Wing Sails

Soon after the triumph in 2017, ETNZ announced: “An underlying principle has been to provide affordable and sustainable technology ‘trickle down’ to other sailing classes and yachts".
Although they cannot be obliged to follow this promise, the question of suitability of the current America's Cup soft wingsail design for regular sailing is highly in place. In physics, the "degrees of freedom" of a system is the number of parameters of the system that may vary independently.
In sailing, a number of operations are conducted simultaneously and continuously, and all of them are interconnected, like control of mainsail, jib and rudder. These would be three degrees of freedom that can basically be dealt with by one person. As the thickness and asymmetry of AC soft wingsails are induced by rotation of the mast relative to the sail plan, at least one degree of freedom is added, which is control of the (counter)rotating mast. When even more degrees of freedom are included (twist, outhaul, Cunningham ...), it becomes obvious that an AC75 boat should have even larger crew. Or, as a matter of fact, the whole system integrated into a sophisticated 'black box', seen through that PlayStation-style interface. Is such a system applicable to leisure boats? No. Would leisure sailors accept a 4+ degrees of freedom, batten-based soft wingsail? No. Is their only choice in those traditional, inefficient membrane sails? Most probably yes, unless somebody devised a non-batten based soft wingsail ... like this

This.com

Discussing recently America's Cup wingsail design and if it could be better, some agreed that current AC75 wingsails do not have nearly 'the same cross-sectional shape as aircraft wings', while others maintained that their shape is determined by the rule. (To make it clear, the present wingsails are thickest at the mast tapering toward the leech, while aircraft wings' maximum thickness is at about 30% behind the mast). The rule actually says that wingsail (mainsail) shape is open to design, with some constraints given for battens. Btw, the battens are not mandatory, but are usually perceived as the only means of inducing a camber into the leeward skin. As forceful bending of battens requires counter-rotating or blocking the mast, the rule makers obviously wanted to eliminate such a clumsy solution and restricted the use of battens. Strangely, there are better solutions that somehow escaped the designers' attention.The point is that the rule should be read carefully. On the other hand, the rule should be written very precisely, to avoid any greyness and eventual interpretations by the Rules committee. If the rule says that 'intentional openings through sail skins are prohibited', then by running a rope through the sail the INEOS TEAM really broke the rule. One can only wonder why they did it at all, but also what was the reason for such a rule, as the rules do not always make perfect sense. For instance, stayed rigs and non-triangular sails are clearly in collision, as a single running backstay would hinder a rectangular mainsail movement. Therefore, designers introduced two backstays fixed at the transom's corners, that allowed some movement - but naturally not beyond the backstays. The price was paid by the American Magic, whose mainsail hit a tensioned backstay, preventing the sail from being eased and contributing to the capsize-triggering forces. Perhaps AM could sue the rule makers for forcing them to adhere to an inherently dangerous layout? The LRPP team tried to mitigate this nonsense (for other reasons) by sailing without its running backstays, but both the Rules committee and the Arbitration panel refused their appeal.Unstayed or free-standing rigs have many advantages over stayed ones. Eric W. Sponberg said that freestanding rigs have two critical points to be solved, while stayed rigs have around 500 failurable moving parts. Why then a more intelligent solution is prohibited? In two previous editions of the America's Cup, Oracle Team USA created the rule that limited the wingsail's weight from BELOW, preventing other teams from developing lighter rigs. They said they wanted to limit expenses. They capsized a couple of times, totally destroying their cat, with a damage incomparably greater than expenses they 'wanted' to save. Well, it happens when you have too much weight aloft...What is equally worrying is that there were no public questions, comments or discussions on this important issue. One thing is to exercise a formal right, another to be responsible to others ... and to the Deed of Gift.

The following graphics were taken from the America’s Cup official Youtube channel’s video (The AC75 | Designed to Fly), in which the head of ETNZ design and AC75 class rule team stated that both the wingsail and the foil wing have much the same cross-sectional shape as aircraft wings.
True, the foil (underwater) wing is made solid, therefore can be given any of ‘tested and proven wing sections’ of aircraft wings.

But what about the soft wingsail and the chief designer’s false statement about its cross-sectional shape?
This graphic they provided is just an artist’s impression, as there is absolutely nothing to support the necessary curvature of the leeward (upper) skin. In real life the leeward skin of such a poorly designed wingsail is nearly flat (as can be seen on videos), making the wing much thinner than it is claimed, with the maximum thickness just at the mast, as opposed to the true aircraft wing’s optimal thickness position at about 30% behind the leading edge.

a well designed wingsail should be much thicker than two skins hung on a D-section mast - take a look at wingsails.com

www.wingsails.com

One could rightfully assume that solid wingsails can easily be made asymmetrical, according to the science of aerodynamics - but what about soft wingsails? Well, wingsails below are definitely soft, not less than the current 'one design' wings employed by all the AC teams, and equally light. But they are better shaped (read more efficient), which is crucial in a 'sailing game where seconds and millimetres count' (Sir Jim Ratcliffe). Proudly produced in Wing Sails Co. modest shop!

this is Vestas Sailrocket, the current speed sailing record holder; again, it can be seen that its wingsail's maximum thickness is not at the mast, but some 30% aft; seconds and millimetres count ...

pictured below is a nicely shaped swedish wingsail designed to break the sailing speed record; naturally, it is solid, and in this case set for starboard tack; its maximum thickness and its position are clearly visible - seems like these guys knew what the most important issue in a 'sailing game where seconds and millimetres count' (Sir Jim Ratcliffe) is!!!

