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Cambered Panels and the Split Junk Rig.

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  • 15 Mar 2012 14:02
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    Reply # 859692 on 856059
    Anonymous member

    Slieve,

    thanks for your excellent and very detailed description of your split rig.  I was inspired by your previous report of Round The Island Race, and that awe inspiring photo of you trashing the pointy rigs.   Have you ever had chance to sail along side a Bermudean rigged Longbow, there are not that many around (almost a shame you had not gone for a Centaur, which a two a penny).

    Making the jiblets adds complexity, how much more time involved over a 'standard' cambered sail?  I guess you gain something back on the simplified running rigging.

    Performance wise, how much better do you think it is?

    If I ever get around to going junk, my preference is for a wing sail, as David & Bertrant.  How would you think the split rig would compare?

    Wharram uses a very efficient sail sleeved around the mast, I wonder if this could be added to performance version of the split rig?  Probably not for cruising as it would not drop too easily.

    Would short battens help the jiblets?

    cheers

    Mark Thomasson

     

    Last modified: 15 Mar 2012 14:03 | Anonymous member
  • 14 Mar 2012 10:57
    Quote
    Reply # 858525 on 856059
    Anonymous member

    Hi David,

    Thanks for the quick response. You made three points so –

    1. The loads on the hauling parrels are low on Poppy, because there are no hauling parrels fitted. The rig is designed to hang down naturally without being pulled into shape.
    2. Woops! Yes, PJR does say that, and I have modified the text accordingly. Flat sail aerodynamic design is not my strong point, and I have no desire to get involved.
    3. Why? Simply because the rig was designed to be low stress and hang down. I’m aware that there can be advantages in forward rake but also possibly additional stresses on both the mast and on the rig. For me the answer was simple – upright. It’s part of the KISS system. Anything else involves thought and compromise.

    I’ve replaced Pages 1 to 9 with an updated version.

    Thanks, Slieve.
  • 13 Mar 2012 23:42
    Quote
    Reply # 857913 on 856059
    Anonymous member
    Slieve,
    Comments on chapters 1 and 2:

    "One clear feature was that the pressures on the battens were lower with the low angled yard and high sail balance rig compared with a high peaked Hasler-McLeod rig."

    I agree, if you say that the loadings on the hauling parrels are lower.

    "In Practical Junk Rig, Hasler and Mcleod advise on how to find the Centre of Lateral Resistance of the hull and the Centre of Effort (or more accurately Centre of Area) of the rig and then discuss the amount of ‘lead’ to allow. With a flat or flattish rig the amount of lead probably has to be greater than the lead that would be used with a Bermudan rig, because the forces are centred much further aft in the flat sail."

    No, it's the other way around. A flat junk sail needs less lead than a cambered bermudan sail, and PJR confirms this.

    "When it came to deciding about sloping the mast fore or aft the answer was simple - upright."

    Why? I don't think it's as simple as all that. There are benefits to be derived from a forward raked mast. Or perhaps conveniences, in fitting in with the accomodation.
  • 13 Mar 2012 15:41
    Quote
    Reply # 857495 on 856059
    Deleted user
    Congratulations Slieve on opening a whole new dimension in the great Junk Rig debate.
    There is loads for us all to consider, to analyse and to try and understand.
    Thank you very much for such a detailed and thoughtful exposition, 'warts and all'.  You will have us scratching our heads for years to come!!
  • 13 Mar 2012 02:45
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    Reply # 856805 on 856059
    Anonymous member
    Slieve,
    Many thanks for releasing the draft of your thoughts about your rig. There's a great deal of food for thought in it, and I'll study it carefully before commenting.
  • 12 Mar 2012 15:58
    Quote
    Reply # 856228 on 856059
    Anonymous member

    Slieve,

    Many thanks.  "The best is always the enemy of the good!"  It all looks good to me. 

    I have printed it because it is the only way I can really cope with these things, and I look forward to digesting it and, please, the subsequent installments.

    You may be interested to know that a sailing friend came back from the London Boat Show very excited and bursting to show me what he had brought back.  It was the January 2010 Number 37 copy of Catalyst, the Journal of the Amateur Yacht Research Society.  "You should see this!" he said.  It was your article about Poppy and her split rig.  I thought that it was a very good read with excellent photos.  I don't know if it has appeared in the JRA Nwesletter/Journal or on the web site but I think not.  If not, would it be possible please for you to add it?  I thought that it is a very good general exposition and that we could benefit from it. 

    Jonathan

    Last modified: 12 Mar 2012 18:33 | Anonymous member
  • 12 Mar 2012 14:54
    Quote
    Reply # 856181 on 856059
    Anonymous member

    Thank you, Slieve.

    Quite frankly, anything will do for the more curious of us. I never believed that curiosity killed the cat.

    Cheers

    Ketil
  • 12 Mar 2012 11:16
    Quote
    Message # 856059
    Anonymous member

    Hi Guys,

    Life is so busy that it is now clear that if I wait until the write up on the Split Junk Rig is complete it will never be produced. I therefore plan to place sections on the web, even in draft form. Who knows, but it might help the process along. As the sections placed on my pages on the Public Pages are only in draft form, and the diagrams are only sketches for my benefit and have not been properly drawn, they are subject to change at any time. Similarly there are photographs missing. I apologise for the shambles, but hope it will help the debate and encourage readers to get involved in the junk rig movement. If anyone finds my (deliberate?) mistakes please mail me direct rather than clutter the forum with details of my bad spelling.

    Cheers, 

    Slieve.
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