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64865RE: [bolger] Re: Micro rudder

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  • Kathy Kreamer
    Nov 14, 2010
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      End plates help a low aspect ratio rudder, if it's shoal water you're after, but a high aspect ratio reduces drag the most.  The high aspect ratio rudder can be smaller and you will get some reduced helm effort.  For more greatly reducing helm effort, the "balanced" aspect of a rudder is more important.  You can mix and match - a low aspect rudder can be balanced to get low helm effort.  You're arms are happy, but the rudder is draggy and the boat is not moving as it could.  - Bill


      From: bolger@yahoogroups.com [mailto:bolger@yahoogroups.com] On Behalf Of etap28
      Sent: Sunday, November 14, 2010 10:34 AM
      To: bolger@yahoogroups.com
      Subject: [bolger] Re: Micro rudder

       


      correcting myself... actually, the high aspect rudder doesn't reduce the amount of drag, it just changes the "gear ratio" so to speak of the steering

      so it doesn't have much effect on speed but it does lighten the helm drmatically... the longer and skinner the blade, the less leverage the blade has over the relatively longer tiller

      --- In bolger@yahoogroups.com, "etap28" <dave.irland@...> wrote:

      >
      >
      > I'll tell you what's
      funny about those traditional catboats... if you make a high-aspect rudder, a typical modern blade, the weather helm is mitigated hugely. Obviously if you have a "barn door" sticking out the back, with about the same lever arm pulling against the tiller as the tiller is pulling back, it's gonna hurt--especially with a low aspect sail sticking out over one rail about 20 feet.
      >
      > Also, if you wanted to make a clever semi-balanced rudder, of a type
      Bolger actually used on a lot of his designs, you could totally eliminate the weather helm and hide that force vector in sideways torque against the rudder shaft
      >
      > I used to preach this all the time to the traditionalist
      cat boat types but nobody was all that interested . . . (PS I actually know first hand that it works. I've had a few catboats, including a Woods HOle Spritsail boat, one of about 3 in existence, and I made a nice foil shaped kick up rudder for it and it sailed like a bullet... the absence of massive weather helm obviously gets rid of a lot of drag).
      >
      >
      >

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