'Sailing'?? Directly to Windward

One has been made that can go in any direction - it's here http://www.youtube.com/watch?v=NNbNNSDljGI

 

So please go right ahead and make it work in the real world of real boats. Nobody else can. If it did we would be using them on large scale for something besides making electricity in static wind farms. Scientists and engineers around the planet are looking for ways to get around our oil use, so this sort of thing has been looked at by them and rejected as an impractical toy. But what do they know? They're just employed by huge corporations looking for a cheaper way to transport goods for profit, obviously stupid people who are prejudiced against this brilliant concept.
Reasons it would not work: fragile and complicated like a helicopter is, suited to limited conditions, only works on a narrow range of relative wind (won't go downwind in light air due to relative wind speed), quite dangerous in large size if it fails (flying blades and bits), can't be furled or reduced in present form (how do you leave your boat at the dock?) so needs more complexity in form of feathering/reefing blades, quite expensive to build and maintain so an economic bad idea.
What is the advantage of going straight upwind versus the trade offs needed?
Think about it. You replace or augment something as simple as a sheet of cloth that's been doing the wind powered boat thing for many thousands of years and had its problems worked out to the point it works well off bloody CAPE HORN, with a delicate whirling gadget with shafts and gear trains and wind and water propellers and gyro effects and expect it to actually do useful propulsion work in any conditions other than a mill pond and a 10 knot wind? Yes, a few experimental craft have been built, usually multihulls, but it is not economically viable, or someone would be getting rich off it.
In other words, a wonderful fantasy having nothing to do with the real world, like the stuff that comes out of the mouths of politicians and economists.

 

Sure would be nice to make it practical. These sorts of things require development work to iron out the drawbacks which emerge. This costs time and money. For example, in the aero industry a lot of effort and cost has gone into perfecting vertical takeoff and supersonic airliners, both have acheived limited success but there have been a lot of failures in the process. The argument that "if it worked they would be everywhere by now" could (and has) been applied to every new idea since the Wright brothers. Huge corporations don't have a good track record when it comes to innovation, they have often been bested by amateurs and entrepreneurs. Do you think helicopters are fragile? Have you ever looked into the design parameters? When did the last helicopter fall to pieces in the air? Just because something has been used for thousands of years doesn't mean that there is no improvement possible, no doubt they said that about horse transport, oil lamps, open sewers, coal fire heating, semaphore signalling etc. (the list is endless). This idea is not an attack on traditional sailing, neither does it seek to supersede it. It's just an interesting possibility which merits some attention and research. No doubt when it was suggested that motors (of any kind) could be mounted on sailing boats there were some who said it was not necessary "because we did without them for thousands of years" (some still say that I believe). However, it is now rare to find a boat without one. As for being complicated, there are nothing like as many moving parts as in a boat engine and everyone accepts them. But this works without using any fuel!
You're quite right about the politicians and economists though.

Note: As suggested in this instance the rotor blades are not "whirling" they only travel at windspeed with a tipspeed ratio of 1:1 therefore there is no gyroscopic effect. If you would like to study everything on http://www.sailwings.net/rotaryhome.html you would be aware of this. It's fine to argue about something when you know all the facts, but if you have not researched thoroughly your observations are often wrong or misplaced.

 

My research has been 50 years of good and bad conditions at sea so I admit my prejudice since I have seen some mighty strong things break and get destroyed by wind and wave.
The helicopter analogy still holds. A heli is a highly complex thing that is very expensive and liable to failure if the slightest malfunction occurs to the blade pitch mechanisms. That this is extremely rare is a tribute to maintenance, billions in military development dollars and the fact that the heli is a very useful and necessary machine of war that has gone through a long, taxpayer-funded development process where lots of them fell out of the air before modern designs and materials made the thing work so well. They still crash, though rarely from mechanical failure these days unless not maintained. It's usually pilot error. That applies to this windmill powered boat too.
I'd love for something like this to work and be a practical machine that helps humanity in some way, and have really looked at it from an engineering view but just can't see how to do it. I'm not enough of a genius engineer to overcome the many many drawbacks. It's a toy. Please make it better in the real world. We all want the idea to work.

