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Thread: Non powered boat move upstream

  1. #1 Non powered boat move upstream 
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    Question: If the hull of a boat was dynamically configurable such that it could take on an airfoil design at will would it be possible for such a boat to move up stream? Using the principles of a sail on a sailboat the hull would allow the boat to propel itself up stream by tacking back and forth.


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  3. #2  
    Forum Senior TheObserver's Avatar
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    lift works at right angles to the motion of the current, you can't get parallel motion from an airfoil design.


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    Oh, gee. What a shock you'd pull that out...
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  6. #5  
    Forum Radioactive Isotope skeptic's Avatar
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    That proposal is similar to the many made for balloons, to 'sail' upwind by tacking. Cannot be done. A balloon drifts in the wind, at the same speed and direction as the wind. Tacking is not possible.

    A yacht can tack upwind because it is pushing against the water. The wind provides the energy, but the yacht's keel provides a second force, stopping the yacht simply moving with the wind, and forcing it in the set direction.

    The proposal in the OP lacks that factor.
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    True. There must be a keel, leeboard, or daggerboard/centerboard to prevent the boat drifting before the wind like a balloon. Frequently this has a "foil" section, but it is the sheer area of lateral resistance which is of greatest importance. Sails function much like airfoils as well.
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  8. #7  
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    In fact, by definition, sails ARE airfoils
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  9. #8  
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    Yes, laminar flow and all that. This is the general case, but is a big spinnaker or a round parachute truly an airfoil? That is why I (perhaps erroneously) qualified the statement. No question that a modern sport parachute is in fact an airfoil, generating lift as well as drag.
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  10. #9  
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    Here's a similar fun idea to stretch peoples ideas... a windmill driven boat that can go directly upwind:
    Windmill Driven Boat - YouTube
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    “The Holy Land is everywhere” Black Elk
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