Self-rotating Flettner rotor

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

  1. 1J1
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    1J1 Senior Member

    I recently came across a patent & a pic showing a sail boat that utilizes the Magnus effect by means of a Flettner rotor with installed Savonius rotor to make it self rotate:

    [​IMG]

    Looks something promising but then Savonius rotor should have a special complex mechanism to reverse the buckets in case of wind coming from a different direction. I thought what if instead of a Savonius rotor there would be mounted like 4-8 vertical blades, half of which will be opened for the wind to rotate the whole thing. With wind coming either from left or right side the rotor would rotate accordingly. The half-bucket shield could turn to optimize the flow around the blades depending on wind direction, and is able to turn on 180 degrees as well, so the boat would go backwards with same wind.
    What are the possible problems / issues that might be in such design, without carrying out a deep research?
     

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  2. philSweet
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    philSweet Senior Member

  3. 1J1
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    1J1 Senior Member

    I would like to know if the Flettner rotor will be effective if the peripheral speed of it + wind turbine will, as I understand, be some less than a wind speed?
     
  4. TeddyDiver
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    TeddyDiver Gollywobbler

    Effective in what sense? Compared to wing and sails it produces a lot of lift and a lot of drag. The amount of lift varies by rpm, not so much by wind speed..
     
  5. 1J1
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    1J1 Senior Member

    Exactly that it's rpm depends on wind speed in my case.
     
  6. TeddyDiver
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    TeddyDiver Gollywobbler

    Then your case stinks, sorry to say..
     
  7. 1J1
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    1J1 Senior Member

  8. rwatson
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    rwatson Senior Member

    Not so much drag. The two rotors on the Flettner ship had less windage than its equivalent conventionally sailed version under 'bare' poles, due to all the rigging etc.
     
  9. rwatson
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    rwatson Senior Member

    Savonius rotors can only drive a prop or similar, they dont propel a boat directly like the Rotors.

    The are nowhere near as efficient as the rotors, and are hard to get 'started', especially in light winds.
     
  10. 1J1
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    1J1 Senior Member

  11. 1J1
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    1J1 Senior Member

    Here's an old book about the Savonius rotors, Magnus effect & such - might be of intrerest to you:

    http://www.prh.fi/stc/attachments/innogalleria/savonius_kirja.pdf

    On pages 24-25 there are infos about that boat with 2 Savonius rotors installed & it's trials. No propeller, moves only by means of Magnus effect.
     
  12. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Savonius rotors are not particulary efficient because they are, in
    effect, primarily drag devices as opposed to the propellor type
    which are lifting devices.
    They also require a lot of material for the rotor, and a strong
    support structure to hold them in place. In their favour, they are
    fairly cheap to build and require little technical ability: I've
    seen several made out of 44 gallon drums cut in half and then
    welded.

    As for Flettner rotors, they have been proposed many times over the
    years, but have failed to live up to the hype. If they really were
    efficient and feasible, many more would be seen today.
    In short, you are wasting your time and effort on these dinosaurs.
     
  13. rwatson
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    rwatson Senior Member

    Its an interesting article, but has a few 'anomalies' that need investigating..

    The big question that would need to be solved is the one of vibration. In actual service, I have read that the Flettner Rotors suffered from excessive wear due to vibration. I would expect that the Sav Rotors would be even more prone to that, due to their less streamlined design.

    Despite Leos comments, Flettner Rotors are the only 'device' of their types, that actually have been put into commercial service, which cannot be said of any other device.

    The latest Flettner ship E-Ship 1 has not proven commercially successful, but the company is not saying why. is it the propulsion system, the cylinder configuration or what ??

    I personally think the topic is worthy of further research.
     
  14. 1J1
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    1J1 Senior Member

    As I remember, vibration was the main problem for me when I built a rotor ship model back in the years.
    Obviously, Thom-Flettner rotor, like those on Cloudia trimaran, no matter of all the advantages would be the most suffering from vibration. Same if it's a telescopic retractable rotor.
    I remember I read about E-Ship 1 that her rotors restrict the ship from entering many ports. Rotors provide obstruction during loading/unloading operations, can damage harbour equipment like cranes, etc. Might be this?

    And a possible design of a catamaran with selft-rotating rotor... :p
     

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  15. rwatson
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    rwatson Senior Member

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