the square boat

Discussion in 'Boat Design' started by Gilbert, Jun 7, 2008.

  1. Gilbert
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    Gilbert Senior Member

    Years ago I met a young man who was telling me about his experiments with models to develope a rudderless trimiran. He was rather disappointed with the results he was getting so he tried thinking of other shapes that might be amenable to sailing without a rudder. The best results he came up with were with a square boat. The formula for the hull was to take a square pyramid whose sides sloped at 45 degrees and cut it off at one third of it's height and close the resulting hole, then turn it over and there is your square boat. He put two groves in the bottom to make three longitudinal bottom panels.
    To demonstrate the boat's seakeeping ability he had numerous pictures of the model coming through surf unfazed.
    The sailing rig had the mast in the middle and the only sails were two self furling jibs, one on a stay to the left front and one on a stay to the right front. To sail on the starboard tack the port sail was unfurled with the starboard sail furled. The port tack was just the opposite. Of course both sails were used for downwind sailing. For lateral resistance he had shallow full length skegs on the port and starboard bottom panels.
    I intended to attach a bitmap of the lines for the hull but since that doesn't seem to be an option I will see if I can make it a jpeg file and attach it in another post.
     
  2. Gilbert
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    Gilbert Senior Member

    Ok, I think I'm ready to post the jpeg image.
     

    Attached Files:

    Last edited: Jun 7, 2008
  3. rwatson
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    rwatson Senior Member

    If he used a skeg for directional ability, he built a hull with a fixed rudder.

    A flat bottom hull handles surf fine, but you would be in trouble if you picked a course that was taking you onto a bunch of rocks and you had no rudder.

    I would be interested to know what it is you are aiming to achieve with such a simplistic design - besides just curiosity.
     
  4. Gilbert
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    Gilbert Senior Member

    If you took the rudder off of a Star class sailboat, would you say that the keel was the rudder?
    The skeg on the square boat is to counter leeway when sailing. Sheeting the sails adjusts the course sailed.
    As I said earlier, I did not come up with this idea. But is seems very interesting to me. It is roomy for its dimensions, carries a lot with shallow draft and according to the designer is very maneuverable without having a rudder. It is also seaworthy and is easily propelled. And, as you say it is simple.
     
  5. rwatson
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    rwatson Senior Member

    No - without a skeg in a star class , you are totally rudderless and will go around in circles.
    Rudders do counter leeway when sailing, and their area is taken into account when calculating lateral resistance.

    The concept of building an awkward boat to control to avoid the "complexity" of 4 stainless steel fittings isnt my cup of tea, but as you say, it is roomy.

    Keep us posted - and send pictures
     
  6. Gilbert
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    Gilbert Senior Member

    Let's say we reef the mainsail on the Star a certain amount. It now doesn't go in circles. You have now changed it's keel into a rudder. Correct?
     
  7. rwatson
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    rwatson Senior Member

    Lets also say you make the mast adjustable so that you can move it aft and forrard easily like a windsurfer, so you can steer the boat with the sail too.

    Lets say that the complexity of the rigging to achieve this is vastly less complex than a traditional rudder arrangement - voila, you have proved a point.

    Cant wait to see it.
     
  8. Gilbert
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    Gilbert Senior Member

    It appears that the strongest point I've made is that you really don't want to talk about your assertion that the keel or skeg is the rudder.
     
  9. rwatson
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    rwatson Senior Member

    My assertion that a skeg has the same effect as a non moving rudder doesnt need any defense.

    If this square boat had a skeg then the hull didnt have all that good inbuilt directional stability as this person claimed.

    If they have to go to the trouble of putting a skeg on this 'simple' hull, then the aim of avoiding 'complexity' was defeated, and they may as well gone for a rudder as well.

    I am not interested in having an endless debate about definitions, I *was* interested in saving you from persuing an inherently badly designed hull with dangerous lack of manouvarability - but I have changed my mind.

    I think you should go ahead and build the hull as quickly as possible and prove all the classical design preferences are rubbbish, and a total waste of time.

    The best method would be to plan a really long coastal voyage!
     
  10. Gilbert
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    Gilbert Senior Member

    I am trying to find where I said the young man that developed this concept claimed the hull had good inbuilt directional stability. His initial efforts with trimaran hulls could sail without a rudder and their directional stability was excellent but they were not very maneuverable. His square boat models had excellent maneuverability but required a shallow keel on the port and starboard bottom panels to counteract leeway.
     

  11. rwatson
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    rwatson Senior Member


    Maybe I thought 'seaworthy' meant good directional stability ... who knows.

    I thought I was getting into a discussion about proper hull shapes, not a nit picking "who said what" bunfight.

    I have no further interest i nthe topic, like everyone else.

    Just post any proper questions to others in general - I quit.
     
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