another idea

[yipster]

"sailboat" going straight upwind fast

[plymouth]

I've been curious about whether this really works for a while - this was the first one I remember seeing:

[plymouth]

And here's the schematic for the later version described on this site: http://www.oceanblueone.com/art.htm

[plymouth]

I don't know the designer and author of that site, but it's interesting...

[yipster]

Don’t laugh when I remember I placed sunshade blades in my bicycle wheels trying to get forward lift as a kid… this upwind sailing always intrigued me. Got that anigif from a multihull (magazine) site I cant find back easy now but saw your photo there among other experimental boats. Reading that site was interesting. How about a wave powered catamaran? Here another serious experimental boat site http://www.stevproj.com/Carz/XBoats2.html

:) yipster

[gonzo]

Let's see. The Law of Conservation of Energy should hold for boats too. That means that there will be losses in heat and fricton between the wind vanes and the propeller. Add to that surface friction of the hull and wave resistance. I don't see how the residual energy could possibly move the boat forward.

[Polarity]

For sailing dead upwind ....Isn't there something about every action having an equal and opposite reaction? ....:confused:

[BrettM]

Gonzo,

Remember that the surface friction and wave resistance will only occur if the boat moves forward which is the point of the exercise. The concept really only needs to overcome the resistance of the wind itself to gain any forward movement.

I don't know much about these things but maybe they do work. There once was a time when it was believed that you couldn't sail faster than the wind itself which we all know to be possible.

brett

[gonzo]

How do you move through the water without friction or wave resistance?

[BrettM]

You can't.. My point was that to achieve forward motion you only need to develop effective propulsive force greater than that required to overcome the resistance of the wind (if going to windward). The suplus force then would equal the hull resistance (Total inc added wind resistance etc) at the final hull speed. (which may not be that great). As I said before, I haven't seen these things but maybe it is possible to get sufficient efficiency out the system for it to work). Don't see myself trying it either.

On the other hand at the very least I can see it will go downwind if that is where you wanted to go.

[gonzo]

The Law of Conservation of Energy says that in a case like this the force of the wind on the vanes plus the hull will produce "an opposite and equal reaction". That is, in the opposite direction of the wind or downwind. There is not enough energy left to propel the boat forward.

[yipster]

its an intriging idea i agree.
its one of those things i always wondered of before. i belive it to be possible and think brett is giving the explanation in his first reply.

from plymouth's site http://www.oceanblueone.com/art.htm i read this:A word is required here about the "impossibility" of sailing directly against the wind. I hope those who fully understand the situation will bear with me if I explain once more that it is possible, and, in fact, presents no special problems. I was quite sure that everyone understood this, but have been surprised that there seems to be an inbuilt natural disbelief from some traditional sailors.

http://www.oceanblueone.com/lit2.jpeg
Peter Worsley (who has this design patandted) and pictured here i asked to reply and i hope he will. i would be very curious to hear some more as i dont belive the movie model at the top is sailing downwind. wish i could find that site back where i got that video from, it also had many variations on the theme.

when not having my fingers still in bandage and engaged in building a crazy enough model allready i would run out to a model shop for parts needed, build and test it. i dont know why i allways want to check upwind, downwind indeed is easyer :D yipster (guess i better wait trowing more "crazy's" in?)

[BrettM]

As I remember it, the law of conservation of energy has nothing to do with equal and opposite reactions. It merely states that energy can neither be created of destroyed but merely changes form. ie kinetic, plus potential etc is always constant. On the other hand equilibrium occurs when all forces are balanced.

Unsing Gonzo's approach, no yacht or dinghy sailing in the world can go to windward at all. Nor would it be possible to sail downwind with an apparant breeze from forward of the mast. As I said, I'm no expert with these things but I keep an open mind. They may very well spend all day tacking back and forth and getting nowhere.

no offence Gonzo:)
Brett

[gonzo]

My approach shows that no boat can sail straight to windward. As we all know, we tack upwind. The forward motion is the result of the force of the wind in the sails and the lateral resistance of the boat in the water. There are parasitical losses in friction wind and wave resistance and heat. I think the "Law of Conservation of Energy" applies because for that model to go upwind, energy would have to be created out of nothing. I am convinced that is not what happens there. I may be missing something when calculating the force vectors, but can't see what. If this works, it will revolutionize sailing. However, seeing is believing. All the designs I've seen that claim to go straight to windward don't work.

[BrettM]

Unlike a yachts sails , a rotating wind vane as fitted here will provide the same power to the propeller independently of the direction of the hull (neglecting any increase/decrease in apparent wind) due to is ability to maintain a constant angle of attack (unlike a yacht).

It is easy to see that this may work when travelling downwind or across the wind. The problem with upwind is the drag of the hull and windage is aligned in the same direction. Hence you only need produce sufficient power to beat the uphill drag. It is this balance which will tell if it works. The movie above and the attached diagrams indicate that it probably does for some cases.
Any excess energy is absorbed by the drag of the hull through the water ie the boat moves forward.

PS I agree that the conservation of energy law does apply. Afterall it wouldn't be a law.

[yipster]

The designer of the drawings Peter Worsley wrote me back, for witch my thanks. On his site I noted he intends going to show us some calculations and make diagrams. Having proved the concept works i belive ideas like this should be developed further, not strand as other modern sails and wind rotary devices unfortunatly often do. Ideas like this (and a lot of R&D) may indeed revolutionize sailing i belive...
Hi
Your email reminded me to repair the site, I have done so and the link you mention is now working (<http://www.oceanblueone.com/rot.htm>). Several discussion groups have brought up the subject over the last few years, and, it is usual to have believers and unbelievers, believers being usually in the majority. I'm a bit shy of joining in these discussions after one degenerated into insults and I was accused of being a fraud and having "hidden electric motors" etc. I think if those that are interested would read the article I wrote, it explains things well. Also, careful reading will reveal how to make a successful design, although I have never heard of anyone doing this yet - its patented anyway. You are welcome to quote this email in the discussion if you wish.
Peter Worsley

[yipster]

http://www.users.globalnet.co.uk/~fsinc/yachts/videos/index.htm
Where earlier I found the “upwind sailing” anigif and other experimental boats, interesting site!

[Tom Lathrop]

I've been away from the forum for awhile and came back to find this interesting tid bit.

There is no problem with the law of conservation of energy but there is a problem with its interpretation. Mr Worsley's boat can happily go straight into the wind without violating any natural laws that I am aware of. Many others have built such craft that could power directly upwind under windpower alone and I see no reason to doubt Mr Worsely's claim that his will boat will also.

I don't know what he has patented. Probably some parts of the apparatus since the idea and working applications have been in the public domain for a long time.

It's pretty clear that the boat will accelerate into the wind until the force to the drive propeller, derived from the spinning turbine, is ballanced by the drag forces of water and air on the boat That is what the law of conservation of energy says.

I would think that an ice boat would be a better application of the principle since wave making drag would be zero, frictional force very small and the only retarding force would be air resistance. No propeller of course, but a spiked wheel(s) would do nicely.

All members of the flat earth society may ignore this post.

Where is Trouty when you need him?

[dionysis]

I see nothing surprising about the principle. I think the reason it has not become popular is:

1. you can't reef the turbine: a monster in a blow; as solid wingsails are.
2. you would be limited to flat water. Those short chord blades would suffer a lot more from disturbed flow that our forgiving sails.
3. that is a lot of machinery up high.
4. the noise would be incredible.
5. on a reach, while you gain speed with lower wind restance, you lose speed by generating side force.

On the other hand, if you could design a high reving wind turbine, and you got a very efficient water propeller...

This is were the maths comes in. I don't have the calculations at my fingertips, but it is an interesting approach.

We cannot go directly to weather because we need the hydrodynamic side force, which in this contraption is directed sternwards. In all other respects it would behave just like a boat.

[gonzo]

The Law of Conservation of Energy applies to this problem. It tells us that the total energy available in the system is the wind's. Part of it is transformed into torque by the turbine. The rest is drag. For the turbine to produce torque, it needs an "opposite and equal force". In other words, the push against the propeller in the water equals the force of the wind on the turbine. However, because of mechanical inefficiency only part of the wind force gets transformed into torque. Also, there is the extra wind drag and the resistance of the water on the hull. I can't see enough forward force to overcome the drag. As for boats working to windward, they move because there is a residual force forward. It is a small percentage of the total.

