The Wind Powered Sail-less Boat

Discussion in 'Boat Design' started by DuncanRox, Oct 20, 2008.

  1. spork

    spork Previous Member

    As it happens, there are a number of ways to see that such a vehicle can self-start in a tail wind, accelerate to and beyond wind speed, and maintain a downwind speed faster than the wind. Our videos show all of the above. We've also provided analyses that show this.

    But even if we hadn't done so, it's not necessary to show that the vehicle can achieve this state unassisted to prove DDWFTTW is possible. Afterall, you'd be stuck at home if your car's starter broke, but you don't claim that I.C. engines don't work.
  2. Guillermo
    Joined: Mar 2005
    Posts: 3,644
    Likes: 183, Points: 63, Legacy Rep: 2247
    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    Rick, what if at the end of the day it comes to be demonstrated you are the one deeply mistaken? Would you then eat your hat? :)

    I find your demos either full of wishful thinking (when you address available energy) and/or misleading as your proposed mechanical apparatus do not address the energy problem, just the mechanics. Of course we can get dozens of apparattus multiplying/reducing/inverting the applied initial force-speed, but that proves nothing from the DDWFTTW energy point of view.

    Of course I can be wrong, but nobody has demonstrated to me it up to this moment. I still want to be explained how it is possible for the wheels of the cart to take energy from the floor as the force applied to them by such floor is just a reaction force to the power transmitted by the rotor.

    About Goodman:
    "The flag often flies rearward to indicate DWFTTW, however until I see it fly back steadily for a hundred yards or so..." As this was not possible to achieve, then he went to the treadmill experiment, which, as I have said, IT IS NOT equivalent, in my humble (and of course wrong) opinion. I think the treadmill thing is what is mistaking people and the cause of all this confusion.

    All the best.
  3. Guillermo
    Joined: Mar 2005
    Posts: 3,644
    Likes: 183, Points: 63, Legacy Rep: 2247
    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    No, I'm afraid your videos do not prove this, as the treadmill test is NOT EQUIVALENT to the open air test. And let me respectfully tell you I find your analysis incorrect. Maybe I'm wrong, as said, but none of you has been able to properly explain to me the cart or boat thing yet. And I do not consider myself as 'thick' as some of you may think. I recognize I can be wrong and if a proper (to me) explanation is showed, I'll gladly adhere to the thing, as said.

    Cheers. :)
  4. Guillermo
    Joined: Mar 2005
    Posts: 3,644
    Likes: 183, Points: 63, Legacy Rep: 2247
    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    Question from a "fool"

    Nobody is questioning going upwind. That has been proved many years ago. Have you tested going DDWFTTW? Can you post here traceable data showing it is possible?

  5. Guillermo
    Joined: Mar 2005
    Posts: 3,644
    Likes: 183, Points: 63, Legacy Rep: 2247
    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    You have said:
    "THere is never a mill. It is always a propeller producing thrust as long as the vehicle is moving. The energy ultimately comes from the air but there is an energy exchange from the wheels because these are geared to the prop and are being forced along by the wind acting against the propeller."

    To act as a propeller, the pitch of the blades needs to be oriented for such purpose. Now please explain to me how the wind can initially propel the cart if the rotor is not a turbine (so pitch in the opposite orientation). I'm sorry but I don't get it.

  6. Guillermo
    Joined: Mar 2005
    Posts: 3,644
    Likes: 183, Points: 63, Legacy Rep: 2247
    Location: Pontevedra, Spain

    Guillermo Ingeniero Naval

    I am with you (and the others) in that going DDWFTTW is possible with a theoretical device propelled by one (or more) ice boats. But, as said, the energy there is taken from a bigger amount of wind (because of the angled direction of the iceboats' movement) than the one available when the propulsor is going dead downwind. What I question are the rotor based devices' ability to go DDWFTTW, as at the moment the rotor ceases to get energy from the wind (when the blades feel no real wind component) the craft can not longer accelerate.

  7. Joakim
    Joined: Apr 2004
    Posts: 819
    Likes: 35, Points: 28, Legacy Rep: 422
    Location: Finland

    Joakim Senior Member

    Just by drag. The propeller causes drag, just like a spinnaker (remember it is BIG for a DDWFTTW craft/cart). The drags, pitch(es) and gearing needs just to be such that the moment caused by wheels/turbine is bigger than the moment caused by the propeller.

