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.

[MPraamsma]

This website describes a turbine with some of the ideas I have raised earlier for the more efficient production of mechanical output.

http://peswiki.com/index.php/Directory:FloDesign_Wind_Turbine#Patents

Notice the use of a fixed stator at the inlet to create a swirled inflow that strikes the blades at a much higher angle of attack.

[MPraamsma]

Rick,

Just wanted to keep you updated as to the progress of the bicycle trailer project. I attached some pics, and a small video of it in operation after I got it all assembled. So far we tested it behind a bike for structural and mechanical integrity, but no wind this weekend as fate would have it. We towed it up to about 20 MPH and that blade really cranks! Without the trailer we can still only get the bike up to about 22 MPH. Since we can't test it in the desert this weekend I will make a small vane steerable front wheel this week that can be detached so that it resembles the little model only bigger. I had to keep the chain off for the pictures, because any slight breeze wants to make it take off.

Michael

[Rick Willoughby]

Michael
That is really nice work.

If you can set this up to sit low so you minimise your windage using a small front wheel for steering it should give impressive performance. I believe this a better option than setting it behind a bike.

You could find a small decline to get it going if the wind is not very strong. Or just kick it along to get some speed. In strong wind it should be trying to take off on its own.

This will be a very useful test bed. You could fit bike gearing to it as well.

I would appreciate an approximate pitch angle and blade profile at about 5 points down the blade if you can provide that.

With the one I made I was staggered by the power it generated and the blade deflection under load. It was 2.2m in diameter. The blades used aluminium flat bar as a former with balsa for shaping and then all glassed over the balsa. The section was constant MA409 foil with 100mm chord. The blades were not a work of art but demonstrated that they need to be well designed to cater for the potential loads in a good breeze.

Your blades may flex a little more than you would like but hopefully they will not break.

Rick

[MPraamsma]

...but very useful to subject it to some punishing road tests to make sure it can stand up to higher speeds. It has three speeds, but I have to change them by reconfiguring the chain and all the turnbuckles. I need to change the axle, I made it solid to both wheels, but need to have one freewheel like my earlier model, because this thing is impossible to steer.

[Windmaster]

Interesting video on http://www.youtube.com/watch?v=NNbNNSDljGI

[ancient kayaker]

Michael: you were a bit sceptical about beating the wind on a downwind course earlier. Check out this thread: http://www.boatdesign.net/forums/sailboats/tacking-downwind-faster-than-wind-24761.html
Of course, it can't be done without tacking so you're quite correct as far as a downwind heading is concerned.

[MPraamsma]

ancient kayaker

Sailing on a heavy 40 foot sailboat with a massive keel and draft, one never can get the notion what true downwind possibilities are, however, these land yachts can demonstate it better because they have for all practical purposes three almost frictionless wheels on the ground. I've been sailing for many years, and I'm familiar with the usual wind situations and limitations. What I am attempting to do is to put that insight into downwind performance into a wind collector to harness wind power for forward propulsion. As many of us here have proven to ourselves, by the building of models and such, is that 100% upwind performance is possible. My discovery when testing mine is that the turbine prop starts to look like as someone said here earlier, 'like a spinaker'. I have termed this effect as ADVERSE thrust. In our case, this adverse thrust works against propulsion, and propulsion is what we are trying to achieve. I have proposed an arrangement, where the entire input to a generator is fed into a venturi trough first, then sent spinning through stator blades into a vortex. The turbine blades are then spinning inside a high speed tangential flow. This flow combined with the rotation speed of the blade will allow the torque to be transmitted to the shaft without adverse thrust penalty. These turbine blades are 'flying downwind' to use a sailing analogy, and, and their speed then controls their angle of attack. Drawing off torque will cause the angle of attack to increase in direct proportion, so it can be regulated using generator output. The other advantage of flying downwind is that the blades feather, or luff as we sailors say, at maximum RPM of the turbine, when there is no load and the angle of attack becomes zero degrees.
I have attached a close-up of the turbine as I see it evolving.

If the whole turbine is then turned so that it is spinning in a horizontal plane, any residual thrust is then only capable of lifting or weighing down on the vehicle/vessel weight. Since a freefloating vessel is sensitive to ANY thrusts it sees, they all must be considered when designing a system to produce useful thrust.

[robherc]

OK, my opinions on the subject so far (after reading this thread, and the one that ended up becoming a DDWFTTW debate, entirely):

1. When approached with an open mind, DUW & DDWFTTW become obviously feasible "wind-powered" possibilities.

2. A ducted fan (whether energy-gathering, or energy-expending) will, all things being equal, ALWAYS be able to operate more efficiently than the same fan, unducted. (by elimination of tip losses)

Michael:
Good: I like, and thoroughly agree with, your idea of using a venturi-style duct to allow you to improve the angle of attack for your fan blades in order to improve the ratio of torque-produced vs. drag.
Improvement: IYHO, would it be possible to improve the efficiency of this by installing 2 turbines with opposing blade angles (and spin directions) to incite the spin of the stator, and harness a (slight) bit of energy by the first turbine in the process?
Bad: Your idea of reversing your blades at the tips seems to merely be expending unnecessary energy in pursuit of "free energy" to me. From all that I can infer there (sorry, haven't developed an equation to show you) you're trying to use a portion of your energy-harvesting turbine as an energy-spending turbine. The only eventuality I see happening here is an extra loss due to air-friction on the added surface area on the reversed-tip, along with the expenditure of some efficiently harvested energy (from the inner portion of the blade) being wasted to accelerate air that has already bypassed the tips of that section to about the same speed as it's actually moving. Even if you adjusted the attitude of the tips high enough to create real acceleration on the air they touched, assuming your hypothesis worked, couldn't I then design a turbine/prop. that powered itself to move forward by harvesting power from the air in front of it moving backward (relative to the prop's motion)...seems like a free-energy theory to me. (and yes, I know my explanation here sucks)


Everyone:
I found this patent: http://www.google.com/patents?id=XlQDAAAAEBAJ while reading through the link on the ducted wind-turbine patent Michael referenced earlier. What are everyone's thought on the applicability of adapting a design similar to this (patent expired over a year ago, so it's legal now) for a DUW, wind-powered craft?
My thoughts are that it'd be VERY doable for a fixed-position (land-based is misleading, as the cart designs are land-based) generator where drag is a minimal factor, but for our purposes, I'm thinking the drag would be greater than the extra torque it's allow us....

