Schilling Rudder Question

Discussion in 'Boat Design' started by Biggles, Jun 12, 2011.

  1. Biggles
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    Biggles Junior Member

    Hello

    I am building a schilling rudder for my boat. I have just noticed reading elsewhere that these will work at up to 2 x 70° The ram I have but not fitted yet is 2 x 35°.

    My question is, is it a waste of time having a shilling rudder only working to 35°?

    The boat is a wide beam narrowboat. Max speed is 7mph

    Thanks

    Biggles.
     
  2. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    The answer will depend on the geometry of your rudder. Can you give some more info about it's dimensions?
     
  3. Biggles
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    Biggles Junior Member

    It's appox 560mm tall by 700mm long. I have no specific dimensions accept to say I have created it to look like a fish cut in half looking down on one.

    The pivot point is 230mm from the front. The front is made from 60mm tube then it widens out to 100mm, 240mm back narrowing to 10mm, 400mm back then flat for 200 mm then a tail which is 100mm and about 30° angled.

    Biggles
     
  4. Biggles
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    Biggles Junior Member

    On further reading I think mine that I'm building is probably a fishtail rudder. I read that these are good a 35°.

    Still would welcome com met though.

    Biggles
     
  5. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Some call it Schilling rudder, some call it MacLear Thistle rudder, some call it Mystic rudder (http://www.mysticrudder.com/index.html), go figure... It was probably invented and re-invented several times in history.

    Anyways, apart the considerably higher drag at zero rudder angle it won't show you any sensational difference or advantage over a conventionally shaped foil, due to a very low aspect ratio of your rudder (AR=0.8). The lift characteristics of rudders of such low aspect ratio (or low height-to-length ratio, for rectangular platforms) are dominated mostly by tip-vortices, and in much lesser extent by the foil shape. End plates will somewhat improve things from the lift point of view, not when it comes to drag - as this rudder will anyways make some huge vortices at high angles.

    Overall, you will probably gain some 5 degrees before it stalls, when compared to a conventional-foil rudder. But due to the said very low aspect ratio, the lift curve will be so flat that these 5 degrees will probably not yield much in terms of lateral (lift) force.

    But anyways, it's probably still better than a flat-plate rudder, because the rounded leading edge area will prevent the creation of a leading-edge vortex, which is another important source of drag.

    Cheers!
     
  6. Biggles
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    Biggles Junior Member

    Hello

    Thanks for that. The link was very useful and the hand drawing could be mine. I will put it up on my blog when it's made and I will put a photo on here hopefully later today if I finish it. I just need to put the skin on and I'm not sure if I will be able to do that without heating it. If it needs heating I will have to take it to a local fabricators and borrow their oxy-propane kit. They are very accommodating.

    Biggles
     
  7. Biggles
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    Biggles Junior Member

  8. Dhutch
    Joined: Oct 2008
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    Dhutch Junior Member

    Just bumped into this so am a little late, but I made a Schilling rudder for our boat (a 58ft dutch barge style narrowboat with a steam engine) by adding profiled sections to our 'conventional' flat plate rudder. As well as writing the wiki artical!

    The rudder is too short to be ideal and without doing a lot of steel work there no room for any more which lead to looking into profiled options and while its not transformed it into a nibble craft (she is still 22ton after all) its made a worthy improvment to handling, so hopfully you find the same.


    Daniel
     
  9. Biggles
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    Biggles Junior Member

    I am delighted with my rudder and so glad I researched and made one. I will put a video up at some point showing just how quickly the boat can do a 180 wind. It almost makes one giddy :)
     
  10. HJS
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    HJS Member

    M/Y Indepéndance

    CG Pettersson

    This type of boat it is well known to have poor maneuverability at low speed. To deal with this, we built a new rudder on the basis of Thistel Rudder.

    The control characteristics improved significantly and several other similar boats have been equipped with similar rudder accordingly.

    I can only recommend to put similar rudder on most slow-moving boats, especially the long and narrow ones, which can be difficult to control at low speeds.

    JS
     

    Attached Files:

  11. Dhutch
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    Dhutch Junior Member

    As the author of the wikipedia article on the subject as well as a member of this site, I would be very interested in people comments on the current article and or any further developments that can make or suggest.

    http://en.wikipedia.org/wiki/Schilling_rudder


    Daniel
     
  12. Leo Lazauskas
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    Leo Lazauskas Senior Member

    I corrected some grammar and spelling, but I don't know what you mean by
    "aka" in the sentence:
    Around 40% balance should be provided, aka, rudder in front of the rudder
    pivot.

    If you are using "aka" in place of "also known as", then it sounds a bit odd.
     
  13. Dhutch
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    Dhutch Junior Member

    Thanks. I guess 'aka' could more correctly be replaced with 'I.e.' in that context.



    Daniel
     
  14. Biggles
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    Biggles Junior Member

    The article as far as I can see is fine. I can't comment on the maths as I managed to get a drawing of one for almost exactly the same as I needed.

    This is a link to my 60' x 12' widebeam narrowboat doing a 360 with just the shilling rudder.

    Linky

    This is how I made it
     

  15. Dhutch
    Joined: Oct 2008
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    Dhutch Junior Member

    I have only just linked you with 'Biggles' from a-another forum of a certain canal related bent.

    Small world! How is the rudder going?


    Daniel
     
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