Headwind power

Discussion in 'Hydrodynamics and Aerodynamics' started by Windmaster, Oct 12, 2023.

  1. Windmaster
    Joined: Nov 2006
    Posts: 296
    Likes: 25, Points: 28, Legacy Rep: 56
    Location: Norwich UK

    Windmaster Senior Member

    A windmill powered boat can sail directly into the wind that powers it.

    Recently, I put up a page on my website of a simple model to demonstrate direct-into-wind sailing,

    Direct Into Wind Demonstrator https://windthrusters.net/windoppose.html

    This model has more drag behind the clr than in front and weathercocks automatically to windward.

    Therefore, when released at the downwind end of a pond, it automatically sails directly to the upwind shore.

    I'm hoping that publishing these plans will encourage others to make similar
    models.

    If two or more of these models are released at the same time, the one that reaches the upwind bank first will have demonstrated the greatest efficiency of direct into wind sailing.

    Many attempts have been made to predict mathematically the best setup for this kind of craft, but no matter how good the calculations, they mean nothing unless they can be proved by practical testing.

    For example, one variable that cannot be accounted for, is the random variation of the natural wind all the time in both strength and direction.

    There has been some dispute recently about what is the best setup for these models; whether it is better to use many windblades with a low tip speed ratio, turning at a low speed, or to use a few blades running much faster with a high tip-speed ratio.
    These are the kinds of issues that could be resolved by this sort of comparative testing.

    The only "rules" that would be required in a competition between different designers with different opinions about setup, would be that the swept area of the wind-rotor disc would be the same, therefore the same amount of potential power-producing wind would be intercepted for each case.
    All other parameters would be optional.

    Here in Norwich, UK, we are fortunate in having a purpose built model boating lake, free to use, which would be very suitable for this kind of testing (Eaton Park).
    So I'm obviously interested to hear of anyone within reach that builds a model of this sort, so that comparative tests with my own model could be made.

    see: Experimental Windmill Craft https://www.sailwings.net/windmill.html
     
  2. portacruise
    Joined: Jun 2009
    Posts: 1,476
    Likes: 178, Points: 63, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    I believe something like that would have to be done in some kind of a wind tunnel testing facility to get good data. Anyway, that's the way they do it for aircraft. It might turn out that there are other factors that are more significant than the swept area of the wind-rotor disc. Maybe things like total weight, shape of the hull, gearing and size of the underwater prop, Etc. JMHO.
     
    bajansailor likes this.
  3. gonzo
    Joined: Aug 2002
    Posts: 16,836
    Likes: 1,734, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    In the video, the hull and structure is below the air flow so it does not generate any downwind force.
     
  4. Sailor Al
    Joined: Feb 2021
    Posts: 652
    Likes: 27, Points: 28
    Location: Sydney

    Sailor Al Senior Member

  5. gonzo
    Joined: Aug 2002
    Posts: 16,836
    Likes: 1,734, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The video does not have any smoke trails to show flow. I suspect there is backflow in the tub where the hull floats.
     
    portacruise likes this.

  6. portacruise
    Joined: Jun 2009
    Posts: 1,476
    Likes: 178, Points: 63, Legacy Rep: 218
    Location: USA

    portacruise Senior Member

    It does appear to work in this video with a larger model,



    May be kind of complicated to build and operate, and slower compared to tacking?
     
    Sailor Al likes this.
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