Your Guys' Thoughts???
(I'll try to post drawings later, if I can ever get them to match the confused jumble of images in my head...lol)

[dsuursoo]

OK, my opinions on the subject so far (after reading this thread, and the one that ended up becoming a DDWFTTW debate, entirely):

1. When approached with an open mind, DUW & DDWFTTW become obviously feasible "wind-powered" possibilities.

2. A ducted fan (whether energy-gathering, or energy-expending) will, all things being equal, ALWAYS be able to operate more efficiently than the same fan, unducted. (by elimination of tip losses)

Michael:
Good: I like, and thoroughly agree with, your idea of using a venturi-style duct to allow you to improve the angle of attack for your fan blades in order to improve the ratio of torque-produced vs. drag.
Improvement: IYHO, would it be possible to improve the efficiency of this by installing 2 turbines with opposing blade angles (and spin directions) to incite the spin of the stator, and harness a (slight) bit of energy by the first turbine in the process?
Bad: Your idea of reversing your blades at the tips seems to merely be expending unnecessary energy in pursuit of "free energy" to me. From all that I can infer there (sorry, haven't developed an equation to show you) you're trying to use a portion of your energy-harvesting turbine as an energy-spending turbine. The only eventuality I see happening here is an extra loss due to air-friction on the added surface area on the reversed-tip, along with the expenditure of some efficiently harvested energy (from the inner portion of the blade) being wasted to accelerate air that has already bypassed the tips of that section to about the same speed as it's actually moving. Even if you adjusted the attitude of the tips high enough to create real acceleration on the air they touched, assuming your hypothesis worked, couldn't I then design a turbine/prop. that powered itself to move forward by harvesting power from the air in front of it moving backward (relative to the prop's motion)...seems like a free-energy theory to me. (and yes, I know my explanation here sucks)


Everyone:
I found this patent: http://www.google.com/patents?id=XlQDAAAAEBAJ while reading through the link on the ducted wind-turbine patent Michael referenced earlier. What are everyone's thought on the applicability of adapting a design similar to this (patent expired over a year ago, so it's legal now) for a DUW, wind-powered craft?
My thoughts are that it'd be VERY doable for a fixed-position (land-based is misleading, as the cart designs are land-based) generator where drag is a minimal factor, but for our purposes, I'm thinking the drag would be greater than the extra torque it's allow us....

Your Guys' Thoughts???
(I'll try to post drawings later, if I can ever get them to match the confused jumble of images in my head...lol)


i dunno, seems a bit complicated. the math involved in crafting a duct that would be efficient at any single wind speed(and that's how it'd be, only one wind speed, unless you use a stepped concept, or had multiple ducts you could install), well, that's a lot.

why not contrarotating blades on the turbine? they eliminate tip loss inefficiencies also(and they're an order of magnitude simpler to build), and if you got fancy with your shaft arrangement(rather than make the second set of blades free-spinning), you could extract even more energy from the wind.

just thought i'd bring that up.

[Rick Willoughby]

Very unlikely a nozzle of any sort will perform better than the best unducted design.

The sort of applications where duct offer an advantage is where there is a constraint on prop or turbine diameter. If these are not an issue then run unducted.

You have to include any ducting in weight and drag components as well.

Any direct mechanically connected system of propeller to wheel or turbine propulsion is of limited use.

1. In the upwind case the power handling ability of the transmission quickly becomes a constraint.

2. In the down wind case you are looking at a very narrow angle of operation. Outside that range you are better off using the turbine and making use of the apparent wind. I believe DDWFTTW is of curiousity value only as a concept. It might have limited practical merit for a land vehicle constrained to travel on roads. But you can still get along here with a turbine vehicle just going a bit slower.

3. The propeller for the DDWFTTW case will not resemble anything required for the turbine to go upwind. They are fundamentally incompatible particularly where you have substantial drag such as a hull or slight incline on land.

4. To get anywhere near the best range of performance you need variable transmission. At minimum you need two gears if you want to use upwind and DDWFTTW potential on the same platform.

All this considered I believe it only makes sense to combine these ideas in a vehicle with electric transmission where you can store energy even when stopped and release it as required. In periods of high wind you store energy and don't waste it going just a tad faster. In light winds you release stored energy to keep up a good average. You can add solar cells for a little extra boost in dead calm air. Such a system also gives the ability to achieve bursts of speed at any time.

As a practical means of getting about current sails offer much greater utility than propeller/turbines, at least on water, unless the latter is tied into energy storage.

Rick W

[Rick Willoughby]

I think Michael is in transit. He has not been active here for some time.

Rick W

[robherc]

Improvement: IYHO, would it be possible to improve the efficiency of this by installing 2 turbines with opposing blade angles (and spin directions) to incite the spin of the stator, and harness a (slight) bit of energy by the first turbine in the process?
why not contrarotating blades on the turbine? they eliminate tip loss inefficiencies also(and they're an order of magnitude simpler to build), and if you got fancy with your shaft arrangement(rather than make the second set of blades free-spinning), you could extract even more energy from the wind.
Yes, I was thinking of combining that with the ducting, but at least we're thinking on the same page here. I'm in (partially) complete agreement!:cool:

Very unlikely a nozzle of any sort will perform better than the best unducted design.
Yeah, I kinda figured the nozzle would be worthless for our purpose here, but wanted to bring up the option, see what everyone else thought.

