Direct Upwind Sailing

The terrain is flat - clearly you will always find some excuse to say it is not working when anyone can see that it is.

 

It doesn't matter that Force can be multiplied using leverage. The Work is the same. It is either concentrated on a smaller/larger area or it is distributed over a longer/shorter distance or time. Both sides of a lever do an equal amount of Work. Force x Distance = Work. The same holds true for area, F/A = P.

However, I see nothing in the sailing upwind and ddw concept that would make it impossible to scale. Practicality aside, exploration makes the experimentation worth doing. Get the ratios of blade size, pitch, gearing and configuration right, and one never knows the limits of the potential for real-world applications.

-Will

 

I didn't say the terrain wasn't flat, but that it is higher than the water in the pond.

 

No its not - the water is higher than the terrain (that is why it has to be a pond with sides) This pond was built for vane controlled "pond" yachts in the 1920s

 

You should watch the video posted by yourself. There is a concrete parapet and vegetation all around it. I would like you to explain how the water in a pond is higher than the terrain around it.

 

Gonzo, how much effect do you think the wind drag on the hull will change the force diagram? Do you think that might be the tipping force that turns the forward force into a holding or reverse force? The full scale experiments I've seen have been on bays and larger bodies of water. The terrain will certainly have an effect on overall energy, but is the wind gradient going to be that different over a few inches of elevation on a model?

It seems to me, the point of the experiment is that a wind turbine can obviously generate and convert enough energy to drive that turbine into the wind. If the hull that supports that turbine makes it an impractical application, it still shows energy can be taken from the wind/water difference in motion to harvest useful energy. There is clearly more energy in that difference than we typically can use.

I remember this very question was posed in my high school physics class and our unanimous response, directed and supported by our teacher was, no. A wind turbine cannot move into the wind. We were all wrong.

-Will

 

Take a journey on Google Maps fill in "Eaton park Norwich" take a trip with the little yellow man onto the environs of the pond. There you will see how the water level is in fact higher than the concrete path around it. The pond was made especially for model boaters who can lean over and start their boats whilst standing on a lower level. That is obvious. You are clutching at straws.

 

The wind gradient goes to zero at the surface and grows exponentially. The issue is not whether a wind turbine can generate enough energy to move a boat, but if the boat can generate enough force in the opposite of the wind direction. For that, the thrust of the propeller has to be grater than the force of the wind on the turbine and the drag of the hull, turbine supports, inefficiency of the turbine, etc. Each step has a loss of efficiency, so the question is if it is possible to generate more thrust than drag. A model behind a parapet is not in the same conditions as a boat in open water, in respect to drag. In a land based turbine, the drag is opposed by the inertia of the planet. A perfect turbine would be about 59% efficient (Betz limit). In practice, small turbines are less than 30% efficient. Substract the combined drag and efficiency percentage of a propeller and then see if the thrust can be larger than the drag.

 

You have not thought about leverage. How if the wind turbine blade moves more than the boat then there is mechanical advantage. You need to read this page Headwind Assistance for ships and boats https://www.windthrusters.com/pushmepullu.html where it is all explained. If you have any questions about this page please say so. (at least it will demonstrate that you have actually read it) If you do not read it you will not understand the principle.

 

A lever does the same amount of work on either end. I watched the video. The claims do not follow the laws of physics, or at least show a lack of understanding of them. Pulling from strings is not a proper analogy to a turbine connected to a propeller through a gearbox. He shows an increase in torque with a decrease in velocity. This would mean that the thrust on the propeller will be less than the thrust on the turbine. The turbine does not work unless there is a force opposite to that of the wind against it. The diagram is missing the reaction force necessary for the forces applied on the string. The flaw in the argument is by giving the correct answer to his question: So where does the extra force come from? The answer is: from outside of the system (the guy pulling). Further, a wind turbine has much lower efficiency than a pulley, so once again the analogy does not apply. His proof is to connect a carriage to a fixed post, which is another flawed analogy since a propeller is not a fixed attachement point. As an engineer I work with numbers, collected data and calculations based on proven measurements. Show me a full size boat in open water going straight upwind, and I will change my mind and revise the known concepts of physics.

