Sailing Directly Upwind

Discussion in 'Sailboats' started by ancient kayaker, Nov 1, 2009.

  1. ancient kayaker
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    ancient kayaker aka Terry Haines

    This is an idea I've had for some time, an offshoot of another thread. It's nothing to do with turbine driven propellers.

    The process of tacking upwind requires that the boat's heading be changed from the port tack to the starboard tack and so on. The entire boat is rotated including the mast, sail, center board as well as the hull. The rate at which this can be done is determined -and therefore limited- by the boat's turning circle radius and the speed that can be maintained through the change of tack. It is a particular problem for a light, long-hulled slow moving boat such as a sailing canoe in light airs.

    So my idea is to separate the hull from the rest of the boat, i.e., mast, sail and vertical hydrofoil (call it the keel, daggerboard, centerboard, whatever). We put all that together as a separate assembly that we call the sailing machine. So long as we prevent it from sinking and keep it more or less upright it will sail in whatever direction we point it, other than directly upwind.

    Now we attach the sailing machine back on the hull, but using a vertical axis pivot. The rudder becomes a simple skeg at the stern of the hull. To change tack we simply rotate the entire "sailing machine" to point to the new heading. it will immediately start to sail on the new heading; the hull will follow along behind, adopting the new heading in due course (sorry) under the influence of the skeg.

    Such a sailboat need never be in irons, can adjust to wind changes almost instantly and and can sail in a narrower seaway. It would be advantageous with this arrangement for the hull to have minimum lateral resistance, so the hull design drivers are different; perhaps a skimming dish design.

    If the sailing machine is connected to the hull by a linkage that permits both rotation and sideways motion while still able to propel the hull forward, then it should be possible to have it zigzag forward while the hull moves in a straight line: directly upwind! To prevent seasickness being induced, the hull may have a small retractable keel to keep it running straight.

    I can see some interesting mechanical challenges to be overcome, and it may be limited to small boats, but I don't see any fatal flaw that would prevent it from working.
     
  2. capt vimes
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    capt vimes Senior Member

    if the rig and keel/daggerboard/centerboeard/whatever is on the same vertical axis as the sails and points the same direction, the ship will follow this underwater part of your 'sailing-machine' since it makes up for the major part of the lateral plan.... it will not matter which way the hull is pointing... the hull will be draged along....

    either this or i did not understand your idea correctly.... ;)
     
  3. ancient kayaker
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    ancient kayaker aka Terry Haines

    You are correct. With a small skeg at the stern the hull will eventually point along the new course but sail thrust along the new course is established virtually instantly, independently of the direction of the hull.
     
  4. alan white
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    alan white Senior Member

    What about heel? The sailing rig wants to heel quickly once tacked while the hull is at right angles to the new course. As soon as the sail fills, the rig wants to sail forward, but that would be at right angles to the hull. The question is whether that force is easily counteracted by the sailer's weight.
    Also, I can see the drag component causing the hull to go backwards, the force lifting the bow and sinking the stern (maybe not a bad thing to get the bow around quickly).
    As far as practicality goes, no comment, since I don't believe you are trying to invent anything practical, but just noodling with new ideas, which is always healthy.
     
  5. capt vimes
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    capt vimes Senior Member

    i do not think that this is going to work...
    the sails create a force (forward and sideways) only if kept in the wind... therefore you need to control the sails and their angle...
    this is done by having the sheets fastened on the winches... with a hull rotating freely around the mast you will not be able to control the angle of attack of the wind on the sails... you need some force to counteract the sideways forces on the sails otherwise they will just bail out...
     
  6. ancient kayaker
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    ancient kayaker aka Terry Haines

    I don’t think the heeling is much different from any other sailboat; heeling forces will be countered by the hull’s righting moment. The rig is mounted on the hull by a linkage that permits only sideways motion and rotation about a vertical axis. Heeling forces will be transmitted from the sailing machine to the hull through the linkage. It will have to be robust, but no more than a rotating mast.

