Why a kite?

[Glom]

A kite powered boat (http://news.bbc.co.uk/1/hi/world/europe/7201887.stm)

I don't get it. If you want to return to wind powered vessels, why not just have rigging like the old ones do. They look much cooler and can sail (well tack at least) into wind as well.

[Fazor]

The advantage to the kite-powered boats are that the sail is hundreds of feet in the air, and can take advantage of stronger winds.

[Argos]

As they say, the rigging is a hindrance to loading operations. Also, it is meant to be just an auxiliary system.

[undidly]

The kite is tethered to a low point on the ship so that the ship does not lean away from the wind as with a sail.

[Fazor]

Well, there's three very good advantages right there.

And as Argos said, it's not meant to be the sole means of locomotion...it's more to help reduce the cost of fuel, when the conditions make it possible to do so. Which is my fourth advantage: lower cost of fuel.

[NEOWatcher]

Which is my fourth advantage: lower cost of fuel.
4th advantage of doing it, but not necessarily an advantage over traditional sail.

Somewhat along the lines of this from the article.

could cut fuel consumption by as much as 20%.
They also hope the state-of-the-art kite will help reduce carbon dioxide emissions, as it tugs the ship.

"also hope" gives me the impression that it's not related. It may be one of those British things again. It just sounds bad to me, and could be better worded.

[Fazor]

4th advantage of doing it, but not necessarily an advantage over traditional sail.


I know, I thought that as soon as I hit that pesky "post" button. It's early, I haven't had any coffee, and forgot what we were comparing :lol:

Good thing it takes three swings-and-misses before you strike out.

[NEOWatcher]

Good thing it takes three swings-and-misses before you strike out.
Yeah...but I've lost track of how many times I've been at bat.

[JustAFriend]

Also.... a sail requires sailors with a knowledge of SAILING.

A kite just tows you. Less efficient, but requires no skills.

Another dumbing down of modern man....

[Fazor]

Another dumbing down of modern man....
So it takes no knowlege or skill to get a kite of that size hundreds, or thousands, of feet up into the air? And actually, the kite system is steerable. Finding a more economical way to propel a ship while not sacrificing cargo space is not "dumbing down", IMHO.

[Frog march]

I wonder if it would be possible to have a whole string of these sails, going up into the sky, like these?

7033

[tofu]

A sail works because the canvas creates the shape of a wing. I wonder if you could just mount a giant aluminum airplane wing on a ship and get the same effect. You wouldn't need rigging, and the sail could be folded down in port. It's thin so it wouldn't take up too much cargo space (to be economically viable, it'd have to save more in fuel costs than is lost from carrying less cargo). And a computer could control it.

http://www.maj.com/gallery/tofu/babb/sail.gif

[NEOWatcher]

... I wonder if you could just mount a giant aluminum airplane wing on a ship and get the same effect...
Yes... and that has been proposed before.
I have a vague memory of a decades old PopSci where a ship of that type was illustrated on the cover.

I do like the kite idea better though. A wing concept will have a lot of the same limitations of a sail (stability, cost, takes room, etc).
I don't know the aerodynamic advantages, but I can't see them as being a major factor.

[tofu]

A wing concept will have a lot of the same limitations of a sail (stability, cost, takes room, etc).

I'm guess the "takes room" part is what makes it impractical. You'd lose one whole row of cargo containers.

But a sail can do one thing a kite can't, it can go upwind.

[01101001]

I wonder if you could just mount a giant aluminum airplane wing on a ship and get the same effect.

Less complex might be the turbosail (http://en.wikipedia.org/wiki/Turbosail) in Cousteau Society's Alcyone. But, that didn't seem to revolutionize sailing.

http://upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Rotorship_Alcyone_in_harbour.jpg/180px-Rotorship_Alcyone_in_harbour.jpg

Navy Ship Propulsion Technologies: Options for Reducing Oil Use -- Background for Congress (http://www.ibiblio.org/hyperwar/NHC/CRS/propulsion.htm) has a few pages on wings, kites, even solar-electric. (One anlysis of a wing said: "Collapse of world oil prices destroyed the economic case for use of wingsails in commercial shipping...". Ah, the price collapse. I remember it fondly. I guess maybe wingsails are worth another look now.)

[TrAI]

A kite powered boat (http://news.bbc.co.uk/1/hi/world/europe/7201887.stm)

I don't get it. If you want to return to wind powered vessels, why not just have rigging like the old ones do. They look much cooler and can sail (well tack at least) into wind as well.

Well, let them try this way, a certain amount of trial and experiment is not a bad thing, you know...

Now, I am not really much into the workings of sail and ship related things, but wouldn't it be possible to design a loading crane where the crane had a large tubelike thing in the middle, that could be used for mounting a mast for a modern variation on traditional sails, or as a base for some sort of rotosail, turbosail or some such? The tube would have to be strong enough to withstand the forces from having a sail mast in it, and I would think it would have to continue down into the ship, so that not all the forces involved would be placed on a single deck, so I guess a bit of space would be lost...

[Moose]

A kite rig, even as a supplement, is probably not as efficient as a good spinnaker, although if the cable is mounted below the ship's center of gravity, it'll tend to raise the bow a bit which could be beneficial.

But I suspect a kite rig could be dangerous if a strong wind or squall were to suddenly come up out of nowhere. It seems to me that retracting it in seas could be dangerous, which limits its use. The cable could be a hazard as well if something were to go very wrong with the kite.

And as others pointed out, you certainly can't use one as your primary source of propulsion, you're almost certainly limited to running or an inefficient broad reach (http://en.wikipedia.org/wiki/Points_of_sail).

You're probably better off with a more traditional rig, like a sloop or gaff rig among others, that can take either a spinnaker or some jib or another as conditions warrant. The higher you can point into the wind, the better off you are in general.

[Stregone]

It can probably be deflated at will. To varying degrees so it can be retracted or even used in very high winds.