What would be the effect of wider rudders?

  I know they won't be as efficient as rudders with a higher aspect ratio, but that's not really the question.  If someone wants or needs to sail in shallow water, and the current high aspect rudders don't provide enough submerged foil area to handle leeway resistance while steering, would going wider help?  If so, would this be more or less efficient than a third foil?

  Lower-aspect rudders should help with steering at very low speeds, such as in locks, especially if they are far apart.  And if they can both kick up, then there's one less disaster to worry about in a grounding (daggerboard in a trunk).  But I don't know if this would be worth the drag as boat speed picks up.

        - Mike

 
 
Arto Hakkarainen wrote:

 

--- On Mon, 3/7/11, Rob Denney <harryproa@gmail.com> wrote:   Rob.   I mostly agree with what you say below. However, I keep coming back intuitively to the fact that the rig is pressing the lee bow hard and even though it has lots of buoyancy it still could be pressed down by rig forces more or less. I know there has been a lot of discussion on the subject and whether the dynamic forces on the hull will counter that force or not. Things that lead me to this theory were two sources that support each other, namely what Rudolf reported here about the experience on new rudders and Todds model testing. In BD reducing the sail force seemed to help (no luffing without jib wven though that moved the CoE back). Also on many of the videos and tests Todd made with his models they did the same many times: heeling due to too much sail -> bow pressed down -> luffing in more or less uncontrolled way. With all the righting moment of visionarries boat hardly heels but the bow may still go down. Big boats behave differently to models. Both cases support my intuition that the problem is caused by bow pressing down.   The visious circle you described supports different foils for leeway prevention and steering doesn't it? That way the board takes loads and you don't need to have too much angle on rudders. I know it is against your idea of minimising the number of foils...   Still I acknowledge that there are many people here with more experience so please correct me if I'm wrong.   Arto Arto, Bow down trim does cause weather helm, especially on boats with no rocker.  However, the bow down in this case is caused by the drag from the partially rotated rudders.  A vicious circle.   On Rare Bird, even at 17 knots on a broad reach, the steering remained light and the bow was not noticably submerged, although it was difficult to tell because of all the spray.  I think it would be less on a light boat with the same hull, but could be wrong. rob

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