[jehardiman]

In other words, the push against the propeller in the water equals the force of the wind on the turbine.

I think I see the misunderstanding that you have. Energy and force are vector quanities. As the turbine spins, the wind generates a force on it which is a vector quanity. We break this force down into two compnents, lift which is perpendicular to the radial axis and drag which is co-linear with the radial axis. Now in this case the radial axis is dead into the wind, therefore only the drag counts against us. Lift because it is perpendicular and tangential has no effect on trying to push the craft back (do the vector math on the torque). Furthermore, lift (for a good turbine design) is about 20 times the drag so only about 5% of the winds energy going into a backward force.

Think of it this way, if your argument was correct, then the steam velocity on a 100,000 shp steam turbines blades would rip the rotor out of the ship. But this does not happen, and rotor thrust is only a couple of hundred pounds.

Yes there is a backwards force, and yes the mechanics lose energy, but the toruqe, and therefore the energy, available is so much larger that the vessel goes ahead. Tell me if you need me to draw you an energy vector analysis and I will.

BTW, this is the reason that turbine designs make poor propeller designs. ;)

[gonzo]

Everyone that believes it is possible uses vectors, force and other measurements without magnitude. The statements make no sense.

[dionysis]

There is nothing for it, you just have to do the maths. Here is an informative first step for wind turbine blade calculations:

http://metp02.mw.tu-dresden.de/Merz_McLellan/windenergy/Aero.htm

[K4s]

There is a 45 foot trimaran riggeg just like this,vanes that turn a propellor under the boat.(not sure if you still call it sailing).This thing has been cruising around Whangarai harbour and surrounds for about ten years now.Funnily enough it has no problems going directly into the wind or reaching(as in sailing) but doesnt seem to like downwind work
K4s

[Richard Petersen]

While none of us brought up in a conventional sailing backround would beleve a boat can go directly up wind. Hundreds of years ago, boats could only go down wind. People are selling short on this upwind stuff again. Simple, flappy sails, probably right. Different (" SAILS ") whatever it may be , held aloft by at least 1 mast, VERY, VERY possible. Face it, nobody is trying. Sailors love the peace-quiet-simplicity of the present sails system. Rich ----I was just watching a sailboat show which spoke of a over 100' boat which has those ROTORS on masts and the boat was throwing a good bow wave. It was on Direct T V in the last 3 weeks. Rich---------Up wind use rotors or propeller types----- Down wind use sail types. Does that sound about right?--- I will split all royalties with the first good design. Rich

[gonzo]

Dyonisis: I checked out that websit. It assumes that the turbine is firmly attached. The calculations don't work for a boat with a propeller.

[yipster]

Fiona Sinclair makes a good read on autogiro boats (http://www.users.globalnet.co.uk/~fsinc/yachts/auto/index.htm)

[yipster]

http://www.cousteau.org/en/cousteau_world/our_ships/calypso2_inc/medias/zoom_artistic_view_of_calypso_2.jpg
although not sailing upwind, not mentioned here yet are the turbosails of Jacques-Yves Cousteau's (http://www.cousteau.org) ALCYONE and Plans for CALIPSO II

anybody has a good story on these turbosails, the savonius and/or darrieus rotor?

[dionysis]

From one of Costeau Society's PDFs:

"A small fan draws air into the 33-foot towers, boosting wind speed over the leeward side and creating forward lift several times the power of traditional sails.

Specifications :

Length: 103 ft.
Draft: 7 ft. 8 in.
Width: 29 ft. Passengers (& crew): 12
Cruising speed: 10.5 knots Turbosails: height 33 ft. 5 in.
Surface area: 226 sq. ft.
Diameter: 4 ft.5 in. "

"The Turbosails work in conjuction with twin diesels and save ~ 30% in fuel."

That is a lot of power generated by the paltry 226 sq. ft. of 'sails'.

An open60 can sail at high speeds across, and downwind. At say 20 knots, the propeller would be doing ...at least it would be turning very fast = some serious gearing = weight.

[trimix]

all the web links seems to be dead ? do you have new ones ?

[cyclops]

The Sail and Gasoline companies killed them.

[yokebutt]

To understand this contraption going straight upwind from a traditional sailors perspective, first look at the propeller, it's rotating, ie. the blades are moving at right angles to the wind, then look at the boat itself, its moving into the wind.

Now, combine those two and look at the path a propeller blade takes, it's oblique to the wind! just like a regular sailboat! albeit in a corkscrew motion instead of a straight line.

Of course, it's not really that simple, but it's a good picture to start from.

Thoroughly confused yet?

Yokebutt.

[MattZ]

The law of conservation of energy always applies. There's a tiny exception in nuclear physics where a minute amount of energy can be "borrowed" for a near infinitesimal period of time.

The blades on the wind turbine have a very steep pitch, allowing the wind to pass through them, the creates rotational power, but also creates a force pushing the boat in the direction of the wind. By using a propellor with a fine pitch and/or steep gear reduction, it will be able to turn. Selecting the correct turbine and propellor pitches, as well as gear ratio is the key. As long as the propellor makes more thust than the turbine and hull creates wind drag, the boat will more forward.

[Chickadee]

Revelation II (http://foxxaero.homestead.com/indrad_007.html)

They say downwind is more a problem than upwind. I think it must be somewhat slower than with normal sails?

I do remember an article in a sailing magazine, more than 20 years ago, with pictures of a 1-2 meter model sailing upwind.

[MattZ]

They should be just as capable of sailing downwind as upwind. The gearing between windmill and propellor would be different though.

[Chickadee]

Sorry, I have never sailed a windmill, that's just what they say on their website. "Unlike a normal sailing craft this vessel makes its' best time sailing straight into a headwind."

Downwind is great, but in light airs the apparent wind is more variable in direction, and with high wind and waves you'd better not leave the helm too long ! The windmill boat must react differently, same problems, but different effects ? Windmill performance must be affected by these quick changes, how much, I don't know.

But I still believe it must be a bit slower overall than the same boat with sails - except for headwind, obviously -because of the additional losses in gear and prop.

Maybe the primitive of the performance prediction curves (0-180°) could be the same in both cases ? :confused:

[Renneriffic]

I've had a riff on this idea for a while, based more on the ability of a rotating wing having the same lift capabilities of a fixed wing, based on the abilities of both a helicopter and a plane to be able to glide similiarly without engines. Last night I met a guy at the Antigua Boat Show who told me about a guy in RI that made one of these (with a propeller in the water powered by the windmill) and used to sail "directly upwind" as he put it. He may be mistaken, but I think the more important thing, which I hope to try, is whether a boat can propell itself with the windmill exclusively. Not directly upwind, but a reasonable sailing angle. I will be forwarding these and other links to him and try to find out who he was, and if there is any more info I can pass along. I have seen the wave boat that can go directly into the wind/waves, but that involves one very important factor not relevent to this machine...Gravity!

[masalai]

Yipster, I was just going through some old stuff which I thought may be interesting, It is but it appears the website of Peter Worsley's has been captured by "crap promotions" and the like. Advise him to get his ISP to run linux as a more secure system. I would love to see his stuff.

http://www.oceanblueone.com/rot.htm

[masalai]

Jeees has this degenerated into a crap shoot. If half the unbelievers went to NZ and saw the aforementioned cat they would become instant aliens and praise this superior being who could defy the laws of their own tiny brain = idjit. Think outside the box, get a life and look beyond your own nose.

Sorry Yipster, but some wankers could restrain/retrain themselves and make a model. Easy enough done, but that would spoil their self-righteous ignorant pontification.

[yipster]

your right, this were all interesting but now broken links, some popping crab up and it is a shame XP hasnt even virus protection
Peter Worsley has a wingsail (http://www.boatdesign.net/forums/showthread.php?t=15252&highlight=Peter+Worsley) site now i see, a while back he posted upwind turbine movies here but cant find them back quikly now
better contact Peter Worsley yourself as i share the linux ideology but my programs cant work with it

[masalai]

Thanks Yipster. Much appreciated. May save you some research ???

[yipster]

you may want to read Peter's post (http://www.boatdesign.net/forums/search.php?searchid=1118185) on the forum

[masalai]

I clicked on "post" but boatdesign could not find it, but in the name of Peter Worsley, only came up with your two citations in this thread????

