Inflatable wing sail ?

[xarax]

From http://www.catsailor.com/forums/show...86&page=2&vc=1
"I wonder why (any sailmakers please chime in here) someone has not developed some type of an inflateable wing sail, sort of like the parasail, only on it's side, that could be run up a conventional mast, with inflatable battens, more camber and more of a true wing shape, collapsable for storage too, made of mylar or a coated nylon."

[RHough]

Originally Posted by xarax

From http://www.catsailor.com/forums/show...86&page=2&vc=1
"I wonder why (any sailmakers please chime in here) someone has not developed some type of an inflateable wing sail, sort of like the parasail, only on it's side, that could be run up a conventional mast, with inflatable battens, more camber and more of a true wing shape, collapsable for storage too, made of mylar or a coated nylon."

It has to work on both tacks. A parasail will not fill and fly inverted.

[TeddyDiver]

It can be inverted. Installing a foil to the head of selfstanding mast (somewhat like lateen) it can be swinged upside down to chance tack. So there must be symmetry btw foot and head. In this case there no matter wheather the foil is "soft" or not.

[RHough]

Originally Posted by TeddyDiver

It can be inverted. Installing a foil to the head of selfstanding mast (somewhat like lateen) it can be swinged upside down to chance tack. So there must be symmetry btw foot and head. In this case there no matter wheather the foil is "soft" or not.

By inverted, I meant that a parasail will not 'inflate' to the designed shape if designed upper surface is on the bottom.

For a sail behind a conventional mast, it would fill and have the design shape on one tack but not the other.

Your idea of attaching the foil at the head of the mast is a very clever way to use a foil on both tacks ... well done.

In the context of A Class catamarans, I don't know that such a rig would provide a performance advantage.

[TeddyDiver]

Originally Posted by RHough

In the context of A Class catamarans, I don't know that such a rig would provide a performance advantage.

Neither do I but I love to play with the idea of having one for a gaff rigged ketch I'm building.

[Cheesy]

Originally Posted by xarax

From http://www.catsailor.com/forums/show...86&page=2&vc=1
"I wonder why (any sailmakers please chime in here) someone has not developed some type of an inflateable wing sail, sort of like the parasail, only on it's side, that could be run up a conventional mast, with inflatable battens, more camber and more of a true wing shape, collapsable for storage too, made of mylar or a coated nylon."

Sounds very similar to a kite surfing traction kite with a bottom skin and a mast added

[masalai]

From what I have read they MUST be worked continuously following a "figure of eight" pattern, to tack, jibe, but not if you have a mast in the way as it will wrap and cause grief (capsize?)

There was a utube posted here somewhere where a 23 ft beach cat & 3 guys had a lot of fast & wet fun but at the expense of very sore shoulders & arms (looked like the kite flyer was tied to where the mast was, one worked the tillers and the third got wet & rested...)

[Cheesy]

Not quite how I meant it, to me what Xarax was explaining sounded very similar to the construction of a kite, so if you imagine a kite made with no arc in it and a second skin on what would have been the bottom side attached behind a conventional mast.

From first hand experience they generally don’t need to be flown in a figure 8. This is only done when there isn’t enough wind and more power is required, it generates a massive apparent wind.

The sore arms bit isn’t entirely accurate either, the newer generation bow/flat kites have 4 lines, the front lines go through the bar (free to move up and down on the lines) and are attached to a harness (or boat) via a quick release the back lines go to the bar ends, the only load on the bar is steering and altering the angle of attack (generally less than most dingy mainsheet loads)

And the final myth, personally I can go up wind at a similar angle to a beach cat, not great but definitely going upwind, something other than a kite board is probably better still.

[TeddyDiver]

And with a rudder and a couple of flaps it could be done with a joystic.

[Erwan]

Hi Teddy,
A french guy , Phd in fluids mechanics tried a deltaplane wing on a short mast fitted on a Tornado plateform. It was at least 20 years ago, they sailed vs a mattia 18 on a very small lake near Paris, with no wave, nor wind, and concluded a slight advantage of the deltaplane system.
Later they went to the little America's Cup with an asymetric section wing with slot and flap.

They had a slight pointing advantage windward, as they could point highter, but the other challengers were sailing twice faster, and downwind it was worse.

Cheers

Erwan

[xarax]

Have a look at the "sailrocket" concept :
http://www.sailrocket.com/gallery.htm
An inflatable, pivoting sailwing would be much lighter,wouldnt it ?

[yipster]

Herreshoff two skin padded sail got banned for outperforming more conventional sails at the time, here another thread on (inflatable) wingsails
alinghi did experiment with inflatble battens at the last AC but i never read up on the results..

[RHough]

Originally Posted by yipster

Herreshoff two skin padded sail got banned for outperforming more conventional sails at the time, here another thread on (inflatable) wingsails
alinghi did experiment with inflatble battens at the last AC but i never read up on the results..

The battens work. They allow changes in stiffness with no weight penalty. IIRC they work well enough that a rule was made that they could not be adjusted during a race.

A problem I see with a soft foil is the shape depends on internal pressure. On a para sail the lower surface is cloth under tension and the upper surface shape depends on using some of the high pressure air from under the leading edge to inflate it. The energy in that air could be producing lift. There is a reason that high performance aircraft, like sailplanes, use rigid wing skins ... fabric would be lighter, but fabric does not hold the foil profile very well.

[ancient kayaker]

Many years ago I and a lot of other model plane builders got very good performance using fabric-covered wings.

There is some merit in this suggestion; a sail is close kin to a glider wing. A wing with one fabric surface is inferior to a wing covered on both sides.

An asymmetrical section is superior to a symmetrical section although planes designed for frequent inverted flight use symmetrical sections.

So we want an asymmetrical wing for this job, but how to change tack? I would want it attached to a mast to provide stiffness, kites may be fun but are not entirely practical. I considered this idea some years back and was considering pivoting the wing at its center and attaching it to a stub mast so the wing could be flipped over 180 deg, but I didn't like the thought of the rigging and what might happen when changing tack.

I also thought about collapsible wings which can be "furled" and reefed. I was considering sectional hinged wood battens that would change section when tacking, pivoted around the mast at their forward tip with the fabric running around the leading edge spar to take up slack.

I didn't think of inflatable battens. How would you inflate the battens? More to the point, how long would it take?

If you have a quick method then maybe the inflatable battens could be doubled, one set for each tack; you'd inflate whichever set you need. If you get into a situation where you need to frequently change tacks you could simply deflate both sets and go with a regular sail.

[xarax]

Originally Posted by ancient kayaker

was considering pivoting the wing at its center and attaching it to a stub mast so the wing could be flipped over 180 deg, but I didn't like the thought of the rigging...

. How would you inflate the battens?

Having the wing being dragged by a short mast forward through some lines simplifies the rigging of the classic mast/sail/battens configuration.
Now, we can have some high pressure inflated battens with the help of a pump , or the whole wing can be low pressure inflated by the wind, like in a parasail. The main advantage in both cases is a short mast forward (or no mast , as in the case of "sailrocket").