    For a craft rotation is not necessary at start and it may help to lock the shaft. The craft will have some downwind velocity with locked shaft (say V=1/3W, depends on drags). From that point it will be necessary to have the propeller rotating in the correct direction.

    The cart need to have it correct from the start unless the wheels slip. The blades probably have quite low pitch, thus very high AoA while not rotating. Thus they produce not much moment, just drag, at the beginning.


    PS. have you read my "energy analysis" #491
  8. Guest625101138

    Guest625101138 Previous Member

    I spent the time to analyse with an open mind and scientific enquiry and KNOW I am correct so it is not something I need to be concerned with.

    I have been wrong before (once or maybe twice) and there is a good chance I will be wrong some time in the future but I have no doubt about the feasibility of sailing DDWFTTW.

    You simply fire off silly responses without taking any time to properly analyse what people take the time to put to you.

    You still think it is a windmill. At no time is it a windmill. It is always a propeller by virtue of the gearing enabling the wheels to overcome the reverse torque the propeller will develop before it starts to turn. Power flow is from the wheels to the propeller.

    If the gearing is the other way around such that the rotating blades can overcome the wheels then the blades in the air become a turbine and it goes upwind rather than downwind. Power flow is then from the turbine to the wheels.

    I have no doubt that you will regret having persisted with the silly points you have made so far when the light turns on. You will review this thread and wonder why anyone would bother trying to answer your silly questions.

    I regret not having the patience to suffer the "fools" that Windmaster yearns for but I believe anyone who reviews this thread in its entirety, and with insight, will find that I have taken great pains to achieve understanding.

    Rick W.
  9. Guest625101138

    Guest625101138 Previous Member

    At standstill the blades are stalled and have high drag relative to lift. The body of the vehicle also has air drag. The downwind force produced by the drag causes the vehicle to start moving down wind. As soon as this happens the wheels start to turn and the gearing to the propeller causes it to turn. Once the propeller turns it causes the airflow to reverse through the blades and the vehicle gathers speed downwind.

    If you look closely at the test in this video you will see the prop turns in the forward direction as soon as the cart moves under the influence of the fan generated wind. At no time does it act as a turbine:

    If the gearing was such that the blades could overcome the wheels then the blades become a turbine that power the wheels and the vehicle climbs upwind.

    Hope this clarifies this key issue for you.

    Rick W
  10. Windmaster
    Joined: Nov 2006
    Posts: 233
    Likes: 4, Points: 0, Legacy Rep: 56
    Location: Norwich UK

    Windmaster Senior Member

    No, I personally have not tested DDWFTTW, I leave that to Goodman, Spork, JB and others - who are doing a great job that I don't need to emulate at present.

    However, it seems reasonable me that if a craft can sail through water directly against the airflow that powers it. Then a craft can also sail through air directly against the water that powers it.
    The only difference is that in the upwind case the craft is supported by the medium it wants to travel through, and in the downwind case the craft is supported by the medium it is gaining power from. This makes it more difficult in the downwind case because of the drag incurred by the need to support the craft.

    The perfect case would consist of an airship, supported in the air, which dropped a turbine into the water as it is carried along by the wind. The turbine then turning and powering a propeller on the airship which would drive it through the medium it is in (the air), to an observer in the water - it would be going downwind faster than the wind.

    This is the EXACT opposite of sailing directly into the wind and there is NO REASON why it would not work - it is a simple reversal of the two fluid mediums.
  11. spork

    spork Previous Member

    I assure you that my videos do in fact prove DDWFTTW. Your assertion that the treadmill is not equivalent to a stationary road with a tailwind is just that - an assertion. You have NOTHING to back that up. And several people have explained to you exactly why it is so. If you can find yourself a high school physics book you should scan through chapter one to learn about intertial reference frames. That will address your concerns.

    I'm sure you do. But let me make two points perfectly clear:

    1) They're not
    2) Since you absolutely refuse to ever tell us where you find error, it's impossible for us to help you.

    You're wrong. Several of us have explained it. You are making the classic mistake that because you've failed to understand it we must have failed to explain it. Do you claim that Einstein has failed to properly explain his derivation for special relativity because you're unable to understand it?

    No one does. But if you refuse to even attempt to tell us where you think our analyses go wrong, what are we to think?

    It's the SAME THING. The boat is captured between two fluids. If it is going upwind relative to one, it is also going downwind faster than the wind relative to the other.


