Moth on Foils: 35.9 knots(41.29 mph)

Discussion in 'Sailboats' started by Doug Lord, Apr 11, 2006.

  1. cmaas
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    cmaas Junior Member

    That all makes sense - except I wonder if there is an appreciable difference in wind speed in the 5 feet to 25 feet or so off the water that the Moth rig lives in?

    As for twist in a sloop rigs main - I have noticed on my International Canoe how much flatter the main needs to progressivly become towards the foot because of the jib changing the flow direction. The fastest shape seem to be a kind of odd combination of more camber above the jib relative to the top and bottom. The top being flattened and twisted to shed lift as needed.

    I wonder if USA 17, sailing with the wing sail and jib, has any relation to the same rig on an IC? Would a sloop rigged wing sail be worth a look?

    My fellow IC sailors would hate me if that rig was fast.
     
  2. Doug Lord
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    Doug Lord Flight Ready

    Moth on Foils!-----The Wing#2

    This is from post # 7 in the "Why so Stable?" thread under "multihulls" by Tom Speer. I thought it was extremely relevant to the discussion of sail aerodynamics,particularly, when you realize he is talking about THE WING. The comment highlighted in red is worth some serious thought!

    "Really, the wing is not that much different from the soft sail rig. There's a rotating mast and a mainsail attached to that. For the wing, the mast is larger in chord and the mainsail is thicker. But the cross section topology is the same for both rigs - a teardrop shaped mast, a small gap, and a much thinner mainsail that is articulated to be cambered relative to the mast. The hinge points where the flaps attach to the main element/mast are just like batten cars that are fixed in position instead of being on a track. The flap ribs are just thicker battens. The covering is also a woven material, so USA 17 could be said to have a more traditional sail material than A5's molded 3DLs!

    Despite its size, the main (forward) element of the wing can be considered to be a leading edge device for the mainsail, just as the mast is for the soft sail rig. Deflecting the flap one degree while holding the main element fixed relative to the apparent wind will produce more than 80% of the lift one would get by rotating the whole wing one degree while holding the flap fixed relative to the main element. Which also means that rotating the main element while holding the same orientation of the flap relative to the apparent wind will only change the lift by less than 20% compared to rotating the whole wing. So qualitatively, it's where the flap points that matters.

    That's one reason why twist control on USA 17 is all done with the flap instead of by twisting the main element as was done with Cogito. It was a simpler and lighter way to go for a wing that size. This is another way that the wing is similar to the soft sail, where twist is all in the mainsail, too.

    It may look different, but it really is a sloop."
     
  3. MalSmith
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    MalSmith Ignorant boat designer

    Regarding wind speed, if you are talking about wind gradient, there should be more for a Moth than there would be for an AC boat, as the effect is grater near the surface.

    Regarding main/jib combination, it is useful to think of the whole rig as a combined airfoil. If you were to take a section through the main and jib together, you could draw a single airfoil section over both the main and the jib, leading edge of which is the jib luff and the trailing edge is the mainsail leech. You would see that to fit this shape, the mainsail needs to be quite flat (as it is) and the draft in the main should be quite well aft in order to get a good slot. Sails have evolved this shape, despite the fact that people still tend to think of each sail as an individual entity.

    The sloop rig is a slotted airfoil. However it differs from solid wing rigs in that the slot between main and jib does not divide the rig in the same proportion along the entire span. In fact the sloop rig (3/4 rig, say) is a slotted airfoil at the foot, and a non slotted airfoil at the head, with a gradual transition between the two along the span. Hence the head of the mainsail is a full airfoil section, whilst the foot is a distorted shape that forms the trailing portion of the combined airfoil. The foot of the jib is the leading edge portion of the combined airfoil. At the head, the jib basically just disappears.

    The main drawback of the sloop rig is that it works fine going to windward, but when you ease sheets for downwind, you loose the combined airfoil effect, and you end up with less lift, when you actually want more. For this reason, I've always been keen on trying a ballestron rig on my IC. It's on my list of many things to do which never get done due to lack of time and money.:D The ballestron rig maintains the combined airfoil at all sailing angles.

    I even suspect that a well set up balestron rig on, say, a C-class cat, could be lighter, more powerful and more adjustable than the current wing rigs. The wings evolved during the dacron sail era. They offered a means to get better planform shapes, and the slot effect enables huge CL for offwind. But they are still relatively heavy and you don't get the full range of twist control available with soft sails. Today, new sail materials and wide head mainsails, combined with ballestron boom for a consistant slotted airfoil, should make it appealing to revisit soft sail technology for the C-class. Wings do look pretty cool though.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Moth on Foils!------The Wing: no go

    Adam May has committments to Team Origin that will prevent him from taking The Wing to the Europeans.

    from the blog:
    I've done a brief bit more testing. Lining up against Nathan the other day. I had height upwind, he had pace downwind. I came away with a long list of improvements in my head, pleased with the potential I know it has.


    http://foilborne.blogspot.com/2010/08/wingless.html
     
  5. Doug Lord
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    Doug Lord Flight Ready

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  6. Doug Lord
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    Doug Lord Flight Ready

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  7. Doug Lord
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  8. Doug Lord
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    Doug Lord Flight Ready

    Moth on Foils!------Euros-Day 4

    You can't get closer than this! From the Euros site:

    "The American Bora Gulari and the Australian Nathan Outteridge are still leading the championships, and there is a tie between the two athletes for the first place on the general ranking. As Nathan Outteridge says it, tomorrow is the last day, but three races are still to be sailed and there is still a long way to go! The conditions are fantastic on the lake and the competitors sail their boat to the extreme, at speeds regularly exceeding 25 knots! The concentration is at its maximum and must remain as such up to the last race of the championships. The third position is also under heavy competition: only two points separate the Swiss Arnaud Psarofaghis, the British Simon Payne and the Australian Scott Babbage ! "


    Day 4 video: http://www.youtube.com/watch?v=WJXjBA1oEbQ&feature=player_embedded


    (images from euro site/click and click again...)
     

