Seeking advise for changing old wooden battens to aluminum or bamboo

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  • 08 Sep 2023 17:50
    Reply # 13251903 on 13243182

    It's time to put my money where my mouth is. I ordered a 6m x 4m white 180GSM tarpaulin & a week later, a 200gsm green tarpaulin arrived. I have now received a full refund, including the carriage charges & have been informed in writing that it's mine to keep. So, I already have the boat cover.

    A few hours ago, a 6m x 4.5m white 110GSM tarpaulin was delivered. The quality is exceptional & at half the price, I am very satisfied. Bamboo spars are on order. They are mostly 4m in length; the yard is 80mm in diameter, the battens are split poles 45mm in diameter & the bottom batten is 55mm in diameter. I'm making a hollow wooden mast from spruce, 6.5m in length & 10cm in diameter, instead of a bamboo mast. Cheaper!

    The Johanna shaped, flat sail will be about 18 sq m & have 5 panels, only the 3 lower panels are to be slotted. I shall lace the split bamboo battens to the sail with 200mm cable ties threaded through 2 rows of 4mm brass eyelets inserted above & below the battens & set at 50 mm intervals. For UK sailmakers, 2 rolls of 1163CW Polyester basting tape 6mm x 50m are available from for £15-06 including delivery from Viking Industrial Products Ltd in Yorkshire

    That's it for now. Build it & they will come.



  • 06 Sep 2023 04:45
    Reply # 13250594 on 13243182
    Anonymous member (Administrator)

    Karl wrote: I like Your idea of splitting the bamboo in half and attaching it on each side of the sail ...

    Bamboo is a most wonderfully engineered natural product, a light tube with diaphragms at regular intervals. I've seen it used in China as scaffolding on 15-story buildings and if you have ever hauled conventional steel scaffolding (as I have done, tonnes of it) you would marvel at its strength/lightness and versatility. I am keen to find a way to use bamboo for battens.

    But splitting it in half? I don't think it would have anything like half of its strength. If you want to use split battens, and screws through your sail (I've done it - it works - but I won't do it again) maybe it would be worth looking at getting some spruce. I can't see the point of split bamboo.

    If 25mm is too small a diameter, I still think maybe sewing on wider batten pockets - and still looking at bamboo... or have a look at Paul T's lacing method - just my 2 cents worth.

    Afterthought - Arne might be able to think of a way for you to put a bit of camber into your sail at the same time as replacing the batten pockets...  it wouldn't take long ...

    Last modified: 06 Sep 2023 04:49 | Anonymous member (Administrator)
  • 06 Sep 2023 03:14
    Reply # 13250577 on 13243182
    Anonymous member (Administrator)

    Perry writes (quoting Parker): Full length battens are very useful devices in creating good sail shape & have been known & used for centuries. This is a doubtful statement, since their main purpose is to support the leech of a triangular sail with a very large roach – and with modern sail-making materials they can perform the secondary effect of assisting good sail shape - neither of which has a history which goes back "centuries”.

    Anyway, Perry,  it is a misleading paradigm in relation to junk rig. It’s a common mis-understanding due to unfortunate terminology. Junk rig “battens” have no relation to what people normally regard as full length battens (they merely look like it to the casual observer). A better terminology for junk rig would have been “boomlets” since their purpose is not at all to create good sail shape, but to divide up and transfer to the hull some of the driving forces of the sail – like multiple booms – via sheetlets - thence to the main sheet. (As well as, in combination with the lifts, to give an incredibly simple reefing mechanism). However, history has given us the terminology “battens”, which we can’t really change now. They are not “battens” in the usual sense of the word, they are spars.

    To do their job, they are best as rigid as possible (though on a SJR with its multiple downhauls, being able to induce a very slight downward bend helps to keep the luffs nice and straight).

    (We should ignore the case of bendy spars in modern bermudan racing rigs - their purpose, when the sail is sheeted in tight, is to reduce the draft of a cambered sail in moderate to heavy wind, not to increase it).

    The problem with bendy junk battens is that they bend more in strong wind and less in light wind, which is the reverse of what you want. Furthermore, they will bend differently depending on which tack.

    An exception is “articulated battens” which do bend for the purpose of giving shape to an otherwise flat junk sail, but they are a special case and the articulation is deliberately limited mechanically, to a constant amount. These are the "hinges" referred to by Alastair in a previous post. It is arguably simpler  and easier for most people to use rigid battens and create sail shape mainly from the cut of the sail.