[yipster]

sorry, "see all post by windmster" dont work in a link
http://www.boatdesign.net/forums/showthread.php?t=15252
finds him, click public profile than see all post by windmaster
i'm sure he posted some more movies

[masalai]

Hell, it's 2:20in the morning. Good night all and thanks for a most interesting read.

[Fanie]

Actually, if you sail upwind you have a better chance of making way. Since you sail upwing the wind power generator gets driven by the wind speed plus the speed of the vessel. The hull drag in any direction will be the same for a given speed.

When sailing upwind the vessel will require low windage otherwise it will not be able to move foreward. Considering a closer to zero wind force on everything above the water line, it is only the wind prop that produces some drag. Due to the densitiy of water the water prop should be able to produce more torque than the wind prop drag.

You shouldn't look at it as the never ending motion... the energy source is still the wind as with a sail. The wind prop reduces it's drag as it spins up also.

[charmc]

Interesting discussion. On the face of it, sailing directly into the wind seems to defy the law of energy conservation. What is happening, however, if I understand it correctly, is just a different distribution of the forces. Because sails and keels/centerboards are fixed, lift/thrust can only be created at an angle to the wind. The turbine and prop rotate, so lift/thrust is created independently of the hull's angle to the wind. I think that's the basic explanation.

Ross Garrett explained the physics involved much more clearly and completely in his The Symmetry of Sailing. http://books.google.com/books?id=0VLXORumEF4C&pg=PA83&lpg=PA83&dq=%22wind+turbine+boat%22&source=web&ots=Bj8yXHNyhh&sig=bUmJzx5U8fQXXvBPSdcY2Wj3IFY#PPA84,M1

According to him, the theory has been proven by Jim Bates' Te Waka , a full sized sailboat hull which has sailed directly into the wind on wind turbine power, with carefully recorded data.

[jzk]

There is absolutely no problem with this design going upwind. All that it needs is a wind turbine that pulls more energy out of the wind than the drag it creates plus the drag of the vessel. I am not saying anything new here, as this has been well stated in this thread.

Harnessing the wind's energy and using it to move a boat is no more remarkable than harnessing the energy of a gallon of gasoline and using it to move a boat.

And in going upwind, the boat has the added benefit of an increased apparent wind as the vessel accelerates. Again, this concept is well stated above.

Now, it has been said that this design could sail downwind faster than the wind. Now try to wrap your mind around that one!

[longliner45]

can I ask ?so if going upwind (20 knots blowing ),,you go 5 or 6 knots,,there is a factor or equasion? ,,it can be done ,,but at what expence,,,longliner

[gonzo]

For a turbine to produce more energy than the drag it creates, it would be necessary for it to create energy. An ideal turbine, that is 100% efficient, would produce an equal and opposite reaction to the power produced. This means that the forward force and the opposite reaction cancel out. In a real turbine and propeller system, the added losses produce a net force directly downwind. Apparent wind is the result of movement, that is expenditure of energy not a gain.

[jzk]

For a turbine to produce more energy than the drag it creates, it would be necessary for it to create energy. An ideal turbine, that is 100% efficient, would produce an equal and opposite reaction to the power produced. This means that the forward force and the opposite reaction cancel out. In a real turbine and propeller system, the added losses produce a net force directly downwind. Apparent wind is the result of movement, that is expenditure of energy not a gain.


How so? These are lift based turbines, not drag based. The same way that a sail can produce more lift than drag, the turbine can also.

[masalai]

Jeeees, stop this pointless pontificating, (That is my entertainment domain, disguised as casting communist fish - red herrings - into the oceans of intolerance & disbelief) build a model and see that it works! The difference is that the drive is in the water & the turbine is in the air! By your logic a hang-glider is an impossibility??? Yet many people run into the wind and take off from a small hill into the breeze, to fly up into & downwind as well as other directions.

A rotor assembly from a model helicopter, a model catamaran hull, toy mechanicals to link an efficient water screw and a bit or r/c stuff and your proof that engineering is magic, and beyond unfounded fundamentalist beliefs.

If a disbeliever, and it is within ones capacity to make a working model - do it. Only then will you be satisfied - but then a true bigoted fundamentalist will never believe, instead of checking his/her build quality and flaws in construction, subconsciously and/or deliberately inserted.

[Rick Willoughby]

can I ask ?so if going upwind (20 knots blowing ),,you go 5 or 6 knots,,there is a factor or equasion? ,,it can be done ,,but at what expence,,,longliner

LL
I did a full design for a small, easily driven hull. It has 1:1 mechanical linkage between the props. The air turbine has a pitch of 1495mm and the water prop has a pitch of 540mm. So effective gearing of 2.7:1.

They are both high efficiency, low slip props. In a 20kt breeze the boat would do 8.4kts.

The "cost" to achieve this is an extra 320W of power transfer in the system. The air prop takes in 761W while the hull only needs 347W to do 8.4kts. There are losses in the water prop and mechanical linkage and it takes 240W to drive the turbine into the wind at 8.4kts over sitting still.

It is possible to get faster than 8kts in 20kt wind but you would need to have adjustable gearing so you can keep tuning it as you gain speed. The small air turbine has low efficiency at low wind speed. So 2:1 effective gearing would be fine if you could always guarantee 20kts but if you want the boat to move in 10kts wind then you need to have gearing that does not bog down the air turbine.

The whole thing is about GEARING. Propellers and turbine actually have good "grip" if they are efficient. They just need to be big enough to be efficient for the required power handled.

Electrical systems are not as efficient as a mechanical linkage but they are very easy to adjust the effective gearing with modern controllers so they are a good option. They make it quite easy to go faster than the wind downwind as well without complex gear changers.

If you want to make a system I can do prop/turbine designs and nominate gear ratios if you give me some basic hull details.

Rick W.

[longliner45]

thanks Rick..longliner

[jzk]

Jeeees, stop this pointless pontificating, (That is my entertainment domain, disguised as casting communist fish - red herrings - into the oceans of intolerance & disbelief) build a model and see that it works! The difference is that the drive is in the water & the turbine is in the air! By your logic a hang-glider is an impossibility??? Yet many people run into the wind and take off from a small hill into the breeze, to fly up into & downwind as well as other directions.

I also believe that it works, but the hang glider is not analogous. The hang glider is moving within one fluid - the air. The hang glider is not powered by the wind except to the extent that a thermal pushes the hang glider up.

The turbine sailboat is powered by the diffrential between two fluids moving against eachother - the air and the water.

[masalai]

True, but the pontificating was getting to me and I couldn't think of an appropriate working example offhand.
My alluded contention more related to "non-powered" heavier than air flight.
Rick Willoughby did the technical honours with clarity & technical skill.
Gonzo was more the target on this page but there were and are many other 'disbelievers'.
Thanks jzk.

[longliner45]

is there alreaddy ,sailboats that have props or turbines being used?

[masalai]

See Charmc's post at the top of this page. It apparently still plies waters of NZ?

[Frosty]

Hey mas I strongly suspect that the word pontificating is one of your favourite words since 1st Jan 2008?

[masalai]

Not necessarily, but it has lots of occasions for use hereabouts, in pursuing my leisure activities in distribution agent for the communist fish market. You yourself ensured my appointment to the said honourable distributorship.

Oh %hit #1007 & no bells & whistles blew? Maybe the desire of said dung marketing is not encouraged. Will have to develop a serious persona indulging in intellectually higher persuits.?

[Rick Willoughby]

is there alreaddy ,sailboats that have props or turbines being used?

LL
Post 47 above has a good example. It roughly agrees with what I have determined although both the turbine and prop are larger diameter than I believe is required but then it looks a heavy boat.

I made a model boat many years ago that would make slow progress to windward but discarded the idea as ineffective. However that was before I knew how to design efficient blades.

Overall I believe the combination of solar and wind via batteries in an electrical system provides the best solution for a cruising boat. With decent batteries you can store energy to make real speed when required or average out the energy collection to set good steady speed. Placing the batteries low means you can build an easily driven narrow hull and still have ample stability.

Fitting a turbine to a deep keel boat would not make a lot of sense. Fitting a turbine to a catamaran would be better. You can do away with keels/dagger boards and big rudders as leeway can be compensated for by just sailing more directly into the wind.

The electrical system gives great flexibility. Of course all the components need to have good efficiency as each link in the power transfer chain robs a little power.