3. The propeller for the DDWFTTW case will not resemble anything required for the turbine to go upwind. They are fundamentally incompatible particularly where you have substantial drag such as a hull or slight incline on land.
Yes, I agree here, I only mention the two together as they seem to follow inherently linked thinking patterns, though I also see few uses, other than curiosity, for DDWFTTW tech.

[MPraamsma]

robherc et al,

Actually I am stilll active here, but no-one commented for some time on this concept, so I have been silent until someone offers something I can respond to. I will compose something to address your questions and get back. I am in Holland now.

[MPraamsma]

robherc,

I'm not sure if you caught the discussion we had on this some months ago, but the reverse blade tip idea was just a way to do something with one blade system that I later realized needed to be done by several co-operative fan wheels and a stator. Those ideas ended up in the 'turbo ducted turbine' or enhanced duct. I will repeat the total concept diagram here that was on the other thread. My main point to make was that we need to carefully separate what causes a force in a system of blades, and where these forces are exerted. These total forces consist of various contributions from friction, drag, and most importantly, the force developed by lift but vectored in a direction adverse to the thrust we are trying to utilize to power the vessel/vehicle. This force can quickly swamp any useful output, as my bicycle experiment clearly proved. The thrust (torque at generator) and the adverse thrust are on intersecting curves, and when that point is reached, the vehicle stops accelerating.

In the full (ducted) concept, the air is accelerated by a duct (I use this term acceleration with hesitation, because the air molecules never actually travel any faster in a venturi, they are simply more likely to be travelling in the flow direction the closer to the throat they are), then the air enters the high pressure area of the turbine. Before the air can strike the turbine, and produce thrust, it needs to be re-directed so that any forces developed are perpendicular to the plane in which the vehicle has freedom. Since vehicles/vessels (aircraft excluded for now) have no degree of freedom in the vertical plane (since they are on wheels or they are afloat), that is the axis on which the turbine must operate. In other words, the entire flow needs to be turned 90 degrees before we try and extract any energy.

You are correct, the first set of blades uses some power from the turbine to further speed up the flow, and to force a prefered direction to the vortex entering the turbine. Jets do this all the time, it is called power feedback, and occurs entirely within the machine, with no loss. It is important to get the flow up as high as possible first, because the power in the flow goes up exponentially with speed. The maximum speed is therefore when shocks start to form inside the duct. However, shocks only form if the relative velocity of air and blade are near the speed of sound. If the blade is rotating in such a manner that it is moving 'downwind' so to speak, the effective air velocity is then considerably lower.

The diagram was on this page, review our discussion to see how this was evolving.

http://www.boatdesign.net/forums/projects-proposals/windmill-wind-turbine-powered-boats-how-many-out-there-they-viable-14182-18.html

[robherc]

hmmm...read the other thread (from where you came in)...considering the data...dug out my "Aircraft Engines and Gas Turbines" textbook...will get back with you once I've reached any theory-level conclusions ;)

[MPraamsma]

robherc

Looking forward to your input. Let me know if you have questions.

[robherc]

1st thing that comes to mind: the "power feedback" you're referring to in jet engines (at least according to this book, and my understanding) is actually a compressor stage. Unfortunately for us, when you're not burning any fuel later, the compressor just wastes energy...wanna inject some alcohol & make a ramjet boat? (hmmm...now there's an Idea...lol)

Also, the idea of turning the turbine vertically in the duct doesn't seem to me to accomplish anything benenificial. Although you ARE changing the plane on which the TURBINE experiences drag (from horizontal to vertical), the vehicle will still experience the drag on the horizontal plane because your "bent venturi" shroud is still facing fore & aft. I.E. there will be a stagnation pressure (or temperature, if you will) fore (the energy being used to turn the turbine), and a lower-than-atmospheric pressure (or temperature) aft (energy was harvested). This pressure differential fore-aft will create slightly more drag (due to friction losses inside the figure "S" venturi duct) than the design with the turbine mounted on the horizontal plane.
I still think it was an excellent idea, and kudos to you for thinking outside the box there, but I don't think that one's workable.

I'm still loving the idea of enclosing the turbine in a venturi though, and I'd still like to hear what you guys think on the movable stator/counter-rotating turbine idea...be able to harvest a little energy from the stator/forward turbine spinning, in addition to the energy harvested by the second turbine.

Any thoughts?

[MPraamsma]

robherc,

This is more than just an idea that came to me in a flash one day. This is a technology I have been working on for many years. I'll try and answer some of your objections and doubts about the viability. First, feedback means taking some of the power output and re-routing it AHEAD of the input. This way, the energy is always caught in a loop, and is not wasted. All the compressor does for us here is to increase the pressure slightly so it will flow into the next venturi stage. At each stage the venturi gets narrower, and the flow inches closer to the speed of sound. Part of this flow is that caused by the vehicle motion, and is also power returned by feedback. By driving the wheels the vehicle moves forward and causes a flow which is maintained by the mass and momentum of the vehicle.

You need to revisit the idea of air friction to see it more as an acoustic wave that dissipates energy into the surrounding atmosphere as heat. As I pointed out in other posts, this acoustic loss becomes very obvious when you approach the speed of sound. However, a properly designed internal body reflects this wave in on itself and captures that energy in an enclosed space, and forces the flow to behave exactly as defined by an idealized flow channel. While the flow is in the venturi section, it barely makes contact with the wall, as a measurement of the static pressure at the wall will show.

