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Cambered Sail, different batten design (or, segmented sails, take two)

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  • 27 Feb 2014 14:25
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    Reply # 1507019 on 1506125
    Anonymous member

    Rather than tracks, as Paul suggests, a version of Roger Taylor's 'hinges' would be most simple, (and very much JRA ethos).

    With Roger's sail there are quite large gaps between the panel and hinge, which cannot do much for efficiency.  If each panel is formed as a cambered panel so the edges rest against the batten, then secured with hinges, the gap would be minimal.  Perfect?!
  • 27 Feb 2014 11:29
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    Reply # 1506933 on 1506125
    Deleted user
    Thanks for all the positive and negative input, now I'm really confused if it's a good idea ;-)

    Yes you are all right it would be very hard to change the battens at sea, I never thought of that. So that's a big negative.

    As for Annie's (love your book) comment on the heavy battens and sail I think I have to disagree. Looking at Aphrodite she is a serious big boat with big sail and yes heavy battens. My thinking is to find alum tube with the two "tracks" extruded into the tube, so no need for tracks riveted on to the battens, and not use rope but the luff tape used for roller furler sails. This way the sails and battens or not much heavier then normal, and the panels should slide in very smoothly. I love silicon spray.

    The main reason is of course the easy way to make the cambered sail panels, without to much room and struggling maneuvering a big sail using a domestic sewing machine.

    I have to take the comments of the kiwis serious since I lived in NZ for 10 years and know they are world famous (in NZ) for there kiwi ingenuity. Guy in my town had a dingy with a complete lawnmower on top of a seagull outboard leg go fishing for the day and in the evening mow his lawn.

    Sako
       
  • 27 Feb 2014 10:25
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    Reply # 1506903 on 1506125
    Deleted user
    Hi Paul. Knew you'd say that. Paradox is, according to original brochure, 18,500 lb (8,400 kg), ie minus cruising gear, displacement. Sail area as Freedom schooner was 76 m2. As a junk she is, I think, almost 80, not got the precise figure at hand. One day I'll get to update my profile :-)
    Last modified: 27 Feb 2014 10:27 | Deleted user
  • 27 Feb 2014 03:33
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    Reply # 1506772 on 1506693
    Anonymous member
    Brian Kerslake wrote:Performance is fine. It's just another way to build a sail or to have one built. Back off you grumpy Kiwis :-)


    Us Grumpy Kiwi's stand by every word we wrote :-) The difference between your experience and ours is probably the size of the sails involved.
     
    Aphrodite is a big  heavy boat and the sails were 2 x 65 Sq.M each with 7M battens. A trifle bigger than your baby!
  • 27 Feb 2014 01:25
    Quote
    Reply # 1506693 on 1506125
    Deleted user
    Hi Sako. Welcome aboard. The thread I remember is this one. I searched the Tech Forum for 'batten bolt rope'. It may be worth looking at some of the other threads that show up. Good memory and advice, Graham, thanks. Paradox's sails were built by Chris Scanes who agreed to try this idea.

    • Complicated? It's just a bolt rope top top and bottom of each panel. Some members have bolt ropes around the whole perimeter of their sails.
    • Heavier? By 2 bolt ropes per panel and 2 tracks per batten. Doesn't add up to much. We have an electric halyard winch anyway: came with the old Freedom rig. Massively heavier? No. One day I'll work out by how much.
    • Difficult to replace battens at sea? It would be, but why would we do that when we could lash out a broken batten or a damaged panel in the standard way?
    • Hard work assembling? We built each sail bundle on shore then carried them onto the boat; we used to do that with the flat panels we had on earlier boats. We could have assembled them just as easily on the boat: two of us did that when we had some mods made to one of the sails.
    • Anti-chafe problem? Tracks are top and bottom of battens. Anti chafe material goes on the side of each batten where they rub the masts. Conventional.
    • No need for separate panels? It's just another option.
    • Difficult to work on? If a sail has localised damage and you're in port, then to remove a batten attach a line to its front or back end and tug the line. One person does that while the other sorts out any sticking sailcloth, which can bind in the track. Much quicker than removing all the battens on a standard sail if you want to get the sail to a sail repair shop. We're not handy with sewing.
    • Needs less space when building? Big advantage.
    • Bonus 1 : alloy tracks help to stiffen the alloy battens, which is useful if the panels are cambered.
    • Bonus 2: Permits easy experimentation? It would.
    • Bonus 3: Nice to try something different.

