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Thread: A Flettner rotor freighter

  1. #1
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    Default A Flettner rotor freighter

    Century-old rotorsail design gets modern makeover

    From towing kite propulsion to sails fitted with solar panels, modern engineers have been working hard to find ways to make our increasing reliance on big cargo shipping more energy efficient and environmentally friendly. Finnish company Norsepower has looked to the past for inspiration, finding a solution in a nearly century-old engineering innovation relegated to the annals of quirky mechanical history.



    In 1924, German engineer Anton Flettner revealed his first large-scale rotor ship to the public. Named the Buckau, this retrofitted schooner astonished the general public with its large, imposing metal cylinders rising from the deck.

    Two years later, the first rotor ship designed from the ground up appeared in a shipyard in Bremen. Inspired by Flettner's prototype, the German naval authorities designed a three-tower rotor ship dubbed, the Barbara.


    Both ships employed an innovative new engine design pioneered by Flettner and utilized a process known as the Magnus effect for propulsion. Named after German physicist Heinrich Gustav Magnus who investigated the effect in 1852, the principle was initially used to illustrate how balls or artillery can curve away from their principle flight path depending on the airstream that surrounds the object.


    The idea behind the Flettner rotor is that as wind passes a spinning cylinder, the air flow accelerates on one side while decelerating on the other. This creates a thrust perpendicular to the wind direction.

    The Flettner rotor-propelled ships of the 1920s were popular at the time as a novelty, but the considerable capital costs and the looming Great Depression caused the design to slip into the oddspot pages of engineering history. As these engines still required traditional fossil-fuel based power to function, the technology wasn't of a great interest to most in the 20th century's age of omnipresent fossil fuels.
    In our modern era of environmental concern and shifts towards sustainable energy engineers began to hunt for ways to make current large shipping processes more fuel efficient.

    It has been reported that 3.5 to 4 percent of all climate change emissions are caused by the global shipping industry, and one recent study estimated these rates could rise by as much as three times by 2050.


    In 2008, German wind-turbine manufacturer Enercon developed the first modern Flettner ship, the E-Ship 1. With its four giant rotorsails, the E-Ship 1 reportedly achieved fuel-savings of nearly 25 percent after several years of testing and 170,000 sea miles (195,633 mi/314,840 km) traveled.


    More recently, Finnish company Norsepower has snatched the rotorsail baton, trialling the technology on several large-scale ships. Norsepower initially reported successful results, noting the technology had the potential for fuel savings of up to 20 percent on routes with favorable wind conditions.The biggest move forward for the technology has been the recent announcement of Norsepower joining forces with shipping giants Maersk and Shell to being testing the rotorsail motors on their giant tanker vessels.

    Initial estimates from Maersk and Norsepower expect the rotorsail technology to reduce average fuel consumption by 7 to 10 percent. The collaborative effort between the companies will implement the prototype engines and test the efficiency through to the end of 2019 before analyzing the overall results.

    "Our Rotor Sails have the power to reinvent the existing market and make auxiliary wind propulsion a natural choice for merchant shipping," CTO of Norsepower Jarkko Vainamo explained.

    Over 50 years after innovative inventor Anton Flettner passed away, one of his earliest designs has finally been rediscovered and it may prove to be a vital step towards a more environmentally sustainable and efficient cargo shipping industry.

    http://newatlas.com/norsepower-rotor...default-widget






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  2. #2
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    Default Re: A Flettner rotor freighter

    So how well do they go to windward?

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    Default Re: A Flettner rotor freighter

    Contemporary accounts report that Buckau performed better to windward with the rotors than with the original gaff schooner rig.

  4. #4
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    Default Re: A Flettner rotor freighter

    How exactly do they work? Drawings? Diagrams? I don't think I quite get it.
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  5. #5
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    Default Re: A Flettner rotor freighter

    Here you go - a comprehensive introduction here:

    http://students.iitk.ac.in/projects/...ttner_apps.pdf

  6. #6
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    Default Re: A Flettner rotor freighter

    It's the same effect that makes a ball with backspin lift, this pic is from Wikipedia.

    The spinning object influences the air around it so that a force is generated from the side where the direction of spin goes against the airstream to the side where the direction of spin goes with the airstream.
    The resulting force vector is always perpendicular to both the direction of the airstream and the spin axis of the rotating object

    https://en.wikipedia.org/wiki/Magnus_effect
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  7. #7
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    Default Re: A Flettner rotor freighter

    I've read that they have an uncomfortable way of pitching and moving. Has anyone else heard the same or knows how it's uncomfortable?

  8. #8
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    Default Re: A Flettner rotor freighter

    I can imagine there's a lot of gyro effect.
    Grab a bike wheel by the axle and have someone spin it up to speed. Then move around and feel what it does to your movements.
    Quote Originally Posted by Yeadon View Post
    Probably the greatest thread in the history of the WoodenBoat Forum.
    Quote Originally Posted by Duncan Gibbs View Post
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  9. #9
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    Default Re: A Flettner rotor freighter

    Quote Originally Posted by Ryden View Post
    I can imagine there's a lot of gyro effect.
    Grab a bike wheel by the axle and have someone spin it up to speed. Then move around and feel what it does to your movements.
    That should damp roll quite well.
    '' You ain't gonna learn what you don't want to know. ''
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  10. #10
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    Default Re: A Flettner rotor freighter

    How did Cousteau's work?
    Ratus ratus bilgeous snipeous!

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  11. #11
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    Default Re: A Flettner rotor freighter

    The Alcyon had turbosails, not rotors.
    More like a fat wing and I think there was some sort of fan inside the airfoil.
    Quote Originally Posted by Yeadon View Post
    Probably the greatest thread in the history of the WoodenBoat Forum.
    Quote Originally Posted by Duncan Gibbs View Post
    Probably the greatest post in the history of the WoodenBoat Forum.
    -~: Roughshod Riding Rabble Rousing Rebel :~-
    Peer of The Most Ancient and Noble Order of the Lauging Polar Bear

  12. #12
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    Default Re: A Flettner rotor freighter

    Interesting, albeit fugly.
    Gerard>
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  13. #13
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    Default Re: A Flettner rotor freighter

    So, no stalling angle. You would start to receive an advantage as soon as the wind went slightly off the nose. Because at that point the lift vector goes slightly ahead of the beam.

    I wonder how fast it has to spin and what the relationship is?

  14. #14
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    Default Re: A Flettner rotor freighter

    almost 10 years ago on BoatDesign-dot-net . . some nice details.

    http://www.boatdesign.net/forums/boa...ion-22126.html
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  15. #15
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    Default Re: A Flettner rotor freighter

    Quote Originally Posted by Dave Hadfield View Post
    So, no stalling angle. You would start to receive an advantage as soon as the wind went slightly off the nose. Because at that point the lift vector goes slightly ahead of the beam.

    I wonder how fast it has to spin and what the relationship is?
    No trimming either, as long as the rotor is spinning in the correct direction for the tack you are on.

    Best lift to drag ratio seems to be achieved when the surface of the cylinder is moving about 2-3 times faster than the apparent wind speed. It looks like the gust response would be quite friendly too since transient high wind speeds would move you back down to the less efficient ratio of rotor speed to wind speed.

    I know that there are practical issues and that the l to d ratio is no better than good soft sails (about 8:1 maximum) but I find Flettner rotors fascinating.

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