The other point to make is that the external flow is unaffected, and the amount of air in the tunnel has no direct relationship to it. The transit time in the tunnel can be longer than the external path. In plain speak this means the turbine chamber itself can be 'pumped up' to higher than ambient pressure while in the dynamic operating state. The best analogy to this is the LASER, where there is a lot more energy trapped inside the cavity than makes it out to the outside world.

We don't want to confuse drag and lift force, because any lift force directed along the same vector as drag will be hard to distinguish from drag. Since we don't have the luxury of a fixed pedestal to oppose the drag axis, we have to subtract this force from the useful output. I can assure you that the adverse thrust developed on a turbine prop with a high tip velocity is considerable, and turning the turbine 90 deg is necessay to avoid this force becoming the determinant factor in output.

[robherc]

OK, having just read your post, then taken about 4.5 minutes to think it over before replying:

1. I am starting to see how your compressor/force-feedback idea might have some more merit than I had seen before. I'm not convinced there yet, that takes a LOT more thought, but I'm keeping an open mind, and I'm still working on chasing down energy-losses in my head, too see what I come up with.

2. I still believe that the "bent" venturi or "S" duct will gain us nothing, though I'm not 100% sure there & I'll still approach anything you use to explain its benefits to me with an open mind...but right now, I'm still pretty skeptical of it. (though of this after I typed the above...aren't the primary gains from you compressor stage, the fact that it can neutralize the pressure wave to the front, and the vacuum force left to the rear, of the energy-harvesting turbine by acting as a "one-way-valve" per se? ... thus nullifying any gains realized by changing the axis of the turbine's operation?)

3. I'd really like to discuss your views on using a counter-rotating turibne in place of the stator. So far, here's my thinking on the subject:
* Inciting "spin" to the air, through any means, has an inherent drag/entropy penalty, and an inherent energy harvest in the form of torque opposite the new wind flow.
* A fixed stator develops this thrust, and transfers it to the duct directly, where it is unwanted, and causes more weight to be necessary in the mounting equipment...to counteract the torque & hold the assembly in place.
* A counter-rotating, >= 2 stage, turbine still incites an amount of spin to the air, which still improves the efficiency of the 2nd stage, but the first stage actually transfers most of the torque it develops to the drivetrain. Thus increasing energy output, reducing necessary weight, and improving overall torque/drag ratio i.e. efficiency.
*CON: Using this design necessitates some form of mounting hardware where the stator had performed this function itself. I still believe it can be mounted without suffering losses high enough to negate the improvements listed above, but haven't developed a model to test it on yet.

5. I studied lasers in-depth about 14-16 years ago, so I'm fairly well educated in basic laser tech. This is actually what caused me to see the poss. benefit of the compressor stage to us (just had to see it as a "mirror" first), but now you're being cruel by making me dig THAT far back ;)

[robherc]

Oh, by-the-way, it took about 23 minutes' thought, and 2.5 minutes' typing to post that reply. Now, 30 minutes later, I believe I've reached at least stage 3 :cool:

[yipster]

without thinking just recalling what i've read lately...
big bended blade tips seem to give notable better result
so how bout a virtual ducted counter rotating mill ?
tv last night here showed vibrations and forces in mills

[robherc]

yipster

Yes, as I recall, the "bended" blade tips you're referring to are usually called "swept blades" on aircraft and were developed to reduce the tip speeds on near-sonic aircraft. might work really well if you reversed the sweep for our purposes...I'll have to think on that some.
Also, yes, I do think there would be significant gains realized in your "virtual ducted counter rotating mill" as opposed to a "normal" unducted turbine. I think there would be a bit more room for progress with a ducted fan, but you are probably on to something quite useful. Who knows, you may even be able to tweak that idea enough to compete with, or beat, most ducted designs. Go for it! :)

[MPraamsma]

robherc,

Thanks for the feedback and the observations. To reflect on what you said about the torque developed at the stator, it is not that severe a force because the stator doesn't rotate. The way I envision this type of thing in practice is always to use high speed rotating turbines with high gyroscopic and other forces in pairs. These would have opposite blades, rotations etc, to cancel any of these gyro forces. The reason I am favoring this type of thing, is simply my gut feel as an engineer, to always find the system with the least number of moving parts. There is only one moving part in this arrangement, sitting on two perfect bearings. Sort of like the turbines at Hoover Dam, running continuously for decade upon decade.

It is possible to find a combination of blades and pitch angles that completely cancels axial thrust, but that would only be at one particular speed and load combination. Since this might vary widely as conditions of speed and wind vary, it seems better to render any residual forces moot by confining them to the vertical (Z)axis. This (Z)axis is immobilized by the fact that we are dealing with either vessels or vehicles, which are free to only move freely in the X and Y planes. Turning the turbine 90 deg is the best way to prevent any residual forces affecting the motion of the vessel/vehicle. Also, any excess force could be used to help support the weight of the rotating components.

Your visualizing this as an energy mirror is the key.

[MPraamsma]

robherc,

To elaborate on your question of the compressor purpose, it is to 'pump' up the pressure to the next stage of the venturi. All venturis are essentially the same basic shape, about a 4:1 reduction in area. It is not possible to make a venturi that has 20:1 for instance, because it would stall. The (bent 4:1) inlet is part of the initial 'on ramp' to get the air moving as fast as possible using just the motion of the vehicle. Even if the vehicle goes 50 MPH groundspeed, the duct still only goes 200 mph. However, if you place a propeller in that flow, it is already going 200 mph! We want to kick it up a notch to around 500~600 mph after it squirts out of the stator exit. The stator exit is the highest stage of venturi throat in the system.

