This won't work, will it?

Re: This won\'t work, will it?

[ QUOTE ]

Won't it just go downwind more slowly than windspeed?

[/ QUOTE ]

One half of the Amateur Yacht Research Society is busy trying to prove it possible to 'Go Downwind Faster Than The Wind'. The other half is busy trying to find even crankier ideas to propose.

Join in. You'll be in compatible company....

/forums/images/graemlins/grin.gif
 
Re: This won\'t work, will it?

There are lots of windmill-driven boats that can do that. What's harder is down-wind faster than the wind. There are lots of threads on this on the AYRS site. (Amateur Yacht Research Soc - a likeable bunch of nutty scientists just like me!)
 
Re: Theres nothing new....

Lord Brabazon fited his Bembridge Redwing 'Kestrel' with what he called an 'auto - gyro' in 1938 - a large propellor mounted on a steel mast, with a view to heading straight upwind. But I never heard whether it worked!
 
Re: This won\'t work, will it?

All a question of the wind generating enough propulsive force to overcome drag. Like an aeroplane engine, and it does not even have to generate lift.
 
Re: This won\'t work, will it?

Many boats have been built that use a wind turbine driving a propeller to go straight into the wind. The only thing that separates this one from others is that it appears to be unmanned, so that it will need some sort of steering to keep it facing into the wind.

The more interesting case is of sailing downwind. As we all know, as your downwind speed approaches the wind speed the apparent wind decreases thus reducing the available thrust from the sails. Going directly downwind, if the boat speed were the same as the wind speed there would be no sail thrust to keep the boat going and the boat would slow down.

But it is possible (by "tacking" downwind) to go downwind faster than the wind. The polar diagram for the Sydney Harbour Skiffs shows that at about 135 degrees from the wind they can have a downwind component faster than the wind, but that's not directly downwind.

In theory it should be possible to use the water propeller as a turbine driving an air propeller, thus driving the craft downwind even faster than the wind. It's just that AFIK no one has managed it yet!

PS I've just found my reference polar diagram. In a 10 knot wind at 145 degrees from the wind the skiff will make 15 knots, giving a downwind component of 12 knots.
("The Symmetry of Sailing", Ross Garrett)
 
Re: This won\'t work, will it?

This is old hat, there was one here on the Blackwater based on a Prout quest cat in the seventies. It did go upwind but not sure about running. We all thought it was a waste of a nice cat.
Could be quite confusing near the offshore windfarms when one starts moving though.
 
Re: This won\'t work, will it?

turbinex.jpg


"Falcon is an unusual boat and created for a wind power project run by the University of Glasgow in the early 1980's. It's a small yacht fitted with a windmill, and the small wind turbine on the boat enables Falcon to sail directly into the wind, which is not possible with conventional boats."
<ul type="square"> - Undiscovered Scotland: The Scottish Maritime Museum [/list]
 
Re: This won\'t work, will it?

Yes it will - but it's hardly new or ground breaking.
I climbed all over Cousteau's (spelling??) vessel 'Alcyone' in Freo about 18 years back. She was a pale blue cat, had a turbine set into a short but wide round 'mast' with a slot to to scoop wind and power her props.
Cheers
JOHN
 
Re: Theres nothing new....

[ QUOTE ]
Lord Brabazon fited his Bembridge Redwing 'Kestrel' with what he called an 'auto - gyro' in 1938 - a large propellor mounted on a steel mast, with a view to heading straight upwind. But I never heard whether it worked!

[/ QUOTE ]

As they only made the one, I guess the answer's no.
 
Re: Theres nothing new....

Brabazon's winmill Redwing is at the Classic Boat Museum, IoW. I have seen video of it or a replica in the past and will try to figure out where.
 
Re: This won\'t work, will it?

[ QUOTE ]
www.tecsoc.org/pubs/history/2002/may9.htm

[/ QUOTE ]

The Flettner Rotor ships were different. When the cylinders were rotated in a wind they were equivalent to an aerofoil with a circulation, thus giving a 'lift' at rightangles to the wind. When moving either directly upwind or downwind the force generated was at rightangles to the course and the rotors were ineffective. And they had to be spun, usually requiring electrical power.
 
Re: This won\'t work, will it?

I saw a piece on this on Discovery channel. It does work, but it is not effective. The boat can go dead upwind, but it does so slower than a conventional yacht tacking. I think they even had some kind of race in that show to prove it.
 
Re: This won\'t work, will it?

The trouble is that as you go faster the windspeed over the deck increases so that turns the turbine and the propeller faster so you go even faster, so the windspeed over the deck increases so you go faster etc etc until something nasty happens or the system is depowered by one means or another.

You dont even need any wind, you just need a little bit of push from a small outboard to get you started, then the turbine starts driving the propeller and the faster you go etc.etc.

They same logic will get you going down wind faster than the windspeed provided you have a bit of extra push to accelerate you that first little bit above the wind speed and bring the apparent wind onto the bow.

The article does not say if the drive is mecahical or electrical. The snag with a mechanical system is that it requires a reversing gearbox to accomodate the change from a following wind to an apparent wind on the bow. An electrical system in which AC is generated does not; the turbine simply spins in the opposite direction but the motor driving the prop continues to turn in the same direction.

The electrical system also has the advantage that some of the power generated can be used for on board electrical systems and the power for the "extra push" comes from batteries charged during the initial period, powering a second DC motor. Hybrid systems are also feasible of course. /forums/images/graemlins/wink.gif
 
Re: This won\'t work, will it?

Nah - I suspect the thrust is proportional to the speed, but the drag increases, with the square of the speed, or something like that.

It would be useful if you could add such a setup on a conventional boat, for manouvering in tight spaces under sail.
 
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