You can design turbine blades that do not require much force to generate useful power. I have designed a 2.2m diameter turbine that will produce around 1500W with 150N of drag in 12m/s (say 25kts) wind. So the best blade design is somewhat different to a normal land-based wind turbine where you are not too concerned about the force to hold it against the wind.

Rick W.

[ancient kayaker]

I remember a concept from the 50's that involved vertical windmills a la Calypso II. The idea has been around a long time and does not violate any natural laws.

Given that it will/should work, the question then becomes, why bother? It looks complicated, expensive, risky and unseaworthy. The only advantage I can see is the ability to negotiate narrow waters without tacking. I doubt if it is as efficient as a sailboat and imagine having to take in a reef ...

On the other hand (as the guy in Fiddler on the Roof was fond of saying) it looks like a lot of fun and allows one confound the sceptics, something that always gets my vote.

[Bijit Sarkar]

I am sure it is possible to go against the wind with such a device as shown.
When the wind is incident on the rotor vanes, it does exert a pressure on the hull, and the rotor, depending on the frontal area.
However, its the kinetic energy of the wind that make the blades go round and that rotary motion can be translated into a propeller rotation. The energy that is delivered to the propeller after the losses, should still be enough to overcome the air pressure, if the wind speed is high and the wind mill is efficient enough.
A Savonius type wind mill could trap wind from any direction, including dead ahead.

I think I will make a model and try it out :)

[Richard Miller]

I don't know the designer and author of that site, but it's interesting...


The designer is ¨Windmaster¨. He is a member of ¨Boatdesign.net¨ and a frequent contributer. He is very knowelgable about WT boats and if you need info look him up here. I have always found him very helpful.
And yes, these boats DO go up-wind very well. They preform great too.
Richard Miller; Chile, SA

[MPraamsma]

Hello everybody,

Since this is my first post to this forum, I would like to offer my credentials for posting comments here. I am 61 years old and have been sailing around 8 years in conventional sailboats that must tack to make headway to the wind, and as an engineer I have often wondered, as I was sailing, why some way of heading directly windward wouldn't be a lot better since the force of the wind is maximum at that point. Recently, during a discussion with other sailing comrades the subject of direct windward sailing came up, and of the 5 participants all of them without exception made the usual claim that such a feat was impossible, some in an insulting fashion that irked to the point of creating a strong desire to prove them wrong. I rushed to the machine shop and furiously cobbled a small vehicle together from hobby components that laid waste to their ignorant claims, and settled a gentlemens bet to everyone's satisfaction. This took the form of a small wheeled car that had a wind turbine driving a belt to the wheels. A small rudder vane keeps it automaticaly pointed directly windward. It zips along quite briskly into the wind, and actually accelerates once moving because it generates a large relative wind as a result of it's new forward motion. There is no reason why this would not work with a boat hull as the vehicle. The argument most often heard is that the drag on the turbine would kill the whole idea, but that is nonsense, because in this situation the drag is tiny fraction of the thrust (torque) developed. Another point worth mentioning is that that the force of the wind increases as the cube of the wind velocity, so going faster only makes it even more effective.

One more comment I would like to inject, and that is that an airfoil is a mechanical amplifier, converting a small pulling force (against drag) into a relatively large lifting force. Few people realize that this lift is actually energy liberated from the atmosphere in much the same way as energy is extracted from expanding steam, the only difference being that the venturi effect does the expanding, and the atmosphere is the 'steam', which technically speaking is the superheated gas of liquid air. Sails, wings, propellers and windmills all extract caloric heat from the atmosphere and leave a 'cold wake' behind. This energy is what creates the lift, not the drag forces or engine thrust.

If anyone is interested, I would be glad to attach designs and further info as to my current efforts in this direction.

[Rick Willoughby]

MP
Welcome aboard.

I am interested in basic data from your vehicle. Some pictures would be useful to enable an estimate of drag. The type of prop, gearing, wheel diameter and performance such as speed in different wind conditions.

I am after data to verify my engineering model of the system.

If you are interested in refining the design and putting it on a boat I can help you with hull and turbine/prop design.

I just have too many things to do to test all these things out to optimise their performance.

Rick

[cnc4wood]

I am new to this forum, so if this has been discussed, I am sorry to put you through it again.
I am building a light weight 18ft electric boat, and am in love with a stern shape that is called a "ducktail".
I would imagine that because it is such a bear to build, there must be a purpose to it other than its looks alone.
As a woodworker, I almost have to build it just to prove to myself I can.
Does anyone know its original purpose, or is it just for looks.
It is clear of the water, but adds length, and weight. does it do anything usefull so that I can justify building it on, or is it just added ballast?
I don't know which catagory this question would fall under, but the people on this page seem to know their stuff.
Can any one help? Thanks in advance.

[Rick Willoughby]

I am new to this forum, so if this has been discussed, I am sorry to put you through it again.
I am building a light weight 18ft electric boat, and am in love with a stern shape that is called a "ducktail".
I would imagine that because it is such a bear to build, there must be a purpose to it other than its looks alone.
As a woodworker, I almost have to build it just to prove to myself I can.
Does anyone know its original purpose, or is it just for looks.
It is clear of the water, but adds length, and weight. does it do anything usefull so that I can justify building it on, or is it just added ballast?
I don't know which catagory this question would fall under, but the people on this page seem to know their stuff.
Can any one help? Thanks in advance.

You need to consider the boat in operation to appreciate the merits. As the speed increase the hull will squat and the transverse wave will create a trough that the ducktail squats into. This increases the waterline length. There wake is left less disturbed than if there was a transom leaving a low pressure trench behind the hull that adds extra drag.

So it does make sense for a displacement hull. Less energy is lost to wave making and turbulence.

A canoe type stern where the sides come together at an acute angle similar to the bow will also leave a clean wake.

Rick W

[MPraamsma]

Rick,

Thanks for the quick response. My next step may seem not related, but I am building a bicycle sized version of my first stab at this. My first model was not sophisticated enough to gather useful data, but was more to recover my good name as an engineer, and to make sure that my friends did not think I was crackers. One thing I figured out is that it is not really the actual wind that matters, but the relative wind the rotor perceives. In principle if it is possible to feed some of the wind energy back into forward motion, the turbine would have a hard time separating that new wind that was caused by the forward motion from any existing wind. I reasoned that what the bicycle version might be able to do is to use muscle power to bring the vehicle up to 'flying speed' of the turbine, after which a small residual rider imput might be sufficient to keep it rolling along. I realize this starts to sound like free energy, but that is not true, because there is a fantastic amount of caloric energy trapped in the atmosphere at all times, it just takes some form of machine to extract it. We plan to run some tests of this idea soon out here in the California desert at El Mirage dry lake, which has an almost constant wind condition. We are using bicycle components because they are extremely well developed and very reliable and available. In a nutshell what are building is a bicycle trailer with 5 ft diameter 8 bladed wind propeller driving the wheels via a standard bicycle chain and sprocket.

[Rick Willoughby]

That looks good. Clever simple test set up.

One of the problems with small scale, low speed turbines is their poor performance at low Re#. The bigger you go the better it gets. So scaling up as you have done will improve things anyhow.

I made a 2.2m diameter 2-blade horizontal turbine mounted on a right hand gearbox with a vertical shaft. I waited for a nice windy day to test and I could not stop it once it got going. The tip speed was around 8 times wind speed. I had to jam the blades into bushes to stop it before it took my head off. The gyroscopic force was amazing. The blades were only fibreglass over balsa with an aluminium former but they developed a huge amount of energy. Damaged the tips when I stopped it.

I am not sure there is merit in going to more than 3 blades. The aim is to get the most efficient turbine not to maximise the energy recovery from the stream. I am only using 2-bladed turbine. I aim to work with low velocity ratios over the prop so I get high efficiency. This application is quite different to a static turbine where the aim is to get as much power out of the air stream as possible. You need to extract the power at high efficiency so the drag or thrust force on the turbine is low.

I used an MA409 foil section for my blades as I have found them to be a very effective foil for low Re# applications. What you have drawn look like standard wind turbine blades and I do not believe these provide the most efficient result. If you have a section profile I can have a look. A slightly simpler foil to make is an E193.
http://www.ae.uiuc.edu/m-selig/ads/afplots/ma409sm.gif
http://www.ae.uiuc.edu/m-selig/ads/afplots/e193.gif

I am certainly interested in your testing and results.

