Flat, hinged or cambered?

  • 26 Aug 2018 08:24
    Reply # 6639073 on 6638897
    Gary wrote:

    Now I know that most JR battens extend fwd of the mast but why can they not be finessed into the required curve ?

    They can. This is what Nils has done (see earlier in this topic). But because we sail on both tacks, we need to be able to flip those battens from one side to the other, around their long axis. Nils has written at length in the magazine about how he does this.

    Thats with stiff battens, which is what we really must have with JR. Flexible battens were tried, a long time ago, and found wanting. They bend too much in heavy airs, and not enough in light airs.

    Last modified: 26 Aug 2018 08:48 | Anonymous member
  • 26 Aug 2018 01:02
    Reply # 6638897 on 6638174
    OK,


    I need to ask a really dumb question here, please excuse my ignorance but .....

    why are hinges needed at all ?

    when I was younger, so much younger than today,

    we didn't make our battens in this way ....

    in fact we used some sort of cane which we sanded planed thinned in both directions varnished (to prevent them going soft from water ingress after capsize) until they took our ideal shape. 

    We did not need hinges just patience.

    Now I know that most JR battens extend fwd of the mast but why can they not be finessed into the required curve ?

    Just asking.


  • 25 Aug 2018 11:20
    Reply # 6638174 on 461931
    Anonymous member (Administrator)

    David,
    you cannot take Annie’s experience with Passepatu and just transfer them onto Malena. The biggest difference is that Passepatu’s hinges were inside hinges (see newsletter 50), with the hinge bit no stronger than the battens of Malena, and I guess Passepatu is 4-5 times heavier than Malena. It appeared that the hinges on P. either worked themselves out, or the hinges or battens simply bent in stronger winds. The whole ship appeared to be really clapped out.

    Malena’s hinges would operate fully from F1 (when I learned to use a THP and ease the LHP): By sitting on the lee side, the light boat would heel 3-4 degrees which let the sail swing out and the hinges go to their stops. I did some remarkable stunts in F1-F2 with boats around me just sitting there. I never had problems with the hinges working loose, with that internal line set up with some tension in it.

    As for wear and tear of my hinges for long term use, you may be right; only trying it will tell, but your experience with GRP-hinges cannot be transferred straight onto my aluminium hinges. Although aluminium is quite soft and vulnerable to scratching, it is still a lot tougher than GRP. Now I had another look at one of those hinges (sitting in my cellar and used for ‘spares’). They only saw a few hundred miles sailing, but there is just about no sign of wear on them. I had hedged my bet, though  -  the top batten was straight.

    As for aerodynamics, and number of hinges, I basically made two hinges on each batten. Each hinge was lengthened a bit to smoothen out the curve, so it appeared more like four hinges, each with 8° bend. I did it this way because I was afraid of sharp corners in the camber of the sail. I needed not have worried as the sail cloth between the battens appeared to even out the curve.

    The symmetric shape of the camber was surprisingly efficient. One evening I had the chance to test Malena against a sister boat with the original rig. To our surprise, we tacked inside the other boat, and were even a bit faster. The main drawback was that the sail’s CP had moved aft, so weather helm increased. One will of course also need rather roomy batten pockets for this sort of hinges. Malena’s 40mm hinges just made it into the pockets.

    If I were to make a JR with hinges again (I am not), I may well make a copy of that 1991 rig, but with the shorter MkII hinges (JRA Mag. 54, p.33). I would ensure I had tall enough mast to let the THP easily haul the sail well aft. Then the fore hinges would work well.

    Finally...
    As for the English saying about sucking eggs; we Norwegians also have a fitting saying:
    “The fact that you know something, doesn’t prove that you know everything”.

    Arne



    Last modified: 25 Aug 2018 22:44 | Anonymous member (Administrator)
  • 25 Aug 2018 08:40
    Reply # 6638136 on 6637694
    Arne wrote:
    David Tyler wrote:

    Jim and Arne, are you both "armchair sailing" on this topic? Have you done any more than talk about it and observe what others have done?



