Need help identifying rigging type

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  • 17 Oct 2020 10:29
    Reply # 9309022 on 9306172
    Anonymous member (Administrator)

    Funny that, Paul.
    I surely see the point in raking the foremast of a JR schooner forward.  I guess this is partly to move the sail as far forward as possible, and partly to avoid that the sail gybes back and forth in the turbulence of the main. However, for the main mast and for a sloop mast, I have seen very little of this. Below is a 14.5m sea-going junk, showing what I mean.

    Now I have looked over photos of your La Chica. I notice that the foremast has a moderate forward rake while the mainmast appears to stand pretty upright.
    What problems did that mainsail give you, which you did not have with the foresail?
    I remember Annie Hill once told that in her area, one could have an annoying old swell from the sea, combined with light winds, and that was her main argument for raking the mast forward. I can see that point. I just wonder why the Chinese didn’t think that way.

    Sheet gearing:
    I notice that many use as much as 5- and 6-part sheets, even on small boats.  This must cause a lot of friction and make sails reluctant to swing out in light winds. I tried 5-part sheet on Johanna, the first couple of weeks, but soon changed to 3-part. With this setup, and with an upright mast, the sails swing out in so light winds that the panels have not inflated properly yet. Pretty flat waters, though, mostly...

    Arne


    Last modified: 17 Oct 2020 17:24 | Anonymous member (Administrator)
  • 17 Oct 2020 01:01
    Reply # 9308588 on 9307252
    Frankly,

    If I could choose, I would avoid forward-raking masts on junkrigs. Forward rake soon moves the mast top a foot or two forward of the partners, and this tends to give a halyard angle which constantly pulls the sail forward. This may lead to added friction when hoisting and lowering the sail, unless one does ‘clever things’ (read: add complications). I have studied a number of traditional 2-3-masted Chinese junkrigs (diagrams and photos), and the big mainsail always sits on a vertical mast.


    Sorry Arne, I totally disagree with you on this one. I always advocate forward rake if it can be done. It goes a long way to stabilising the sail once you ease the sheets. I've found none of the issues or complications that you mention.

  • 16 Oct 2020 17:36
    Reply # 9307861 on 9306172
    Anonymous member (Administrator)

    The Tube Tabernacle, or...
    ...how to make a mast taller without lengthening it.

    I read somewhere below that the original mast for that unstayed gaffrig was a little short for a JR. Actually, I have recently been pondering on how to make a mast ‘one panel taller’ without making a taller mast. The answer is to install a tube tabernacle, and then plonk the mast into that, but with the mast step now raised as much as needed. If one does the sums right, this will produce a taller mast without having to raise the boom, unlike with ordinary tabernacles.

    This solution has some advantages, and only one drawback:

    • ·         The T-tabernacle can be firmly installed ‘forever’ in the boat without problems with leaks or movement.
    • ·         The mast (shimmed out to make a tight fit) just slides down the tube until it is stopped by a stout bolt or whatever, well above the original mast step.
    • ·         As said, the boom of the sail does not need to be raised to clear a tall tabernacle.
    • ·         Any wires from the masthead can just drop out of the bottom end of the mast, and then be fished out through an oval slot near the bottom of the t-tabernacle.

    The downside is of course that the mast needs a crane or derrick when installing it, so is not for everyone.

    On the diagram below, I have tested the idea on that Kelt 8.50. Here I imagine that the owner one day comes to his senses and decides to add a seventh panel on his sail. That tube tabernacle lets him raise the mast enough for that panel without ending up with too little bury of the mast in the t-tabernacle.

    Just an idea.

    Arne


    Last modified: 17 Oct 2020 17:39 | Anonymous member (Administrator)
  • 16 Oct 2020 16:57
    Reply # 9307773 on 9306172
    Anonymous member (Administrator)

    Graeme,

    I haven’t given the correct position of the CE for this boat a thought. My comment was just about mast rake and sail-to-mast balance.
    I am pretty sure I could make a junk sail work with a forward-raking mast, possibly by adding downhauls.
    However, I am humble enough to regard the old Chinese junkies to be the pros, with me just scratching the surface of their knowledge. Since they go (went) for vertical masts for the biggest sails, so do I.

    Cheers,
    Arne


  • 16 Oct 2020 14:12
    Reply # 9307422 on 9306172

    Hi Arne, I wasn’t advocating forward rake (though I have come to rather like the look of it - and some people do say it has advantages. I have not had the experience of it.)

    I was just looking for a way to get a junk sail to look about in the right position in relation to the underwater profile, without having to shift the position of the mast partners.

    Just eyeballing it, it actually looked to me as though vertical mast and a Johanna rig with the minimum of balance would be close to about right on that boat with that mast position. But not sure, and I was interested in what you would think about that. I don’t think a SJR or any high balance single mast rig would work on that boat, unless the mast were shifted aft a bit.

    Correct me if I am wrong. The purpose of the conversation, for me, was hopefully to learn something.