The object of the optimization is to direct the fluid (air) through the smallest possible venturi at the highest possible speed. Also, we want the blades to be as short as possible so they don't need any twist. This is best done by arranging the geometries to favor a very narrow, large diameter annular shaped prop chamber with lots of short stubby blades.

[robherc]

Mike,

I understand your strategy of going for the fewest possible moving parts. i can very well appreciate that as MANY, MANY of my own designs/improvements I've come up with were created with "simplify" as my watchword; it does VERY MUCH improve the reliability of many end products. In this case, though, I think there is a statistically significant amount of energy to be harvested here, which could counter-balance the losses due to increased number of moving parts. I don't know here ,but I think I'll pursue the contra-rotating turbines a bit further myself before giving up on it.

As far as the Z-axis turbine concept of yours, I still have yet to be convinced that it will achieve what you're expecting of it, due to the reflection of the forces in the duct (I'm looking at the duct as a mirror as well) "bending" the force back onto the X or Y axis. I'm not sure of this, it is just my theory, as the opposite is yours, so I won't attempt to argue you further on this point until one of us has experimental results to support our case (since we're obviously not going to convince each other any other way).

I understand fairly wall what you're saying about the compressor helping to prevent the venturi from stalling. I'm not completely sure that you'll end up gaining any useful amount of power this way, but I don't see any real flaws with your principle there...I'm just not sure of what the ratio of losses would be. This DOES seem like a good way to enable yourself to reduce the size & weight of your turbine though, so to that end I believe you're definitely on to something.
My one nagging question immediately after reading your last post, however, is does the stall-ratio of the veturi depend on speed? Or is 4:1 fairly well universal? In my mind, it seems that it would remain fairly fixed, but I'm sure I've seen aircraft that successfully used as high as 8:1 ratios before the first compressor stage, without stalling their ducts...is there something I missed there, or do I just need to recalculate my area measurements & see that they're really at 4:1 & just LOOK to be running higher ratios?

[MPraamsma]

robherc,

Yes, the stall point varies depending on the pressure, temp, speed and venturi design. If you have tons of pressure on one side and a vacuum on the other, it would be possible to make really high ratio venturis, but at atmospheric pressure and temp, and normal speeds of vehicles, we can say that a naturally aspirated duct won't go over about 4:1. On jet aircraft, the inlets are very modest, around 1.5:1 to 2:1 because they are already flying near the speed of sound, and shocks will form if the flow reaches supersonic speeds. After each row of blades, the pressure increases, and the duct gets a little smaller, until at the end the ratio could be very high. Each time the flow passes a row of blades it is still travelling at the local speed of sound, which is changing as the temp and pressure increase. By the time it reaches the combustion chambers it is almost (relatively speaking) standing still, and is at a very high temp and pressure. (That's probably because blasting air at 50 degress below zero going at 600 mph into a combustion chamber doesn't seem to work very well, ...lol.).

In nature, air can only expand, it cannot compress and raise in temperature unless power (heat, mechanical input) is transmitted to it. Nature only has venturis. When heat (thermal or mechanical) is added to air, the velocity of the molecules increases, and so does the speed of sound. Our feedback of power from the output accomplishes this, and boosts the flow into a more efficient flight regime.

In our case we want to keep in mind that the mass flow is the same at each point (section) in the flow once it reaches a steady state. In other words, the same volume of air goes in the front as comes out the back. In the perfect venturi, the flow is adiabatic, meaning no energy is added or extracted, and the molecules do not change their speed, just their direction. Once you introduce a compressor element, that all changes, because now you can introduce additional energy into the flow temporarily, and retrieve it later. This pushes the flight regime higher while it is acting on the turbine.

After the turbine, all we need to do is return the flow to the ambient stream at a slightly lower temperature, but the same pressure. This is a matter of the inlet and outlet ratio, which don't have to be exactly the same. In fact, a variable exit geometry seems like the answer here, like flaps to control the discharge flow.

[MPraamsma]

robherc,

I made another little diagram of how the ducts can be arranged side by side to make a payload space.

[robherc]

Aha! So you're not planing on putting these turbines on a tower up in the wind at all, but more having them BE the gunwhale of your boat? Wouldn't that cause issues with water aspiration into your turbines (from waves)? So, are you trying to design your venturis to reject the water, or your turbines to be sturdy enough to handle the water w/o damage?

Or did I mislead myself, and you're still planning on mounting the ducts on a tower, just with payload space between them?

[MPraamsma]

robherc,

Before I even consider that aspect of the final configuration, I want to try and get the ideal generator concept. Maybe there is a way to integrate the duct into the entire hull in some fashion. The payload space is already sort of boat shaped. I think even some sort of hydrofoil arrangement might help keep everything out of the water. I am still looking at it as a vehicle too.

[robherc]

You could prob. use some form of counter-weighted louvers to allow MOST of the water to escape, if you put the ascending portion of your bent-venturi forward. That should allow MOST, if not all, of the water to escape (and it'd solve our disagreement about the bent venturi improving efficiency...it'd no longer matter as the bent venturi is now necessary to prevent aspiration...lol)

I'll work on an illustration to show my idea...post it in a couple minutes once I've completed it.

[robherc]

Ok, sorry about hijacking your diagram, but it made my job a bit easier ;)

[MPraamsma]

Robherc,

Actually, the duct needs to be hermetical sealed all along it's length. The pressure at the end of the first venturi section is about .3 atmosphere at the throat. If there are holes, air will leak in and spoil the flow. The duct is subject to an outside crushing force of about 9 lbs./sq. in. near the throat.

[robherc]

Have these pressures been measured, of are they only theoretical? I'm sorry, I'm not completely seeing the physics behind the reduced lateral pressures at the throat of the venturi.