 

Not "any size". That is a "toy" as far as naval architecture is concerned, and a dangerous one at that given the inability to reef and reduced stability. As much the uninformed would think the design space is continuous, it is not because of the Cube-Square Law. While small (sub 1m to ~15m) horizontal axis vessels can be built (the Bates craft or Revelation II) which provide 100% propulsion, larger systems (John Marples’ Cloudia 10.4m, Alcyone 31m, the proposed Calypso II 66m, Baden-Baden ~100m, Pyxis Ocean 229m) all use vertical axis windmills or Mangus/Thom rotors to augment propulsion, not provide it.

I will be kind enough to assume you are not a troll even given the pauparcy of you posts, and I will be happy to answer most questions within my knowledge, but please do a modicum of research beforehand. I would suggest you start with A History and Philosophy of Fluid Mechanics by G. A. Tokaty who discusses the issues with windmills and the history of the Flettner rotor design.

 

You must be a very poor engineer to disbelieve what you see with your own eyes. All of the work demonstrates it works and there is encouragement and plans to make your own models to prove it works. There are many videos of full size boats going straight into the wind.

 

To suggest you should read a book to prove something does not work when it obviously works in real life is ridiculous.

 

There are two subjects that are forbidden on this forum. Politics and religion. Windmill powered sailing, the best anchor and a few other topics may have to be included.

Here we see that sailing borders so closely on religion that there are devil's advocates defending the orthodoxy. If a low concrete parapet blocks all wind Gonzo may be correct in saying that you can't sail on an artificial pond. I have to ask Gonzo, who is basically a well meaning devil, if there is a lake or pond in the world where the water is not below the surrounding landscape. I have been sailing on ponds and lakes for 60 years and with the exception of sailing on lakes behind dams on rivers I have never found the water to be above the surrounding landscape. As you can see in the attached photo, there is concrete surrounding the reflecting pool and no wind on the water. If there is a windier city than Chicago, this picture was taken there. I should tread lightly here because the nickname windy city refers to Chicago politicians, not meteorology. Having sailed in Washington DC, I can attest to the fact that meteorological wind is not always very strong there.



The following abstract seems to argue that a windmill can be used to sail, but not very well on most points:

click to see rest of preview

It is obvious that while Revalation II was able to make better progress directly into the wind with the windmill than it did under sail it was pretty slow on all other points with the windmill. The Scirocco 26 is known for its excellent sailing performance according to the link. Hull speed was given as 7.5 kn Classic: 6.36 kn by sailboat /guide/prout. sirocco-26. Unless you were dedicated to the idea of the windmill or sailed on a slow moving narrow meandering river, there isn't much incentive to use the windmill.

None of the few windmill powered boats that I have seen appears to have employed a centerboard. As far as I know, the only reason that a conventional sail can propel a boat in most directions is that there are several airfoils below the surface that produce thrust at an angle to the thrust produced by the sail and it is the sum of the vectors that moves the boat. The points of sail diagram may be of some help if anyone can draw in the thrust vectors from the keel, rudder and sails.


A sail produces thrust in a direction more or less perpendicular to the wind depending on the angle of attack and a fair amount of drag which is always downwind. A person who is too focused on extracting the maximum amount of power from a windmill always seems to point the windmill directly into the wind, and if he is on a boat, may pay little attention to lateral resistance. The windmill pointing directly into the wind will always produce a drag vector pointing straight downwind and the prop will produce thrust in the same direction that the boat is pointed. I suspect that some advantage can be taken of the drag on the windmill by rotating the windmill and or a daggerboard to gain some additional thrust while sailing on a reach. For downwind sailing the optimal windmill blade angle for shaft horse power might not be the ideal angle if the effect of some additional drag in the right direction can exceed the effect of the reduction in shaft horse power.

I think there is room for improvement, but I don't think that a windmill can perform as well on all points as a conventional sail. And no, I would not care to try one in a storm. If it can't be laid flat on the deck under some semblance of control, and if the boat doesn't capsize, the windmill will be laid flat somewhere under no semblance of control.