Flat, hinged or cambered?

  • 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.



  • 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.

  • 22 Aug 2018 12:46
    Reply # 6633730 on 6603539
    Nils wrote:

    My hunch is though that if you would go for curved battens, your wingsail would become even more efficient and develop more force.


    To David Tyler again,

    I found that you could perhaps misunderstand what I quote above.  I think your box hinge is fine, so when I mentioned curved battens, I thought of keeping your hinge box and make a slight curvature in the batten.  We easily see that the wishbone and the hinge box together make most of the desired camber, so the slight curvature of the batten is just proposed to make the profile a little closer to the ideal - to my eyes at least.  If the batten is not restrained against rotation, it will tend to rotate by itself after the tack, as the rotation makes the batten go from a labile to a stable equilibrium when it has a curved shape.

    Nils

  • 21 Aug 2018 12:25
    Reply # 6603539 on 461931

    David,

    The wingsail I built around 8 years ago was using the hinge details I ‘doodled’ in Newsletter No. 50 except for that I used standing parrels AB and AC and placed a swivel in “C” (the batten fore end) in ‘doodle’ Fig 2.  The reason for having the swivel is that when the curved batten flips during the tacking, it sometimes continues the rotation from last flipping and makes a full turn instead of rotating the half turn back again.  Therefore, anything fixed to the batten end can get an undesired twist.  My way of connecting the wishbone to the batten worked quite well, but I saw that the batten was worn where it passed through the “Donut” ring.  The Donut was just an aluminium plate with a hole giving plenty clearance.  Dry aluminium wears badly when it slides on dry aluminium at high contact pressure, so if I would do it again, I would have made a different material for the ‘donut’ and maybe a “wear layer” on the batten where it touches the donut.  I still like the look of the wingsail profile when the batten is curved, but I easily admit that your thoroughly made wingsails without curved battens look far better than the wingsail I made from tarpaulin.  My hunch is though that if you would go for curved battens, your wingsail would become even more efficient and develop more force.

    I liked the wingsail experiment, but went back to H&M style with steeply peaked yard, because the wingsail gave too much forward lead when it was reefed, so my boat got unmanageable when the wind was at its strongest (history can be found in this website’s Technical Articles section).  So now I am back quite close to my ‘doodle’ in Newsletter 47, except for the straps that are now reduced to short loops of thin round line around the battens and through the sail.


    Last modified: 21 Aug 2018 12:28 | Anonymous member
  • 21 Aug 2018 08:20
    Reply # 6585420 on 461931

    Nils,
    It's interesting to go back to JRA Newsletters no. 42 (2004) and no. 46 (2006) and particularly, in no. 46, to compare and contrast your 'doodle' of how flipping battens might be incorporated into a wingsail, and my description of Tystie's first wingsail rig, which went on to cover 40,000 miles without too many issues. There's certainly some scope for combining flipping battens and wingsails, but I think I'm going to stay with my tried-and-proven hinges. 

       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
                                                               - the Chinese Water Rat

                                                              Site contents © the Junk Rig Association and/or individual authors

Powered by Wild Apricot Membership Software