    We have eyelets at the top of the top panel so we can lash it to the yard as a fail-safe against eg a track problem. Same with the boom. A few more eyelets at top and bottom of each panel for lashing a panel out would have been a good idea, and is a mod we'll get done some time (a panel at a time).

    Performance is fine. It's just another way to build a sail or to have one built. Back off you grumpy Kiwis :-)

    Last modified: 27 Feb 2014 10:05 | Deleted user
  • 26 Feb 2014 21:25
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    Reply # 1506542 on 1506125
    Anonymous member
    As one of those involved with rigging Aphrodite, I would second everything Paul says.  The sails ended up being massively heavy and it was a real struggle to pull the panels along the battens when initially rigging the sail.  In one's mind's eye, the batten stays obligingly in place while you slide the panel along.  In reality, that only works for the first batten.  Sliding the batten onto the cloth, is surprisingly hard, and then holding subsequent battens still while sliding the cloth onto them is a real struggle.  One also forgets that in the 'replacing at sea' scenario, your batten - several metres long - has to somehow be supported over the bow or stern of the vessel as you line up the slot in the end with the boltrope.  It was hard enough with someone standing on the opposite finger in a marina!

     

    Last modified: 26 Feb 2014 21:31 | Anonymous member
  • 26 Feb 2014 20:20
    Quote
    Reply # 1506476 on 1506125
    Anonymous member
    I did this when I designed and built the rig for Carl Bostek's Aphrodite as Carl was keen on it. It worked fine in practice but in my view, it was unneeded and just added extra weight and complexity to the rig.

    In addition, taking out a panel and replacing it at sea is unlikely to be a viable option if you are using "rope luff grooves". On Aphrodite it took 4 people to change a panel. Two to hold the batten, one to feed the panel and one to pull the panel along. It was not particularly easy in a marina. As for doing it at sea, good luck to you.

    Using alternating short batten pockets with the batten being the "hinge pin" works better (have done this as well in a small scale experiment) but I really do not see the need. With a junk rig, damage to a panel is a small matter and is unlikely to be disabling. The sail does not care about holes (look at photo's of traditional junks in China) and if you really needed to, you could just tie two battens together and take the affected panel out of service.

    As to the anti-chafe gear, in Aphrodite's case, I just riveted some polypropylene strips directly to the batten.

    Separate panels is one of those ideas that seem good when first thought of but there is actually little need for them in practice. A more real reason for going to separate panels would be lack of space when building the sails but even there, I'd look for other ways of doing things before I went that route.
  • 26 Feb 2014 10:39
    Quote
    Reply # 1506128 on 1506125
    Anonymous member
    Hi Sako, welcome to the JRA fora.  I believe Brian Kerslake, our Webmaster, if my memory is correct, has battens similar to the ones you describe, with individual sail panels slotted into them.  I seem to remember he was finding them a bit complicated.  Perhaps he can reply to your post.  If you conduct a search of the fora using the search term "batten design" you will come up with numerous discussions about the topic but none specifically addressing your concerns that I could find.  It is not a bad idea but I'd be interested to know how you would attach the fendering to the battens to stop them banging against and even possibly gouging the mast (my battens have done a bit of that where the fendering came adrift).
  • 26 Feb 2014 10:24
    Quote
    Message # 1506125
    Deleted user
    Hello,

    Just become a member, but a long time visitor and very interested in junk rigs.

    I like the idea of a cambered junk rig but think to make the sail is a bit complicated, so I came up with the following.

    Use battens like the the aluminium  profile of a roller furler but then with 2 groves, one on the top and one on the bottom. Then make the panels with on the top and bottom of each panel a luff tape (or boltrope)  which slides into the top or bottom of the battens.

    The advantages are:
    -easy to make one panel at the time
    -if a panel is damaged, easy to repair or replace
    -if a batten is broken, just slide in a new batten or remove the broken batten and a panel then lower the sail and slide in to the next batten
    -possible to have different colored panels and change them around, just for fun
    -very easy to alter or change the panels for experimentel purposes

    Maybe this idea already exists, but didn't find it anywhere. What do you think is it a good idea, or am I missing something. The only problem is finding the right aluminium extrusion.

    Greetings from Holland,

    Sako
      
    Last modified: 28 Feb 2014 11:19 | Anonymous member
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