Sail planform,yard length, sheeting arrangements

  • 04 Aug 2015 10:10
    Reply # 3463837 on 3455614
    Anonymous

    Hi Don.

    The Help page (from the menu, lower left) has instructions on how to upload photos to your member album, and how to link to them in a post (under the heading "PHOTOS - ALBUMS - How do I  include a link to an image in one of my own photo albums?"

    For photos not in your personal albums, just go to the photo, copy the URL from the address bar and when editing your post, select the text you want to link, select the little chain icon in the toolbar, click 'insert link' and in the address bar which appears, paste the URL. As an example I have done this for your sheet photo in your post below. If you edit the post you can examine the link and see how it works.

    Chris

    Last modified: 04 Aug 2015 10:26 | Anonymous
  • 04 Aug 2015 06:27
    Reply # 3463628 on 3455614
    Deleted user

    This has been bugging me for a little while now. My apologies for muscling in on the thread but I figured it was topical and not necessary to start another.

    I have added a photo of my sheet assembly to the technical illustrations. I changed it when re rigging with new ropes and the photos I took to record the original assembly disappeared into cyberspace so I re rigged using The Junk Rig. 

    I do recall that the original assembly had the sheet attached to the first three battens with numbers one and two joined with a running thimble as in the diagrams in illustrations but being relatively inexperienced I was left bamboozled, hence my current set up.

    What I want to ask of you experienced folk is, looking at the photograph, do you think I would benefit from changing the assembly back to the original?

    I can see that if I were to do so that I would then have the sheet attached to the uppermost batten. As yet I've not noticed any occasion when this has been necessary but at risk of repeating myself, I am relatively inexperienced and would really appreciate the benefit of more knowledgable opinions!

    Oh, and if someone could enlighten me as to how to link from post to photo that would also be handy!

    Last modified: 04 Aug 2015 10:22 | Anonymous
  • 30 Jul 2015 05:49
    Reply # 3457155 on 3457078
    Annie Hill wrote:
    Graham Cox wrote: I suspect Blondie got it pretty much right the first time, apart from the issue of camber - which he speculated upon.
    I suspect you mean the second time, Graham :-P and not the Jester style of sail!

    Oh yes!  I stand corrected.  The second time, and to be 100% historically correct, one should say that Blondie and Jock got it right (almost, perhaps..  let me not be too absolute...) with the standard Hasler/Mcleod sail plan, as seen in Practical Junk Rig.  Certainly, with the addition of some camber and Arne's transitional panel, one has a sail that performs well across the whole spectrum of conditions.  Besides the heavy-weather potential of those three top panels (which come close in profile to the famed Polynesian crab-claw sail), I have found that Arion's sail is a phenomenal ghoster in light winds and flat water.  With barely a breath of wind across the deck, the boat keeps moving at about one knot and even tacks.  In the open sea in drifting conditions it can be different, as there is often some residual swell that makes the yard and battens crash about.  In those conditions, I'd like to drop the junk sail and hoist a huge, gossamer-light Code Zero drifter, keeping one hand on the sheet and one eye on the horizon!  But all in all, the cambered H/M sail with a transitional panel is a magnificent design.
  • 30 Jul 2015 02:23
    Reply # 3457078 on 3456932
    Graham Cox wrote: I suspect Blondie got it pretty much right the first time, apart from the issue of camber - which he speculated upon.
    I suspect you mean the second time, Graham :-P and not the Jester style of sail!
  • 29 Jul 2015 23:23
    Reply # 3456932 on 3456462
    Arne Kverneland wrote:

    Graham,

    In my view, there are a number of factors playing in to control the behaviour of the deeply reefed junk sails.

    • ·         Both the Fantail sail and the modified Hasler-McLeod sail, that I use, have high-peaking yards. However, if the Fantail sail is reefed down to 3 panels, the yard angle is lowered to about 47° (from about 68°) while sails with parallel lower battens will retain the yard’s peaking angle (around 70°) down to 3 panels. My experience is that the 3-panel section on Frøken Sørensen (FS) sets extremely well. A combination of just a bit panel camber, plus just a bit twist-based camber adds up to produce really good upwind performance. As can be seen on FS, here and here, the yard is supported by the lee topping lift. A fanned sail reefed this much should be likely to twist more, as much more of it will stick out aft of the topping lift. I quite frequently sail under just 4, 3 or 2 panels, partly because FS is so tender when I am alone on board, and partly because I need to reduce speed when trolling for mackerels...
    • ·         Room for the sheeting. I frequently nag about this matter: A longer boat (for its displacement) is likely to give less steep sheeting angles to the upper battens. If the sheeting angles are steep, I am sure that separate sheets for the upper and lower section makes sense. I have seen it in use on the mainsail of the schooner Samson for 15 years, now, and it works well.
    • ·         My experience is that high AR sails need less attention to set well. My guess is that their mass centre is closer to the mast. Still, that is not a big enough deal to keep me from making lower AR sails.
    • ·         The position of the lazyjacks. I think the aft part of it  -  in my setup, they are plain topping lifts  -  should go as far aft as possible without letting the yard or battens fall forward of them. That gives good anti-twist support to the deeply reefed sail.

