galen
     
  2. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    Any differences in balance will be small, and very easily accommodated by the person at the helm.

    Moving the gudgeons as shown on the drawings will not affect balance because the pivot axis appears to be very similar. The side loads on the gudgeons will be significantly increased.

    What do you want to happen if the rudder hits a rock or other solid object while sailing since the rudder will no longer fold up:
    Lower gudgeon pull out or fail? Gudgeon failure is more likely with the raised gudgeons as the load from a rudder impact will be significantly increased.
    Gudgeon stay in place but the rudder blade break off?
    Gudgeon and rudder survive but the boat come to a sudden stop which may throw the occupants forward?​
     
  3. GalenP
    Joined: Dec 2012
    Posts: 25
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    Location: Washington State

    GalenP Junior Member

    All good points. Thank you. I may move the gudgeons down a bit to help with the side loading. Generally, with the dagger board down, the boat will take a hard stop on impact. It's very rare, since I am careful around shallow waters. So I will likely design the Gudgeon and rudder the same in strength.
     
  4. messabout
    Joined: Jan 2006
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    Location: Lakeland Fl USA

    messabout Senior Member

    Why do you prefer to use a fixed rudder as opposed to a kick up rudder? It is acknowledged that you are careful and sail mostly in water of sufficient depth. It is written in the stars that you will, sooner or later, hit something no matter how careful you are.
     
  5. GalenP
    Joined: Dec 2012
    Posts: 25
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    Location: Washington State

    GalenP Junior Member

    There is a daggerboard down most times sailing on this boat, so a kickup rudder is a little after the fact when it comes to hitting something. And since I don't use the kick up function for beaching I prefer the simply rudder.
     

  6. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    A "cassette" style of blade approuch will work here. The blade fits between rudderhead "cheeks", but instead of a pivot bolt, so the blade can rotate, simply leave the aft edge of the rudderhead open, wrapping with a couple of bungee cords. On the occurrence of a bottom strike, the blade will rock/shift aft, stretching the cords, but can remain with the boat/rudderhead, to be reset after the incident.
     
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