Rick

[MPraamsma]

Rick,

...is so that I can remove blades from my design and reduce it to a 4 or two bladed version for comparison. Adding blades to a 2 bladed prop would be harder. Also, I have tried to focus on developing torque rather than rotor speed, so that more of the effort is directed radially and not axially. I know what you mean about the power these things develop once they get going, running without a load is as dangerous as hell. If I told you what I am using for blades you would probably laugh, and because they are shaped more like curved scoops rather than foils. I made them from sections cut from large diameter new Schedule 40 ABS pipe that I cut along a spiral path on the tube. This material is made with a skin and a foam core, and is flexible and virtually indestructable. It is thick enough to dress a very nice leading and trailing edge profile on it. And it is dirt cheap, so easy to modify and make more blades. By cutting along a spiral I can vary the amount of lead change further out on the blade. At the base I have a relatively large area exposed to the flow so it has some considerable startup torque. I'll try and get you a picture of the propeller soon.

[cnc4wood]

Rick,
Thanks for the fast response.
My boat will indeed be a displacement type hull, and very slow speed at that.
Should the ducktail be located at a certain height in relation to the waterline, and should it be flat in profile, or slightly "V" shaped like the hull.
Considering that the ducktail will be a semi circle the width of the transom, It will add about 24" of length when submerged.
I will also be putting the propellers near the end of the transom step, so they will be about 24" also from the end of the ducktail.
Will this have any adverse affect?
I am using 2) 50# trolling motors slightly modified as the power for the boat.
They will also do the steering.
The boat is 18 ft LWL, with a 60" max beam, slight vee bottom for stability, and the ducktail will add about 2 ft more if it hits the water.
I am using using a rounded chine, and want that old boat look.
Is the ducktail worth all the work?
It sure does look cool.
Thanks in advance. Tom

[kengrome]

My approach shows that no boat can sail straight to windward.Maybe, but the boat in the picture is not sailing to windward -- it is motoring to windward using a water prop for forward propulsion instead of the wind.

There is a 45 foot trimaran rigged just like this, vanes that turn a propellor under the boat. (not sure if you still call it sailing).It is not sailing, it is motoring by using the wind INDIRECTLY via the water prop for propulsion.

On the face of it, sailing directly into the wind seems to defy the law of energy conservation.Maybe, but motoring into the wind does not and that's all that's going on here.

The difference is that the drive is in the water & the turbine is in the air!Right, it may not work if the drive were in the air but it is not.

There seems to be a couple of guys here who like to argue and theorize and confuse the issue rather than paying attention to the simple facts. What's so hard to understand about extracting 10 HP from the wind and using it to spin a water prop that moves the boat into the wind?

It is possible to get faster than 8kts in 20kt wind but you would need to have adjustable gearing so you can keep tuning it as you gain speed.Sounds like a good application for a continuously variable transmission.

[Rick Willoughby]

Rick,
Thanks for the fast response.
My boat will indeed be a displacement type hull, and very slow speed at that.
Should the ducktail be located at a certain height in relation to the waterline, and should it be flat in profile, or slightly "V" shaped like the hull.
Considering that the ducktail will be a semi circle the width of the transom, It will add about 24" of length when submerged.
I will also be putting the propellers near the end of the transom step, so they will be about 24" also from the end of the ducktail.
Will this have any adverse affect?
I am using 2) 50# trolling motors slightly modified as the power for the boat.
They will also do the steering.
The boat is 18 ft LWL, with a 60" max beam, slight vee bottom for stability, and the ducktail will add about 2 ft more if it hits the water.
I am using using a rounded chine, and want that old boat look.
Is the ducktail worth all the work?
It sure does look cool.
Thanks in advance. Tom

Tom
Have you got a picture or drawing of what you have in mind.

To my mind there is not much point having something unless it affords benefit. Agreed that could be just to get a certain look.

I would need to see more detail on what you have in mind and hope to achieve overall with the boat. Even a simple sketch would improve my understanding.

The overhanging stern really only comes into play when reaching hull speed. It does not sound like you will have the power to get there in the first place.

Unless you have a good idea of what you are building it will pay to buy proven plans of something that looks like what you want. There are thousands of plans for small boats and a lot of people here who can guide you in selection.

Start a new thread regarding your boat and see what comes of it.

There are no dumb ideas or silly questions.

Rick

[Rick Willoughby]

Maybe, but the boat in the picture is not sailing to windward -- it is motoring to windward using a water prop for forward propulsion instead of the wind.

It is not sailing, it is motoring by using the wind INDIRECTLY via the water prop for propulsion.

Maybe, but motoring into the wind does not and that's all that's going on here.

Right, it may not work if the drive were in the air but it is not.

There seems to be a couple of guys here who like to argue and theorize and confuse the issue rather than paying attention to the simple facts. What's so hard to understand about extracting 10 HP from the wind and using it to spin a water prop that moves the boat into the wind?

Sounds like a good application for a continuously variable transmission.

Ken
Your use of the term motoring is misplaced. A motor motors not a turbine. The term sailing might be misplaced but motoring makes less sense.

Maybe wind powered water propelled boat.

I agree with a CVT. It would be really nice. Variable pitch on the turbine or prop are alternatives but the CVT is probably the best way. It is just like tuning sails then. You can keep pushing speed until the turbine begins to stall. With fixed speed transmission you have to set the gearing so it will make way in light air and this is not optimal once you get moving. The efficiency of the turbine really picks up once it develops speed.

Rick

[kengrome]

Maybe wind powered water propelled boat.Sounds good to me, I was just trying to simplify the explanation of what's really going on for those who didn't seem to be getting it.

I agree with a CVT. It would be really nice. Variable pitch on the turbine or prop are alternatives but the CVT is probably the best way.My first experience with a CVT was in a snowmobile that used a wide v-belt between two variable width sheaves that adjusted themselves automatically by the use of springs and centrifugal weights based on engine RPM and torque. My understanding is that belts provide something like 98% efficiency so a similar CVT might work well in this application.

[MPraamsma]

Rick, Ken (et al)

I posted (attached) the pictures of my model which I constructed to settle a dispute about going windward. For those familiar with the idea, no explanations are necessary, as the way it works is self explanatory. It has a small spring wire that keeps the steering centered, but allows the windvane to correct it to windward. The nature of the bet required I could demonstrate it totally windward at all times, and this is not what the final controls would try and emulate. Keep in mind when I made this thing I had no idea of others that were working on this stuff, so what you see is my intuitive understanding of the issue, and what a general solution would look like.

Michael

[MPraamsma]

Rick,

I tried to catch up on your older posts last night to see where you were going with your concept, and I have to pretty much agree with how you understand the matter. As to the transmission of the power to the driving prop I would have the following suggestion: Since wind is a variable resource in both the long term (windless days) and in the short term (gusts, puffs etc.) and strong and weak winds, it will be necessary to have a torque management system in play to keep the power to the vessel approximately constant. You mentioned a CVT type of trans, well have you considered using a Solomon type of drive? Let me describe how I would tackle the problem. First, the turbine needs to be mechanically coupled to the load with some kind of very efficient chain drive first, not via the indirect generator to motor electrical coupling. The reason for this is that the purely electrical syatem would have to be robust enough to handle the entire power of the turbine, so it would be unnecessarily large. The turbine shaft would drive the input sprocket through a sprag clutch that allows the output propeller to overrun the speed of the wind turbine. The turbine therefore only produces output if it can catch up to the rest of the drive train. However, since the no load speed of the turbine is always many times higher than the nominal operating speed, it is always running at the operating speed, but not always producing enough torque to keep everything running by itself. This power feeds into one of the inputs (ring gear) to the Solomon drive. Briefly, the Solomon drive is a three input planetary transmission with each shaft both an input (power in) and an output (power out/generator). One of the other outputs (the planetary ring) drives the output propeller, and the third shaft (the pinion) is connected to a control motor/generator. In tandem with the output propellor is a direct drive bi-directional electric motor/generator equal to the capacity of the wind turbine. This may sound complicated, but really isn't, because the Solomon trans acts as a CVT since it can feed torque into and out of the system in response to the actual input coming from the turbine. That way you take what you can get from the turbine, and the rest of the time you are either 'bucking' or 'boosting' the output to produce a smooth ride. During the 'bucking' you are generating electrical power and storing it, during the 'boost' you are using electrical power. It is possible to run such a system as a 'net zero' power consumption at the power level of the turbine at ambient relative wind, or the relative wind can be augmented by inputing power from the electrical system, which I believe will amplify the turbine output by artificially increasing the vessel velocity.

