Sailing ships with a new twist

The Economist (Paid subscription required) ^ | Sep 15th 2005

[Polybius]

Its just a spinnaker...

Just what we need.......cargo ships that can broach. :-)

[The_Reader_David]

Okay, but can they tilt the kite so that the lift from the wind blowing obliquely to the direction of travel helps pull the ship? If so, then there would be
an analog of tacking.

Hmm, someone suggested helium: if one filled some of the chambers with helium and others with air, one could get the kite to tilt, making a sideways airfoil like a mainsail. Is there a way to do that within the parameters given in the article?

[USFRIENDINVICTORIA]

"... get the kite to tilt, making a sideways airfoil like a mainsail. Is there a way to do that within the parameters given in the article?"

The article didn't provide too many other details about the technology. Your idea seems reasonable to me.

Kite-boards can literally run circles around sailboards. They can also jump over them if they have to -- but, I don't foresee freighters getting much air. :-)

[pabianice]

Not mentioned in the article is that these new sailing ships will also have a new auxillary drive, the Sterling Perpetual Motion Machine, driving a coaxial, transwarp, variable dimension propeller.

Details available at http://www.spacealiensarecontrollingmybrain.com.

[USFRIENDINVICTORIA]

Skeptism is healthy -- so far this is just a concept. However, you've also maligned a couple of proven technologies.
:-)
Excerpted from: http://www.gombergkites.com/nkm/hist1.html


"The exact date and origin of the kite is not known but it is believed that they were flown in China more than two thousand years ago. One legend suggests that when a Chinese farmer tied a string to his hat to keep it from blowing away in a strong wind, the first kite was born. "

Sterling engines exist; and they stop moving soon after the fuel runs out.

[USFRIENDINVICTORIA]

After TChad posted his picture, I went to the Sky Sails site, and found this picture, which does a better job than I could of explaining the upwind thing, and establishing the limitations. It seems that the minimal heading is 50 degrees from the wind.

[TChad]

It almost looks as if they, by using the variable tracting point, could tack.

Sure does. I bet that the software that runs this was not trivial to write.

One advantage of this design is that heeling of the ship in response to wind is minimized.

[TChad]

One advantage of this design is that heeling of the ship in response to wind is minimized

As I now see was already mentioned.

[Richard-SIA]

And when the wind suddenly reverses?

How many of these kites does a shipping company lose before they stop buying them?

I expect few takers for this product, just not that reliable, or cheap!

[ApplegateRanch]

God forbid they drop a reactor in, and replace the diesels altogether.

[mrmargaritaville]

That looks like some kind of freaky Dolly Parton lingere.

[ApplegateRanch]

I wonder how often the kite has to be fished out of the ocean.

If it doesn't pan out, at least they could use it as a sea anchor.

[telebob]

All very interesting but the upwind component is just not worthwhile. The vari-trac gizmo is just there to change the kites attitude to the hull, not for tacking. The more the ship is sailing downwind, the closer to the bow the kite is sheeted. Closer to the wind, the kite is sheeted aft.

The kite will not tack. It will collapse. Even if it could tack, it would now have the normal trailing edge (leech) as the new leading edge (luff). It is not a symmetrical foil.

50° to the wind is nothing to write home about. In practice it would be a bear to try to sheet in every puff, lull and oscillation and I would imagine that steering a wide, heavy ship up and down the apparent wind angle would be out of the question.

This thing could have some practical applications but time is still money in the shipping business and wandering all over the ocean will not be popular with shipping agents, port authorities who are expecting your arrival or customers.

[TChad]

If it doesn't pan out, at least they could use it as a sea anchor.

Might do better as a liferaft.

[Fraxinus]

There are some shipping routes where it would give significant savings. There are others where the savings would be minuscule.

On those routes where you have strong steady and predictable winds this would be an excellent way to increase the fuel efficiency of the ships propulsion system. If the wind is going against you pack this devise away and crank the engine. If the winds are with you fly the kite.

Also note that depending on the length of line this kite could be catching the wind as much as 300' above the ship. The winds are normally steadier and stronger at higher altitude.

[Abathar]

That makes a lot more sense - Thanks for showing this. I have one question, what happens when the wind dies and this thing goes into the water, how much of a problem is it to get it back aboard as the ship will pass it by?

[MeanWestTexan]

The fact that this is (partially) filled with helium (patially) solves the the problem with luff.

That said, I think sticking wings of old DC-10s on the deck with some clever software and adding an adjustible keel would be a better solution.

There are also metal rotating cylinders that can be placed together that work well --- this was the big idea just as steam came along and replaced sails, as you could tack just shy of directly into the wind. Just a few years ago, I saw lots of small boats in the Phillipeans (sp?!) with things that looked for all the world like twin toilet paper rolls spinning where a mast would be --- apparently very useful in shifting wind currents and easy to maintain.

[norraad]

Most important problem, as usual, flys over the head of brainiacs;

All shipping companies have lowered payroll to the slavewage level.

They'd rather continue to buy black-market crap fuel than pay anyone to fly a kite.

[MeanWestTexan]

"what happens when the wind dies and this thing goes into the water"

I believe it has helium cells, so it remains lighter than air.

[USFRIENDINVICTORIA]

"... what happens when the wind dies and this thing goes into the water,..."

It will be interesting to see how well the prototype the company says they're building will work out in practice. As some others have pointed out, the winds are steadier a few hundred feet up, where the kite would be flown. The rest would be up to the autopilot software. As someone else mentioned, that would not be trivial code.