WishBone Sailing Rig

Discussion in 'Boat Design' started by brian eiland, Aug 17, 2003.

  1. High Tacker
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    High Tacker Junior Member

    High Tacker (www.damsl.com)

    Sea trials of a real superyacht with A-frame sailing rig

    Just heard from the designer(s) of Greenpeace's 840-ton Rainbow Warrior III, with two 50-meter A-frame masts, five sails all on furlers. She was launched a couple months ago, is in sea trials now and so far has sailed in winds of 10-25 knots, all has gone well, everything is working fine, no problems, no real surprises, according to Gerard Dykstra of Dykstra & Partners, who also said, "Working the rig is safe, though the individual sails are rather huge." No kidding!

    Dykstra & Partners did extensive wind tunnel testing and chose the A-frame rig for efficiency and practicality. The design of their A-frame structure is identical to that of the 20-meter A-frame on Catbird Suite. Uh, well, Catbird Suite doesn't have any need for all that spyware, antennae, etc., on the outboard sides of the mast(s).

    Below are some pics of Rainbow Warrior III sailing. See www.damsl.com for more on A-frame sailing rigs.
     

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  2. High Tacker
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    High Tacker Junior Member

    High Tacker (www.damsl.com)

    SOME OF THE BENEFITS OF FURLING SAILS WITH MOVABLE TACKS

    Here is a pic of Catbird Suite (looking aft) on a reach, port tack. Tacks of mainsail, staysail and genoa are attached on port side. Everything is inboard for easy handling in contrast to a conventional rig in which substantial portions of mainsail and genoa would be outboard to starboard, levering the boat around, increasing likelihood of broaching. Entire width of boat is available for sheeting down to, maintaining ideal shape on all sails with no booms necessary. Accidental jibe has become a non-event.

    See www.damsl.com for more pics and detailed explanations.
     

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  3. Kojii
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    Kojii All is remodelling

    Is it just an optical illusion or do those legs have bow?

    Good luck selling your boat.

    It looks like there is bow or arc to those legs in the bi-pod. I wonder if that is so and why would the designer do that?
     
  4. High Tacker
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    High Tacker (www.damsl.com)

    Hello Kojii,

    Them legs do look kinda bowy. Maybe the designers are Dutch cowboys, but that seems kinda unlikely. Hey, maybe they subscribe to that ol' Southern stoic philosophy from way down yonder in Ms Slippi, to wit: Bow up an' take it, boy...iudicium difficile...but do you yourself not tend to tension up, like, go into a state of isometric tension when you sense that a load is about to come on?
     
  5. High Tacker
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    High Tacker Junior Member

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    Kojii

    I think you can see the bow more clearly here.
     

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  6. High Tacker
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    Kojii

    One more bowy pic:
     

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  7. Kojii
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    Kojii All is remodelling

  8. yipster
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    yipster designer

  9. sharpii2
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    sharpii2 Senior Member

    The legs have bow outward probably to keep them from buckling inward. Also, that gives them a bit of 'spring', so the inward leg of the mast can bend a bit, relieving shock loads on the hull substantially, in the event of a sudden squall or a sharp roll.
     
  10. sharpii2
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    sharpii2 Senior Member

    This is an interesting look at the future. I imagine smaller ships will start sporting sailing rigs by the 2nd quarter of this century, as fuel extraction gets ever more costly and precarious. The rigs will be everything from sail assist to primary propulsion.

    I wonder about the main tri-sail on this rig. I see it is boomless and can only be sheeted to one leg or the other of the mast. From what I've read from Mr. Bolger, this is very poor sheeting, even for upwind sailing (he calls for a 10 deg. offset for this). For reaching or running, this must be even worse.

    My guess is that this sail, along, to a lesser extent, with the others, is cut flat or nearly so. This way it will furl easier and bag less with poor sheeting angles.
     
  11. upchurchmr
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    upchurchmr Senior Member

    Doom and gloom.

    The last 30 years of reading the same story that fuel will begone tomorrow, and everyone will have sails has proven to be a colossal joke.

    There are fewer sailboats sold now than in 1980, before the gas crisis.
    People will just get use to paying more for their fun.

    Most enthusiasts who get on the eco kick produce boats that fail, cause enthusiam does not equal commonsense and knowledge.
     
  12. Kojii
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    Kojii All is remodelling

    Timing

    For centuries the ignorant had the people convinced the Earth was the center of the Universe, long after it was widely known by the intelligentsia not to be true. The status quo continued to burn people for thinking and speaking the truth.

    The conventional assertion is that sailing is just too slow and will never become accepted over the faster petro-fueled vessels.

