Soft Wing Sail

Discussion in 'Sailboats' started by Pericles, Jul 17, 2007.

  1. Joakim
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    Joakim Senior Member

    Ilan
    You should take a careful look at the polar you are providing: http://www.omerwingsail.com/performance/

    You are clearly confusing TWA/TWS with AWA/AWS. Certainly you are not sailing into less than 20 degrees TWA with good speed. Also you are not going to be faster than standard Elan 37 with spinnaker sailing downwind.

    According to the current polar you are sailing with BSP=TWS directly downwind, thus AWS=0.

    The standard Elan 37 curves are TWS/TWA and also they seem very slow upwind. I would expect 4.6 kn at 45 TWA, 6 kn TWS, but your polar suggest 4 kn, which I can easily do with my 28 footer, which is very clearly slower than Elan 37.

    Joakim
     
  2. Ilan Gonen
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    Ilan Gonen Junior Member

    Thanks Yoakim for drawing my attention.
    You are right that there is a problem with downwind data. I'll check it.

    Right now I can think of the fact that I use two different wind vanes, one on top of the mast and the second one at the bow, as the source of the problem.
    The wind vane at mast top measures the apparent wind speed and Angle of Attack only (because the mast rotates, you can't measure wind angles). True wind is calculated according to the bow wind vane readings.
    When sailing down wind, air flow over the bow wind vain is disturbed by the wing and also, the wind velocity up there is 20% (average) bigger than the velocity at the bow.

    Please look again at the polar. We do not sail less than 20 degrees true wind. Also, please have a look at the attached photos where you can see the forward wind vane location, the wind apparent angle on it and all other instruments readings. Very nice performance and I don't think there is any problem in up wind readings.

    The standard Elan 37 curves where taken from Elan designer Rob Humphrys.

    I hope that in the coming summer, I'll be able to race the standard Elan 37. I'll update the web site once I have the results.

    Ilan

    [​IMG]

    [​IMG]
     
  3. Pericles
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    Pericles Senior Member

  4. CT 249
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    CT 249 Senior Member

    The translation I can get from the article about the two-boat test (which may not be correct) said that the Omer wingsail was higher and a fraction faster upwind, no faster reaching, 10% slower downwind, and had troubles with acceleration and getting into irons. That doesn't sound like the rig is 10-30% faster as has been claimed.

    There really does seem to be an epidemic of over-claiming for the performance increases of wingsails. One builder (X Wing) shows figures which indicate that a Laser with an X-Wing would be competitive with a 505, but when they put an X-Wing on a Force 5 (similar to a Laser) it was slower than the standard rig according to the class forum and from what I could see on the video.

    The extent of such exaggerations is shown by the fact that, if the X-Wing builder's claims about his rig and the Glide Free foil kit were true, a foiling Laser with an X-Wing could beat a wing-sailed foiling Moth around the racecourse.

    In other words, if you cut the back off a Laser and then stuck an X Wing and Glide Free kit on it, you could win the next Moth worlds for half price, with a boat twice the weight and with a smaller rig and no racks.... Hmmm.
     
  5. CT 249
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    CT 249 Senior Member

    PS - The above post was not meant to be negative, but to be positive towards the conventional rigs, which are often heavily and incorrectly criticised.
     
  6. Pericles
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    Pericles Senior Member

  7. CT 249
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    CT 249 Senior Member

    Can we get some more details?

    I've looked back over a few years and can only find a result of 201st in last year's race, and 3rd in Class 9 (out of 16 or so) with the Seascape. Given that the race is basically held in LOA classes, so a modern sportsboat like the Seascape is up against little cruisers like Beneteau 210s and 21 footers from the '70s, that's not proof of vastly superior performance.

    We still appear to be left with enormous claims and very little backup. Put it this way - the Seascape 18 has a German yardstick of 102. Some have claimed the "Wally Omer Wingsail" is 10-30% faster "in any condition". If the Seascape with the wing was at the bottom end of the range (ie 10% faster) then going by yardsticks it would beat J/80s most of the time and Melges 24s some of the time.

    If the wing made the boat 20% faster (ie in the middle of the claimed range) the Seascape with the wing would beat ALL other sportboats on the yardstick list (Thompson 870s, Magic 25s with three trapezes, Mini Transats with their vast rigs and canting keels, Melges and Esse 850s, etc). It would also finish just astern of Formula 18 catamarans and Formula 16 catamarans (which can weigh around 100kg and have wing masts up to 28' high) and beat Farr Mumm 30s and 36s.

    If the wing gave 30% more speed (at the top end of the claims) then the Seascape 18 would be beating 18 Foot Skiffs, and the wing-masted A Class, Tornado and Formula 18 catamarans over the line. Sorry, but does anyone really reckon that an 18 foot sportsboat with a wingmast can beat a 75kg A Class cat, which also has a wingmast, or the Tornado which has a wing and a spinnaker, is dramatically lighter and has twin trapezes?

    If this little boat achieved such performances, let's see the proof. If it did not achieve such performance, why are the commercial promoters claiming that it can?

    I've checked out the Beneteau vid and the other link..... no big deal. I suppose it could just be because some of us are coming from a different background; one in which rigs quite similar to this are quite normal, quite old fashioned, and just another way of doing things, rather than any "modern breakthrough".
     