    Also, I didn’t read the specs very carefully – at 5.7 tonne it’s a bit more substantial than just a little sharpie.

    I think I see what you mean about "halyard angle", though I would have thought the ability to rake the mast forward a little, if that is necessary to get the sail in the right place, would have been an advantage of the Johanna rig. I don't know if it would be the right thing to do in this case, though.

    PS on second look,  "halyard angle" seems not to depend simply on mast rake. Within limits, it looks to me as if you could rake the mast forward a little, and increase the balance a little - and thereby move the centre of the sail forward quite a lot -  without actually changing the angle of the halyard to the vertical. To my uneducated way of thinking. Within limits. If you wanted to.

    Last modified: 16 Oct 2020 14:33 | Anonymous member
  • 16 Oct 2020 12:16
    Reply # 9307252 on 9306605
    Anonymous member (Administrator)
    Graeme wrote:

    . (I would be interested to know what Arne thinks of the Johanna sail - with vertically raked mast and minimum balance through to a good forward rake and more balance - there seems to be enough scope for adjustment to get things just about right?)



    Frankly,

    If I could choose, I would avoid forward-raking masts on junkrigs. Forward rake soon moves the mast top a foot or two forward of the partners, and this tends to give a halyard angle which constantly pulls the sail forward. This may lead to added friction when hoisting and lowering the sail, unless one does ‘clever things’ (read: add complications). I have studied a number of traditional 2-3-masted Chinese junkrigs (diagrams and photos), and the big mainsail always sits on a vertical mast.

    Maximum balance for a low AR Johanna-style sail is about 17%. If I need more balance, say up to 22-24%, I would rather design the sail with only 60° yard, as on the diagram below. This results in a nice halyard angle. If even more balance is needed, I would rather go for the SJR.

    Arne


  • 16 Oct 2020 03:53
    Reply # 9306833 on 9306172

    Wow! JRA is such a wonderful resource of great minds. Thank you all.

  • 16 Oct 2020 00:42
    Reply # 9306605 on 9306172

    Congratulations to David for figuring out the sail plan (it had me bluffed.)

    However, the builder seems to have rigged the boat with something a little more conventional. The actual set-up as seen in the photographs, seems to be nothing other than a conventional gaff sloop, the only odd thing being it is unstayed, except for a forestay to the stemhead, and a naked bowsprit. Perhaps the bowsprit is intended to be used for a flying jib or a ghoster or something like that, in light weather. As David pointed out, the "spinnaker pole" in the drawing doesn't look like a very good idea, but setting  such a sail to the end of a bowsprit is not quite so impractical, if you want to fool around with that sort of thing in light weather.

    I imagine the sole purpose of the forestay is to allow a moderate-size working staysail to be easily managed.

    As actually set up, with gaff main and a staysail hanked to that forestay, it is not all that off-the-wall. You would never get the forestay as tight as some people would like, but it would be plenty good enough. It might quite possibly sail very well just as it is. As a plain gaff sloop it looks like a delightful proposition for sheltered shoal water. I don't think every boat with a free-standing mast necessarily has to be converted to a junk rig.

    If you want a junk rig, David is right - but don't forget, an unstayed aluminium mast can easily be extended - extended aluminium poles seem to be de rigueur here in NZ, where we can't get tapered lamp poles. You don't need to settle for a short mast , though I don't think this little boat wants too large a sail area. 

    Couldn't resist spending 5 minutes to plonk some junk sail plans on this neat little adventure boat, with a slightly extended mast in its current position. The low AR Johanna sail looks good, to me. Actually, they all look a little too far forward on the hull, especially the SJR which looks plain wrong - but there are ways around every problem. (I would be interested to know what Arne thinks of the Johanna sail - with vertically raked mast and minimum balance through to a good forward rake and more balance - there seems to be enough scope for adjustment to get things just about right?)


    Last modified: 16 Oct 2020 02:09 | Anonymous member
  • 15 Oct 2020 22:12
    Reply # 9306334 on 9306172

    Zooming right in on the sail plan, I can see a gaff mainsail that's just a bit unusual in that it has a sprit to hold out the clew, rather than a boom. I can also see a large headsail that is not tacked down to the bow or bowsprit, but instead attached to a kind of spinnaker pole ( though I can't imagine how that pole could attach to the mast with the gaff sail's hoops sliding up and down). So it has something in common with modern asymmetric spinnakers/code zeros and the like. I would hazard a guess that Bolger might have drawn such an off-the-wall rig, but a practical seaman wouldn't have built it like that.

    If you were thinking of converting it to JR, the mast is rather short, and being well aft, the sail would need a lot of balance area, so could be a low AR SJR or possibly something similar to the one I've drawn for Annie's Fanshi. 

  • 15 Oct 2020 21:49
    Reply # 9306326 on 9306172

    Wikipedia tells me that catboats were traditionally gaff rigged. The Com-Pac Horizon Cat has a spar at the top of the sail.

    Last modified: 15 Oct 2020 21:51 | Anonymous member
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