WishBone Sailing Rig

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

  1. brian eiland
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    brian eiland Senior Member

    I don't think the SMG cat had staysails,...only a roller furling/reefing genoa and main?
     
  2. Spiv
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    Spiv Ancient Mariner

    They give the rig rigidity, balancing side loads and flexing, similarly as diamonds in single masts.
     
  3. sharpii2
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    sharpii2 Senior Member

    Actually, for most practical purposes, the 'main'' is a Stay Sail. It sets on a Jack Line just aft the mast, for its entire luff length. For this reason, it has all the liabilities of a Stay Sail, such as losing its shape, should the Jack Line sag too much. Granted, with the Jack Line being nearly parallel to the mast, this is far less likely to happen than if it were angled away from the mast, but it's a real concern, none the less.
     
  4. brian eiland
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    brian eiland Senior Member

    Spiv, you might find this interesting. A few days ago I discovered there was an old friend of mine in town with his current catamaran Ppalu (the original Peter Spronk built one).

    Had dinner with him the other night. Randy West has had LOTS of experiences with all types of vessels over the years. He was also the skipper of Procyon for several years when she was first built. We talked a little about her A-frame, wishbone mast rig.
     
  5. Spiv
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    Spiv Ancient Mariner

    That is the first cat-ketch I see!!
    I wonder why they are not popular with cruisers, but then we have the heard mentality to deal with.


    Please tell us what Randy said about Procyon's rig, I remember reading they had problem with the masthead junction of the two masts.
    Once again, torsion loads at work... did they solve the problem?
     
  6. brian eiland
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    brian eiland Senior Member

    If you can find photos of the early Peter Spronk catamarans you will find that he was a big fan of lower aspect sail plans that involved two mast. Most were schooners, some were ketches.
    Spronk catamaran images

    We talked a little bit about that 'connection problem', and perhaps we will again this morning when we meet up again. Interesting solution involving titanium.
    But I have even bigger fish to fry....;)
     
  7. brian eiland
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    brian eiland Senior Member

    De-ketchification of America

    Perhaps have a look at this article from Eric Sponberg
    De-ketchification of America
     
  8. Spiv
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    Spiv Ancient Mariner

    Brian,
    this is perhaps not the best thread for these pic, but forgive me.
    You can add it to your collection.
    One of the best cruising rig I have seen cruising the last 5years when I was in Fiji:
     

    Attached Files:

  9. brian eiland
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    brian eiland Senior Member

    So far I know of several features to avoid:
    1) Do NOT mount the bases of the mast legs at the gunnels of the vessel, particularly with a mono-hull. There are too many situations where the lower legs of the rig will interfere with high dock surfaces, and/or with tall pier pilings. Procyon experienced damage on several occasions.

    2) Do not utilize carbon fiber/nomex-core construction. It's thought that this combination is too brittle for these bendy mast tubes, with some resultant skin-core delaminations having occurred.

    3) They resorted to some sort of a fixture at the upper join made of titanium. There are two considerations here;
    a) there is a lot more potential difficulties at the upper masthead if the two bottom bases are also limited in their degree of movement.
    b) Procyon's tubes were built of straight sections, then torture bent into their arch shapes.
     
  10. brian eiland
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    brian eiland Senior Member

    Here is a posting that needs repeating.

     
  11. brian eiland
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    brian eiland Senior Member

    Double A-frame Rig

    Recently a gentleman, David Slater, viewed a posting I had made on the unusual rig onboard "Diomedea Exulans". He wrote to tell me of a rig his father, Alan Slater, had designed and built back in the early 1970's,.... (for those that don't recall, Alan Slater was the gentleman who brought us the PDQ line of catamarans).

    What first caught David's attention was the manner in which the two mast on Diomedea Exulans meet at a single point at deck level approx in the middle the boat, then projected upwards, one forward and one rearward from that central point. David wrote to tell me of his father's experiment with a similar concept, but involving A-frame masts rather than single mast tubes.

    So here is the document (a copy of a Multihull article) that David just sent to me (attached PDF), and a couple of photos.
     

    Attached Files:

    Last edited: Nov 28, 2016
  12. brian eiland
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    brian eiland Senior Member

    BTW, here is the letter David sent along with that material

     
  13. Kojii
    Joined: Oct 2006
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    Kojii All is remodelling

    Some thoughts...

    Bring legs together at hips, not at head. Form arc at layup, organically. Arcs are inherently stronger (done right) than straight lines. Birds have no straight bones.
    Tootles
     
  14. Kamelisko
    Joined: Aug 2016
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    Location: Finland

    Kamelisko Junior Member

    Hi. There is a this boat with this kind of rig for sale in Finland.

    Don't know anything about it, just happened to notice...

    In english:
    Iveco Aifo 8061 - 145 hp, special rig, single handlable, electrich winches, generator 6,5 kW, hydraulic stem- and aft props, anchorswinches in stem and aft, accessories for charter usage.

    http://www.nettivene.com/purjevene/alumiinivene/636870
     

  15. brian eiland
    Joined: Jun 2002
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    brian eiland Senior Member

    Interesting. I tried a save a copy of the photos of this rig, so I might post them on this subject thread and another subject thread dealing with aftmast rigs.

    I was unable to save a copy of the photos. My concern is that these 'for sale listings' disappear fairly soon, and then we have no record of the vessel's existence.

    I would also be very interested in asking the owner about his satisfaction/dis-satisfaction with the rig.
     
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