Sailing Without Wind.

Discussion in 'Motorsailers' started by Will Gilmore, Jul 21, 2022.

  1. Will Gilmore
    Joined: Aug 2017
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    Location: Littleton, nh

    Will Gilmore Senior Member

    So...
    I had this thought.
    Remember the controversy over the statement made by AC team Artemis about sailing upstream on the Amazon River just from a ten knot current against still air?


    I was thinking about how to use that idea on open water. What if you had neither current, nor wind, or current and wind moving together, so no wind across the deck?

    Originally, when I was struggling to come to terms with this concept and had accepted the physics of it, I thought, 'could you just motor up to speed and capture that wind?' Answer, 'No'. In such a situation, you are always generating a head wind, so no usable variant is created.

    But...

    What if you used thrusters? What if you drove your boat sideways to create a beam reach?
    upload_2022-7-21_16-8-44.png

    Can you picture a sailboat driving along on a heading, under sail, but there is a smaller amount of energy being put into a sideways force that, under sail, moves the generated AW forward by a vector, to create a greater force that drives the vessel forward faster?

    Some of the issues to consider:
    1). actual sideways speed that can be generated would have to be small, well below the ten knots suggested in the video. There's a lot of lateral resistance to overcome.
    2). The heeling force generated by a large underwater thruster. This force would only add to the heel of a powered up sail. (Catamaran might address that issue).

    But, is this something, maybe impractical, but doable? What do you think?
     
  2. seasquirt
    Joined: Dec 2015
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    Location: South Australia

    seasquirt In the beginning there were waters.

    Nice alternative thinking Will, but if there is no 'energy' to be had, what powers the thrusters ? What replaces the lost energy from prop slip, electrical resistance, rolling resistance, and all the other losses ?
    I'd suggest procuring the same ACME catalogue that the Coyote uses.
     
  3. Will Gilmore
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    Will Gilmore Senior Member

    I'm not proposing running thrusters without power. They would be powered in the usual way. I'm just wondering if headway can be achieved through sailing by creating sideways movement. With the aid of sail lift and vector math, maybe a small amount of energy into side slip could translate into a larger amount of forward movement.
     
  4. Robert Biegler
    Joined: Jun 2017
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    Location: Trondheim

    Robert Biegler Junior Member

    All you need to do that is a boat with VMG downwind faster than true wind speed over the water, and these boats have been recorded doing just that. That is also the reason why they sometimes can improve VMG downwind by going into a contrary current, because that increases true wind speed over the water. It helps if you switch between the different frames of reference, like here: DDWFTTW - Directly Downwind Faster Than The Wind https://www.boatdesign.net/threads/ddwfttw-directly-downwind-faster-than-the-wind.25527/page-30#post-911173

    That would be a perpetuum mobile and would (unlike VMG downwind faster than true wind speed, or even going dead downwind faster than the wind) violate conservation of energy. You would not be extracting energy from the relative movement between two media, as Team Artemis did, so your proposed scheme is fundamentally different from what they did.
     
  5. Will Gilmore
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    Location: Littleton, nh

    Will Gilmore Senior Member

    Yes. True, but my issue, I think, is with my use of terminology. Where I wrote,
    I'm wondering if a sideways force to create a small sideways movement, might convert to a larger forward movement. My use of the word 'force' was not appropriate in this case. Of course in a system where a given force is applied, a greater force is not retrievable. However, like a small movement with a given force, can be converted to a large movement that may not have the same ability to do the same work over the small distance, but over the whole distance, the same work is done.
     
  6. seasquirt
    Joined: Dec 2015
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    Location: South Australia

    seasquirt In the beginning there were waters.

    I can visualise a long deep keeler being borne along by a swift river or tidal flow, in perfectly still air (by the land's reference), and making way. With the hull axis greater than 45 degrees to the apparent head wind and current flow, and sails set for sailing close to the wind, the hull would be under some actual wind power and traveling forward, but also sideways to the water flow, and backward according to lee slip, and likely confined by river banks, so tacking regularly. The water flow speed would be faster than the hull, (drag), and every tack would wash off momentum and speed, becoming even slower in the stream, and slow to get going again, that's if you can even steer, with nothing flowing over the rudder . I don't know fancy maths, but I reckon deploying a drogue, sea anchor, or storm sail as substitute, or better - two, and playing them for steering the hull by its attitude, and keeping it at 90 degrees to the water flow, bare sticks against the 'head wind', and go with the flow sideways. Just watch out for river snags and shallows. The air friction above, and hydraulic inefficiency below would wipe out any advantage of an 'apparent' head wind drive, I think, after working so hard to get it.
    Sorry if I sounded sarcastic earlier, but I could just see it: Wile E. Coyote, sail up, electric fan blowing from behind a square rig, (mysterious power source), pushing a bow wave and defying logic, perpetual motion with no resistance and perfect efficiency.
    Resistance and entropy wins the long game.
     
  7. Will Gilmore
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    Location: Littleton, nh

    Will Gilmore Senior Member

    Actually, I also had that picture pop into my head. But I'm talking about continuously putting energy into the system with the thrusters. Using mechanical force to create that all important relative lateral resistance and the AW on the beam. Just a thought. It should work, but what kind of energy would one need to transfer that energy from sideways to forward via sail and keel?

    I think the short LWL created driving by driving the boat sideways, LWL then equals WWL, would make generating a significant wind, very hard.
     
  8. seasquirt
    Joined: Dec 2015
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    Location: South Australia

    seasquirt In the beginning there were waters.

    If there must be some type of small input into the system, to gain a greater or different type of output, the slowly rotating column systems may be useful to adapt. Eg. large driven 'mast' drums taking advantage of the high/low pressure differential generated on the outside diameter, and driving a small propeller or paddle wheel directly somehow, avoiding lossy gear and belt drive systems. But then the weight and complexity makes it all come back to greater hull and top sides resistance, which negates the gains.
    Also, with delicate light weight. weight/energy saving equipment, a line squall or king wave will see it off in quick time.
    Rocket launch a kite up into a higher atmospheric level, and and jet stream it along. ACME rockets of course.
     
    Will Gilmore likes this.

  9. Will Gilmore
    Joined: Aug 2017
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    Location: Littleton, nh

    Will Gilmore Senior Member

    Of course, a name you can trust.
    upload_2022-7-24_8-7-30.png
     
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