    David,
    I described my Mk1 hinge from 1991 in JRA-newsletter 24, p.22. I used it on Malena that season plus on and off  for two half seasons, in '92 and '93. I sailed it and gybed it in various conditions, although I never used it for ocean voyages. I still have them in my cellar and haven't found any signs of wear  on them. 
    I'm aware that you used hinges on Malena. I meant, of course, that you have no direct personal recent experience of making and using double cone hinges. A rig used for daysailing at weekends is unlikely to show much wear and tear. It's the mileage that matters, not the number of seasons. Where you went wrong with those early hinge experiments was to put in too many hinges, extending too far aft. Annie found the same when she brought Passepatu from Bluff to Whangerei (JRA magazine issue 65) - the rig was unmanageable, with too much articulation. There should only be one or two hinges, and the aftermost hinge should be no further aft than 50 -60%.

    What surprised me was that they were completely quiet, without any click-noise of any kind.

    Hinges of all kinds are quieter than cambered panels when they empty and fill with a bang in a swell and light winds! Take a trip out to Utsire and you'll see!

    The reports from England that some of the plastic hinges broke  -  was that fake news?

    I don't remember hinges breaking, though they may have done, as I think I remember that they were made from acetal resin, which is strong, but a bit brittle and inclined towards developing fatigue cracks. Nylon 66 is tougher and better. I do remember that they separated within the pockets, due to excess slackness longitudinally and bad pocket design. I had one hinge separation at the end of last season, as I'd allowed a little too much slackness because it seemed to be needed even with the tiny little bit of barrel-cut camber I'd put in. I had to make some longer hinges to take up the slack, and tolerate a less good set than I'd have got if I'd have built in that little bit of camber with tucks.

    Arne

    PS: I understand you only have a lathe for turning wood? Those made for turning metal can be fitted with a chuck to hold the work piece, and a drill bit can then be inserted into its dead center.

    We have a saying in English: "you are trying to teach your grandmother to suck eggs!". I have been turning since I was in secondary school. I have a standard hobbyist's metalworking mini-lathe, with a 12" bed. This is long enough to turn a 280mm double cone between centres. A much longer bed, or a headstock able to pass the full bar diameter through it, would be necessary to drill an axial hole through a double cone. In short, a much bigger lathe. Even then, the tailstock would not have enough travel to drill without moving it and drilling in stages, and an extra long drill would have to be fabricated. It's much easier to drill a transverse hole, and just as good.


    Last modified: 25 Aug 2018 09:18 | Anonymous member
  • 24 Aug 2018 22:55
    Reply # 6637694 on 6637659
    Anonymous member (Administrator)
    David Tyler wrote:

    Jim and Arne, are you both "armchair sailing" on this topic? Have you done any more than talk about it and observe what others have done?



    David,
    I described my Mk1 hinge from 1991 in JRA-newsletter 24, p.22. I used it on Malena that season plus on and off  for two half seasons, in '92 and '93. I sailed it and gybed it in various conditions, although I never used it for ocean voyages. I still have them in my cellar and haven't found any signs of wear  on them. 

    What surprised me was that they were completely quiet, without any click-noise of any kind.

    I agree that the Method B of making batten pockets (which came many years later) would not be good for hinged battens. I only had hinges on the flat Lucas sail with D-shaped pockets.

    The 'outside' hinge I showed below is an armchair product, for sure, but it was based on the Mk1 hinge in NL 24. Its main difference to the Mk1 hinge is that hinges could easily be made with different angles (just like your hinges) without altering the overall length of the batten.

    The reports from England that some of the plastic hinges broke  -  was that fake news?

    Arne

    PS: I understand you only have a lathe for turning wood? Those made for turning metal can be fitted with a chuck to hold the work piece, and a drill bit can then be inserted into its dead center.

    Last modified: 24 Aug 2018 22:57 | Anonymous member (Administrator)
  • 24 Aug 2018 22:17
    Reply # 6637659 on 6637434
    Jim wrote:

    Any comments?

    Arne, do you remember either of these?

    Jim, I remember that you mentioned this not so long ago. My answer is still  that spherical contact is unnecessary, as the longitudinal force is not that great. Further, rubbing contact between two aluminium surfaces is bad; they fret and gall each other. Did you actually make these and sail any distance with them? I couldn't make them on a simple home lathe, I'd need to get them made, very expensively, by a CNC turning company. A simple flange suffices.

