I don’t understand why there is any doubt that it could work. A boat like this could go, maybe, 3 or 4 knots and say in a 15 knot head wind the windmill would still be spinning with mostly ‘true’ wind force as opposed to aparent wind. You don’t need a battery and you don’t need anything sophisticated.
Well, it seems to go against most people’s intuition and it did go against mine (and tcburnett) for a while. Now I know better but if you did a survey I bet most people would say it is not possible.
And since I am here I would point out I was just looking for the theoretical possibility which has been proven but, in practice it would be very difficult to build a large ship that used this principle. Sails are difficult enough to handle and they are stationary. Having a huge windmill would not be practical.
A ship sailing dead into the wind would roll like crazy and the blades of the windmill would be in the water in no time.
A catamaran would be a better choice…
What you could conceivably build is a huge floating platform which would have big windmills to provide power enough to provide movement and local power needs. Your own floating country could be powered like this.
Seems to me that if you’re using any sort of propeller, you cease to be sailing, and start being motivated by the propeller instead of the wind.
Am I crazy in this?
Well, this is totally a matter of semantics. I vote that, as long as the wind is your only source of power to move you as you move, you are sailing. (thus having the boat at anchor for a week while charging the batteries with a wind generator and later moving it with an electric motor is not sailing).
But if you are using a wind generator that directly feeds an electric motor, without intermediate storage, you are sailing.
Don’t forget a boat, to go to windward, has to have a keel to provide lift. The screw propeller does exactly the same thing. In both cases the motive power is provided by the wind and both provide lift to windward.
Some musings about the nature of sailing:
Sailing takes advantage of two layers of fluids moving respective to each other. A body at the boundary layer, with foils in each layer can move itself from any point to any point. This means:
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sailing is impossible if there is no relative motion between air and water.
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sailing is possible between two layers of air or two layers of water that are moving relative to each other. You could have a “sailing submarine” and a “sailing blimp”
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- As a gadget that proves the theory, the propeller thingy may work but if you want something you can ride around on there’s a few big problems: you can’t steer it, it would need fairly deep water to operate in, and it would be very weight-sensitive. I’d bet that you could build any variation of one of these things as big as you wanted, and a 16 ft Hobie cat would still make faster upwind progress by tacking. - MC
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MC, you are letting your “intuition” get in the way and I think you could well be wrong but, of course, I haveno way to prove it. But think of this: In a boat tacking upwind the entire hull is traveling a long distance in the water which creates drag both in the water and in the air. With a boat propelled with this system, only the windmill and the screw propeller in the water are traveling the same long distance while the hull itself has much reduced drag. A boat tacking at 45 degrees upwind needs to go 1.4 times the distance at 1.4 times the speed of one going dead into the wind.Also a hull pointed dead into the wind has less windage than one sailing across.
On the other hand, the windmill boat would require a transmission which the sailboat does not need and which would introduce some losses.
This would be difficult to compare also in the sense that, to be meaningful you would have to have the two boats with equal sail (windmill) area. But this introduces another whole set of problems because a boat can carry more sail than windmill area (I think off the top of my head) so, in a sense you would have to handicap the sailboat…
But the theory would say to me that of two boats with equal sail area, if everything else is maximized, the windmill bot will make more progress to windward.
Don’t know if anyone is still interested in this topic. I found it looking up something I was involved with in 1981.
I was working for what was at the time, the largest solar manufacturer in the southwest - Sunpower Systems Inc., in Tempe, Az. We hired a former aircraft mechanic who had already obtained a patent on a windmill design that he had actually mounted on a sailboat and sailed it directly into the wind.
It used four vertically mounted glider wings with a cam at the top to keep the leading edges at the proper attack angle into the wind as they rotated. We were going to build them to generate electricity, but Reagan destroyed the alternative energy industry before we could even start. I went to his home and saw all the models and prototypes. His first name was Dave, but I can’t recall his last name. He would probably be in his 70’s by now. He had a son named Victor.
It’s possible for exactly the same reason that it’s possible for a wind-powered vehicle to move directly downwind faster than the wind. Intuition just gets this one wrong too often.
(Noted zombie thread)
I’d swear that there was video making the rounds awhile back on the sailing forums where a windmill driven prop on a model boat did make headway upwind. I can’t recall if it was directly upwind though. But I think its possible. It just depends on the relative effieciencies of the windmill part and propellor part and a bunch of other variable variables.
Off the top of my head I’d say if the windmill part can extra more energy for thrust than the backwards force/drag it creates than the boat can move forward, which at first blush doesnt at least break some fundamental law of physics IMO.
It would be the same as a wind-powered vehicle able to move into the wind faster than the wind. For a vehicle traveling with the wind, once it reaches the same speed as the wind, it’s stationary with respect to the wind, and I don’t see how to extract more energy from the wind to go faster.
It’s possible because it’s extracting energy not from the system of wind vs itself, but wind vs the ground (or water).
It’s not only possible in theory, but has been done in practice - here’s a thread in which it was discussed:
You’re right. I remember that thread. The most succinct explanation was, I think, The Hamster King’s:
It just occurred to me. Sailboats can definity sail upwind. But they can’t sail directly upwind. They go at an angle to the wind, but upwindwards, then they “tack”, changing direction, going at about the opposite direction, but still relatively upwind. Zig zagging their way upwind. Rinse, lather, repeat.
Going directy upwind could be thought of as “tacking” at a very high rate. If that is possible, then going directly upwind by some means aint that different is it?
Near enough, I’d say. Sailing at any angle to the wind is the physics of inclined planes, and so are propellors.
You are all missing the point. The genius of the design is that the glider wings were not acting as sails or blades, they were providing sideways lift! The wind direction above the hull is irrelevant since the cam keeps them providucing maximum lift at all times. The lift is converted directly into torque to a propeller through a transmission. The wings are angled by the cam on top to present minimum resistance to the wind, but maximum lift.
Seeing is believing and I actually saw it.
The closest design I have found so far is this one:
The one I saw had four wings tapered like actual glider wings so the assembly was conical, not cylindrical, to reduce weight and bearing friction. Narrow at the top and widest at the bottom. The concept is the same, just more efficient, with fewer parts and less turbulence for the other wings.
It did sail directly into the wind quite easily.
Been around for years. Saw one in St. Martin in 91. Fug ugly but it works.
A good boat can beat it port to port. But it can & do go directly into the wind.
Several different ones if your Google Fu is good nuff.
also on 21-24 foot sailboats if of proper design and a two man crew that can roll tack ( we used a Catalina 22 ) it can be walked so tight to the wind that is will bogglle the mind the actual track made good.
A real killer on the body and we could only do it maybe 10 - 15 tacks in a row but we could get to the up-wind mark from a position that no one else could. Works better in heavy air.
Has Mythbusters done this one? Seems right up their alley…
Great users name thread topic combo.
Wouldn’t it be more efficient to mount a wind-powered electrical generator on a boat, and transmit the power by a cable to an electric motor driving the propeller? This would avoid energy losses caused by mechanical transmissions and drive shafts.