    Then our work is done here. That's all I need to prove. There's certainly no need to prove every possible architecture for achieving DDWFTTW - particularly if someone prefers not to understand some of them.
  12. robherc
    Joined: Dec 2008
    Posts: 432
    Likes: 5, Points: 0, Legacy Rep: 102
    Location: US/TX

    robherc Designer/Hobbyist

    If you watch the two of their videos here in sequence (preferably with the sound turned OFF), then you will see:

    1.) 3 good shots of DDWFTTW vehicles self-starting (while only one demonstrated wheel slip and turned the prop the wrong way at first).
    2.) A good shot of a BADLY done open-air experiment where even I do not believe the craft was actually going any faster than the wind (please, for the love of PETE, be scientific & put the flag somewhere OUTSIDE of the reverse flow from the fan)
    3.) One VERY well done demonstration where a craft (the same one as self-starts itself in front of a fan in vid. 1, and in the open in vid. 2) climb UPHILL faster than the actual wind. (windspeed relative to the belt...remember, the belt is standing perfectly still relative to itself, so the wind is coming from behind the craft in this respect)...also, if you watch the craft before it's set on the belt, you can see that airspeed in the room is 0 (or at least negligible) relative to the frame of the treadmill, which the craft moves forward (downwind) relative to.
    4.) Unfortunately, Zero demonstrations where the craft self-started, and overcame the DDWFTTW without some form of assistance...still proved the possibility of the principal, but didn't demonstrate the conversion...maybe an open-air experiment with the flag mounted AHEAD of the props could show us that?

    I think I'm understanding this well enough now to begin explaining it (the best way to learn) if I just had the money & experience to design a foiling multihull with broad sterns & knife-narrow bows...put a water turbine @ the bottom of a foil (centered port-starboard under the CG of course) & gear it to a large enough prop....I think that might become a usable (for theory demonstration) DDWFTTW boat model...hmmm
    Anywise, if you'd like to debate the theory orally, pm me your phone # and a good time (use GMT, or at least tell me your offset) to call & we can discuss it that way...which I find to be a supremely more effective medium at times... :)
    Last edited: Jan 5, 2009
  13. ThinAirDesigns
    Joined: Dec 2008
    Posts: 126
    Likes: 5, Points: 0, Legacy Rep: 40
    Location: USA

    ThinAirDesigns Senior Member

    Please, for the love of PETE pay attention to the location of the flag before you make such comments.

    Following are two stills taken from the video in question. Notice that the first shot establishes the angle of the rod holding the streamer to be parallel with the rear axle -- it doesn't extend to the rear, but rather straight out to the *side*. The second shot shows how long the rod is relative to other parts of the cart.

    Due to the angle of most of the filming, this is one of the common misconceptions about Goodman's video -- that the streamer is behind and in the prop wash. Simply not true.

    The streamer is off to the side and in undisturbed air.


    Attached Files:

  14. Jimbo1490
    Joined: Jun 2005
    Posts: 784
    Likes: 41, Points: 0, Legacy Rep: 527
    Location: Orlando, FL

    Jimbo1490 Senior Member

    I have not posted to this thread yet, just read all the posts from page one forward. I get that the propeller is AT NO TIME acting as a power recovery device, that is, a turbine. It is instead ALWAYS acting as a propeller, being driven by the wheels. But what is the source of power for the wheels? It must be the forward motion of the cart due to the drag (as a parachute) of this same propeller, correct? So the 'non-intuitive' part of this whole apparatus is then that the propeller can act both as a sort of parachute or spinnaker, driving the cart downwind by simple drag, and yet also simultaneously provide drive thrust by virtue of being driven by the wheels, which are the power recovery device, NOT the propeller, thus providing the power to exceed the wind speed downwind.

    Intuitively this SEEMS impossible, yet it's obviously both possible and repeatable. The only question is how to wrap one's mind around the whole thing.

    Is my understanding correct?


  15. spork

    spork Previous Member

    That's a bit of a tricky area. It's true that the prop acts as a prop and not a turbine. However the medium works against the prop, so the cart can said to be powered by the wind acting on the prop from the frame of reference of the ground - just as it can be said to be powered by the ground in the frame of reference of the cart.

    Not exactly. Initially the prop acts sort of like a parachute. But once it gets spinning pretty good (being turned by the wheels) it becomes a lifting surface and provides the thrust to push the cart forward.

    The whole secret (at least viewed one way) is that the prop has to do less work on the air (since the air is moving relative to the ground) than the wheels are able to harvest from the ground to drive the prop.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.