    As the sail fills on the new course the rig will want to sail in that direction and the front of the hull is going to be dragged sideways. Much the same as happens to the stern of a conventional sailboat due to rudder force, but it will happen much faster; the regular shape of stem is not going to work well here.

    I didn’t understand your point about the drag coefficient making the hull go backwards.

    As far as practicality goes, I plan to try this out; the plan is to install it on a cruising kayak or canoe: rather than a purpose-designed one. That may compromise the performance but it should identify the challenges better than noodling. Hopefully it will not have an adverse effect on my health!
     
  7. TeddyDiver
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    TeddyDiver Gollywobbler

    How about installing that sailing machine, instead of a canoe, to a "non directional" hull. By this I mean either a rigid hull without bow and stern or a hull with variable form.. :D
     
  8. ancient kayaker
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    ancient kayaker aka Terry Haines

    -do you mean a coracle?
     
  9. gonzo
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    gonzo Senior Member

    The wind will be on the same side of the sail. You are not sailing straight upwind but are on a tack. If you turn the hull or "the sailing machine" as you call it at 90 degrees to the course, the boat will stall. You will never sail straight upwind. This is nonsense.
     
  10. yipster
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    yipster designer

    may i ask for a simple 1000 words picture telling the forces
     
  11. ancient kayaker
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    ancient kayaker aka Terry Haines

    Think of the sailing machine as a separate sailboat towing the hull, but the sailing machine does not have its own hull because it is suported by the linkage. The linkage attaches the sailing machine to the hull and permits it to rotate (mast and keel rotate together) and move sideways with respect to the hull. The sailing machine tacks upwind, zigzagging in the usual way, but the hull moves in a straight line.

    In the figure, to keep it simple I have not shown sheets or steering provision for the sailing machine, but it will obviously need them.

    Note: there is a mistake in this picture: in figure F) the sails should be shown to port
     

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    Last edited: Nov 5, 2009
  12. Hunter25
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    Hunter25 Senior Member

    I remember an idea like this years back. I think it was on a cat hull, but could be wrong. The jib and main shared a common boom that rotated with the mast. The jib would weather vane out to leeward, while the main would cock up to windward. The hull could sail directly up wind, or nearly directly up wind with the sails set for a more ideal angle of attack. Leeway is an issue on this point of sail and it would not be a point of sail used much, but possible. The hull could be steered around, while the sails remained in an ideal angle to the apparent wind.
     
  13. zerogara
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    zerogara build it and sail it

    Like you said a sailing machine (sailboat) and a tug heading steady up wind. The sailboat is tacking upwind like a normal sailboat does and drags a tug boat.
    Question, are you on the tug or on the sailboat? How big (displ.) is the one and how big is the other. Why would you want to use a sailboat instead of a diesel? What would you be rather be doing, sailing or motor boating?
    The freight/tug you are drawing can be probably be carried on an appropriate sized sailboat just tacking up wind to get to its destination faster than this system of those two boats.
     
  14. alan white
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    alan white Senior Member

    Honestly, it's hard to imagine what's going to happen, though when I first "saw" it, it appeared that the tacking of the sail rig would encounter leeway, causing the hull to go backwards and therefore not come around, at least not for a critical moment.
    But I may not be seeing it clearly.
     

  15. ancient kayaker
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    ancient kayaker aka Terry Haines

    -it would be great if you could find out more about it. Were you thinking of the Flip-tacker by any chance? That's a different concept, see http://www.boatdesign.net/forums/sailboats/highly-assymetrical-wing-sail-25362-2.html. I was thinking a cat hull might be good for this concept, with the rig tacking between the amas, instead of ahead of a monohull as I sketched it. I was also thinking a garvey style hull might work.


    - I assumed the crew would be on the hull being towed as I think this idea is best suited for small craft. Why would anyone want a stinky diesel when they could be sailing? I think this idea has the potential to outperform a conventional rig upwind, although it may be handicapped on other points of sail.


    -yeah, there are bound to be some interesting learning experiences with anything this far from normal. I think steering and sail control will be the main challenges.
     
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