[MPraamsma]

Rick,

If you need to look at the Webpage of this thing, here it is:

http://www.solomontechnologies.com/wheel.htm

Michael

[MPraamsma]

Rick,

This is the shot of my prop under construction for the bicycle experiment. It has blades that are 24" long. The swept circle has an area of about 1720 sq. in. Should be interesting.

Michael

[MPraamsma]

Rick,

Prop picture...

Michael

[Rick Willoughby]

Rick,

I tried to catch up on your older posts last night to see where you were going with your concept, and I have to pretty much agree with how you understand the matter. As to the transmission of the power to the driving prop I would have the following suggestion: Since wind is a variable resource in both the long term (windless days) and in the short term (gusts, puffs etc.) and strong and weak winds, it will be necessary to have a torque management system in play to keep the power to the vessel approximately constant. You mentioned a CVT type of trans, well have you considered using a Solomon type of drive? Let me describe how I would tackle the problem. First, the turbine needs to be mechanically coupled to the load with some kind of very efficient chain drive first, not via the indirect generator to motor electrical coupling. The reason for this is that the purely electrical syatem would have to be robust enough to handle the entire power of the turbine, so it would be unnecessarily large. The turbine shaft would drive the input sprocket through a sprag clutch that allows the output propeller to overrun the speed of the wind turbine. The turbine therefore only produces output if it can catch up to the rest of the drive train. However, since the no load speed of the turbine is always many times higher than the nominal operating speed, it is always running at the operating speed, but not always producing enough torque to keep everything running by itself. This power feeds into one of the inputs (ring gear) to the Solomon drive. Briefly, the Solomon drive is a three input planetary transmission with each shaft both an input (power in) and an output (power out/generator). One of the other outputs (the planetary ring) drives the output propeller, and the third shaft (the pinion) is connected to a control motor/generator. In tandem with the output propellor is a direct drive bi-directional electric motor/generator equal to the capacity of the wind turbine. This may sound complicated, but really isn't, because the Solomon trans acts as a CVT since it can feed torque into and out of the system in response to the actual input coming from the turbine. That way you take what you can get from the turbine, and the rest of the time you are either 'bucking' or 'boosting' the output to produce a smooth ride. During the 'bucking' you are generating electrical power and storing it, during the 'boost' you are using electrical power. It is possible to run such a system as a 'net zero' power consumption at the power level of the turbine at ambient relative wind, or the relative wind can be augmented by inputing power from the electrical system, which I believe will amplify the turbine output by artificially increasing the vessel velocity.

Michael
My Solar-Wind boat is a balance between solar and wind with a slight bias on solar. The motor/generator I have for the wind prop will have much higher power handling than the turbine/prop is capable of in most wind conditions and I have very large energy storage. My goal was to keep it reasonably simple, at least in concept. Electrics give me complete flexible for a modular set up.

Your little model looks nice. You will find the bigger one will be more inclined to self start. The blades look OK. How well did you determine the pitch angle?

Rick

[dsuursoo]

a vertical axis turbine would solve a lot of the pointing problems, as well as simplifying the whole machine.

*draws feverishly*

[MPraamsma]

Rick
Doing some thinking about the idea of windmill powered propulsion, and I had a few thoughts I wanted to share and get some feedback from you, since you have given this some considerable thought as well. I believe there are some significant differences between just generating power from a fixed land based location, and one that is aboard a moving vessel. The most important is the magnitude of forces that are generated in the axial direction, since these are directly contrary to the forces that are required for propulsion. In a land based arrangement these forces are irrelevant other than the mechanical requirements to handle the thrust loads and stresses on the blades etc., since the pedestal is firmly anchored into the earth, and offers infinite resistance to movement. In a moving vessel these forces not only need to be mechanically resolved, but the forward thrust required must first counter this negative axial load before any net forward motion can be achieved. Using turbines with high tip speed ratios works counter to this goal, because as the speed increases the pitch must flatten out, and this shifts a large portion of the lift component to the axial direction, effectively making further gains in generating output useless beyond the point where these negative axial components equal the vehicle drag. In addition, the actual drag on the blades increases with higher RPMs so that negative axial component of this also increases.
The obvious answer to this dilemma is to find an arrangement where the tip and root speeds are very similar, so that the amount of pitch change is small, and never exceeds around 45 degrees so that no large axial component actually develops, and most of the energy can be converted into torque. This will require that the RPM be limited so that no large pitch changes are needed. To get the required air velocity, it would be better to augment the flow in a venturi duct first, and draw the air out the back with a flared diffuser. I have attached a sketch of something like this for those interested.

[ancient kayaker]

There is an earlier thread on this topic. I created a posting there http://www.boatdesign.net/forums/showthread.php?t=14182&page=12&goto=#174 that dealt with the rough math of why it is feasible to head directly into the wind with this concept. On that thread, this was a recurring theme of disbelief. My simplistic treatment might suggest how to analyse the problem of forces on boat-based vs land-based systems. The simplest case of heading directly into the wind is dealt with in my posting which however ignores energy losses. I suspect the level of math will become serious ...

Regarding turbine blade design all that is needed in principle is a constant pitch design. However, that assumes that the turbine is permitted to revolve at a speed that is efficient which requires a variable speed transmission.

[Rick Willoughby]

With regard to ducting I am near certain that the added drag of all that area exposed to the air stream will more than negate any benefit that could be gained in turbine efficiency.

What I have shown is that the system performance gets down to overall system efficiency.

This means the combined efficiency from taking power out of the air stream, through the mechanical losses and then the efficiency of applying the power to the water. The important variable is effective gearing between the air turbine and water propeller while the only performance parameter of interest is the efficiency of power transfer. The system equations are:

Power In = Turbine Thrust x Apparent Wind Velocity

Power Out = Propeller Thrust x Boat Velocity

Propeller Thrust = Turbine Thrust + Boat Drag

Apparent Wind Velocity = Wind Speed + Boat Velocity (when going directly to windward)

Boat Drag = Function(Boat Speed) (For slender hull approximately Constant x Speed^2)

Power Out = Power In x Air Turbine Efficiency x Water Turbine Efficiency X Mechanical Efficiency

These are the equations that you need to know to determine system performance. Efficiency is KING and gearing makes it work. With a really efficient system turbine pitch can be as little as 1.6X the propeller pitch x mech gear ratio.

I design high efficiency propellers (or turbines) and I find they have quite high tip speed to get the best performance. This is particularly the case with small air turbines. My blades look more like they came off an aeroplane than the typical wind farm. The latter is designed to collect energy by extracting as much power as possible. They are defined by their power coefficient not efficiency. Your choice of propeller for you little cart is close to ideal I suspect. (Was this a well calculated selection or just inspired good fortune.)

The force acting on the blades is most commonly resolved into lift and drag components for calculation purposes. I recognise that at high tip speed the apparent velocity at the tip will be acute to the direction of travel and likewise the lift component but the small component generating torque is moving at extremely high velocity so producing heaps of power. Also the drag component is quite small and is at an acute angle to the direction of travel.

I have not seen any examples of properly designed boat systems that show designers understood what they were doing. They are usually a combination of a standard wind turbine and a standard water propeller. Neither are the best for best overall performance.

My interest in propellers grew from designing and building high performance pedal boats. My best design gets 12kph with 150W input. (When the engine is small efficiency is paramount.) This link shows one of my prop designs:
http://www.adventuresofgreg.com/HPB/uploaded_images/P9010014-783297.JPG
This one achieves an efficiency of 86% at design conditions. I can get slightly higher efficiency with a decent size air turbine; up around 88% at windspeed 3m/s and above. So plug these numbers into the above equation and see what is possible with a hull drag of 38N at 12kph where boat drag equals Constant x speed^2.

Rick W.

[Rick Willoughby]

MP
I looked at a 5-bladed turbine of 1.5m (5ft) diameter designed for 10m/s (22mph) apparent wind with 100mm maximum chord blades.

The best speed is around 800rpm for these conditions. You should be able to extract 630W from it at this speed at 79% efficiency. The pitch curve is attached.

The foil I based this on is a NACA4410-44. It would be harder to model your tube section but if it is set up properly it could work quite well.

The tip speed ratio is 6 so it is a little lower than I expected. The efficiency is better at lower speed but the power extraction gets to be very low at low speed.

