Site is up on Wingsails

WOW! I had forgotten about this one.

Whos gonna be first?

Very interesting. I like the inflatable pocket. No more sinking sail.

Send one to Luderitz quickly for testing.

Have a look on the mens facebook page :

www.facebook.com/stanislav.mostoviy

There you will find answers and some rigging and sailing video's .

Here's other single surface sails showing lots of tufts on the windward side, all streaming with no indication of the turbulence your figure shows.







Those tufts are just ribbons of cloth, lying in the airflow. If the airflow stalls, as shown in your diagram, then the tufts whirl around. These tufts are all lying back, showing non-turbulent flow over the windward side of the luff rather than the vortices and turbulent flow shown in your diagrams.

As long as the Aoa is high there will be perfect airflow on single surface sails winfward site (as all sailers know ) but if you have to let go the leading adge collaps ---> center of lift travels back ! = no big problem on a boat but out of controle for windsurfers !

From the site :

In general, sailing with wing is no different than with conventional sail. There is no adaptation period or change in sailing technique. Wing sail delivers better performance in all aspects. All lessons learned with regular sail will be greatly enhanced using wing. Wing doesn't have fatigue as traditional sail and it's very predictable in all conditions. Because wing has fixed center of lift, ride is much more stable and much easier. There is no back hand and back leg pressure, no leading edge stall, no sudden loss or gain in power. In fact it is so easy to handle that you will never shred skin on your hands. Wing easily outperforms any traditional sail of equal size, especially cross and upwind. Wing has near unlimited wind range. I mean, if you take wing on 45kt wind, you probably experience more problems with aerodynamics of your board and your own body than with wing. We all know that jibe is very difficult and advanced move and probably we all experienced the fact that in different wind condition jibe technique is different. This happens because traditional sail has different behavior on different conditions. Regular sail needs to be tuned up according to wind and water conditions, and with different tune it has different characteristics. Wing has only one setting for all conditions. Wing delivers that same performance and behavior in all winds. It does exactly what it is designed to do, pull forward. Compare to conventional sail, with wing it much easier to master perfect jibe as well as other sailing techniques.Is wing faster?Strait answer YES. Wing easily outperforms traditional sail of equal size with same sailor, board, mast, boom, and fin. But, if you expect that sailing the wing will instantly make you fastest guy on the bay, probably not. There will be a guy who is heavier, has bigger sail, smaller board, better skills, smaller fin, etc. and he will be faster than you sometimes. But you will go faster with wing than with your regular sail of equal size. Also because lift component is directed more forward you can use smaller fin. Coefficient of lift that wing generates is just 0.2 better than traditional sail generates at its best. Also wing has no fatigue. If you can utilize and use properly all advantages of the wing, than you will be faster than others. Who should consider wing sailing?Sailors who consider getting wing, should more take in account such values as stability, reliable ride in all winds, better performance, freedom of sailing, and perfecting sailing techniques. When sailing on a good windy day, you will see people go over 2- 3 conventional sail sizes, while you just having more fun with more wind on your wing. With wing you can go safe as fast as you can and as slow as you want. Wing is an engine, not a crazy machine.

on :

www.facebook.com/stanislav.mostoviy

Video's of testing and lots of info on the wing

This has to go on a foil board!

Such a a great journey to finally be able to offer something new to us.

Not a multi million $ corp with R&D in 5star Hotel.

A fellow sailer with an idea and ability determination to follow it through, well done.

To to get it out in the market place in Aust we need to see it in the flesh, that's the hard bit.

I don't think anyone could realistically argue with a straight face that in 99.9% of conditions a wing sail isn't going to be more efficient on a craft that develops high apparent wind, IE an AC50. There are simply too many efficiency gains to ignore in something that can travel 3 or 4 times the windspeed, a soft sail isn't going to be even in the same league. However, as stated above to maintain this efficiency requires extreme attention to twist, camber, AoA etc which is why they are effectively sailed by a computer; someone following what the computer tells them what to do anyway ;)

I think if someone developed a wing sail for a moth that had a huge, easily manageable tuning range it would be faster (if dialled in) in almost every condition...but it doesn't exist and poses lots of other problems like cost, longevity, how hard it is to tune etc. Just look at the effort they go to end plating sails to booms, decks, tramp aero etc all in the name of efficiency.