 

Catbird Suite, Wind Turbine Rig

I'm not particularly interested in getting involved with this discussion at the moment, ...but let me make reference to a gentleman who did lots of experimentation with these concepts on hie 63 catamaran over in New Zealand.

http://www.damsl.com/
...click on 'Wind Turbine Rig'

I think if you write to him he will be glad to refer you to other successes he has experienced.

 

I read the stuff on that site and wonder what your point is.
It didn't seem too successful since the experimenter junked the turbine rig after some initial development successes and went to a somewhat unconventional sail rig because it was all around faster and easier, just wouldn't go straight upwind, and he wanted to sail, not keep spending money forever. His idea of a smaller turbine together with solar to auxiliary power an otherwise sail powered boat is interesting, but again complex and expensive, much more so than a comparable diesel while adding greatly to drag and windage.
Sails are simple and cheap and easily repaired or even made new at sea with low-tech needle and thread (I had a close friend who was a square rig sailmaker his entire career with many roundings of Cape Horn on the "P" line sailing ships before and after WW1 and he could make a new royal of 600-800 sq ft in a few days, sewing all by hand, seaming at 12 feet per hour).
Wind turbine rigs are complex, expensive and much more difficult to repair if any part goes bad, plus you need to be a mechanical engineer to run it instead of a sailor, plus it's impossible to add sail area in prolonged light conditions. Any time you are underway there are multiple spinning mechanical parts trying to wear out their bearings in salt spray conditions. What is the advantage besides the straight upwind in flat water part?
It's interesting idea and worthy of exploration, but seems a dead end due to the laws of economics. Something has to have a reason to be developed, and this seems to be only a novelty with no profitable use. Remember, it has to show the potential to make profits to be respected in the modern world or to attract development money.
I am not a Luddite and love and use hi-tech a lot when it is to my advantage. I use Sony XDCAM digital cinema cameras because they are better than film in many areas of moviemaking as they save money, lots of it, over the much simpler film cinema camera without 90 feet a minute of film zipping through at a dollar a foot. A ten minute reel is $900 just to film. Storage for ten minutes of hi-tech footage costs nothing but space on a drive and wiping the lens clean, so I can afford to make feature films.
The argument I'm making is that complex is better when it's saving money and time, and this windmill rig does neither. It takes more time to build and costs much more than a sail rig, with only one advantage and many disadvantages.
This is very mechanical and hi-tech compared to sails, costs several time more than even an expensive sail rig and many many many times more than a cheap and simple one, and still only works over a more limited range of conditions. And sails are faster most of the time, even crude ones.
It comes down to dollars per mile and the wind turbine rig loses heavily, no matter how you look at it.
When someone takes one across the Atlantic in winter successfully, I'll pay more attention. Until then, it's inferior to sails and a pleasant toy.
If a $1000 dollar spritsail rig or a $10,000 marconi rig makes the boat go just fine, why spend $100,000 for less all-round performance? And don't say it's cheaper than that unless you are an engineering fabricator with extensive shop facilities and plenty of retired time to tinker.
This is as encouragement to all to prove me wrong by putting up money (lots of it) and making it work.
Until then, I'll stick with my 1000 square foot Swatow battened Chinese lugsail and sail anywhere I wish to go, just slower dead upwind, but very fast off the wind in rough conditions at sea with low low low maintenance and costs. My 23 ton fat old boat will move when the wind is so light it won't blow out a match, not upwind, but under control and on her course. A windmill rig will never do that due to the start-up friction losses and necessary engineering compromises of the system which must accommodate low winds and high.

