another idea

[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=0VL...j3IFY#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]

Originally Posted by 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.

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]

Originally Posted by 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

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]

Originally Posted by 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.

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.?