An interesting boat : matinbleu (free standing "wing sails" goélette)

Discussion in 'Sailboats' started by yves, Aug 21, 2012.

  1. capt vimes
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    capt vimes Senior Member

    eric:
    do these rotating masts have a free rotation of 360° or are they limited somehow to rotate only by say 160° to both sides of the centerline?
    if they rotate freely - how would one prevent them getting swapped accidentally to the other tack by a gust when running downwind?
    thank's
     
  2. Eric Sponberg
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    Eric Sponberg Senior Member

    Generally, the masts can rotate 360 degrees. You can control the rotation a few different ways. One is to have a tiller underneath the boom with a lanyard from the end of the tiller to the boom. It prevents the rotation of the boom from going past a certain limit, anywhere from 0 degrees to say 45 degrees. Or, you can have a tiller on the bottom of the wing, generally facing forward, with sheets going back to the cockpit. In this case, the tiller and rigging gear prevent full rotation, but there is nothing in the bearing assembly itself that prevents full circle rotation.

    Eric
     
  3. yves
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    yves Junior Member

    And what about at the harbor ?
    Isn't it necessary to leave the masts freely rotate in order not to have them fixed on a beam reach in strong winds ?
    And in that case how do you "manage" the booms or wishbones (and sails) ?

    Note : this subject mentioned below I think, where they sail that when the wing is left feathering in the wind, it in fact creates less force than a normal rig.
    http://www.harborwingtech.com/technology_wingsail.htm
     
  4. capt vimes
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    capt vimes Senior Member

    thank's!
    that's then 5 lines you have to take care of if you go for the wing-tiller configuration - sheet, 2 lines for the traveler, 2 lines for the tiller... but you could trim the alignment of the wing to the sail/boom...
     
  5. Eric Sponberg
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    Eric Sponberg Senior Member

    Yves, in fact, in my experience and for my types of mast designs, the opposite is true. Harborwings I believe are a special case that will stay feathered. In my designs--single-stick wingmasts with soft sails--if you let them weathervane, the boat does not stay still. Watch one at a mooring, and the boat sails all around the mooring if the mast is left to weathervane. I know of another instance involving someone else's design where the wingmast (sloop rig) left to weathervane, caused the boat to start rolling, ever violently, until it almost capsized, heel reaching well past 45 degrees either side.

    The best thing to do is to secure the mast tacked to one side of the other. For a sloop on a mooring, I would set it to 90 degrees to the boat centerline. At a dock, pick a number for offset angle, it depends on local conditions, but fix it down, don't let it freely rotate. On a cat ketch, it's dead easy. Set the forward mast to 45 degrees one side, and the after mast to 45 degrees the other side, and the boat sits absolutely still at a mooring, similarly at a dock. Other boats in the harbor continue to swing somewhat on their moorings, but the wingmasted cat ketch hardly moves.

    What is happening? At a boat sitting on a mooring, the freely rotating mast will generate some lift practically all the time. The boat will start sailing due to the lift generated. As the boat moves, friction in the bearings may prevent the mast from turning a like amount, and so the angle of attack changes, usually getting larger, creating more lift, causing the boat to swing even more. But there comes a point when the tether to the mooring snubs up and pulls the bow around, so everything swings. The mast tacks, and now the forces are on the other side, and the process repeats. The boat sails the other way until the tether snubs, and the boat tacks again. And so it goes, the boat tries to sail circles around the mooring. Similar things happen at the dock, but there are usually more lines holding the boat in place.

    On the cat ketch with the wingmasts set to opposite sides, there is enough flow separation and drag to prevent lift from really generating. The boat just settles back downwind of the mooring. It's quite remarkable to see.

    So the key is, tie the wingmasts down so they don't weathervane, and this applies to my style of wingmasts, single sticks with soft sails.

    Eric
     
  6. yves
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    yves Junior Member

    Eric,
    Yes on a mooring I can understand that fixing it on opposite angles would work, at a dock though, would be a bit scared to leave the boat with sizeable wing masts surfaces, especially in a location were strong winds from different directions are common (the case in south France with Mistral and east winds for instance), has to be a liveaboard maybe :) ... (or moderate surfaces)
     
  7. Eric Sponberg
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    Eric Sponberg Senior Member

    Exactly right. And this is why it is necessary to design only the minimum size wingmast consistent with strength and stiffness. You don't want the wing too big, and this is one of the primary concerns of all my customers when they approach me about designing a new mast for their boat or for a new boat design. If you cannot put the boat to bed and go home, what good is it? You don't want to have to babysit your boat 24/7/365 if you are not living aboard. My design for Wobegone Daze is a perfect example. The wingmasts are just the right size. The owner keeps the boat in a marina. He can leave it at a mooring when he cruises and visits interesting places ashore. This rig is 12 years old now and still going strong.

    Eric
     
  8. yves
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    yves Junior Member

    Very nice example indeed, these days something like that around 11 metres would be my dream boat I think (after having been thinking about tris for a while ...).

