Self-rotating Flettner rotor

Discussion in 'Boat Design' started by 1J1, May 28, 2013.

  1. 1J1
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    1J1 Senior Member

  2. rwatson
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    rwatson Senior Member

    Excellent - for an even weirder Rotor Flying model check out



    and the successful launch



    and even with a Savonious Rotor

     
    Last edited: Jun 2, 2013
  3. 1J1
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    1J1 Senior Member

  4. rwatson
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    rwatson Senior Member

    You might do better thinking of a Sav rotor as a separate 'motor', for the Flettner Rotor, rather than have the problem of driving the two together.

    This would enable you to add in gearing, for optimal drive power, and reversing mechanism.
     
  5. 1J1
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    1J1 Senior Member

    Instead of a Savonius rotor that has a lot of drag, vibration & such, I think I would use the wind turbine that has a shield which covers half of the rotor where the blades go against the wind. Of course, the diameter & height of it should be optimized etc.
    And yes, gearing would be nice to have the peripheral speed of a Flettner rotor be higher than the wind speed.
     

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  6. rwatson
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    rwatson Senior Member

    Nah - you don't need to shroud the turbine, it will always face the wind to provide drive for the rotor, like all good windmills.

    The beauty of a wind 'motor' is that a rotor is only effective if there is some wind to drive the turbine.

    Mind you, reality the reality is that a small petrol motor is a fraction of the cost to install and run compared to a a windmill.
     
  7. 1J1
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    1J1 Senior Member

    It's if the turbine's blades are of a streamlined shape at one side. But in proposed design blades are thin radial foils & 50% that go against the wind should be covered. This would make the open part of the turbine to rotate in the same direction as the wind without having a complex reversing mechanism as it's on Savonius rotor.
    The intention was to make a pure "sailboat" where the sail is replaced by a Flettner rotor, not a motor driven rotor ship.
     
  8. rwatson
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    rwatson Senior Member

    Yeah, yeah - i know that , what I was saying is that the internal combustion engine method is way more efficient financially, and materially.

    The only reason I can think of to go for a totally wind activated Flettner Rotor would be for philosophical reasons.
     
  9. 1J1
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    1J1 Senior Member

    It would be interesting to compare a sail with a wind-driven rotor if it says that the 2nd one gives more lift than the sail or wing sail. Sure, the boat would be equipped with an ordinary engine & propeller, and maybe would be nice to have engine & the rotor be connected in case of light winds where the wind turbine won't be effective as I see.
     
  10. rwatson
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    rwatson Senior Member

    It doesn't matter if the rotor is wind driven or powered by petrol. The lift will be the same. The drag of any secondary wind device will have to be taken in to account, of course.

    Its the efficiency and reliability of the device doing the spinning that is the question.

    Since all boats of any size need an engine, the expense of getting the spin from wind power doesn't seem worthwhile.
     
  11. 1J1
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    1J1 Senior Member

    It would be the same if the rpm would be same for both cases along with same wind. But then, why would I use an engine when I can use wind to rotate it - that's how Savonius obviously thought after looking at Flettner's experiments. So he made a boat with those rotors that not only need a reverse mechanism but create more drag than a Flettner rotor. So I came up with a different simple wind turbine for my design. But then there's a question: why not to just make a windmill boat with propeller then?

    Whenever there will be some time on my hands I might make a model of that catamaran I posted earlier & see if it's any better.
     

  12. Jeremy Harris
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    Jeremy Harris Senior Member

    From the work I did looking at rotor propulsion a year or two ago I concluded that being able to control the speed and direction of the rotor was critical.

    For example, the rotor produces a large overturning moment if the wind is from fore or aft, so you need to be able to either stop it, or change its direction, in order to prevent excessive heel. This could even be a problem with a multihull in strong winds.

    As the power required to drive the rotor is pretty low (it's dominated by bearing losses and motor efficiency, the viscous drag on the rotor from it spinning in the air is very low), I thought of just using the top end plate as a solar panel array. It's slightly better for performance if the top end plate doesn't rotate, and there's enough area there to generate enough power. A small battery could be charged by the solar panel and then used to drive the rotor speed/direction control.
     
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