    Perry, your suggestion of a hollow flexible tube with a semi-rigid and perhaps variably flexible central core is a concept worthy of consideration, but I do not understand your description. If a complex hybrid “batten” capable of being sheeted from the leech is considered a better proposition than simply sewing shape into the sail, then the challenge would be to find a central core which would make it curve most in the first 35% of the chord and be relatively stiff for the remainder – and reversible so it works correctly on both tacks. The forces on a batten are different on different tacks, so how to avoid curve at the leech, and an ”S” curve when on the “bad tack”?

    The nearest I have seen to successfully solving this problem is David T’s soft wing junk sail which is cambered by a combination of: articulation in the otherwise rigid batten, and the cut of the very special first 30% of the chord of the sail. It works on both tacks.

    Another interesting example is Annie's sail which I saw when Fanshi was first launched. This too (Tyler inspired I believe) was a combination of articulation of otherwise rigid battens, together with shape cut into what looks like the the first 50% of the chord of a conventional cambered sail.

    Ancient Chinese junks were not built using modern materials, and a little bit of shape was no doubt gained fortuitously from spars that might have been a little bit bendy, and sail cloth which unavoidably stretched. And there is a theory that the wind 'sees" camber in fanned panels too, which some Chinese junk sails did have. But why wouldn't you just use rigid battens and put the shape you want, the amount you want, where you want it, into the sail - by designing and sewing it in?

    Anyway, Perry, we are drifting away a little from the subject of Karl's thread. Perhaps it would be good to start a new thread, as you progress through the evolution of a special sail for your project build.

    Last modified: 07 Sep 2023 21:40 | Anonymous member (Administrator)
  • 05 Sep 2023 14:45
    Reply # 13250214 on 13243182

    I am re-reading “The Sharpie Book”, 1993, by Reuel Parker. In discussing the 22-foot Cedar Keys Sharpie in page 115, he wrote:

    "Full length battens are very useful devices in creating good sail shape & have been known & used for centuries. In sharpies the battens frequently consisted of two thin oak strips, riveted or bolted through the sail, one on each side. Instead, I sew on reinforced batten pockets & use PVCpipe for battens, with octagonal wood cores inserted inside the after 60% of the pipes to stiffen them. I dip the pipe ends in boiling water or heat them with a heat gun & clamp 2x4 blocks to each side to flatten them. This allows the ends to snugly fit into the batten pockets, as well as allowing a long taper to be made at the forward ends to induce additional camber. I also duct-tape the forward batten ends to prevent chafe. I drill ¼” holes in the aft batten ends (which protrude from the leach 2 to 4 inches depending on boat size) for the tension lacings (battens must be placed under tension). Unless the sail has dramatic draft, the forward ends of the batten, present no problem. They stay in line with the luff of the sail. One reason for this is the extreme flexibility of the PVC pipe; fibreglass & wooden battens don’t work as well”.

    My thought is that if the PVC battens were reversed, rigid end leading, in the pockets of the flat Junk sails (that have pockets), the sheetlets could induce a camber on either tack, especially if the luff or forward end wooden insert was reduced to 40% of the batten length, rather than 60%.

    Comments most welcome.

    It's a pity Reuel make no mention of Junk sails in either of his boat building books. I think he would now be an enthusiast.

  • 02 Sep 2023 10:32
    Reply # 13249337 on 13243182

    Good morning, Karl,

    The challenge with stitching the half round bamboo battens to either sides of the sail, is that unless knots tied at intervals along the battens, chafing on the mast could cause the twine to break & unwind. Instead, I'm now considering using white cable ties of appropriate length & a soldering iron to melt holes in the sail. Each hole will have a reinforcing ring of melted plastic & doing that first, over the whole sail.

    The parrels will be assembled by threading copper 2.5mm twin core plus earth electric cable (used for ring main wiring in the UK) through garden hose & twisted around the battens.  Probably other sailors have already mentioned this; I haven't looked. The article by Eric Sponberg about the Freedom Yachts mast cracking episode is not lost on me & if necessary (suck it & see), my mast will have glass fibre tapes stretched & vertically bedded into epoxy resin before painting. You can see how much Craig O'D's Cheap Pages have influenced me! 