    On very broad reaches, is she actually sailed with the booms well passed 90° from the boat axis ? And what is the idea behind having both booms and wishbones ?
     
  9. Eric Sponberg
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    Eric Sponberg Senior Member

    Yes, she often sails with the sails wing and wing and the booms past 90°--that's part of the point of the rig.

    The two-booms idea was the owner's requirement, which I did not agree with, but he was the customer and was paying the bills. He wanted to have the conventional boom so that the sail, when stowed or reefed, would have a boom on which to sit. He did not like the idea of the sails, as on other wishbone type rigs, to be cradled only in rope lazyjack slings--he thought that looked ugly. So both booms it was. It made engineering and building the rig a lot more difficult, and it is a real bear to disassemble this rig because of the boom situation. But, that is what he wanted....

    On my more recent designs, as I am sure you have seen, I go for the half wishbone, but I am 50/50 on that. A conventional boom with an under-boom tiller to prevent over-rotation, as on Saint Barbara, is fine. Conventional booms do require a vang, whereas the wishbone or half wishbone do not--they are self-vanging. The half wishbone does require a tether to hold it horizontal, but this is small consideration--it's a small line.

    Eric
     
  10. Eric Sponberg
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    Eric Sponberg Senior Member

    One other thing--I have a question about this forum and formatting of text. I noticed you used the degree symbol (°) in your original text. I have never been able to figure out how to get that--an "Insert Symbol" function, as you would see in composing a letter or report in Word, does not appear on my window screen for formatting text. I just copied the "90°" from your message to put into my reply. So what's the trick--how do I get the degree (°), or any other symbol, to appear when composing a message in this forum--in this message I am just copying/pasting from the earlier message?

    Thanks--I am just an old codger trying to learn new tricks.

    Eric
     
  11. yves
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    yves Junior Member

    Thanks a lot for the info, you really are the unstayed rotating wing mast expert ! Maybe you could contact Erik Lerouge, who also is a big unstayed rig fan (he designed matin bleu and its masts, not really the sails), and is working on such a concept for himself :
    [​IMG]
    His site :
    http://www.lerouge-yachts.com/design.htm
    (I've put pointers to your projects and artciles in the thread where he describes his project)

    About the degree sign, it comes standard on azerty keyboards :) (with accents and other things )
    (also because we use it for temperature, and for the n° notation (instead of # as number 4 or 5 etc, although this usage is more or less disapearing)

    but for any symbols, if you know how to put them in MS word or some text processing software, cut and paste should work.
    (there is a generic notation to input symbols through their unicode numbers in html, but don't think it would be taken by the bb or bb code like forum parser).

    Yves

    PS : to put the degree symbol in HTML :
    "The degree symbol, in Unicode: U+00B0 ° degree sign (HTML: ° ° )"
    http://en.wikipedia.org/wiki/Degree_symbol
     
  12. yves
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    yves Junior Member

    By the way, I like Saint Barbara design a lot, especially like these "classical roof shapes" on modern hulls shapes, which in fact are more "to the point" shapes, not trying to be "overly aerodynamic"(which I doubt makes a lot of difference at sail boat speeds), a bit like David Reard's designs also :
    [​IMG]
    [​IMG]
     
  13. Eric Sponberg
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    Eric Sponberg Senior Member

    Yves, Here in America we don't have the AZERTY keyboard, ours is QWERTY. But thanks for the link to Wikipedia as that had a solution for me that solved it, as below:
    The temperature in Florida is 80°.
    And the temperature inside is 80°. (Air conditioning not on)

    The first of these was created by holding down the "alt" key and typing "248" on the keypad. the second was created by holding down the "alt" key and typing "0176". Both of these are HTML codes for the "degree" symbol.

    Thank you very much. Problem solved.

    Thanks also for the Link to Erik Lerouge Yachts. I'll have a look.

    Eric
     
  14. yves
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    yves Junior Member

    Yes I know about the Qwerty! (lived in California for a while, in Santa Barbara in fact :) ), the "French" keyboards are "Azerty" (also the first line of letters starting upper left to right), takes quite a bit of time to switch from one to the other ...
     

  15. capt vimes
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    capt vimes Senior Member

    since i asked the other day in another thread (http://www.boatdesign.net/forums/sailboats/monohull-wing-mast-45994-2.html) about running rigging going up the mast and how they are lead in a wingmast or free standing mast configuration...
    there is an interesting paragraph in the mini class rule:
    from: http://www.classemini.com/?mode=jauge-classe-mini

    this means - if i got it right - you either run all the lines not in but outside of the mast, or you bring them down to the mastfoot and from there back to the cockpit...
    why isn't it enough to bring the lines out just above deck and seal the mast from deck to the mastfoot?
    you do not have any leaks into the boat in the case of a capsize either...
    why has the mast to be watertight up to the 1st halyard?
    deck stepped masts are also not watertight, nor do they have to be...

    this is a stupid rule - makes no sense to me and probably one of the reasons why nobody tried this approach before...
     
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