The "Sib-Lim" Challenge

  • 05 Feb 2015 23:30
    Reply # 3218781 on 3144241
    Anonymous member (Administrator)

    High-peaking yard and the forces in the Throat Hauling Parrel (THP)

    My experience with high-peaking yards on my own boats, is that it depends. On Johanna the THP tension is quite high (but no need for winches.). For a good while, I thought that it was because of the low aspect ratio, AR, of her sail (48sqm/AR1.87). With Broremann’s sail (10sqm/AR2.15) and that of Frøken Sørensen (20sqm/AR1.95) the THP tension is fairly light. My hunch is now that the tension in the THP is more a function of the position of the halyard’s slingpoint on the yard, than of the sail’s AR. On both Broremann and FS I attached the halyard about 5% aft of the midpoint (on Johanna; on the midpoint). I guess this helps to peak up the yard with less strain on the THP. I will look closer on this when rigging Ingeborg (35sqm/AR1.90) this spring, to find the optimum attachment point of the halyard.

    Cheers,
    Arne

    PS: All the mentioned boats have 70° yard peaking.

     

  • 05 Feb 2015 22:45
    Reply # 3218765 on 3218100
    Karlis Kalnins wrote:

    A bit of a tangent, but how do you manage the placement of winches and line cams or cleats so that they are easily accessable and usable from the cockpit and from the pram hood watch position? Do you also run the main sheets back to the hood as well?

    I would hope to have everything on the back of the cabin.  Presently on Fantail, that's where my halliard winch and control lines are and I intend to move the mainsheet there, too.  I find they are better here than scattered around the cockpit and keep me well away from the sheet when I'm tending sail.  I used to be able to pull up most of Badger's sails from the pramhood.  I have a self-tailing winch for the halliard, which I would always choose to have, although I can pull up the whole sail (and usually do) if I'm standing in the cockpit.  A pram hood not only protects you from rain and spray, it also keeps you from getting sunburnt and is the most wonderful place to sit and keep an eye on things.  I still haven't entirely scrapped the idea of putting one on Fantail because I found I enjoyed using it just as much coastal sailing as offshore.
  • 05 Feb 2015 22:13
    Reply # 3218740 on 3144241

    No, it's more like the one on Pugwash (which has a sail that Paul Thompson made when he was considering the sailplan for La Chica), but the principle in both those (as well as in Slieve's), is to use a lower angled yard to reduce the LHP loading, increase the balance, and get better value from cambered panels all the way up the luff.

  • 05 Feb 2015 21:21
    Reply # 3218691 on 3144241

    What's the sailplan you're using there? Is it a Slieve split-rig without the split?

  • 05 Feb 2015 20:40
    Reply # 3218675 on 3144241

    I've added an image of Sib-Lim with a medium AR sail to my photo album.

    Last modified: 05 Feb 2015 23:18 | Anonymous member
  • 05 Feb 2015 17:43
    Reply # 3218515 on 3144241

    Karlis,

    The key to successfully working the rig from a pramhood is to have a platform on which you can stand, or at least kneel, so that the rim of the hatch is at waist height. Then the halyard, and sheet as well on a larger boat, need to be led to self-tailing winches. I find little difficulty with working the rig this way, though to make it easier still, the YHP on a big rig could also do with a small winch to tension it. The sheet should be led around the side of the cockpit, using two extra blocks. 

    I don't know whether Annie is thinking in terms of working the rig through the pramhood, or more of its use as a superb ventilator, and to add natural light below, with a perspex closer. If Peter Scandling adapts the design for ocean-going, it will probably be a different story. If you're going to the trouble of building a bespoke boat, you make it to fit you, and to suit your particular usage.

  • 05 Feb 2015 03:36
    Reply # 3218100 on 3144241

    A bit of a tangent, but how do you manage the placement of winches and line cams or cleats so that they are easily accessable and usable from the cockpit and from the pram hood watch position? Do you also run the main sheets back to the hood as well?

    If I was seated in my companionway looking out from [an imaginary] pram hood, I could definitely release the cams and reach the winches but I don't think there's a chance I could actually raise the sail from inside the hatch (if there was one), there would be no body leverage.

  • 04 Feb 2015 00:49
    Reply # 3217239 on 3217115
    Annie Hill wrote:
    Ash Woods wrote:3215480 of 2nd Feb.I am having trouble keeping up, this thread is moving so fast, Annie is your rotating pram hood made as  drawn in PJR?
    Hi Ash - well, that's what I want.  David's present one is incorporated in a sliding hatch and he's perfectly happy with it.  (No doubt he thinks I'm quite loopy, but is far too polite to say so.) I don't like sliding hatches, but he has now kindly designed me an alternative.  Yes, the thread is moving along quickly!!
    I think (hope) what we'll end up with is the pramhood I described in  the article you'll find at http://www.junkrigassociation.org/junkfaqs_sailing , but not built onto a sliding hatch, built onto a raised wedge-shape extension to the deck instead. The pramhood itself is made using proprietary sprayhood fittings, but is in essence the same as the PJR model.
  • 03 Feb 2015 21:47
    Reply # 3217115 on 3216492
    Ash Woods wrote:3215480 of 2nd Feb.I am having trouble keeping up, this thread is moving so fast, Annie is your rotating pram hood made as  drawn in PJR?
    Hi Ash - well, that's what I want.  David's present one is incorporated in a sliding hatch and he's perfectly happy with it.  (No doubt he thinks I'm quite loopy, but is far too polite to say so.) I don't like sliding hatches, but he has now kindly designed me an alternative.  Yes, the thread is moving along quickly!!
    Last modified: 03 Feb 2015 21:48 | Anonymous member
  • 03 Feb 2015 20:38
    Reply # 3217050 on 3144241

    I've made a very rough comparison of three sails, all at 31.2 sq m, SA/D 15:

    1. Low AR, fanned, yard 4.1m, battens 5.02m, six sheeted points with single sheet, two unsheeted battens, mast minimum LOA 9.5m.

    2. Medium AR, yard 3.77m, battens 4.34m, six sheeted points with single sheet, all battens sheeted, mast minimum LOA 10.5m.

    3. High AR, yard 3.3m, battens 3.8m, eight sheeted points with upper and lower sheets, all battens sheeted, mast minimum LOA 11.5m.

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

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