    I know a lot of power boaters, professional and recreational. Good people, smart, qualified. The cost of fuel is the primary reason their vessels sit at the dock week after week, month after month, year after year. The cost of oil varies from well to well, refinery to pump, but at some point the cost rises above the benefit. The tide turns and it becomes a bad deal "economically". Some people have just reached that conclusion sooner than others.

    For future reference:
    http://www.theflatearthsociety.org/forum/index.php?topic=13876.0
     
  13. upchurchmr
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    upchurchmr Senior Member

    Most people don't use their boats no mater what.
    Most people over buy what they can afford.
    Most people loose enthusiam when some little thing goes wrong with their expectations.

    Its easy to ascribe global calamity to those circumstances.

    I understand and agree that petroleum is a dwindeling resource in a world of increasing population.

    The reason boats become too costly to use is the insistance on too much - power, speed, refrigeration, A/C. While I also dislike miniscule "yachts", there is some reasonable level at which you can use your boat. How many have seen 30 to 50' yachts sitting in a marina with crud on the bottom and ropes rotting and 10 years of dirt on the deck. And by that I mean sail boats, which are not necessarily dependent upon any significant cost of fuel.

    Except for liveaboards and actual cruisers, how much of the cost of a boat is fuel? How much does it have to be?

    I might believe you if the size of cars has not steadily grown in parallel with the cost of gas. Most of them carrying one person.

    Gas prices for boats sitting in a marina is a red herring.

    Respectfully in complete disagreement, mostly.

    Marc

    PS I'm sorry this has nothing to do with Wishbone-sailing-rigs, a thread which interests me. I quit on this off track subject.
     
  14. Kojii
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    Kojii All is remodelling

    Gone sailing -

    Will row the boat out past the breakwater. Sweat - the other green fuel....
    :cool:
     

  15. High Tacker
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    High Tacker (www.damsl.com)

    A note on boomless sails and sheeting, also re motorsailing with boomless sails

    Rainbow Warrior III tri-sail

    sharpii2 above questioned the sheeting of the tri-sail on Rainbow Warrior III to either leg of the A-frame near the top, and that somehow reminded me that I've seen other comments on this forum questioning motorsailing with a boomless sail.

    By the way, sharpii2, on this Youtube video of RW III motoring with all 5 sails furled, they look to me to be pretty neatly furled, so I think they are all flat cut. She's a purpose-built ship, the purpose being to chase environmental miscreants, so methinks she'll be doing a lot of motorsailing with her diesel electric power, and flat-cut sails are better for motorsailing, as per my argument here below.

    See http://www.youtube.com/watch?v=IjncCTnpPSc

    If you search Youtube for Rainbow Warrior III, there are lots of videos, and some with brief bits of her sailing, but I didn't think to single those out. There'll be more, I'm sure. She just went out for a bout of sea trials about a month ago.

    Re sheeting of that tri-sail, sharpii2 has a good question, and I intend to ask the designers. I just got a reply to my 2nd pestering email to them asking for more news. They are going out this next week for the second round of sea trials, so there should be more soon. But re that tri-sail, first of all my guess is that with so much overall sail area, the tri-sail is probably used only in light air and then more often motorsailing than not, and in either case it would be sheeted in much tighter than 10 degrees, say, at about 7 degrees when just sailing close hauled, and even tighter for motorsailing. See:

    http://sailmagazine.com/headsail_sheeting/

    I agree that it looks like a pretty narrow range of sheeting up there to the A-frame legs and not good for reaching, but maybe they have another way of doing it. At any rate, all the sails on that rig are on furlers, and in any thing more than light air, they'd probably just furl that sail and still have plenty of sail area. And when running, maybe the narrow sheeting range doesn't really matter much. Way up there, there would often be enough wind to keep that sail at least part way out to one side or the other, and shape doesn't matter much when running as long as it doesn't just keep flopping down in the lulls, and if it's that dead calm then all of the sails would be useless and they do have motor power. At any rate, the tri-sail would be about as effective running as would a big jib on a narrow monohull without a whisker pole...well, maybe a bit more effective because it's up so high.

    Motorsailing with boomless sails

    I've seen it said in this forum that a boom is necessary, which is absolutely mistaken, by somebody, I imagine, who had only ever motorsailed with a mainsail on a boom, because his jib sheeting arrangement didn't allow the jib to be sheeted flat enough. If he had simply taken both jib sheets to blocks on pad eyes at points farther aft (and closer to the centerline on an arc drawn between the existing sheeting extremes but farther aft than the track for a self-tacking jib) and then sheeted it tight, say to considerably less than 7 degrees, flattening the jib, then he immediately would have seen some effective motorsailing close to the wind with the jib alone...uh, well, it is certainly very effective on a catamaran with the leeward motor balancing the jib, indeed with two big jibs, one on each bow, flat-cut furling jibs. A jib with built in camber would be another story, but most jibs nowadays are flat-cut furling ones.

