Kite + ventilated foil concept

Discussion in 'Sailboats' started by quequen, Jan 3, 2013.

  1. quequen
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    quequen Senior Member

    After the amazing Sailrocket record and all the interesting, professional comments about the evolution of the famous SR foil, I've been searching for this very simple and obvious concept that tries to gather both SailRocket and Kite advantages. Surprisingly, I haven't found nothing similar (not even in sketches). There are hundreds of "T foiler" kites, but not "Ventilated Foil" kites (just to give it a name).
    When SR goes to max speed, there are just two things that matters: foil and sail. All other staff is almost superflous and just contributes to stability and control (not minor isues, however). I'm pretty sure a little device like a kite, avoiding a lot of windage and spending less energy on keeping all that staff out of the water, will divert that Newtons to drive force. What do you think?
    (sorry for this oggly sketch)
     

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  2. Stumble
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    Stumble Senior Member

    Que,

    The concern I have had with kites for a while is that I have real doubts about how much further they can be pushed. Ignoring the equipment for a moment, at some point the human body can't direct the force generated by the kite. Beyond some threshold the body becomes the weak point and further developments of equipment are of minimal value.

    Secondly there is some component of a kite that is pulling upward on the kite boarder at the speeds they are already hitting this is already becoming a problem. Instead of worrying about how to get the rest of the board out of the water, I think a bigger issue is going to be how to keep enough of it in the water that more power can be translated into more speed.
     
  3. quequen
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    quequen Senior Member

    That's why the central line must be aligned with the foil, tranfering lift directly to it, acting over the same line, and leaving the kiter freedom to control his kite (again, this is just an idea)

    Agree, I think the only solution to that is keep the kite very low over water surface, minimizing the vertical component (I think that's the way they fly it at very high speeds)
     
  4. Doug Lord
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    Doug Lord Flight Ready

    ========================
    For some reason I didn't save the video or write down the name but a few weeks ago I found a video showing a guy hanging from a kite with a UFO attached to a line going to the kite guy. So if you really look hard you're bound to find it.
    UFO-underwater flying object-uses a couple of foils to exert a downforce and lateral resistance.......
     
  5. quequen
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    quequen Senior Member

    Doug, couldn't find that video, this other one is roughly about your concept:

    kite + submarine hydrofoil
    http://www.youtube.com/watch?v=1tEw_mlUh7g

    Anyway, this kind of device will reach the same problems SR found when cavitation starts. The concept I mentioned is just an extreme simplification of SR, trying to keep just the foil (a wedge-ventilated one, not a conventional underwater hydrofoil) and the sail (and the guy, if needed ;) ).

    Cavitation starting near leading edge on a "T" hydrofoil
    http://www.youtube.com/watch?feature=endscreen&NR=1&v=DijdU0rmDdc

    Supercavitating (not ventilated) "T" hydrofoil
    http://www.youtube.com/watch?v=se4hzMF4PgI
     
  6. tspeer
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    tspeer Senior Member

    Don Montague has been working on something along this line with his Kiteboat project. The K1 had a ventilated main foil that was intended to operate in a similar manner to Sailrocket's.
    [​IMG]
    However, they weren't able to get the drag down.

    For their next boat, they've gone back to subcavitating J foils and a T foil rudder.
    [​IMG][​IMG]
    This boat won't be capable of Sailrocket's speeds, but it is kite powered and can sail on both tacks.

    Figuring out how to launch and retrieve a large traction kite has occupied much of their development.
     
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  7. quequen
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    quequen Senior Member

    Tom, thanks for the interesting link, seems like they don't follow a speed-record attempt but a more traditional approach having better potential on marine markets. Advantages of the system are very clear.
    I picked up an old post of yours from 2008, related to what Doug mentioned: a submarine-foiled device to provide lateral and vertical resistance. The project has no updates from 2010. Interesting the 3D Javascript to play with vectors involved!
    http://www.noughtinfinity.net/WBH/index.html
    http://www.noughtinfinity.net/WBH/html/WBHF in LG3D.htm
     
  8. Submarine Tom

    Submarine Tom Previous Member

    Doug,

    That sub-kite is too cool.

    Get some control lines and a wing around them and you're in business!
     
  9. quequen
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    quequen Senior Member

    A cup of 3D files to illustrate a bit better the first idea...
     

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  10. quequen
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    quequen Senior Member

    Two more 3D ideas on the same concept (that is: simplifying the SR):
    - a windsurf board with a "J" ventilated foil.
    - a sort of "mini Sailrocket" for very skillful windsurfers, having WIG effect, a rigid wing and the "J" foil (a standard windsurf sail could work also).

    Thoughts?
     

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