[MPraamsma]

robherc,

Air molecules are always moving individually at the speed of sound thereabouts, and constantly crashing and colliding into each other. In stagnant air they are statistically moving in every conceivable direction, so that the pressure is static, and there is no flow. If they pass into a venturi inlet, they are deflected towards the centerline by the venturi walls. Of course, there are other molecules on the other side of the centerline that are being deflected the other way, and these all interact so that statistically more of them are moving towards the throat than any other direction. At the throat, most are moving in the flow direction, almost none are moving against the flow, and very few are able to strike the wall except at very oblique angles. The sum of all these motions is still at the same potential as the original static condition, but now are converted into ram pressure along the axis, and correspondingly less pressure is exerted against the walls.

Any holes into the duct would allow atmospheric pressure to bleed into the low apparent pressure inside, and would tend to frustrate the flow. In the old carburetors this principle was used to draw fuel into the air stream. It is clear that it would be impossible to get the flow to go faster than sound through the throat because that would mean the molecules had aquired some additional velocity.

[MPraamsma]

Robherc,

To elaborate a little on that last post, the characteristic shape of the venturi is due in part because the 'disturbance' created by the venturi wall has to have time to propagate into the bulk of the flow. If the angles are too steep, then this is not enough time for this 'equalizing', and if the walls are too gentle you are simply getting diminishing returns. At some point the ideal venturi will satisfy the design needs for a set of conditions of speed, temp, density and scale.

[robherc]

OK, that works for me for an "ideal" venturi, but I don't think the counter-weighted louvers in my drawing would have any significant impact there due to the following:

1. They are effectively "one-way" valves in that they will swing open, under enough force, to let water out, but would strike against stops (either built into the duct, or the louver before them) if they tried to open inwards...os no significant airflow would be admitted there.

2. I intentionally drew them at the very highest wall-pressure position in your duct...where many/most air AND water molecules will be striking the wall of the venturi for the first time, so no collimating effect has yet been enacted on them. This means that the air-pressure inside the duct will be slightly HIGHER than 1 atmosphere here, and that any water in the duct will be exerting the most possible force to open the louvers & drain itself here.

I haven't physically tested these statements, so they are open to argument, but I'm quite sure of them nonetheless.


Also, on a similar topic, won't your "bent venturi" duct suffer dramatic efficiency losses due to having to redirect & collimate the flow into not one, but 4 directions sequentially, relative to the craft? (Vertical [up], then horizontal [right], then vertical [down, through the turbine], then horizontal again [right, out of the duct])

[MPraamsma]

robherc,

I think you still have a misconception of the flow dynamics in a venturi. The fluid doesn't try and sqeeze through a small hole (the throat), it sees nothing but a low pressure region ahead of it, and wants to expand into it. There is never a point where the pressure is higher than atmospheric.

The entire problem of water ingestion is not very important because it would be easier to place the duct high enough to avoid the problem, and also because venturis are notorious atomizers of liquids. That water will go through like a fine mist, and actually might add to the propelling force since it is more dense than air.

As for the bent shape, all I show is the characteristic shape, it could be stretched to be more gentle. Surely there will be some forces developed, but since the duct is symetrical fore and aft, these forces are mostly cancelled.

Just remember the basic principle of lift, that a small pulling force can generate a large lifting force. Some people might consider that a mechanical amplifier. All we are trying to do is to bend, twist and redirect our flow to insist that the forces work for us and not against us.

[robherc]

I understand most of your theories here, but I don't think your bent venturi, unless it is stretched to an unweildy size, will have the "low pressure region ahead" effect on the fluid stream. The fluid (air) will still have inertia when it comes into contact with the first bend, and part of that intertia will still be exerted as >1Atm pressure against the duct wall. The eventuality of this will be entropy in the form of heat and fluid-friction (wear) imparted to your duct.

Even in your "perfect venturi" concept, I don't believe you will achieve an escape from SOME drag due to entropy & fluid friction, otherwise the airflow behind would delaminate, and be accelerated to the extent that the venturi would develop its own thrust equal to T=MS^2 where M=mass of air flowing through the venturi, and S=speed of sound. Menwhile, you would also be generating drag (vacuum wake) behind the venturi equal to D=Pi(S) where Pi=the pressure-incidence of the vacuum, and S=the surface area (cross-sectional) of the delaminated-flow area behind your venturi (the difference between the throat area, and the total area of the venturi, by cross-section).

I'm sorry, but I really can't seem to wrap my mind around that working....sounds too much like "quantum physics" to me...and I've developed on SEVERAL theories that disprove most "quantum" properties from being anything truly exceptional from the world of "normal" physics...when viewed from the proper frame of reference.

[robherc]

That said, I'm not negating the benefits achievable by collimating the airflow in a venturi...but I think we should exercise some caution in exactly how much we expect to gain; and realize that there will be losses incurred...we ALWAYS have to "pay the piper" in the end.

I believe that the venturi design will give us the improvement of a denser airflow over the turbine, with MINIMAL increased drag. Hopefully to the point of improving our Lift/Drag ratio of efficiency overall. I just don't want to get too excited and start expecting greater returns than are truly possible.

[MPraamsma]

robherc,

There are losses in all machines, it is a question of keeping the losses less than the gains. Try turning an internal cumbustion engine over by hand, and you might wonder how it could ever work at 5000 RPM! Remember the L1011 aircraft with the engine in the tail, it had a tunnel like inlet that made two 90 deg bends, one after the other. The duct was 8 feet in diameter, and the air went through it at 550 MPH. We are not suggesting that we should go that fast, we are looking at maybe 100 MPH vehicle speed tops. The main purpose of the complex ductwork is to position the forces so they don't fight us.