 

So many see this as an "either or" it's not a question of which is best, they are different horses for different courses. Wind Turbine boats are not likely to replace conventional sailboats, but each has its place.
That is why I suggested a conventionally driven boat for offwind courses, fitted with a wind-turbine for the direct to wind bit.
It's a complete fallacy that the wind turbine needs to be enormous. A small one still produces enough force to (for instance) power through a tack. Anyone who doubts that small ones can do the job should look at this page http://www.sailwings.net/gallery/001.html - here the experimenter was building a series of models to see just how SMALL a turbine could be and still power a boat directly upwind. The result (as can be seen) is that the diameter of the rotor need not be as wide as the beam of a catamaran, and I am assured that they all worked.

 

I was having a clear out of very old magazines which I bought when I started sailing radio controlled yachts.

The October 1976 issue of Model Boats had the following advertisement

 

That looks better than the pop bottle ones. The flexible shaft is cool. Who's going to be first to copy it?

 

I can guarantee the "pop bottle" one would work better. This is because the flexible drive, although looking neat, absorbs power, secondly, the "pop bottle" version has six blades whereas this has only two. Instructions for building "pop bottle" - (it doesn't have to be pop bottle, that's just for convenience) - can be found here: http://www.sailwings.net/windspinner.html don't take my word for this - build one yourselves!

 

What makes you believe that six blades have lower losses than two blades? Around a century of research says just the opposite. Multiple blades increases the solidity ratio, which allows a smaller diameter turbine to give a greater initial torque, but turbine losses are directly proportional to blade drag and this is directly proportional to the number of blades; more blades = less overall efficiency.

Overall, two or three blade horizontal turbines are the most efficient practical machines, which is why they are almost universally used for wind power schemes. The only advantage a multiblade turbine will give is good starting at low wind speeds (which is why they are often used to drive high starting torque wind pumps). Its high solidity ratio ensures a high torque at low speeds (assuming its correctly pitched).

Although a single blade would be most efficient (very closely followed by a two blade), both of these configurations have problems starting under load at low wind speeds, again because they have a low solidity ratio. At every other operating region other than very low wind speeds the multiblade design will perform worse than a two or three blade design though.

 

I believe it because I have done it and tested it. The century of research was not about getting a boat to go directly to windward. Study the design I have given, build it, if you can get a 2 or 3 blader to go better you have achieved something. The proof of the pudding "is in the eating".

 

What relative efficiency did you get? Did you measure the relative performance objectively of different blade configurations before choosing 6 blades or have you just built a single turbine and assumed you've chosen the optimum arrangement?

More blades always means more drag, which is why you don't see the countryside littered with multiblade wind turbine electricity generators. Most use three blades, as a good compromise between the high losses of multiblade arrangements and the poor starting torque of a single or two blade set up.

My background is aerodynamics, as some here already know, and I've spent a long time working on propeller optimisation. Propellers and turbines are reciprocal machines, so the principles and fluid dynamics can be applied to both equally well.

There are some good rules of thumb for blade design and configuration that you can see used every day.

- High aspect ratio blades are more efficient than low aspect ratio blades.

- Local flow velocity at the blade tip must always be kept below the transonic region for good efficiency and low noise.

- The fewer the number of blades the better the overall efficiency.

- The bigger the diameter for a given power requirement the greater the efficiency, up to the point where mean local flow velocity drops too low to be effective.

- The fewer the blades the lower the initial starting torque.

- A higher the solidity ratio generally gives greater starting torque at low wind speeds.

- The higher the solidity ratio the greater the mast loading, as high solifity ratio turbines have high drag.