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  9. Doug Lord
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    Doug Lord Flight Ready

    Moth on Foils!-Euros FINAL

    From the Euros site:


    The Australian Nathan Outteridge wins the SYZ & CO MOTH EUROPEANS in the Open category, in front of the American Bora Gulari and the Australian Scott Babbage. The British Simon Payne is the European Champion before the two Swiss sailors Arnaud Psarofaghis and Matthias Renker. Two superb regattas finished a splendid week today, Bora Gulari winning the first one and Nathan Outteridge the second one.
    ---
    From Mr. Gulari on DA:
    "I should probably practice a little more, after the dubai debacle I was a little burned out and only sailed my boat 5 days this summer, before this event"
    and:
    "Rob has the info right. I was throwing up while sailing in the last race and just could not do it"

    ---
    Day Five video: http://www.youtube.com/watch?v=huQcUHq5ZsQ&feature=player_embedded

    Note: watch it once then watch the wand(s)!!

    --

    European Open Championship final ranking:

    1. Nathan OUTTERIDGE (AUS 3750) - 18 points
    2. Bora GULARI (USA 6) - 20 points
    3. Scott BABBAGE (AUS 7) - 44 points
    4. Simon PAYNE (GBR 1) - 44 points
    5. Arnaud PSAROFAGHIS (SUI 4) – 52 points
    6. Rob GOUGH (AUS 3731) – 76 points
    7. Matthias RENKER (SUI 3626) – 103 points
    8. Chris GRAHAM (UAE 9) – 106 points
    9. Chris RAST (USA 3768) – 106 points
    10. Jason BELBEN (GBR 3619) – 113 points


    Podium European Championship :

    1. Simon PAYNE (GBR 1)
    2. Arnaud PSAROFAGHIS (SUI 4)
    3. Matthias RENKER (SUI 3626)
     

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  10. Doug Lord
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    Doug Lord Flight Ready

    Well, on day 4 most of the way thru a Moth championship the regatta is TIED! On Day 5 Outteridge wins by 2 points! What one of those guys might have given for an edge-just a bit more speed....
    Now, look at the video below but this time only watch the wand: every time the back end of the wand moves up the mainfoil flap moves down; every time the wand moves down and forward the mainfoil flap moves up. Can you say flap up, flap down as fast as the wand moves? Can you move your finger that fast? The wand is held against the water by a shock cord so it takes energy to move the thing as fast-and as much-as you see the wand move in the video. This particular video is one of the best illustrations of wand movement ever photographed ,in my opinion.
    You've got a flap moving up and down a lot and it is taking power away from the boat to do that.
    In the early days the wand was necessary because the boats had a lot of refining still to be done. But the time is now to dump the wand and use manual altitude control. It won't be easy initially-it will take a lot of practice and ingenuity to make a viable system. Perhaps using a system that links the main foil and rudder foil at an adjustable mix ratio-something like that was suggested by Tom Speer a long while ago.
    I believe the boats and the sailors are so refined at this point that the next logical speed improvement is to learn to sail without the wand. And if one of those two guys that are tied were to spring a "wandless" surprise on the other what a leap forward for the class!
    Tom, what do you think? Mal?

    PS-the 26' Mirabaud uses manual altitude control finding it a big help particularly when it's rough.....


    Watch the wand:
    http://www.youtube.com/watch?v=HTqtEvTjlaE&feature=player_embedded


    Toms illustration of a system to control both foils simultaneously- for wand input-just replace with manual input(?):
     

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  11. philSweet
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    philSweet Senior Member

    Doug, you are assuming that all that dithering is bad. You may be in for a bigger challenge than you think if you try to remove that highly evolved wand from the system. Engineers have been intentionally adding dithering devices to control systems for years. They can often prevent cyclical control problems more easily than damping systems. This appears to be particularly true in servo mechanisms where the dither can be applied to the servo, but damping would be applied to the driven system after the servo. I'm thinking that this is the case here. The damping of the height control system would seem to come from the tab itself. I suspect a refined dither would have a lower energy budget. You might try an experiment where you retain the wand and only use its dither to flutter an otherwise manual height control and see what happens. This is probably the exact opposite of what most would try to do. Welcome to a rather weird corner of the engineering universe. The wiki on dither is mostly about its uses in digital systems, but it does mention a couple famous mechanical dithers.
     
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  12. Doug Lord
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    Doug Lord Flight Ready

    ------------------------
    Thanks, Phil. I don't know anything about "dithering" but I have foiled a bi-foiler with a manual system-just barely enough to think it might have some potential. However, Thomas Jundt has made a method of switching off his dual wands and controlling the mainfoil flap with a manual lever and considers it to improve performance. Two separate skippers converted their Rave hydrofoils to manual altitude(and RM)controls and said it improved racing performance-and in those boats the skipper controlled lift and righting moment (roll). The Rave used the wand system copied by John Ilett and refined for the Moth.
    The first two person bi-foiler was an I-14 in 1999 that had a manual altitude control system.
    With knowledge of what those guys have done-particularly Jundt last year and this year and my own limited experience- I think there are gains that could be made with a properly implemented manual system on a Moth.
     
  13. Paul B

    Paul B Previous Member

    Why didn't you post anythig about these foiling sessions when they happened? Why did you wait months after the supposed fact before you started claiming this?

    Since you have all the parts for this craft why haven't you taken a day or so and put it together and had a fun summer of foiling?
     
  14. Doug Lord
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    Doug Lord Flight Ready


  15. Doug Lord
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    Doug Lord Flight Ready

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