Collapsible Flettner Rotor Project

Discussion in 'Projects & Proposals' started by Yobarnacle, Jun 4, 2014.

  1. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Anybody foresee any problems with the rotors offset from center?
     

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  2. daiquiri
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    daiquiri Engineering and Design

    You will have a clear wind on one tack and a partial shadow from the hull on the other.

    What is it about these triangle trusses that you like so much? :)
     
  3. Yobarnacle
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    Yobarnacle Senior Member holding true course

    trussses are strong and light weight.

    the rotors can be erected on either side
     
  4. Clarkey
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    Clarkey Senior Member

    I may have missed this in the depths of the thread but what happens if a Savonius rotor is spun by a motor? Do you then get l/d performance approaching that of a rotating cylinder?

    Maybe you could have a motor/generator on a savonius rotor - much of the time (moored, reaching, going downwind) it could be generating power or acting as a low efficiency Magnus effect rotor but when higher performance was required it could be spun to a higher 'alpha' value by the motor to improve the l/d ratio?
     
  5. Yobarnacle
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    Yobarnacle Senior Member holding true course

    That is precisely my hopes and "the unknown".
    Experimentation is needed and planned! :D

    I am severely modifying cabin, profile, and interior of one Albin 25 and intend several experimental drives on board.
    My second Albin 25, I will restore, using best parts from both.

    In addition to the rotors, I plan a modified lateen rig, a propeller "brake", an azimuthing prop drive, a hydromagnetic 'caterpillar" drive, a bow rudder, and various water distillation and battery alternatives, DIY composting toilet, and fish aquaculture/hydroponics on board. I have been working on it for two years, nearly three, and hope to splash this fall, late october.
     
  6. Yobarnacle
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    Yobarnacle Senior Member holding true course

    An easily driven hull with minimal horsepower. Albin 25 with original 22 HP Albin diesel.
    I'll be happy with just hull speed. Click on picture to animate gif.
     

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  7. gdeckert
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    gdeckert New Member

    Really enjoying this discussion thread, along with the related one. Since you're not afraid to go back to the drawing board, have you considered using multiple small rotors instead of two large ones? I'm picturing one or more frames of 4-8 rotors, perhaps each directly driven with its own small electric motor. That might let you size the frames to be easily handled by one person, bolted into place when needed, and stowed when not. I'm not an engineer so I'm going to have to leave the numbers to the experts. Can smaller rotors still be effective? How closely can rotors be spaced before they interfere with each other?
     
  8. Yobarnacle
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    Yobarnacle Senior Member holding true course

    The major factor in effectiveness of rotors seems to be diameter of rotor.
    Doubling height of a rotor appears to double it's propulsive force, a linear progression.
    The diameter appears to factor geometrically in the resulting force.
    Too skinny a rotor calculates would have an un-measurable minimal propulsive effect.
    The rotor needs to be in the neighborhood of 3 ft to one meter diameter to be useful on my 25ft semi-displacement hull.
    Dividing into multiple less tall rotors but totaling the calculated required height, would I estimate be equivalent to a single tall rotor of same diameter.
    I plan 2 half height rotors, while reserving space to add a third central rotor, should the power produced prove insufficient and require augmentation.
    Designing the rotor heights to fit within the boat's beam when horizontal seems appropriate, but reducing rotor heights to much less than beam, I fail to see an advantage.
    Do you see how multiple rotors could be half diameters or similar reduction and still produce required lift? That would be of great interest.
     
  9. gdeckert
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    gdeckert New Member

    If the thrust varies with the square of the diameter, could you halve your diameter and use four times as many? So two 1m rotors becomes eight 0.5m rotors. If it varies with the cube of the diameter, you'd need eight times as many rotors (16) to halve your diameter.
     
  10. Yobarnacle
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    Yobarnacle Senior Member holding true course

    It's actually a polynomial progression.

    The following posts pretty well cover the calculations.
    There are still more posts with calculations spread through the thread.
    take a look.

    15 rwatson
    37 rwatson
    39 me
    57 daiquiri
    59 daiquiri
    69 rwatson
    94 daiquiri
     
  11. gonzo
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    gonzo Senior Member

    A Savonius rotor is very inefficient compared to most other wind generating systems. It seems like an odd choice for a boat where maximum efficiency is required. There are other vertical shaft systems, like a Darrieus type. All of them are susceptible to stalling in gusting winds or turbulence. I understand the simplicity of not having a gearbox, but the drawbacks seem to overshadow that.
     
  12. Yobarnacle
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    Yobarnacle Senior Member holding true course

    Thanks for contributing Gonzo. Always appreciate your posts.
    The rotor/rotors I'm planning are both smooth cylinder Flettners and Savonius type and all electric powered. Can't get sufficient rpms so surface velocity is double wind speed (or faster) without power.
    Primary purpose of the experimental rotors is propulsion by Magnus effect.
    The Savonius IF functional as Magnus effect rotors would be tested/tuned as wind generators also. An auxiliary function.
    It's all proof of concept experimentation.

    The missing gearbox, I'm missing the reference?
     
  13. gdeckert
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    gdeckert New Member

    Thanks for the summary Yb, I'll start reviewing them. Toying with the idea of getting a pontoon boat to play with as an experimental platform, but maybe I'll start with some small scale experiments first.
     
  14. Yobarnacle
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    Yobarnacle Senior Member holding true course

    your welcome.
    I'm in mountains and no water bodies larger than a plastic tub. Only have showers for bathing, so not even a bathtub.
    no small scale experiments for me at this time.
    when I get back to my boats, not going to waste limited time or money on small scale. Going for the cigar! :D
     

  15. daiquiri
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    Check this: https://www.youtube.com/watch?v=NtN1oFB04Jg :)
     
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