[robherc]

You're right, I just was starting to think that your descriptions of the physics surrounding the venturi duct as approaching a religious perspective ;)
...Wanted to make sure we weren't going to try to harness quantum dynamics on a wind-powered boat, that's all. hehee :-)

Anywise, we'll still just have to wait & see what the actual efficiency results of your bent venturi duct are in your first test. Meanwhile, I think I'm going to work on designs for a venturi-ducted wind turbine to power my next home (I'm buying land on an undeveloped section of beach)...so I guess I have gained useable knowledge from this debate, though the bent-duct would gain me nothing, as mine'll be a fixed-position turbine.

[MPraamsma]

robherc,

You are correct, a fixed system has no use for the twisted duct, a straight thru would be better.

I have attached a concept dwg of how I would approach the layout of a vessel using the ducted tech.

I have some other types of forgotten wind generator ideas you might be interested in for a fixed setup.

[MPraamsma]

robherc,

This idea was one done by an Austrian inventor named Oppholtzer. He built a huge model with scoops about 1 meter across that ran for months and months. However the politics of power generation in hydro-electric rich Austria killed it.

[MPraamsma]

robherc,

This is my version of that last idea. A ducted Oppholzer turbine, on a swivel base to always face into the wind.

[robherc]

A very interesting concept...and well thought out. I like his idea immensely, and your duct should improve on its efficiency a bit.
Unfortunately, however, I think it would end up having a higher cost (and amount of airspace used) per KWh than a venturi ducted turbine, in addition to having more exposed moving parts.

I see nothing truly "wrong" with the idea, just don't see it as the most practical for my own purposes. (and I've been in love with ducted turbines since I was a child, truth be told ;))

[MPraamsma]

robherc,

The design I show is for a masthead generator, but the same idea could work in other forms. The advantage of this approach is there is no adverse thrust, as the driving force is always purely axial (to the duct or axis to the wind). This arrangement could be made very tall without such immense towers used on conventional windgens. It is like two huge ferris wheels, where the wind strikes only the top. The recirculating end could actually be sunk below ground level.

[MPraamsma]

robherc,

As an engineer 40+ years experience, I never worry about the cost until the final concept is in place. Do you know what it costs to make a can of CocaCola?.....$10,000,000.......for the first one, $5,000,000 for the second one, $3,333,333 for the third....etc, etc.

[robherc]

LOL, as a strictly self-funded engineer with a fixed income, I ALWAYS worry about the cost before I even start building a prototype.
As the case may be, I can build turbine blisks fairly well with the tools, equipment, and experience I already have. Unfortunately, though, I don't have any experience making parts for a vertical-axis turbine (even if it's turned 90degrees) adn a few of the parts I'd need would take some experimentation to get their strength right. So, I think I'll stick with the concepts that I'm actually qualified to work with ;)

[MPraamsma]

robherc,

Same here, however I never start to build a prototype unless the concept is clear in my head.

[kistinie]

In your opinion what is the percentage of chance for succeeding in doing a light 25/30 feet cat or tri windmill boat going against wind straight using mecanical transmission and the 2 air and water pitch controlled by a clever controller ?
Tri are perfect for the project
But cat could be with two mills
shutting or slowing down the downwind one to prevent pitchpole
Pitchpole would be easy to control with blade pitch

50%
100%
More ? :-)


My opinion is... certain !

Others ? and reasons of doubt

[dsuursoo]

In your opinion what is the percentage of chance for succeeding in doing a light 25/30 feet cat or tri windmill boat going against wind straight using mecanical transmission and the 2 air and water pitch controlled by a clever controller ?
Tri are perfect for the project
But cat could be with two mills
shutting or slowing down the downwind one to prevent pitchpole
Pitchpole would be easy to control with blade pitch

50%
100%
More ? :-)


My opinion is... certain !

Others ? and reasons of doubt

well, to be honest, it'd probably be a 100% success, the question is: how fast could it go?

i'll warrant not very, myself. you'd be better off running on a tack with the wind to one side of the bow or the other. then you wouldn't be fighting a dead-on headwind and the drag from that.

i personally might go with just a cvt transmission and keep both turbine and prop fixed blade. many wind turbines are suited to a wide range of winds, and with the cvt transmission you could keep the screw turning at an optimal speed(or at least try to) for its shape.

much simpler and less work to keep in an ideal state.

[Rick Willoughby]

It has already ben done with success and was not a particularly good design. There is a photo of a large cat in one of the threads.

Such a system will not beat sail in most conditions but it does allow you to go straight to windward.

Rick W

[Windmaster]

You're so certain "it won't beat sail" - but how do you know? Anyway, what do you mean by "beat"? - vmg to windward?

[Rick Willoughby]

You're so certain "it won't beat sail" - but how do you know? Anyway, what do you mean by "beat"? - vmg to windward?

By beat I mean faster around any triangular course.

The reason I know is that I have done the calculations. The system quickly runs into mechanical power limits. If you beef up the mechanicals to handle more power then you add more weight and you need more power and so it goes on.

Rick W

[Windmaster]

Dear Rick

There are other criteria for wind-powered boats apart from racing around triangles. Such as practicallity, the fastest boat around a triangle is usually not very user-friendly practical or even useful.

Sailors (have you ever sailed?) have been dreaming for centuries about being able sail directly into adverse winds. Now it can be done, you dismiss it as not very important. It doesn't matter that you may not be able to go as fast as on other points of sail. The fact that it can be done at all is an amazing fact that some even now find impossible to believe.

