Sky Sails

[djh]

Don't be to surprised if you see some on the Navy's ship's

Do you know something or are you just speculating?

[djh]

kites get lots of their thrust from movement across the wind at several times the speed of the wind. Boat kite wouldn't be able to do that I guess

Yes, they do figure-eights. The box under the kite, where the bridle joins the tether, contains the control unit to tweak the bridle length and control the flight, AIUI. That automatic control system, plus the launch/recovery system, are the most interesting bits.

There's a picture at http://www.skysails.info/typo3temp/pics/079ac34fb4.jpg

[djh]

It looks to me as though the problems, with this beautifully simple idea, revolve around deployment and recovery. The youtube video only shows the first stage of recovery. It must be difficult to collect the aerofoil without damage in serious wind.

Indeed, the launch and especially recovery systems are the bits that have taken a while to get sorted. But the situation isn't a disaster. You control all the circumstances at launch, so that's not really a problem. And you control when to recover the sail, so if it starts to get too windy, you can recover the sail before the problems get worse.

I don't know if they do this, but in bad conditions you could release the outer bridle lines to take wind out of the sail. Ultimately, of course, you can just cut the tether.

[charlieb]

I don't know if they do this, but in bad conditions you could release the outer bridle lines to take wind out of the sail. Ultimately, of course, you can just cut the tether.

Kitesurf kites have a number of variants on this idea for spilling the power from a kite. As long as you have at least two lines (they'd have at least three I imagine)  I don't see any insurmountable problems with launching or recovering these things from the deck of a big container ship.  It could even be helium-filled to mainain buoyancy which means it could be winched back to deck with virtually no wind-drag at all.       Big old sail-boats had much more serious problems in my mind, and they managed pretty well with no other motive power at all.

[Greenbeast]

I don't know if they do this, but in bad conditions you could release the outer bridle lines to take wind out of the sail. Ultimately, of course, you can just cut the tether.

Kitesurf kites have a number of variants on this idea for spilling the power from a kite. As long as you have at least two lines (they'd have at least three I imagine)  I don't see any insurmountable problems with launching or recovering these things from the deck of a big container ship.  It could even be helium-filled to mainain buoyancy which means it could be winched back to deck with virtually no wind-drag at all.       Big old sail-boats had much more serious problems in my mind, and they managed pretty well with no other motive power at all.

Quite, and sailors have been good at modulating the available sail, based on the wind, for hundreds of years