Gyrocopter rotor instead of canvas sail ?

Discussion in 'Hydrodynamics and Aerodynamics' started by CocoonCruisers, Mar 22, 2019.

  1. CocoonCruisers
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    CocoonCruisers Junior Member

    Hi, this is a thought experiment or an idea for an RC project rather than than something that lends itself to full-size experimentation (who'd want to sit next to a large wind turbine for days on end ?); one of these morning thoughts that i couldn't plainly invalidate in the usual 10 minutes of googling. Cheers!

    DISAMBIGUATION first: This is NOT about a wind turbine driving wheels or propellers through some kind of mechanical linkage. ( Such contraptions have been built to prove the counterintuitive points that it is possible to 'sail' directly upwind 'Sailing'?? Directly to Windward https://www.boatdesign.net/threads/sailing-directly-to-windward.27000/page-14#post-571266 , or go faster than the wind dead downwind https://phys.org/news/2010-06-wind-powered-car-faster.html )

    QUESTION: Would it make sense (or has someone tried) to use a rotor in AUTOROTATION instead of a sail, for a sailboat or landyacht ?
    (I mean a freewheeling lifting surface like in all these ultralight Gyrocopters: Autogyro - Wikipedia https://en.wikipedia.org/wiki/Autogyro etc )

    POINTS that could be OF INTEREST:
    - Lift/Drag ratio around 11: won't beat a wingsail, but much better than your usual canvas sail.
    - Easy depowering: brake it and the lift vanishes. Windloads at rest are minimal, contrary to a flettner rotor, let alone a wingsail.
    - Auto-limitation against overloads: Wingtips designed to stall in a storm are a common feature in large wind turbines.
    - Mast height halved - a great match for freestanding masts, or A-frames from both sides of the rotor axis.
    - Rig height at rest (aka bridge clearance) could also be halved using a two-blade rotor with a brake allowing to lock it horizontally, or a single-blade (yeah that exists, they use a counterweight. It's supposed to be the most efficient setup in theory), or these helicopter-style hinges allowing to fold away the blades.
    - Massive wheel effect for roll and yaw stabilisation to help with comfort, but also system efficiency (steadier flow over the lifting surfaces).
    - Reasonably simple mechanical system; there are probably more potential points of failure in a classic sail rig.
    - Unlimited supply of free aerospace-grade blades, after their (few) approved hours before routine swap in helicopter rotors ...


    If, against all odds, the idea turns out viable, some wind power manufacturer could try to scale it for the ominous unmanned cargo drone ships of the future. These companies' composites/cfd/hpc resources far exceed the means of the marine sector; getting them involved beyond their rather symbolic ocean racing commitments might bring a few nice surprises.
     
    Last edited: Mar 22, 2019
  2. JamesG123
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    JamesG123 Senior Member

    Sounds like an interesting experiment.
     
  3. Dejay
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    Dejay Senior Newbie

    Interesting! The sailing upwind faces a tougher challenge on boats though, with electric you get something like 55% efficiency from input to propulsive power. Much worse than the one build in that video.
     
  4. alan craig
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    alan craig Senior Member

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  5. CocoonCruisers
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    CocoonCruisers Junior Member

    Oh, cool !
    So in 1933, King George V, who knew a lot about yachts, said "I have never seen a yacht sail so close to the wind". No videos found, but there is this tiny animated gif on Fiona Sinclair's site. The restored boat seems to live in the Cowes Classic Boat Museum - Wikipedia https://en.wikipedia.org/wiki/Classic_Boat_Museum now.
    [​IMG]
     
    Last edited: Mar 22, 2019
  6. dinoa
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    dinoa Senior Member

    The rotor L/D will be closer to 8
    Braking the rotor is not trivial. Braking faster than depowering a sail would require massive structure
    Centripetal force stiffens the rotor. At stand still it will bend in high winds if not built massively or has provision to turn the tip path plane into the wind or to feather.
    Changing the pitch of the tips to stall to prevent over speed is complicated. A feathering rotor will work but is complicated
    Different relative wind speeds over parts of the rotor disc such as wind gradient or sail masking require blade articulation or massive structure similar to a wind turbine
     
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  7. messabout
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    messabout Senior Member

    Such a device wou[d be hard to reef if or when the situation demanded
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    No-one had their head chopped off yet by one ?
     
  9. JamesG123
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    JamesG123 Senior Member

    As opposed to having it smashed in by a boom during an unexpected jibe?

    You "reef" it by feathering the blades. Like an airplane with an non-turning propeller. Turning them edge on to the wind so they produce minimal drag and thrust.
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    It does appear to be a "clear and present danger" in the one pictured.
     
  11. JamesG123
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    JamesG123 Senior Member

    Life is dangerous. Everybody dies from it.
     
  12. Mr Efficiency
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    Mr Efficiency Senior Member

    Which doesn't mean you should hasten it !
     
  13. rwatson
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    rwatson Senior Member

    Windmill Yachts have been around for nearly 100 years.
    Here's a model


    Then there is the Vertical Axis windmill, which avoids decapitation

    or


    But of course, the only mechanical sail that has ever found its way into commercial use, is the Flettner Rotor, which offers more performance overall, if not head into wind ability.
    .

    Or a combination of both


    A long thread about it here
    Windmill or Wind Turbine- powered boats: how many are out there, and are they viable? https://www.boatdesign.net/threads/windmill-or-wind-turbine-powered-boats-how-many-are-out-there-and-are-they-viable.14182/page-6#post-184637
     
  14. Dejay
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    Dejay Senior Newbie

    Maybe one could use a wing in combination with this "Ion Drive". Something that uses electricity to charge and guide air ions across it's surface.

    Maybe you could increase the lift from a flettner rotor without increasing drag.
     

  15. Mr Efficiency
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    Mr Efficiency Senior Member

    I'd call it Samurai Sailing, LOOK OUT, or get your head chopped off ! :eek:
     
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