About the Junk Rig

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  • 26 Apr 2020 08:28
    Reply # 8928686 on 8921369

    My two pennyworth:

    The music is not unpleasant, but it is unnecessary. Since sound is possible, ditch the music and add a simple voiceover. If possible, add descriptive text with arrows pointing to areas of interest, and have someone with a clear, slow speaking voice read a slightly amplified version of them. Or just say very simply what is going on.

    Only a THP is shown. I don't think this shape of low-peaked sail should have only a THP, more of a combined THP/LHP going to the yard and one of the upper battens would be better.

    No standing tack parrel (PJR fig 3.25) or standing lower luff parrel (PJR fig 3.26) is shown, and one or other would certainly be needed.

    Although the topping lifts are shown as in PJR fig 3.47, I don't think this is a good way of rigging them; the lifting effect is concentrated too far forward. They should be the other way around, to lift the after end of the bundle more effectively. Running topping lifts (PJR fig 3.51) do not act in the same way as standing topping lifts (PJR fig 3.47) and this is one point in which I think PJR is not quite correct.

    On the 3D, (2) is labelled as a luff hauling parrel, when in fact it's a throat hauling parrel, as above. Again, no standing tack parrel (PJR fig 3.25) or standing lower luff parrel (PJR fig 3.26) is shown, and one or other would certainly be needed.

    Why is (3) clew mentioned in the annotations? This has no particular significance in JR. Other items could do with some annotations, such as battens, batten parrels etc.

    Last modified: 26 Apr 2020 08:43 | Anonymous member
  • 26 Apr 2020 03:38
    Reply # 8928409 on 8921369

    FWIW I can only get the 3D model to open on my phone.  It looks pretty informative, but is so 'twitchy' on that tiny touch screen that it is difficult to look at.  No doubt it would work better on an up to date OS on a tablet. 

    The video shows a sail going up and down.  It doesn't show it in any aspect other than hauled hard in, which is a shame.  The accompanying music is both unnecessary and irritating, to this curmedgeon. 

  • 26 Apr 2020 02:20
    Reply # 8928350 on 8921369

    Sorry, Jim, about wandering off the subject of the original post.

    I think the graphics are excellent, and show the important aspects in a way a video could not do. A good video might perhaps compliment what has been done. 

    The suite of three 3-d models on the left, and the moving model on the right, just about capture the basics in a way which should be easy to understand. If some more frames could be put into the model on the right, to create a smooth "moving picture" of the reefing and furling, it would be even better.

    In fact, as it has worked out, the computer graphic demonstrations now open the way for some much more straight forward and easy-to-make complementary video clips.

    (There is a minor bug in this model on the right: the aft lifts and lazy jacks on the port side seem to stop well short of the boom, an error which is presumably easily fixed.)

    Well done, Jim, and thanks to whoever created the software.


    (Strewth! Was the meeting really three years ago?! It doesn't seem that long!)

    Last modified: 26 Apr 2020 02:34 | Anonymous member
  • 26 Apr 2020 00:28
    Reply # 8928183 on 8921369

    In April of 2017, I proposed, at the JRA's AGM in Whangarei, New Zealand, that we commission a 3D interactive APP to illustrate the components of a typical junk rig, including views while reefing. What you see here was the result. It's a beta version.

    We would like your feedback on how it works for you and suggestions for improvement. I would like to think we can build on this foundation as time goes by, to answer new questions.


    The idea is to help the newcomer to unravel what at first is confusing and complicted. Of course it not but a good visual aid should get them sorted out quickly.




  • 25 Apr 2020 09:40
    Reply # 8927080 on 8921369
    Anonymous member (Administrator)

    It is clear that this sort of sail catcher will not allow one to adjust the balance of the sail under way, but I have never used running tack parrels etc anyway, so that is not an issue. I imagine that it is best to first rig the boat with ordinary rope sail catchers, when the rig is new, and when the positions have been  established (as on Ingeborg, now) after some sailing, one can tailor-make a sail catcher to the rig.

    One challenge will be to find where the YHP and THP will go.

