Origami rig comments

  • 31 Mar 2021 06:42
    Reply # 10255067 on 10250108
    David Doran wrote:

    Hi Doug.

    I seem to remember a mention of that unconventional sheeting system when browsing the magazine archive.

    As far as I can remember, it was mentioned in Paul Mckay's original article on the Aerojunk rig.

    If it worked it would cut down a lot on the amount of rope in the cockpit and allowed a more Bermudan style sheeting arrangement in the cockpit.

    Maybe someone has more information?

    Thanks, David, with that hint I was able to find this Q&A exchange in Paul's article on the Aerojunk in I64, p48:

    [Q:]On the all-white sail there appears to be a 'bolt rope' at the aft end of the battens, but not the forward end. But the red & white sail may have a bolt rope at each end.

    [A:]What looks like a bolt rope is actually the single line sheet running through bull's eyes fitted to the ends of each batten. So this design has a halyard, a sheet and 3 (optional) downhauls to make the sail pretty. That's it.

    So yes, it seems that balancing the sail and (in one of several possible ways) fixing its fore-aft movement relative to the mast provides a lot of simplification. Cool.

    Graeme Kenyon wrote:

    PS I have wooden battens, not regarded as the best solution, and I broke one the other day. (Not from sailing forces - I hit a marker pole with the sail while fooling around with a camera). The batten did indeed break at the mast - and the improvised splint arrangement which was easy to make on the spot, looks so satisfactory to me that I am considering putting splints on all the other battens too!

    Yes, after looking at my sketch again, the spool on the batten appeared ridiculously large. Adding a more modest reinforcement to the battens where they bear against the mast should help reduce point loads and prevent the initial damage that can lead to buckling. A bit like the way I sometimes put a knee brace on before going hiking...

    I'm glad to learn that the ideas I'm throwing out are mostly redundant and not utterly stupid. I think I'm learning! I've downloaded both Arne's and Slieve's info troves, as well as every issue of the newsletter. Lots to assimilate in there, fun reading.

    Thanks everyone-

  • 30 Mar 2021 00:20
    Reply # 10250615 on 10239242

    R D Culler (I've dusted off his book and have been reading it again) - has a suggestion to bring the tail of the halyard back and attach it to where it starts - making an endless loop - that seems a clever way of getting rid of some of the rope where the halyard is 1:1 (a dinghy?) - never tried it.

    There is no doubt the JR does involve quite a lot of rope that all has to be kept tidy.

    Doug: I forgot to mention - there are lots of different sheeting systems and some of them are said to be very good at anti-twist. I use a 2-part system myself, and am amazed at how well it keeps the sail, you can eliminate all twist if you want to. Evidently some sails like a little bit of twist, but I quite like to keep my sail with almost none (as far as I can judge by looking up from below.)

    Last modified: 30 Mar 2021 08:56 | Anonymous member
  • 29 Mar 2021 22:06
    Reply # 10250108 on 10239242

    Hi Doug.


    I seem to remember a mention of that unconventional sheeting system when browsing the magazine archive.

    As far as I can remember, it was mentioned in Paul Mckay's original article on the Aerojunk rig.

    If it worked it would cut down a lot on the amount of rope in the cockpit and allowed a more Bermudan style sheeting arrangement in the cockpit.

    Maybe someone has more information?


  • 29 Mar 2021 21:08
    Reply # 10249948 on 10239242

    Doug: I can't claim in any way to be an expert on this, having made just one SJR sail and used it enough to have some idea about the type. But I can't help offering an opinion and clarifying a couple of points.

    Without knocking any of Paul's ideas regarding D-formers, I really just wanted to point out that a plain full length batten works perfectly well, in conjunction with Slieve's spanned batten parrel-downhauls, and (opinion) I don't think that perfect symmetry or improved aerodynamics makes enough difference in this instance to warrant the extra complication. Perhaps the D-formers have some advantage that I am unaware of, as I don't have any experience of making or using them. Batten parrels will no longer be needed, but whether the downhauls are eliminated I do not know. Any reduction in running gear would be an advantage, at least for small boats which need to be de-rigged after each use - a little less so for moored boats (whose rig generally stays in place) I would expect.

    Your third paragraph seems to me to be a solution looking for a problem, as the running spanned parrel downhauls do all that is required for a SJR, including holding the luff of the main panels closely to the mast while at the same time, as soon as the halyard is released, they slacken too, allowing the "parrel" to let go from the mast. This is quite a different arrangement from a soft webbing parrel of fixed length - the conventional parrel is a "long" standing parrel but I have never used them so can not comment further. Of course, all parrel types can be made to quick release for removal if you should want to - my rig has to be dismantled each time after use, so I have a quick release arrangement on my spanned running downhauls.

