Kites, Parafoils and Parasails - after a Demasting?

[transmitterdan]

Originally Posted by s/v Beth

Nobody has mentioned the utility of a kite for rescue. I thing an orange thing hanging 300 feet in the air would be a good thing.

The helicopter or C130 pilot won't like it very much. Better to send an EPIRB message. It goes farther.

[barnakiel]

I too think a rescue orange kite could be used both to attract attention in emergency and to tow one downwind. I think this may work.

b.

[seandepagnier]

Originally Posted by Cotemar

They have automated Kite systems also. Those are the ones cruisers would end up using. They are programmed to do the figure eight, so they make a higher apparent wind and faster stronger pull.

Please give more details. Is it fully mechanical, or does it use computer control. How does it work?

Originally Posted by transmitterdan

Would a helium balloon give enough lift to the "head" of a small lightweight asymmetrical sail so a mast was not required to launch it and keep it flying? Wouldn't take up much space until needed. There is quite a bit of helium in those party tanks at Wal-Mart although they are steel and would rust out in about a month. But an aluminum high pressure canister can hold quite a bit.

No, at least not on a small scale.

The problem is you need a lot of volume of helium to lift things, and this results in an inefficient kite. On a small scale, it is of course possible, but the pointing angle would be less, and the kite would produce a lot less power downwind as well because it couldn't fly in a figure 8 very well.

There are also problems with deployment and obtaining the gas. You can use hydrogen but it takes energy to produce and leaks easily.

Originally Posted by s/v Beth

Couldn't a kite be designed to not require much movement, but rather just sit there and pull? It seems to me that is what regular kids kites do. I know this sounds silly, but how about a regular kite only larger- like a box or similar- that would just sit there and pull. The only other requirement would be a way to depower the kite when the wind got too much, maybe a second string (could also act as a tail) to pull on when you want the kite to collapse.
Nobody has mentioned the utility of a kite for rescue. I thing an orange thing hanging 300 feet in the air would be a good thing.

Yes, probably, but it wouldn't develop much power for it's size.

How about a glider instead of a kite? With control surfaces (and servos controlled by a computer) and it can fly in a figure 8 as well as other patterns, but also easily "land" on the boat when reeled in. It would be more efficient than a kite (but likely heavier) being a fixed wing but simplifies a lot of issues with the kite.

Also a possible combination is to use fixed wing sails on the boat which allows pointing very close to the wind, and good overall performance (without planing), but if the conditions allow, launch a kite and travel at a higher speed.

[estarzinger]

For the kiters . . . The figure 8 thing downwind . . . . Is that simply to get 'more' apparent wind/power/speed . . . . Or is it necessary to get "any" power/speed?

If it is the first ('more'), then it is really not necessary in the dismasting situation. Then you are happy just moving, even slowly, in roughly the right direction.

[colemj]

Originally Posted by estarzinger

For the kiters . . . The figure 8 thing downwind . . . . Is that simply to get 'more' apparent wind/power/speed . . . . Or is it necessary to get "any" power/speed?

If it is the first ('more'), then it is really not necessary in the dismasting situation. Then you are happy just moving, even slowly, in roughly the right direction.

Kite sails are wings, so they need an attack angle and wind flow over them to work. They will stall downwind and simply fall from the sky. I suppose in good winds they will provide some power because they will be connected to a high-drag ship that won't let them fall off fast enough to stall - one could possibly hold them in position to work.

A parachute-type kite would be better at this.

I know you are looking for a solution to get a boat back to port, and not just to shipping lanes where a passing ship can be flagged down for a pickup. But those thinking along that line (or along the orange kite line) seem to forget that is what an EPIRB and similar modern communication devices are for. If one plans to be "rescued" in this type of event, it is inconceivable to not have EPIRB's as plans A, B and C.

Mark

[colemj]

Originally Posted by boat_alexandra

No, at least not on a small scale.

The problem is you need a lot of volume of helium to lift things, and this results in an inefficient kite. On a small scale, it is of course possible, but the pointing angle would be less, and the kite would produce a lot less power downwind as well because it couldn't fly in a figure 8 very well.

There are also problems with deployment and obtaining the gas. You can use hydrogen but it takes energy to produce and leaks easily.

I can't understand how it would work at all. Even a giant helium balloon would simply fall off the wind faster than the boat and the head of any sail held up by one would just fall off and down until no motive force was being applied. He was talking about holding up a spinnaker, not a kite sail. A balloon on a kite sail wouldn't be necessary and would probably interfere with its operation

Mark

[transmitterdan]

I was thinking that it just needs to hold it up until it fills with wind. Once the kite is filled it it will stay up on its own based on the various line lengths. If the wind dies the kite would stay up until the winds comes back up.