The drag on the turbine is 105N at 10m/s apparent wind.

Some rough numbers for the system are:

1. Bike windage at 22mph is 60N (including trailer wheels and frame). So total drag is 165N assuming negligible rolling resistance.

2. The power to the trailer wheels is 630W less mech losses - say 570W.

3. The bike speed over the ground will be 570/165 = 3.4m/s (7.6mph).

4. The true windspeed for this condition will be 10m/s minus 3.4m/s equals 6.6m/s (15mph)

So in 15 to 20mph winds you could expect something like 8 to 10mph with your turbine.

The turbine I have described would need to be geared 2.7:1 to achieve this using 27"bike wheels.

The reason for the relatively poor performance is the high wind drag of a standard cycle. If the rider was in a recumbent style seating performance would be better.

Rick W

[MPraamsma]

Rick,

Your concern about the duct drag is a little pessimistic. I once made a soapbox car for my daughter years ago that had a monstrous venturi duct as the body, with a frontal area 8 sq. ft., and it performed as well as tiny little cars that had about 1 sq. ft. area. A properly designed venturi is a net zero device, where the forces of flow are balanced between the inlet and diffuser. In effect, the car I made was a giant Laval Nozzle similar to a rocket engine. I have added some diagrams a pictures to illustrate what this contraption looked like. Also, the flow plot shows the conditions in the duct at the point that the throat starts to go sonic. Notice that the external flow is almost completely undisturbed.

[MPraamsma]

Rick,

Thanks for the preliminary estimate for the bike experiment. I will use it guage how predictions stack up to real world conditions. Everything is on track to take it out to the desert next weekend the 14th of Sept.

As I was playing around with the problem of high tip speeds and steep pitch angle causing a detrimental thrust component, I had a wacky idea come to mind, and would be curious to hear what you think of it. Let me try and explain my reasoning.... first, I agree that the amount of power produced by the tips is huge, however, if it creates a component of thrust opposing the motion of the vehicle to the support pylon, then it is wasted output. If you look at vector diagrams of the lift vectors, and how they resolve into tangential and axial components, it is clear that at some point they are equal, and further increases in pitch are then counterproductive for a wind powered turbine/propeller combination. Long before that point you are getting diminishing returns. Any axial component of thrust has to be overcome by the drivetrain, which has efficiency issues. The source of the problem is the inevitable consequence of creating power via a rotating device that has long blades that have points that must travel along different helical paths, which produce force components that oppose our goal of producing pure output torque. My idea is, why not nullify this useless component directly at the turbine by making the tip of the turbine, at the point where the pitch flattens out, into a propeller surface instead that works in opposition to axial thrust component. This would entail no mechanical losses, as it is part of the same airfoil structure as the turbine, and it is flying in the best possible attitude, namely almost in a plane perpendicular to the turbine axle, at high tip speeds. The only loss would be the viscous drag on the foil, which is small. To anticipate your response, yes, it will draw power from the output to drive this tip, but better to do it at the source of the problem, rather than through the drive system with all the increased capacity necessary to handle this useless piece of dead ended energy. I carved one out of my choice prototyping material (schedule 40 pipe), and have attached some pics for you.

Stop laughing, it's a serous idea!

[MPraamsma]

Rick,

Just wanted to clarify what I meant by the buildup of the axial forces in a wind turbine blade as the tip velocity increases. In my diagram I show a typical foil at various radial positions along the blade, and the pitch angle at each point. All sections are considered moving with a zero degree angle of attack to the relative wind for simplicity. To keep it simple, we resolve the basic lift and drag, which at zero degrees pitch align along the tangential and axial axes perfectly, into a resultant force. Higher up on the blade, at 30 degrees for instance, it is clear to see that the resultant, when projected on the tangential and axial axes (green vectors), is transfering force increasingly into the axial direction. At 60 degrees, the axial component has swamped the tangential, even though the magnitude of the tangential vector may be many times larger than at 30 degrees. In a stationary wind turbine this is of little to no consequence, other than requiring a very robust support pylon, since in that situation the entire earth is the anchor. However, in a wind powered vessel the anchor consists of the thrust created by the underwater propeller, which in turn is derived from the output of the wind turbine. This explains some of the disappointing performance of upwind runs of turbines, and needs to be addressed if they are to take advantage of the greater energy available directly windward.

[Rick Willoughby]

Rick,

Just wanted to clarify what I meant by the buildup of the axial forces in a wind turbine blade as the tip velocity increases. In my diagram I show a typical foil at various radial positions along the blade, and the pitch angle at each point. All sections are considered moving with a zero degree angle of attack to the relative wind for simplicity. To keep it simple, we resolve the basic lift and drag, which at zero degrees pitch align along the tangential and axial axes perfectly, into a resultant force. Higher up on the blade, at 30 degrees for instance, it is clear to see that the resultant, when projected on the tangential and axial axes (green vectors), is transfering force increasingly into the axial direction. At 60 degrees, the axial component has swamped the tangential, even though the magnitude of the tangential vector may be many times larger than at 30 degrees. In a stationary wind turbine this is of little to no consequence, other than requiring a very robust support pylon, since in that situation the entire earth is the anchor. However, in a wind powered vessel the anchor consists of the thrust created by the underwater propeller, which in turn is derived from the output of the wind turbine. This explains some of the disappointing performance of upwind runs of turbines, and needs to be addressed if they are to take advantage of the greater energy available directly windward.

MP
I take all that into account in the numbers I gave you. I determine best tip speed for your device will be around 6:1 in apparent wind 0f 10m/s. This results in the best performance.

Rick W

[Rick Willoughby]

With regard to tip speed, did you determine the tip speed of the model vehicle. That blade seems quite aggressive.


For your prop I considered rpm from 200 to 900 in 10m/s apparent wind. 700rpm was similar to 800.

Anyhow you will have some data next week. I will be interested to see how it goes.

Rick W

[Rick Willoughby]

Rick,

Your concern about the duct drag is a little pessimistic. I once made a soapbox car for my daughter years ago that had a monstrous venturi duct as the body, with a frontal area 8 sq. ft., and it performed as well as tiny little cars that had about 1 sq. ft. area. A properly designed venturi is a net zero device, where the forces of flow are balanced between the inlet and diffuser. In effect, the car I made was a giant Laval Nozzle similar to a rocket engine. I have added some diagrams a pictures to illustrate what this contraption looked like. Also, the flow plot shows the conditions in the duct at the point that the throat starts to go sonic. Notice that the external flow is almost completely undisturbed.

I usually make an observation from previous experience and then look to check my observation with some numbers.

When I checked the ducted turbine with my turbine model I was getting funny numbers that were hard to believe.

Anyhow I found the attached paper that backs up my numbers. The interesting aspect is that it is possible to exceed the Betz Limit in the example given in this paper:
http://www.ibpsa.org/proceedings/BS2003/BS03_0407_414.pdf
I am not sure if the same result is possible in a turbine isolated from other interference. My model may not have enough detail about far field conditions to give the right result.

I compared a 1m diameter ducted turbine with the 1.5m open turbine. The air velocity over the turbine was doubled. This improves the blade performance even though the diameter and area are smaller.

What I am not accounting correctly for is the inlet pressure due to velocity reduction through the ducting at the turbine. This will add pressure to the inlet area and will increase effective drag. THis has nothing to do with the aerodynamics of the ducting in free flow conditions. I expect the ideal shape of the ducting to be different to what you showed in the original sketch because there will be reduction in the air velocity exiting compared with that entering.

So the fact that the turbine gets into a better operating regime at lower air flows may help overall. It is worthy of further analysis.

Rick

[MPraamsma]

I usually make an observation from previous experience and then look to check my observation with some numbers.

When I checked the ducted turbine with my turbine model I was getting funny numbers that were hard to believe.

Anyhow I found the attached paper that backs up my numbers. The interesting aspect is that it is possible to exceed the Betz Limit in the example given in this paper:
http://www.ibpsa.org/proceedings/BS2003/BS03_0407_414.pdf
I am not sure if the same result is possible in a turbine isolated from other interference. My model may not have enough detail about far field conditions to give the right result.

I compared a 1m diameter ducted turbine with the 1.5m open turbine. The air velocity over the turbine was doubled. This improves the blade performance even though the diameter and area are smaller.