    The yard spar will be 60/70mm in diameter, as I have no idea what the loads will be. As the sail will be a slotted (4 lower panels) rectangle of 6 panels, no peak halliard is needed, only the main halliard. The low angle bridle points of attachment will be reinforced to prevent crushing of the yard spar.

    Very recently, Doug Jackson of SV Seeker fame, had an incident with his foresail, in which the euphroe shattered (spars & sail were also damaged). He made a replacement euphroe from a length of recycled HDPE. Plastic containers for milk in the UK are HDPE; inspiration! Other boat fittings from HDPE?



    Last modified: 02 Sep 2023 10:33 | Anonymous member
  • 02 Sep 2023 06:42
    Reply # 13249328 on 13243182

    Thank You Perry, I like Your idea of splitting the bamboo in half and attaching it on each side of the sail and lets my decision if I should use round Aluminium poles 25 mm diameter in the pockets swivel towards bamboo.

  • 01 Sep 2023 18:42
    Reply # 13249094 on 13243182

    An interesting hour or so has passed. Being an entire novice in the cutting & stitching of any sails, I have chosen a flat junk rig on the basis of no stitching whatsoever (if I can get away from it) & use modern heat activated adhesives to hem edges & attach webbing bolt ropes. Sail repair tapes are extremely hard wearing.

    Back to basics; I cut a piece of baking paper 12 inches by 8 inches to represent my 6m x 4 m tarpaulin. Using 6 bamboo kebab skewers cut to 8.5 inches, I placed them on the baking paper as a fan sail & cut the sail outline accordingly. The 3 lower panels measured 4 sq. metres each. The transition panel is roughly 3.2 sq metres & the upper panel is about 3.4 sq. metres, so in total 18.6 sq. metres. The fan shape loses 5.4 sq. metres, in comparison with an uncut 24 sq. metres pf rectangular tarpaulin Junk sail. My question is obvious; as Slieve Mc Galliard's Split Rig sail on "Poppy" is almost a rectangle, why not slot the rectangular tarpaulin in like manner? The sail area loss would only be about 1.5 sq. metres with minimum raw edge taping, rather than sewing machine needles through my digits. Comments welcome.

    “It is impossible to live without failing at something unless you live so cautiously that you might as well not have lived at all, in which case you have failed by default.”        J.K. Rowling.




  • 01 Sep 2023 16:38
    Reply # 13249012 on 13243182

    Good afternoon, Karl,

    Your question about new battens almost matches my situation, because very soon, I shall be constructing a flat Junk sail with a 6m x 4m white 180gsm tarpaulin that will cost £45. The mast, spars & battens will be bamboo, as the rig is for an open dinghy, loosely based on a 6m Sharpie design & will be sailed on the non-tidal River Thames.

    I did briefly consider square carbon fibre tube for battens, but at £10-85 per metre for 4mm x 4mm x 0.75 mm, they were a non-starter. Black carbon rods 3mm are £3-58 per metre, but only 3 metres maximum length.

    However, there is precedent for tying 2 or more carbon fibre rods together to gain the length required, as shown in this illustration of bamboo battens. The thinner ends might also induce a small camber in the sail? The sailcloth is a credit to the seamstresses!!!

    My sail battens will be 4 metres long, 45mm diameter Moso bamboo, split lengthways & secured on both sides of the tarpaulin with synthetic twine. They are £4-97 each. The 4 metres length Moso yard is 55mm diameter & is £10-19. I shall purchase 2 as the 6.75 metres mast will be assembled by inserting & bonding a 55mm diameter Moso bamboo some way into a 70mm Moso bamboo. If that mast breaks, then there are bamboos up to 120-150mm.

    Best wishes. 



  • 31 Aug 2023 05:00
    Reply # 13248180 on 13243182

    I have just put some photos of the hinges. Not original idea of mine already in the JRA files. I did slightly modify these as I had a hole drilled the length of the hinge to feed through a line. I also had some old dinghy bottle screws which I cut up to tension the line and the keep the assembled battens manageable. I also show my first experiment with the end caps of the tubes on a short section of tube. The concept and design of the sail is thanks to Alan Boswell..

    4 files
  • 30 Aug 2023 06:35
    Reply # 13247657 on 13243182

    Hi Alastair, I should have looked first into Your profile because there is already answered that the battens are aluminium tubing. Open is just round,  rectangular or square the wall thickness and how they are hinged.

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