It may be true that a wind-turbine powered boat can't beat a racing sailboat around a triangle (although it's never been tried) - the sort of conventional sailboat that's fastest in those circumstances is pretty useless for cruising, exploring or getting easily from place to place.
A boat that can sail directly into the wind is pretty damn useful as most would admit.
You've done lots of "calculations" - that stuff about mechanical power limits is just simply plain wrong - there are things about this you have not taken into account or don't understand.
I have found that "calculations" - are not enough to get a reliable answer - you need to try things out practically. I have built two working wind-turbine boats myself (see videos on youtube) plus a number of models. So maybe I know something about this. Have you done any practical testing yourself?

[Rick Willoughby]

I have seen your videos and they do not inspire me. I cover considerably more ground under my own power than you can with all that contraption and the best endeavors of the wind. I have learnt a little about efficient boat design and know a lot about the engineering of mechanical and electrical systems.

I doubt if you have ever handled a boat in heavy weather. If you had you would know the last thing you want to do is pound directly into the oncoming sea. Bear off a little and everything gets much easier. Somewhere around the pointing ability of a modern yacht is ideal.

A fast boat is a safe boat. Your boats are curiosities. They are not really practical as a means of covering any distance. They could be improved considerably with good propeller and turbine design but they still will not outperform a conventional sailing boat.

You could waste a lot of money trying to prove me wrong on this but nothing to stop you.

Rick W

[Windmaster]

Rick

I really think the power of the wind versus the power of your legs is no contest! I think anyone would think such a comparison ridiculous.
Can you go 24 hours a day and for weeks on end without rest? - of course you can't!
I certainly would not have called your boats "contraptions" before - but now you have introduced the term I really think your boats would qualify under the same heading.

Who said anything about heavy weather - you don't use your pedal boats in heavy weather do you?

If you know so much about turbine and propeller design why don't you prove it? Truth is - you've never made a wind-turbine boat, and, until you can provide evidence of your "superior knowledge" you can't really be taken seriously.

I challenge you to build one and prove that you are right! If you can do it and its better than mine then hats off to you!

Meanwhile,
You should really show politeness and respect for others achievements rather than claiming you know better, and trying to belittle others.

[Rick Willoughby]

I have proven it. You simply do not understand. I cannot help your lack of understanding.

The idea has been around for a long time and there have been some fair efforts at making the most of it. None have been spectacular in their success.

I have the proof. Like I said you go ahead and build something that proves me wrong.

Rick W

[yipster]

frends, good to see so many with the same interests :D

[Rick Willoughby]

Rick

.......
If you know so much about turbine and propeller design why don't you prove it? Truth is - you've never made a wind-turbine boat, and, until you can provide evidence of your "superior knowledge" you can't really be taken seriously.

I challenge you to build one and prove that you are right! If you can do it and its better than mine then hats off to you!

.........

Peter
Done and dusted. I have the data to prove it. Mine is faster than yours. And it was made with bits and pieces I had laying around. You have not bothered to acknowledge this. Instead you offer "proof" of a model pulling on a piece of string that your system is superior. You have your head in the sand. You have no scientific method whereby you actually measure performance. It is not good enough that it moves. It has to cover a certain distance in a certain time.

I will do one more test in favourable conditions to see what can be achieved and something for others to aim for. Then I will move on to electric to give a comparison.

Good luck with your fiddling.

Rick W

[Windmaster]

Peter
Done and dusted. I have the data to prove it. Mine is faster than yours. And it was made with bits and pieces I had laying around. You have not bothered to acknowledge this. Instead you offer "proof" of a model pulling on a piece of string that your system is superior. You have your head in the sand. You have no scientific method whereby you actually measure performance. It is not good enough that it moves. It has to cover a certain distance in a certain time.

I will do one more test in favourable conditions to see what can be achieved and something for others to aim for. Then I will move on to electric to give a comparison.

Good luck with your fiddling.

Rick W
Well done!
Now perhaps you will be happy. You are the winner! (Is that what you wanted?)
However, you don't have data to prove anything. To compare one thing with another you need two sets of data not one. This is only your opinion.
I have achieved my object. I have goaded you into making your version and gained a lot of useful information in the process.
To claim such a great success, I can only say that you must have a very low expectation of into wind performance.
The average of less than 4kph is about half normal walking speed.
Personally, I'm not interested in winning or losing, only in finding out the truth.
Time will tell. These conversations a kept a long time.
....

[Rick Willoughby]

Well done!
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....
Peter
Thank you for you gracious acknowledgment.

This was my first effort with a system I just threw together. It was far from optimal but it had no problem making good progress directly into the wind. It took me much longer to get around to test it than I anticipated. I will do one more test of this mechanical system. I believe I can get it to about 7kph directly into the wind in favourable conditions. If I had gearing and the right propeller I could get to maybe 60% of windspeed directly into the wind.

I will look forward to others taking on the challenge and proving what they can do. I am particularly interested in what Michael is doing as it might provide a new dimension.

Your system has some fundamental issues that will limit its performance but I look forward to some hard data from it. The variable pitch certainly has merit as would variable gearing as an alternative.

Overall I am even more convinced that electrical transmission, combined with electrical storage, offers by far and a away the most practical alternative to conventional sail.

This will be the path I follow.

Rick W

[Ad Hoc]

..Peter
Thank you for you gracious acknowledgment...

Wow, how humble and gracious, about as magnanimous as a kick in the face!

..You should really show politeness and respect for others achievements rather than claiming you know better,..

Ah, that requires acknowledgment of ones own limitations...and the respect for others. Wont get that. The desire and need to "be better" than others, just masks a deep rooted personality issue i fear. But as you say, which sums up pretty much most things in life:
..Personally, I'm not interested in winning or losing, only in finding out the truth...
Truth is far more important than my dick is bigger than yours..only those wishing to establish facts/truth understand this simple concept!!! Right and wrong is irrelevant....it is the "taking part"!