What I am not accounting correctly for is the inlet pressure due to velocity reduction through the ducting at the turbine. This will add pressure to the inlet area and will increase effective drag. THis has nothing to do with the aerodynamics of the ducting in free flow conditions. I expect the ideal shape of the ducting to be different to what you showed in the original sketch because there will be reduction in the air velocity exiting compared with that entering.

So the fact that the turbine gets into a better operating regime at lower air flows may help overall. It is worthy of further analysis.

Rick

Rick,

Actually, the shape of the duct I showed is not that far from what would be a practical configuration, other than the exact dimensions and proportions. The inlet in this case would ideally be a simple tubular duct so that the flow is directed outward as far as possible so that it intercepts the blades as far away from the axis as feasible. The flow at the throat has less static pressure, but enormous ram pressure. In the ideal nozzle this flow moves at Mach 1, and represents the maximum kinetic energy of the airstream. Once past the turbine, it must expand back to it's natural state, minus the momentum removed by the turbine. This requires the diffuser to be slightly larger than the inlet to draw the air through (so as not to cause a stall), which is known as diffuser augmentation. The central body can be the almost bloated torpedo shape shown, because it forms part of the venturi wall anyway, and you need plenty of room to house alternators and other mechanical stuff. Also, some form of stators at the inlet would direct the flow more normal to the underside of the turbine blades, effectively allowing better pitch angles. It is well known that ducts are not subject to the Betz limit.

[ancient kayaker]

On a slight tangent to the discussion so far, most of the argument for a wind turbine powered boat is based on its advantage in narrow waters when headed directly upwind compared with a conventional sailboat which must be repeatedly tacked.

I have also read claims that a wind turbine powered boat can continue to "beat the wind" on a run if its speed is first made to exceed the windspeed under power, after the power is cut. Has anyone tried this? It would be easier to demonstrate with a wind turbine powered land vehicle than a boat, just give it a good shove downwind, but would still be valid for demonstration purposes. There seems to be no theoretical reason why it would not work.

I wonder if a wind turbine powered boat is actually more efficient than regular sailboat in a variety of wind and water conditions on various courses or if the advantage is limited to upwind (and maybe downwind). By efficient I mean faster in terms of distance made good in the desired course. I suspect a well-handled sailboat would have the advantage on a reach, due to the lack of transmission loss.

Presumably for a sailboat without auxilliary power upwind performance is generally more important unless sailing the trades.

[MPraamsma]

AK

As a sailor of a conventional ketch rig, I am very skeptical of faster than the downwind wind idea. When I go downwind I am impressed by the calm that surrounds my boat, like nothing is happening and no wind exists, almost no sensation of speed whatever. All I am aware of at that point is the massive drag on my hull, and little power noticeable in the wind. I personally think that all the normal sailing positions from a close reach to a run are well served by regular sails, which should still always be part of a sailing vessel, it is the directly to wind situation that needs a better solution, as tacking can often be tiresome as well as dangerous, and certainly time consuming.

My goal (as an engineer) is to figure out the secret to extracting maximum power from the wind when at it's maximum potency. As I check the web, it is clear that little work has been done on moving wind turbines, which in principle should be the most efficient way to extract wind power.

[MPraamsma]

..it seems we have been beaten to the punch...

[ancient kayaker]

AK

As a sailor of a conventional ketch rig, I am very skeptical of faster than the downwind wind idea. When I go downwind I am impressed by the calm that surrounds my boat, like nothing is happening and no wind exists, almost no sensation of speed whatever. All I am aware of at that point is the massive drag on my hull, and little power noticeable in the wind. I personally think that all the normal sailing positions from a close reach to a run are well served by regular sails, which should still always be part of a sailing vessel, it is the directly to wind situation that needs a better solution, as tacking can often be tiresome as well as dangerous, and certainly time consuming.

My goal (as an engineer) is to figure out the secret to extracting maximum power from the wind when at it's maximum potency. As I check the web, it is clear that little work has been done on moving wind turbines, which in principle should be the most efficient way to extract wind power.

Agree, except your skepticism of the faster than the downwind wind idea.
I've heard of conservation of energy and "you can't get something for nothing" by the way. What is claimed to happen is, the waterscrew extracts energy that is used to drive the airscrew; overall the energy to drive the boat comes from the air which is moving in the direction of the boat albeit slower. Yes, it sounds screwy (sorry, I've a weakness for puns) but the math seems to work. Conservation of energy is not violated.

[MPraamsma]

AK
I'm not saying it is impossible, just that I'd like to see a working model, however crude.

[Rick Willoughby]

AK

As a sailor of a conventional ketch rig, I am very skeptical of faster than the downwind wind idea. When I go downwind I am impressed by the calm that surrounds my boat, like nothing is happening and no wind exists, almost no sensation of speed whatever. All I am aware of at that point is the massive drag on my hull, and little power noticeable in the wind. I personally think that all the normal sailing positions from a close reach to a run are well served by regular sails, which should still always be part of a sailing vessel, it is the directly to wind situation that needs a better solution, as tacking can often be tiresome as well as dangerous, and certainly time consuming.

My goal (as an engineer) is to figure out the secret to extracting maximum power from the wind when at it's maximum potency. As I check the web, it is clear that little work has been done on moving wind turbines, which in principle should be the most efficient way to extract wind power.

It is the same principle as sailing directly into the wind but you use a water turbine and an air propeller. The gearing has to be reversed.

It requires quite a large propeller to work for the reasons outlined earlier regarding low Re# airfoils.

If you have the ability to continuously adjust gearing through a transmission or variable pitch you can get optimum performance in any direction relative to the wind including going directly into the wind and faster than the wind down wind.

100 years ago sailors had trouble understanding you could have VMG 90 degrees either side of the wind direction. Today most people have difficulty wrapping their brain around the idea of using wind energy going directly into the wind. Very few people can understand going down wind faster than the wind but it can be done. It is a matter of getting the foils right and the gearing between them right.

There is a demonstration of a land vehicle about twice the size of the one you built accelerating down wind. Generally all these things are easier to do on land because you have a nice firm medium to react on but water is not too bad if you have a low drag hull and a nice size prop.

I can provide the conditions for open or ducted propellers and open turbines. I have not considered closed turbine until you raised it.

Rick W

[MPraamsma]

Rick,

(BTW I am an old Aussi way back. Lived in Sydney from 1950-1960. Originally from Holland.)

The ideal closed turbine has a small annular throat with lots of tiny stubby blades on a very large radius from the axle. This plus some form of fixed vortex vanes in the inlet to creat a swirl in the direction of rotation.

[MPraamsma]

Rick,

I cleaned the diagram of the ducted system up a little to represent a more realistic configuration. Also, I wanted to expound some of the advantages of this type of system for use on sailing vessels. As you know, my pet peeve on the standard open bladed design is the massive axial component of thrust that develops as a consequence of the pitch angle approaching 90 degrees at the tips of spinning props. This component is highly undesireable from the standpoint of a vessel mounted wind generator that is used to power the vessel's motion through the water, and everything possible must be done to eliminate this force component. Conventional props cannot solve this issue unless they have very low tip speed ratios, and this means very low flows over the prop foils, and therefore low output. This can however be solved by changing two properties of the flow field, the effective angle of attack on the blades, and the speed of the flow field. These two properties can be modified by using a fixed stator that introduces a twist into the flow, and accelerating the flow by passing it through a venturi duct. A properly engineered venturi can accelerate the flow from 100 MPH to the speed of sound, which is around 550 MPH! Since ducted turbine blades are short, this speed acts over the entire blade surface! Once the flow has established, it has enormous inertia, since most of the potential energy of the air has been converted into kinetic energy at the throat, which keeps the flow moving along quite nicely. Once up and running, the venturi acts like a giant vacuum cleaner, drawing air into the inlet from well ahead of it. The air (exclusive of the real wind) is actually moving before the inlet arrives, because the speed of sound is so much higher than the vessel speed.

Some other advantages:


All moving parts are inside a shroud
Much smaller size
Can be built to withstand huge RPMs safely
Operates at speeds compatible with high performance PM alternators
RPMs are independent of the wind speed
Very small blade twist
Blades can be extremely rugged
Gyroscopic forces easier to control
Can be built in complementary pairs that cancel gyroscopic forces so that pointing effort is low
Can be sealed off from the elements with covers
Ducts are simple tubes
Stator acts as unobtrusive support structure for turbine






I could add a few more, but I think you get the idea.