 

I have made many blade configurations and tested them all both with artificial wind (electric fan) and natural wind outside on the water.
What needs to be appreciated here is that a fixed base turbine (such as one on land to produce electricity) is different than the optimum kind to use to go directly upwind on a boat. The fixed base one is designed (quite rightly) to extract the max power from the wind. The forces on the tower (quite considerable) are of no importance. When you want your turbine base to move around then it is completely different. In your analysis you have completely ignored or not even thought about these forces.
If you configure the turbine to extract max power from the wind and attempt to sail upwind you won't do very well. This is because of the strong backwards lift force produced from a fast-spinning turbine.
Consider here how an autogiro works - it produces lift by the rotor spinning in the wind. If you mounted the autogiro rotor on a boat it's more likely to push you backwards even if you did connect it to an underwater prop.
The answer I have found, is to have a very course pitch on the wind-rotor to reduce the backwards liftforce and maximise the rotating force (which goes to the propeller to push the boat along) a tipspeed ratio of 1:1! with this kind of pitch and the low rotating speeds that ensue there is lots of space for the air to go through without getting power from it. Therefore the answer here is to increase the number of blades to get full coverage on the disk. There are 8 videos on Youtube of various rotary sailing tests that have been conducted. I do not think there are any other researchers have shown models (and fullsize) that work so well. The username there is ZKMX7 you can search under that.
A useful side-effect of this design strategy is that you get a rotor that revolves slowly, thus eliminating gyroscopic effects, and is very user friendly and not so dangerous. I hope some may be able to follow this explanation.
Anyway, all this is fine theory, but the point is it has all been borne out by the tests that have been done over many years.

 

I'm afraid to say that you aren't quite right on some of these points. I'll try and explain where, if I may.

First of all, whether a wind turbine is fixed on land or mounted on a moving platform makes no difference whatsoever to the fluid dynamics that determine best blade shape, twist, aerofoil section, solidity ratio etc, as all the turbine sees is the wind speed relative to its own position. For example, if you were sailing at 5kts directly into a 10kt wind, then the turbine just sees a 15kt wind. It will behave in exactly the same way as a wind turbine mounted in a fixed location operating in a 15kt wind. The same applies to any wind vector you choose; some will be additive, some subtractive,

There is a difference between a fixed and moving wind turbine when it comes to response time. Generally, a fixed wind turbine doesn't have to change blade pitch or mast rotation angle very quickly, as wind speed and direction doesn't normally change rapidly. For a moving platform that can manoeuvre fairly quickly this isn't the case and both pitch and mast angle need to be able to be changed more quickly. This control system difference doesn't impact on the basic fluid dynamics of the turbine itself, though, as mentioned above. A wind turbine doesn't care whether it's stationary or moving, as shown by the many hundreds that are used as auxiliary or emergency power systems on aircraft. Years ago these were commonplace on old light aircraft that had no electrical system - they looked for all the world like a model aircraft props, often fitted to an undercarriage leg, like this one on an old Piper:



I have seen your Youtube videos and commend you on making a proof of principle vessel. I did notice that your blades have little or no twist, though, plus they have a fairly low aspect ratio, so they won't be getting as much from the relative wind as they could. This is also apparent from the relatively slow speeds your boat seemed to be doing, notwithstanding the fact that it can do that low speed in any direction.

There is a very famous auto-rotational wing sail boat, the Redwing that sailed in the Solent area many years ago. This proved that this type of rotor (it is exactly like an autogyro or helicopter in autorotation) worked very well indeed.

Slow rotation doesn't eliminate gyroscopic effects, as these will be present even for a very slow turning rotor. It does reduce their magnitude, but reducing blade mass has a greater effect in this regard.

I'm am certain that the performance of your boat could be improved by fitting blades with a chord optimised for the local blade loading (blade loading is much higher at the tip than the root with your constant-chord blades, which is inefficient). Optimising twist for the median range of turbine rpm would also improve efficiency significantly, too. I am guessing that your drive system, although fairly efficient, may require a significant initial starting torque, to overcome stiction and friction, which may well be why your multiple blade design seems to work OK at very low speeds. The downside is that as soon as the turbine is spinning it will be significantly less efficient than one with a lower solidity ratio and better blade design and this efficiency will decrease rapidly with increasing relative wind speed. The drag load on the mast will also be higher than it need be for the propulsive power required..