WishBone Sailing Rig

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

  1. yipster
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    yipster designer

  2. Pericles
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    Pericles Senior Member

  3. yipster
    Joined: Oct 2002
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    Location: netherlands

    yipster designer

    Pericles, yes there is the design i tripped over while i should have looked away
    a new tread somewhere would have been better but many rig ideas allready here
    with the presentation on yachtforums locked for comments i check what we think
    so yes, that concept, and i realy think broadly of concepts, got me confused
    Carl of yachtforums and PBB mails members this info and thanks for that
    at first sight the text and looks are interesting the next second i sat baffled
    why 4 masts, how can sail geometry change moving the straight booms,
    why sideboards, why not the lead in the foil instead of the extra bulb etc etc
    i like dearing concepts but this sounds to my eye unbelivable, nice pic's tho
     
  4. Pericles
    Joined: Sep 2006
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    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

  5. Kojii
    Joined: Oct 2006
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    Kojii All is remodelling

    catenary Q

    Pericles et al,
    Any ideas regarding previous posting on turbulence/drag interaction of sail/catenary mast as in wishbone. Specifically would there be potential advantage on some points of sail? Any ideas appreciated.
     
  6. Squidly-Diddly
    Joined: Sep 2007
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    Squidly-Diddly Senior Member

    Pericles, how do they launch the Launch?

    They must have done something fancy to hide some heavy duty gear.

    I'm sure they don't want that motorboat slamming against the side of the yacht during launching.

    The distance from the top deck to the water would increase pendulum.

    Any clue how that is addressed?
     
  7. brian eiland
    Joined: Jun 2002
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    brian eiland Senior Member

    Any updates to report?

    I have some interested parties who persist to ask questions about this designer and his reasonings.
     
  8. Kojii
    Joined: Oct 2006
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    Location: Ensenada, BCN

    Kojii All is remodelling

    Very little. The bus driver is pulling up distant memories. Did say that the boat performed very well in a blow crossing El Caribe ("as designed" he quotes Mr Greenway as saying). This steady ride in rough water is is our experience as well. It is consistent with Bolger's assessment as a good heavy weather rig and combined with the slender hull you get very good handling in an irregular seas.
    Mr Greenway was probably not a Boeing engineer afterall. There is some indication he was involved in the F.L. Wright Foundation. Who knows. He did build a geodesic dome in Northern California, and we are told the New England style boat shop in Port Townsend where the two North Pacifics were built.
    Will post the latest photos under sail. As you can see the isn't so much as a rifle on the water. We made 2 knots in this very light air which may have reached 6 knots at the masthead from time to time. Not bad for 11 tons. The sails stayed full as long as there was any wind at all. Sailed it to the dock as the light was waning.
     

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  9. basilroman
    Joined: Mar 2010
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    basilroman New Member

    Solid backstays on an A frame rig?

    Wow, I am glad google dug up this long string on A frame rigs. You guys have dug up tons of good info.

    I am working on a 36 foot cat design with an A frame rig and am thinking about making solid backstays. I'll admit I kind of like how it looks drawn up and how it flows with the hard top and targa. The negative perspective would be that the four legs look like an oil derrick.

    Functionally, I like how it would allow the front legs to slope back more steeply moving the peak aft, and spread the compressive load across most of the leeward hull. It would also serve to lighten up the individual legs substantially and lighten up or even eliminate the forestays. I guess one other functional issue would be more cross cabling between the legs which would increase windage and maybe limit the size/roach of the boomless main, though pre-bending the legs by wishboneing them in to the peak could eliminate some of that.

    I'd love to hear your thoughts.
     
  10. alan white
    Joined: Mar 2007
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    alan white Senior Member

    Windage, windage, and windage... The issue of two masts (port and stbd) has been discussed in detail already, and still, looking around, few boats have 'em. But adding two more, the question of windage being excessive, being at least double the amount the A frame rig suffers, it's gotta be a lot of windage aloft.
    With the A frame alone, it's easy to stay the rig from at least 3 points by wires, and wires are very light and thin compared to aluminum sections, not to mention wires don't need to be maintained in column! The complication of stiffening tubes that are skinny enough to present a minimum windage (still too much windage) would be prohibitavely expensive anyway.
     
