Inflated Wing Sails

[Doug Lord]

Interesting development from Scuttlebutt-includes video:

VIDEO: Is This The Future? >> Scuttlebutt Sailing News http://www.sailingscuttlebutt.com/2017/08/22/video-is-this-the-future/?utm_medium=email&utm_campaign=Scuttlebutt%204902%20-%20August%2023%202017&utm_content=Scuttlebutt%204902%20-%20August%2023%202017+CID_408c7bd787eff9f777ca6f3a5c64b72c&utm_source=Email%20Newsletter

 

[David Cooper]

A telescopic mast will surely be heavy or weak, but I suppose that's a side issue. As for the sail, apart from the twist it appears to be symmetrical, which might work at the front but it can't be ideal at the leech. What's needed is asymmetric supports inside which can rotate during tacks, and the sail needn't even be inflatable. Different angles of rotation of the supports could tune the sail to different shapes while extending or contracting their length to take up any slack.

 

[CT249]

Yes, symmetrical wingsails have been tried on monos for about a hundred years and never performed. There's no evidence of them doing any proper objective testing. The one pic where they show the wingsail against a comparable boat is in Lasers, and they were comparing an elliptical sail to the 1960's designer Laser rig in a test in which it appears that the conventional Laser was being sailed way too heeled (significantly more than the wingsailed boat) and with poor sail trim. Okay, it's only one pic but if they want people to be impressed why not provide some proper information?

People have been spruiking wingsails for eons. Tom Speer and Mark Drela have explained the issues that wingsails face here on BDF, and explained why they work so well in some types but not so well in others.

 

[Dolfiman]

Dear Doug Lord,

This other video of the same concept, with interviews (in French) of the two Swiss co-designers Edouard Kessi and Laurent de Kalbermatten. Laurent explained that he previously developed such inflated wings for paragliding and ultralight planes, and then, with Edouard and for fun, they tested one of this wing as such on a boat. As it worked quite well, they decided to develop more seriously the concept to really adapted it for a sailing boat, so this prototype (tested on Lake Leman). The sail is inflated thanks to a light overpressure, the mast inside is telescopic, all can be folded as showed at the end of the video. They are now looking for a more consistent budget to develop the concept at a scale of 12-15m sailing yacht

 

[Dolfiman]

... + more info and sketchs of the wing in their site : Inflated Wing Sails | concept http://inflatedwingsails.com/en/concept/

 

[Doug Lord]

Thanks for the additional info!

 

[Konstanty]

The symmetric cross-sectional view is a disadvantage. Look at this inlet of air: 2 metre rc trimaran project https://www.boatdesign.net/threads/2-metre-rc-trimaran-project.45945/page-2

 

[Dolfiman]

Video of their last test by 30 knots on Leman Lake. The rig structure seems ok, good point, but the 5,5 m heavy hull does not help to judge the speed potential especially downwind, and the sea state of the lake is not in relation with 30 knots. They should now test it in more open sea with real waves, and put their sail on another support, e.g. a boat like Melges 32 :
Inflated Wing Sails | IWS sailing in 30-35 Knts http://inflatedwingsails.com/en/iws-sous-bise-noire-30-35-nds/
Inflated Wing Sails | video http://inflatedwingsails.com/en/category/video-en/

 

[griffinb]

The symmetric cross-sectional view is a disadvantage. Look at this inlet of air: 2 metre rc trimaran project https://www.boatdesign.net/threads/2-metre-rc-trimaran-project.45945/page-2

Seems like some kind of internal wires/cords/frames inside the wing should be able to alter its section (for each tack).

 

[JosephT]

The inflatable sails appear promising indeed. The reinforced boom structure looks well built and up to some serious wind action. Aerospace is already using semi-rigid inflatable structures so this transition makes sense. Definitely going to keep an eye on this! The aesthetics of the inflatable wing (that's what it really is) look good too...reminds me of the Michelin man!

 

[JosephT]

Another thought...I don't know the detailed spec on the inflatable sail, but a HUGE potential benefit would be preventing a capsize. Provided the sail retained its buoyancy that could save lives and minimize damage to on-board furnishings & equipment.

 

[Konstanty]

Seems like some kind of internal wires/cords/frames inside the wing should be able to alter its section (for each tack).

Internal wires/cords/frames are used to putting up the sail and reaction to compressive force from the sail. A flat - convex cross-section of the wing would form from a triangle dystrybution underpressure on the leeward side of the sail and overpressure on the windward side. In addition, in the front middle area is hypertensive from hyper tension point at the top. On the windward side, the diaphragm rests on slats and a frame with wires.

 

[Konstanty]

Look at this: Goodyear Inflatoplane | Aircraft | http://www.fiddlersgreen.net/models/aircraft/Goodyear-Inflatoplane.html

 

[captaingregger]

I love the concept and design. For me it would have limited use due to the required maintainence of the internal inflated bladders. I kitesurf pretty regularly. Bladder valve delamination is an issue for us. Some address it by decicated gear days to their kites, days they spent fixing/ repairing bladder valves or pinhole leaks in the bladder itself. Others address it by buying new kites ever year. Most sailboats sit for long periods inbetween usage. It's that sitting in the hot sun that would eentually cause valve delam. Until the industry comes up with new tech to address this, I don't see this concept as all that useful. Imagine showing up to sail that day and upon hoist the entire sail deflates. But all that said, if the manufactuers of these sails could streamline the bladders down to one or two easy access points for a user-friendly repair, and/ or use a more robust bladder in the first place (the trade-off is a heaviery bladder means more weight aloft), then it could be commerically viable.

 

[CT249]

Interesting points; thanks for that.

I'm still very conscious of the fact that time and time again, the information from experts like Tom Speer and Mark Drela indicates that a wingsail is not faster per se. The only information we can see about their comparative trials shows the inflated wing sail Laser sailing against a Laser that is poorly trimmed and being sailed by someone who is not hiking hard and allowing the boat to heel. That indicates that they were trialling an elliptical outline sail against a Laser that would be at least 2-4 minutes slower around a typical race course than a properly sailed Laser, so it's not a valid trial.

It's odd that time and time again we see people coming out with various wingsail concepts who make big claims but never seem to make the simple step of providing objective evidence by putting their boats in races against comparable craft. You wouldn't buy a used car if the only evidence of its superiority was a pic showing one up against a poorly-driven and untuned competitor so why would we buy a rig on the same sort of evidence?