    Jim and Arne, are you both "armchair sailing" on this topic? Have you done any more than talk about it and observe what others have done?

    Just to go back briefly over my own practical experience:
    I collaborated with Maurice Donovan on his early trials with hinges. Since then, I've made hinges of various types for Ivory Gull, Tystie and Weaverbird. I've sailed with hinges for many thousands of miles, and can claim to know something about them. The design of the batten pockets is important, and method B would be very poor - a symmetrical pocket that "bulges" equally on both sides of the sail is best as far as the hinges are concerned, but that brings with it some difficulties in carrying the vertical tension in the sail, so I have settled on a pocket design that bulges only a little on the reverse side, but mainly on the batten side, as the best compromise. I drill a hole across the flange from side to side to thread a small line through, as it is a very difficult turning job to drill an axial hole the length of a hinge. I use a line to assemble two hinges and a short central portion of batten tube, so that assembly is easier, but have found that it is not necessary to have a line from end to end of the batten if the pocket design is good. I aim for a length of contact of three times the tube diameter, which means that the total length of a hinge for 38mm tube is going to be in the order of 250mm long. I have found that a half angle of 5 degrees is safe, against wedging itself apart. I have made, but have not yet proved, hinges with a half angle of 6 degrees - this is just achievable with the same length of engagement of three times the tube diameter. I have found that nylon 66 is strong enough and resistant enough to fatigue. Other less expensive plastics are not.

    I reiterate - this is practical experience in the design, manufacture and use of hinges, and not just armchair theorising and second hand knowledge from two decades ago about what can be made, what works and what is strong enough.

    Last modified: 24 Aug 2018 22:20 | Anonymous member
  • 24 Aug 2018 20:22
    Reply # 6637535 on 6637434
    Anonymous member (Administrator)
    Jim Creighton  wrote:

    Any comments?

    Arne, do you remember either of these?

    Hi, Jim, yes,

    Now I looked up my early JRA letters from the nineties. That drawing came in a letter from you, dated 30. October 1995. We exchanged a number of brilliant ideas in those days!

    I know that Victor Wintethun also had a similar design which gave a slightly better contact surface between the batten ends and the 'root end' of the hinges. Then Maurice Donovan designed a hinge which I think was the one that Sunbird made use of. 

    In my eyes they all look to be on the weak side, unless one makes them of very strong material.  I know that some of the Sunbird hinges broke, but maybe they managed to put them right later. One problem with them was that they had no hole for a central line in them. Bunny Smith's grandson visited Stavanger in Fenix and showed me how they were set up: To keep the battens and hinges under the necessary compression, this was done with the sail itself. That lead to asymmetric tension, so it took more wind to make the hinges work one way, compared to the other.

    These days, with access to Dyneema ropes, it would be possible to have a thinner hole and line, and thus do away with the tension in the sail.

    Arne



  • 24 Aug 2018 19:41
    Reply # 6637434 on 461931

    Any comments?

    Arne, do you remember either of these?

  • 22 Aug 2018 15:07
    Reply # 6633929 on 6579203
    Anonymous wrote:

    The hinges in Weaverbird's battens, made from nylon 66 - simple, robust, do not chafe the sail or fret the batten tubes, proven over 3000 miles.


    I drew up something similar in 1993. I think I shared it with Arne. Arne? Then I redrew it in 2001. See the two. You may need to darken the contrast on the 2001 version.

    The rim of the batten tube opening should be beveled, rounding edges, to maximize the landing area that is in contact with the spherical centre. No point loading anywhere. I would remove the excess top of the sphere, rounding edges, to lessen sail abrasion.



    2 files
  • 22 Aug 2018 13:27
    Reply # 6633799 on 461931

    Nils,
    Your idea would possibly hold good if I were still thinking along the lines of a big wishbone with convex curvature on its sides, and a hinge box at the after end. But I'm not. I found that concept to be too difficult to make both light and strong, and too inclined to misbehave. I'm thinking of a "Less is More" wingsail that has my present double cone hinges as the basis for the articulation (having found that the articulation should be permitted equally in all directions), with round tubes as the major part of the battens, and with as small a "nose" as possible to shape the luff.

    No more at present, as the ideas haven't yet fully settled down.

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