  11. basilroman
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    basilroman New Member

    I hear you on the windage. However, a comfortable cruising cat already has very high windage, so the percentage increase would be in the single digit percentages for A frame or even double A frame, even considering more air flow aloft. On a mono it looks like it would be well into double digits, so a bigger difference there.

    Plus, even though a negative under power or heavy seas, windage can be somewhat compensated for with sail area while sailing.

    The bigger cat benefit is how nicely the A frame opens up the cat layout. A double A frame would also take some cost out of the hull structure.

    This SMG50 production cat seems to be getting a good reception, pics below.
    http://www.newswinch.com/fr/wp-content/uploads/2009/11/mat-bipole-4.jpg
    http://www.sailawayyachts.co.za/catamarans/images/CC443_big.jpg
    http://www.adrianews.com/images/stories/reports/_a2n7727__large_600750.jpg


    Catbird Suite is 60 foot cat for sale, so pics also available.
    http://www.damsl.com/postcards/popup.html?img=100_catbir24.jpg
     
    Last edited: Mar 18, 2010
  12. ChiefOren
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    ChiefOren Junior Member

    Solid Backstays are dangerous. They can snap, and you cannot redily fix them. It is far better to have lines that can strech a bit and aleviate the stress on the masts. Remember, the masts are working with the wind, and if they are too rigid, the fatigue of the metal struts is much greater. I'm sure George agrees here. I plan to have an A-frame aft-mast rigging, and the back-stays are going to be hefty galvanized lines. Better to go big on lines, but avoid rods. At least with the lines, they don't usually fail at once, but you can see one or two strands that snap, and you have an indication of what's to come. But if the rod, or brace breaks, the intire rigging will go, without notice.
    Good luck with your project.
     
  13. brian eiland
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    brian eiland Senior Member

    We are having some discussions over on the aftmast subject thread about an Italian research paper that did some wind tunnel testing on an A-frame mast configuration. Thought it would be timely to bring this 'wishbone mast' discussion up again, and also put some photos with this A-frame catamaran project.


    http://www.sail-the-difference.com/home/english/the_features_of_the_easy_to_use_smg_catamaran/smg_50plus/
     

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  14. dskira

    dskira Previous Member

    To much time on the computer not enough time sailing.
    It seams that any guy open a "studio" and "design" yacht.
    They think it is a "niche" to get rich. They confound the owner wealth and there own position.
    What a load of crap.
    Daniel
     

  15. gar37bic
    Joined: Feb 2009
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    gar37bic Junior Member

    Maybe I'm not enough of a traditionalist - I like the looks of the a-frame on the cat! Of course, I'm biased, since I bought and am restoring this boat: http://www.sail-works.com/KOLIKA/. ;)

    That cat is a nice kittie! As the cat page mentions, the a-frame mast seems to make especially good sense on a catamaran, because the mast base transfers the forces directly to the hulls rather than a big heavy cross beam.

    I didn't find your thread where you talked about the italian analysis. Can you post a link, or something?

    I was looking back over this thread prior to replying. WRT windage, according to the original designer of my boat, the windage is similar to or perhaps less than a single mast. There are several reasons:
    • The individual legs have much less side load, and share the effort so can be much lighter and smaller
    • They can be designed with a more effective airfoil shape
    • People are not aware of just how much windage the wire rigging causes. IIRC my old fluid dynamics, a round profile (wire) causes as much drag as an airfoil with 10 X the cross section. If true, then think of each wire in the standing rigging of a typical traditional rig as being an airfoil 30/8" (2.75") across.
    • The sail can be more efficient (given the inefficiencies of any roller furling), because the mast does not spoil the leading edge
    • A small thing but possibly significant - the support structure for the two masts is less, as the forces can be passed directly into the hull instead of via a heavy crossbeam - this is true to some extent even for a monohull. In my boat there are a couple of extra frames in the hull, and a big steel bracket that passes the force through the side deck.
    • Of course this also means no big post in the middle of the boat! :D
    • But my side deck has a big 'ol mast sticking out of it that gets in the way when trying to go forward :(
     
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