Sir Jim Ratcliffe, the backer of the INEOS Team UK, "believes there is plenty to benefit from cross-pollination and in a sailing game where seconds and millimetres count, he's determined to explore every avenue to see Britain finally win sport's oldest trophy".Talking about seconds and millimetres, a wingsail of any of the attached four wing sections (NACA7414, NACA5312, Selig1223, Selig1210) would be faster than double-luff, nearly one-design wingsails adopted by all the AC36 teams. It is science and cannot be disputed! But which of them would be the best choice for AC75 yachts? Surprisingly, it seems the AC36 design teams would be incapable of answering this fundamental question. Or they do not care about seconds and millimetres indeed ...

The drawings below were made 50 years ago, but the Princeton sailwing development began 20 years earlier. In spite of its aerodynamic efficiency approaching that of a hard wing, it hadn't been appealing to the America's Cup dummies for decades to come. Much later, a departure from inefficient thin sails took place, but instead of a light Princeton sailwing or its variations, dummies from the Oracle Team USA chose a heavy, rigid wingsail, and even limited its weight and the center of gravity - from below, to keep it heavy!!! They said they wanted to limit expenses other contenders might have incurred in their design and production race for the AC34. The result? A series of capsizes, including their own $10 million AC72 yacht, with huge material damages and a loss of human life.Whoever (and they say Einstein) said,"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former," was right!

When in 1925 the regatta committee of the New York Yacht Club heard of L. Francis Herreshoff's new patented rotating mast design, it promptly passed the rule prohibiting "revolving masts, double luffed sails, and similar contrivances". What a poor both vision and knowledge of the sailing principles! This madness lasted for decades, but nobody ever took responsibility for hindering sail development.

Since the AC75 boats have been revealed, considerable attention was given to the foils and hull shape. Perhaps I am wrong, but do not sails make sailing boats as well? Just cannot remember any discussion on 'revolutionary' wingsails, conceived roughly 94 years ago by L.F.Herreshoff, and pompously re-invented by ETNZ. Could it be that the theory of wing shapes and sections is far beyond their expertise?

A few days ago media pompously announced a ‘revolutionary’ soft wing sail by ETNZ ‘design geniuses’ as ground-breaking, state-of-the-art technology sailing rig.
There are some points that should be addressed here...

Any revolutionary or ground-breaking technology must be patentable, by definition.
Strangely, there is nothing here that could be patented.
A double-luff sail was patented by L. Francis Herreshoff nearly a hundred years ago.
Numerous other ‘double-surface’ designs include Princeton sail-wing (1952), Wharram’s Tiki soft wingsail, etc...

From the ETNZ website: "As with all America’s Cup class developments weight is always a big issue, but especially so with the AC75’s because of their self righting ability it is important to keep weight aloft to a minimum."
Since when the weight aloft is a big issue for ETNZ?
Previous America’s Cup holder, another team of ‘design geniuses’, set the AC50 Class Rule 12.10: The weight of the wing in wing measurement condition shall be not less than 870 kg, and the center of gravity shall be not less than 12.700 m above the wing rotation point.
In other words, going below that minimum was not allowed, but going above was allowed. Was weight aloft really a big issue? Did ETNZ protest against this idiotic rule? Anybody else? What a shame…

http://emirates-team-new-zealand.americascup.com/en/preview-news/269_INNOVATION-CONTINUES-IN-THE-CLASS-RULE-DEVELOPMENT-AT-EMIRATES-TEAM-NEW-ZEALAND.html

INNOVATION CONTINUES IN THE CLASS RULE DEVELOPMENT AT EMIRATES TEAM NEW ZEALAND

So, if it's neither a conventional, inefficient, thin, soft sail nor a clumsy, complex, expensive rigid wingsail, what else it might be? Of course, a SOFT WINGSAIL!!!
Narrow down your search :)

Artemis Racing has a similar line of thought:
"The boat and race format must be seen as bringing the sport of sailing forward and inspiring young and future generations."
Only a highly efficient rig can keep a hull on its foils most of the time, so the only reasonable rig solution is a soft wingsail. No authority can deny this!!!

Check out www.wingsails.com

Wing Sails WingSails - Superior Light Craft Sailing Rigs

From the ETNZ site, after the AC75 boat concept has been revealed: "An underlying principle has been to provide affordable and sustainable technology ‘trickle down’ to other sailing classes and yachts. Whilst recent America's Cup multihulls have benefitted from the power and control of rigid wing sails, there has been no transfer of this technology to the rigs of other sailing classes."

Be sure the solid wingsails will never again be seen on any boat or yacht - and that tells enough about the failed Oracle's mission.

Check out www.wingsails.com

Wing Sails WingSails - Superior Light Craft Sailing Rigs

https://jsca.bc.ca/

Jericho Sailing Centre - Vancouver's Ocean Access Community Centre

http://twistedsifter.com/2015/02/hang-glider-lands-on-sail-planes-wing/

Picture of the Day: Hang Glider Lands on Sail Plane’s Wing Photograph by Samo Vidic/Red Bull Content Pool World class hang-glider pilot Matjaž Klemenčič successfully executes a touch-and-go landing on the wing of a sail plane flown by Nejc Faganelj …

is this the most advanced wingsail :) ?
http://www.sail-world.com/America-s-Cup---Landrover-BAR-capsize-new-test-boat-in-Solent/140796

America's Cup - Landrover BAR capsize new test boat in Solent Whilst out training on the Solent today, the team's test boat T2 capsized off of Ryde, Isle of Wight. The boat was righted quickly and no team members were injured. Damage was sustained to a section of the wing, which the team is currently assessing, but plan to be back on the water in the New Year.