    Your 4th paragraph: If my understanding is correct, all junk rigs have modest sheeting forces. The SJR having a little more balance, I suppose would have even more modest sheeting forces, since the sheeting system used is the same as any other junk rig. (Nothing in the sheeting system is deleted.)

    The last part of this paragraph: I simply don't understand what you mean, so I will just report to you that the halyard arrangement and the sheeting arrangement on a SJR is just the same as for any other junk rig. The difference in running rigging is that with the SJR as designed by Slieve, luff hauling parrels, yard hauling parrles, Hong Kong parrels etc are not needed - the other side of the coin is: the SJR as Slieve designed it has a pair of running spanned batten parrel downhauls - which conventional rigs do not need.

    Your last paragraph: When Slieve designed the first SJR he dummied the entire sail with a strings and dowel model, which he made to hang (drape) to his satisfaction without any hauling lines, and thus chose the shape of the sail. The later SJR he designed (Amiina) is somewhat simpler. I would not alter the shape of the top panel of a Amiina sail form. If someone wanted to make a variation on this simple shape, it might pay to make the identical lower panels first, then dummy the top panel with rope if unsure what its shape should be.

    I suggest reading Slieve's notes on the website: members' area/documents/technical articles - and regarding the D-former and the Origami rig, obviously Paul is the best person to comment.

    PS I have wooden battens, not regarded as the best solution, and I broke one the other day. (Not from sailing forces - I hit a marker pole with the sail while fooling around with a camera). The batten did indeed break at the mast - and the improvised splint arrangement which was easy to make on the spot, looks so satisfactory to me that I am considering putting splints on all the other battens too!


    Last modified: 30 Mar 2021 09:00 | Anonymous member
  • 29 Mar 2021 19:50
    Reply # 10249775 on 10239242

    Greame and Len, thanks for indulging my ignorant curiosity. I'm going to fearlessly lean back in my admiral's armchair and speculate wildly here, so take it with a grain of salt the size of a Buick.

    Paul McKay has shown several, a few, er, a plenitude of D-former configurations. Some assemble fore-and-aft onto the mast, others slide sideways, some have wishbones, others just single battens. The fwd and aft battens on the non-wishbone shapes would be about 1/3 and 2/3 the length of a simple one-piece batten, so as Len points out any spare parts could be shorter than a full batten. The bending load on the batten is maximum where it crosses the mast, and the round-on-round contact is a point load, so some sort of stiffener/load spreader there seems like a good idea.

    So here's a mishmash idea- a built-up batten assembly made from one or two tubes, with a hefty splice that stiffens the joint and serves as a bead to prevent chafing as the sail and batten shift relative to the mast. The batten tube could be a single continuous length if materials are available in that length. The batten parrel is made of webbing with a half-twist to sewn-in loops that go over the batten, and lashings around the batten tube(s) might prevent the parrel from moving relative to the batten if needed. A buckle on the parrel allows the batten to be installed on and removed from the mast. The entire sail can be removed from the mast by releasing the buckles and disengaging the halyard, sheet, and any other hauls, which the SJR reduces nicely. This soft parrel ends up with a D shape rather naturally, and allows some skew while preventing fore-aft shifting. The halyard should, I think, be outside the parrels rather than trying to thread it through the D gap. The buckles would allow trying it both ways.

    An aside- is it true that the balanced SJR has such modest sheeting forces that the multiple sheetlets and their blocks and euphroes can be deleted? Damned if I can find the reference now (I've been binge reading on all things JR), but someone referred to running a single sheet through some sort of loops on the aft ends of the battens and connecting it to the halyard just above the standing end, without the usual JR multi-sheetlet arrangement. If any version of SJR allows this without excessive sail twist, that would be a big win all by itself.

    I love the method of dummying the top panel with ropes, then building a sail panel to match it. This seems to be another strength of the origami method, separating the various optimization tasks into independent, smaller jobs. Imagine the hassle of sewing in a triangular panel, testing it, then unstitching it to sew in another. The modular construction should allow a lot more experimentation with rapid turnaround.

    3 files
  • 29 Mar 2021 00:43
    Reply # 10246065 on 10239242

    All very good points, Len.

    I think you are right, the top panel with its yard angle and yard length is, I think, part of the key to the way the sail drapes, I had just set that aside. Actually, I believe it is possible to leave the top panel out for a start, and just dummy it with ropes, then adjusting the ropes to get the right shape. As a way of designing the Amiina-type sail, similar to what Slieve did when he made his first rope model for the more complex Poppy sail. In fact I think it was Slieve who suggested it.

    Regarding the D-former, it just seems a bit of a structural monstrosity to me, albeit a minor one. Leaving aside the question of symmetry, it seems to me much simpler (and stronger) just not having to make them at all. Wouldn't a short standing parrel be pretty much the equivalent of the D-former?  If parrels can be unclipped or made with some form of easy release, they'll do everything a D-former will do, and snug down better too, I would think.