It's an interesting idea but i'm somewhat sceptical that this particular iteration of a wing much more efficient and has a sufficiently wide range that we'll all ditch out 5, 6, 7, 8... etc size sails. End of the day lift is in part a function of area and a 5.8 != 8.5 in 10kts, right?

Actually CJW, as already quoted, some of the AC wingsail designers DO in fact say that wingsails are NOT more efficient 99.9% of the time on such craft. To repeat, one of them said "There's nothing magical about a rigid wingsail. The soft sail rig on USA 17 (ie the unlimited 90 foot tri that won the America's Cup) was faster than the wingsail in some conditions. Whether a wing or soft rig will be faster depends on the class constraints and the sailing conditions."

To go into more detail from the same source, namely Tom Speer of Boeing and Oracle's America's Cup team, here's him writing about a windsurfer wingsail 15 years ago; "The typical argument goes something like this, "Aicraft wings are more efficient than sails. Aircraft airfoils are thick, double surface sections with modest camber. If a sail has thickness and a double surface it will be better than a single surface sail." The problem with this is that it doesn't take into account the different requirements for wings and sails. Plus, aerodynamic tests and calculations invariably show that for any given design point, a thinner airfoil will outperform a thick one. So why use a double surface sail?

I can only think of three reasons to have a thick foil:
1) The depth is necessary for structural stiffness,
2) A sharp leading edge loses out on leading edge suction, which results in an increase in drag,
3) The airfoil has to operate over a wide range of angles of attack.
Other than these factors, a thick section will generally have more drag and less maximum lift than a thin section.

An aircraft has to operate at a very low angle of attack in cruise because it can't change its wing area, the lift has to equal the weight, and the only way match the weight at high speed is to use a low lift coefficient. It's the optimization for cruise that drives the airfoils to a semi-symmetrical shape. However, for landing, airplane designers do everything they can to change to a highly cambered shape to produce high lift. And when the wing is configured for high lift, drag is actually helpful because it makes the landing glidepath steeper.

The requirements for a sail are quite different. The sail needs to produce high lift with as little drag as possible. The sail doesn't need to operate at low angles of attack because if you are that overpowered, you'll reduce the area by reefing. It's much better to use a smaller area near its maximum lift than a large area that's lightly loaded, because the smaller area has less parasite drag (less wetted surface). The sail does have to perform well for a certain range below max lift, but that range is nowhere near as great for a sail as for an aircraft.

The ideal shape for high lift would be a thin, highly cambered airfoil. This is provided very well by traditional single surface sails. Such a sail has a narrow groove, however. If the sail is operated at too high an angle of attack, the flow separates on the lee side and the sail stalls. If the sail is operated at too low an angle of attack, the flow will separate on the windward side, just behind the leading edge. This causes drag." (My emphasis)

Completely agree that wingsails require intense attention to twist and camber, which is why it's odd that this sail appears to ignore such things. It's also a concern that one diagram claims that the sail is more efficient because of the vector of forces normal to the windward side, when people like Mark Drela say that such things are irrelevant. Drela is an MIT professor of aerodynamics, who holds world records for human powered boats and aircraft as well as being involved in AC designs.

I may seem to be negative, but our MW sails mate insults people like world record holding aerodynamics professor Mark Drela and Boeing wing designers by claiming that they are "desperate" when they create AC wingsails. So basically, he reckons that he can get it right when the people who have been working on these rigs, often with enormous resources, have been getting it wrong for almost 50 years.....

One of the cards that wingsail promoters often play is claiming that people are too conservative to adopt their ideas. For one, that's pretty obviously wrong - look at the reaction to this sail both in the earlier thread here and in the Dutch thread some have linked to. Lots of people are excited.

The other issue is that wingsails have been around for eons (I had a mate who had one in about 1972) and SOME of them have been known to work in SOME boats for years, so they are far from new and therefore conservatism isn't the issue. What is the issue is that time and time and time again, we have been promised the earth by wingsail designers and they have failed to deliver. They also tend to promote their ideas by denigrating other rigs and designers, just as MW does with his sneering and dismissive references to the America's Cup and C Class wingsail designers.

I tend to think the conservatism comes from people who keep on thinking that wingsails are better even when the experts who design them say that thin sails are better in some ways.

Is there really a market for a sail that has 24 steps to rig it? (27 steps if you count all the pages).

Add to that the almost unreadable www.mwsails.com/wingsail-story and you'd have to be suspicious about the reality of the product.