    Another way of looking at it is that many mainsails have too much camber for motorsailing. A flatter sail is better. Even if the clew can be moved farther back on the boom, still there is usually too much camber built into mainsails, that is, too much for motorsailing, when what you need quite often is a smaller angle of attack of wind on sail, and the more camber the sooner the sail will luff. It's counter-productive to try to fight that by pulling the boom on the traveler too much to windward. You add drag that way, and lose power. It's better to have a sail that can be flattened.

    Thus a boomless, furling, flat-cut mainsail properly sheeted can be better for motorsailing than the typical mainsail with a boom. And with the beam of a catamaran and enough sheeting points scattered around the deck, tracks, pad eyes, etc., and using two sheets simultaneously, a boomless sail can be just as good as a boomed sail for any point of sail.

    See the photo below of my Catbird Suite on a reach using the genoa attached to the windward bow. Note that there are two blocks on the clew of that sail, so that there are two double sheets, i.e., four ends of rope that can be easily moved around and attached at different points on deck so that I can put the clew of that sail anywhere it needs to be and with the ideal sheeting angle in the vertical as well as the horizontal, all of the sail and gear inboard, nothing outboard and inaccessible and levering the boat around, no tendency to broach. The same for the mainsail and staysail whose tacks are attached on the windward side deck so that the entire width of the boat is available for sheeting down to. No booms needed.

    This of course won't work on a narrow monohull, in which case a boom or a whisker pole is absolutely needed when the clew of the sail is outboard of the boat. Of course, a monohull is only half a boat, so the answer in the monohull case is to sell the monohull and get yourself a catamaran. See the following link for all the things you can do when you have a boat wide enough to sheet down to the deck on all points of sail.

    www.damsl.com

    With a flat sail, you can add camber when you need it simply by moving the clew in along the chord of the sail, i.e., making the chord shorter.

    A boom is NOT necessary for sailing to windward

    I've also come to realize that many sailors think that booms are necessary for sailing to windward, because so many have questioned the fact that my boat is boomless. And somewhere, in my early days of sailing, I read an explanation of sailing to windward which said that the force of the boom pushing forward against the mast was the actual force that pushed the boat forward into the wind, and hence the necessity of the boom. I don't remember what book that was, not Bolger, I think, but a book purported to be an expert rendering of the physics of sailing. Jibs were relegated to creating the much touted slot effect. I remember wondering then why all jibs didn't have booms, making for both some slot effect and more push??? Of course, with a boom on a jib, you can't have it overlapping the main.

    Anyhow, it was a borrowed book, and much later the boom broke on my little boat, which had a loose-footed main attached to the boom only at the clew. I was able to get home by attaching two sheets to the clew and sheeting to two blocks attached near the corners of the stern, flattening the main somewhat in the process, which was good because there was a pretty fresh wind.

    Lo and behold, she went better to windward than with the boom. And I realized that when you sheet down to the boat, the boat becomes the boom!

    Later on I read about and saw pictures of Arab dhows with lateen rigs, which were the first craft to sail to windward, and without booms, around 800 or 900 A.D., long before European sailors learned to do it.

    The one and only GOOD thing that a boom does is to maintain the chord of the sail, i.e., to keep the clew from riding up and moving in toward the tack of the sail, or toward the luff, i.e., to keep the sail from developing too much belly. And if you've got a wide enough boat, you don't need a boom for that one thing.

    The force of the boom against the mast serves only to put a bending load on the mast.

    I never borrowed that book again, but probably should have, just to see what else could be disproved, so that I might have tried other things sooner. Like, I'm quite sure the book said that it was impossible to sail straight into the eye of the wind. They all said that.

    BTW, many of YOU all on this forum have said that. How do you like the taste of crow?

    As a little aside here, but apropos to being careful with use of the word "impossible" or always insisting that, if an unheard of way is really better, then it would long since have been thought of and everybody would be doing it already:

    see www.damsl.com and on the welcome page look to your left and click on Wind Turbine Rig.

    And on this forum, see:

    http://www.boatdesign.net/forums/boat-design/sailing-directly-windward-27000-4.html

    Back to the subject of boomless motorsailing:

    Here's a quote from another thread on this forum,

    http://www.boatdesign.net/forums/sailboats/aftmast-rigs-623-32.html#post476746

    according to the owner of the boat Lyra in the photo below, the yellow boat with aftmast rig,

    "The contention that the rig won't go to windward is codswallop. We travel at a hull speed equal to the true wind speed at 30 degrees apparent under auto pilot and down to 28 degrees hand steering, and the rig still pulls well down to 23 degrees when motor sailing."
     
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