    Arne

    Last modified: 25 Apr 2020 09:50 | Anonymous member (Administrator)
  • 25 Apr 2020 07:51
    Reply # 8927041 on 8926662
    Graeme Kenyon wrote:

    Ueli, putting the whole thing on one side of the mast will not work. Standing batten parrels would then be certain to hang up.

    you're right, the idea was on the stupid side of thinking – sorry!

    ueli

  • 24 Apr 2020 23:04
    Reply # 8926662 on 8921369

    Ueli, putting the whole thing on one side of the mast will not work. Standing batten parrels would then be certain to hang up.

    Also the split in the SJR has nothing to do with the working of the sail catcher.

    You can be sure of the above two points.

    The goal is to have an arrangement under which which battens will fall easily into captivity when the sail is lowered or partially lowered. The cloth panels will follow.

    I don't say the sail catcher won't work with a contiguous sail - in fact I would have thought it should - but I have never seen it tried. I raised the issue because two people have firmly told me that they had seen a case where it didn't work on a contiguous sail. (I suspect the case in point might have been Feng Zheng.) I queried whether standing parrels might be a problem because this is the only reason that I can see why it might not work with a contiguous sail. I don't know for sure, and look forward to Arne's trials with his variant of the McGalliard sail catcher.


    EDIT

    Just for the archive, I should add that my previous claim that the sail catcher reduces the tendency for lifts/lazyjacks to interfere with sail camber, was an exaggeration. Looking at recent photographs (taken by the crew of Fantail at Russell earlier this year) show that the aft lift still does sometimes quite clearly interfere with the sail.

    I agree with Arne that this probably does not matter much, if at all.

    Last modified: 30 Apr 2020 23:33 | Anonymous member
  • 24 Apr 2020 18:00
    Reply # 8926132 on 8921369

    for full panels (no split) it might be better to hang the whole sail catcher to the port side of the mast.

    ueli

  • 24 Apr 2020 16:39
    Reply # 8925968 on 8921369
    Anonymous member (Administrator)

    Don't worry Graeme.
    I make it and install it and then see how it works. If there are problems, I either fix them or remove the whole contraption. The sail catcher will only be hung up to the outside of the topping lifts and mast lifts. It will not be integral with these critical lines.


    Remember, if I had taken all my worries around the cambered panel sail seriously in the first place, I would have given up before I even started building it.

    The attitude must be:
    It may well work  -  it is not, after all, an airliner we are building.


    As for batten parrels which hangs themselves up (in each other), I soon replaced them with 20mm webbing. 


    Arne

    Last modified: 24 Apr 2020 16:43 | Anonymous member (Administrator)
  • 24 Apr 2020 15:41
    Reply # 8925881 on 8921369

    Arne, there is something about the Slieve-type sail catcher that I should bring to your attention: a couple of people have told me quite firmly that it will only work on a split junk rig. In neither case was any sound reason given, but never-the-less the opinion was firmly held, and it was enough to give me cause for thought, and to wonder why that might be so. I am sure that the spit in the sail has nothing to do with the working of the sail catcher.

    After giving it quite a lot of thought, the only thing I can imagine is the possibility that standing batten parrels might hang up at the point where the starboard edge of the sail catcher lies against the starboard side of the mast. (Assuming the standard port-side-slung rig.) MAYBE that could prevent reefed panels from falling freely into the sail catcher. The cloth of the sail catcher is cut away there - but the tube which gives rigidity to the sail catcher's starboard edge does lie against the mast on the starboard side. I am just speculating here, as standing batten parrels are outside of my experience.

    The thing about the split junk rig, in relation to the sail catcher, is not the fact that it is split, but in the fact that a split junk rig typically does not have standing batten parrels. The running parrel-downhauls which Slieve gave to his SJR design can not hang up at that point, and the reefed panels always drop down into the catcher with no problems. Perhaps this is because (a) the running parrel-downhauls are thin and slippery, or (b) perhaps because they can "run". I don't know if either of these factors might have something to do with the ease of stowing the SJR sail panels, I only know that it works - and I don't know anything about standing parrels or how they would behave.

    We have a saying in English: "Don't teach your grandmother how to suck eggs" so I am making this post with some hesitancy. It is speculation only, not based on experience, and I don't know if it is useful or not. Perhaps you have already thought about this.

    Last modified: 24 Apr 2020 15:57 | Anonymous member
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