  8. Pericles
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    Pericles Senior Member

  9. CT 249
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    CT 249 Senior Member

    /\

    Impressive, but in what way does that relate to anything under discussion? The links between the war in the air and rig design are slim.

    Other guys with experience related to flying in wartime and sail design were Taffy Bowen and Frank Bethwaite. Dr Bowen is said by at least one author to be the real brains behind British air-warning radar in WW2. He and his sons used to use pocket-luff rigs, very similar to that of the Omer Wing, at my old club in the '60s. They gave them up because they didn't work well enough.

    Frank Bethwaite was a ww2 pilot, but in transport aircraft (EDIT - wrong, see below). If I recall correctly, he tried double-luffed sails in the same place as the Bowens, and also gave up on them. He also spent years developing wing masts, and gave up on them.

    Another guy who tried double-luff sails was John Buckland, "Open" 14 Foot Skiff "world champ" (or runner up?)....they were slow and troublesome, so he gave them up. Incidentally, his cousin (multiple world 18 Foot Skiff champ Andrew) created the modern assymetric spinnaker, which was almost immediately adopted in many classes as soon as it proved itself.

    Of course, double-luff sails can work (which is why I own about a dozen of them) but they never show performance advantages of 10-30%, as claimed, and they always come with downsides.

    The significance of the above is that they show how often similar ideas have been tried and abandoned by great minds over the past 70 years, and also how quickly an idea (like the asymmetric spinnaker, or the double luff sail in certain specific applications) will be adopted if it actually works really well. Any belief or implication that wingsails are a new idea is completely wrong.
     
  10. gggGuest
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    gggGuest ...

    Medium bombers (Lockheed Venturas) when he got his DFC AIUI. The flying boats came later.
     
  11. CT 249
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    CT 249 Senior Member

    Yes, of course you're right.... He never really mentioned his WW2 experiences much (in fact I don't recall him doing so at all) but he did mention his commercial and CSIRO flights, so I always (incorrectly) think of those instead. He really was a most impressive man, and a few weeks before he died he came down to talk to us at the NSW Tasar state titles and association AGM; frail in body but not in spirit and still designing and planning.

    The last time I went to his office, when I walked in he was looking at wind readouts and jotting them down, looking for patterns. And, of course, after all these years involved in rig design, he had decided that the standard fractional sloop rig with "pole" mast was the most efficient of them all.
     
  12. Pericles
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    Pericles Senior Member

    Rotating Asymmetric Foils made their appearance in sailboarding about 27 years. A type of soft wing sail. Somehow, the technology did not crossover as much as expected. I wonder if such technology would have increased the performance of the Laser One?
     
  13. gggGuest
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    gggGuest ...

    Not sure about most efficient Chris: is that exactly what he said? I'd go with most appropriate or something on those lines.

    I still think there's unfinished business with wing masts, and I don't think I'd bet against them being in much wider use by the time we're pushing up the daisies and won't care whether we're right or wrong.

    At the present state of the art I think we can say that:

    The aerodynamic benefits are very much smaller than we used to think with our rather simplistic understanding of the aerodynamics in the 60s and 70s.

    As currently developed the basic pole mast is appreciably superior in dynamic response and flexibility of use.

    The pole mast is lighter and a lot easier to set up and tune.

    The tradeoffs are different on different types of craft.

    I wouldn't bet against an advance in materials and manufacturing changing everything. I've heard Julian B speculating that there might be mileage in having a spar with a non structural rotating fairing. It seems to me that were one to put in a really serious manufacturing and development effort it ought to be possible to have a wing mast that has all the dynamic response of a current pole mast and some aerodynamic improvements, but I think it would be a very big development effort involving a lot of prototypes and a lot of carbon fibre. Most wing mast experiments I see appear to be doomed to failure from the start: especially those from people who have a shallow understanding of Marchaj and a lot of optimism...

    I haven't studied the setup in this thread.
     
  14. CT 249
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    CT 249 Senior Member

    /\

    Agree with all that, or just about all of it. As of that last discussion at the class AGM Frank was still proposing that the Tasar drop the wing mast and from my recollection he was certainly claiming that the carbon pole would be faster, and not just because of the reduced weight.
     

  15. CT 249
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    CT 249 Senior Member

    The RAF requires a lot of downhaul tension and a fairly flat shape to stop batten "poke". It also requires lots of heavy battens. In my experience it hasn't got the power in light winds of a "conventional" sail.

    Camber induced sails are faster in windsurfers, but even in Moths it took decades before they were proved to be faster. I think they also work best on fairly rigid and flat rigs, so they suit the low-drag Moth hull but not conventional ones.

    It's really interesting to swap windsurfer rigs around from board to board. The modern flat rigs have super low drag but very little lift or power, so they are terribly slow on a big board in light winds. The old-style sails (like the pre-RAF ones) have lots of drag, but also lots of light wind power. The latter seems to be a fairly good model for a medium-speed boat like a Laser.

    A speed-sailing aero testing guru once told me (on a "no names" basis) that he was hired to run some state of the art windsurfer rigs in a wind tunnel. Just for fun, at the end of the tests they put an old Original Windsurfer (i.e. "boat style" soft pinhead sail with long boom and short battens) rig in the tunnel. When they saw the results, they quickly said "errr, let's not show that" because the old-style rig actually had more lift than the modern ones.
     
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