    Arne

     


    That is an excellent reply Arne and your comments make good sense.  I also really like the look of my sail with just three panels hoisted, but have not had any experience of sailing to windward in heavy weather with it.  My sail, apart from the shorter yard, is based on your modified H/M design.  I have about 4% camber in the transitional panel and about 2% in the upper two.  The fact that the yard stays peaked up, with the hoist point close to the mast and supported by the topping lifts, suggests to me that a cambered, HM sail with a transitional panel may well be the ultimate development in junk rig planforms.  I suspect Blondie got it pretty much right the first time, apart from the issue of camber - which he speculated upon.
  • 29 Jul 2015 15:51
    Reply # 3456462 on 3455614
    Anonymous member (Administrator)

    Graham,

    In my view, there are a number of factors playing in to control the behaviour of the deeply reefed junk sails.

    • ·         Both the Fantail sail and the modified Hasler-McLeod sail, that I use, have high-peaking yards. However, if the Fantail sail is reefed down to 3 panels, the yard angle is lowered to about 47° (from about 68°) while sails with parallel lower battens will retain the yard’s peaking angle (around 70°) down to 3 panels. My experience is that the 3-panel section on Frøken Sørensen (FS) sets extremely well. A combination of just a bit panel camber, plus just a bit twist-based camber adds up to produce really good upwind performance. As can be seen on FS, here and here, the yard is supported by the lee topping lift. A fanned sail reefed this much should be likely to twist more, as much more of it will stick out aft of the topping lift. I quite frequently sail under just 4, 3 or 2 panels, partly because FS is so tender when I am alone on board, and partly because I need to reduce speed when trolling for mackerels...
    • ·         Room for the sheeting. I frequently nag about this matter: A longer boat (for its displacement) is likely to give less steep sheeting angles to the upper battens. If the sheeting angles are steep, I am sure that separate sheets for the upper and lower section makes sense. I have seen it in use on the mainsail of the schooner Samson for 15 years, now, and it works well.
    • ·         My experience is that high AR sails need less attention to set well. My guess is that their mass centre is closer to the mast. Still, that is not a big enough deal to keep me from making lower AR sails.
    • ·         The position of the lazyjacks. I think the aft part of it  -  in my setup, they are plain topping lifts  -  should go as far aft as possible without letting the yard or battens fall forward of them. That gives good anti-twist support to the deeply reefed sail.

    Arne

     

  • 28 Jul 2015 23:54
    Message # 3455614
    Graham Cox wrote (to David Tyler):

    It looks to me that your new rig is working well, CF issues aside.  Now that you have sailed it in a variety of conditions, do you think it is as powerful to windward when deeply reefed as your Fantail sail was?  Is there any advantage in having a high-peaked yard now that we have sails that are cambered (by one means or another)?

    David Tyler replied:


    I don't think I can answer that directly, as the power depends on the amount of camber that one chooses to build in. I can only say that I now much prefer to sail with this kind of planform, finding it much more manageable than one with a long, high-peaked yard. When reefed down to three panels, and when using the double (upper and lower) sheeting, I find it much easier to keep in shape, whereas with the deeply reefed fantail sail under those conditions, I thought there was too much twist.

    Graham Cox responded:

    Very interesting, David.  The original sail planform you developed for Arion had a yard length of 4m.  I later cut the head of the sail (from throat to peak) down to 3.3m because I wanted to use a lighter yard of that length (which subsequently broke).  When I replaced the yard with one of the correct specs (100mm x 3.3mm) I increased its length to 4m again, as I had difficulty keeping the end of the shorter yard clear of the topping lifts, though the sail is still 3.3m.  I intend to revisit this one day to see if I can resolve this issue, as I'd like to go back to the shorter yard. (At the worst, I might fit a lightweight plastic extension to the end of the yard, to guide it through the lifts.)

    Next up, I'd like to try your double sheeting system because I can see how much more control over sail shape it would give.  Because I do controlled gybes, hauling in the slack in the sheet as the leech of the sail comes through the eye of the wind, then letting it run out through my gloved hands (don't try that with bare hands, anybody!), I'd have to pull in both sheet tails simultaneously (if the sail was fully hoisted or both sheets under load) but that should be ok as long as they have the same purchase.

    Also of interest is Tystie's extended mast and high-aspect ratio sail, with its shorter boom and battens for a given sail area.  This planform was inefficient with flat sails because of too much twist (I wonder if David's double sheets would have made a difference?).  With cambered sails it seems to be an effective planform, with the added benefit of less stress on the battens and boom for a given sail area, a centre of effort that is closer inboard when reaching and running, and easier gybing.

    Where would the rest of us JRA folk be without the innovators in our midst!


    Last modified: 29 Jul 2015 09:02 | Anonymous member
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