    In any case, I think both would have to fit to the thickest part of the mast, and a "tapered" hybrid mast should have a smooth transition from one diameter to the next. Short parrels could perhaps be eased over the transition by having parrel beads, D-formers might be more likely to hang. Just surmising.


    Your really interesting point is regarding swinging the entire rig up and brailing it to the mast. You have anticipated Arne's current thinking for a dinghy rig. It has great possibilities and - regrettably - does not fit well with either the D-former or the short standing batten parrel. 

    Last modified: 29 Mar 2021 10:17 | Anonymous member
  • 28 Mar 2021 20:51
    Reply # 10244944 on 10239601
    Anonymous wrote:

    Doug, also you may not be aware, but the SJR as designed by Slieve already eliminates all those hauling parrels you refer to. The sail design/top panel/yard attachment point are worked out so the sail drapes properly without them.

    I think (you might know better having one to play with) that part of the reason it hangs well is that the top panel is still angled and the halyard is shorter than the rest of the battens. So the OP idea of just adding panels to make the sail might cause binding without at least one odd panel on top.

    I think the Origami rig can be further simplified. Does the D-former actually make any real improvement, in practice? I doubt it, and would far prefer to keep the plain full length battens as in the SJR (spit junk rig). KISS.

    I am not sure which is simpler, I have had a similar idea for a while with the addition that one side of the D-former would be removable (and I just had a square/rectangular hole) so that any batten might be removed without having to dismount the mast. A D-former would not work with a tabernacle I think but a tapered mast should be fine, the D would have to be the size for the widest part is all. In a hybrid mast more care would have to be taken at the join, though I guess that is the case anyway.

    I think the D is simpler than the ropes, straps or what have you that hold the battens to the mast and position it for and aft. The batten to D-former join probably evens that back out or makes it more complex. Also on the plus side for the D-former, is the storage of spare parts would be easier as spare battens could be 1/3 ish the size. So I am not sure which of the two comes closest to KISS.

    hoped-for dinghy rig which could be quick and easy to make - and able to be assembled or dismantled in less than 2 minutes. So far its just a daydream - nothing actually tried yet.

    This is another place the D-former might be less practical. I would imagine the sail bundle, battens and all might be folded flat against the mast and left all in one piece for transport and storage. With the D-former, one would have to have a tie around the D-formers to keep them in order and lift the mast out from the middle. Really, trying it both ways for a few trips would tell and even then, a person's preferences might get two answers from two people.

  • 27 Mar 2021 01:40
    Reply # 10239601 on 10239242

    Hello Doug. Welcome.

    What fascinates me about the origami jib is its uncanny resemblance to the usual much more complicated-to-make 45 degree shelf jib, when inflated.

    I'd like to try one on a dinghy. Paul admits to an unavoidable small wrinkle near the luff, but it probably doesn't matter, and I can't see it anyway, in the photos (JRA Mag #85) it looks pretty good.

    Doug, for a full size sail it is said that its best if the orientation of the cloth is parallel to the leech of the sail, so if there is batten rise (which seems to be usual) it may not be quite so simple to make full-width-cloth panels as you describe - you'd need to check that with someone who knows more about sail-making, I am not sure. (I notice Paul's origami "hybrid" rig seems to have zero batten rise.)

    Doug, also you may not be aware, but the SJR as designed by Slieve already eliminates all those hauling parrels you refer to. The sail design/top panel/yard attachment point are worked out so the sail drapes properly without them. (Well, almost). Instead, however, you still have to have two paired-spanned-parrel-downhauls (see Slieve's notes for explanation) which need to be attended to when reefing. I suspect a dinghy with an un-tapered tube mast would probably get away with very short standing batten parrels - but might still need downhauls, I haven't tried it yet.

    I think the Origami rig can be further simplified. Does the D-former actually make any real improvement, in practice? I doubt it, and would far prefer to keep the plain full length battens as in the SJR (spit junk rig). KISS. A tiny little bit of asymmetry doesn't hurt, and I bet you couldn't tell the difference between port tack and stbd - I can't anyway. And although the D-former might eliminate the need for batten parrels, I suspect downhauls MIGHT still be needed - it would be great, for a dinghy at least, if downhauls too could be eliminated.

    I see Paul's origami jibs, in a SJR arrangement (with full length battens and not the D former), with short standing batten parrels and PERHAPs just one spanned-pair downhaul (hopefully not even that) as a starting point for a hoped-for dinghy rig which could be quick and easy to make - and able to be assembled or dismantled in less than 2 minutes. So far its just a daydream - nothing actually tried yet.

    By the way, I've never had a fan-up with my Amiina Mkll SJR - touch wood! I currently remain hopeful that the planform eliminates it - maybe I'd better not speak too soon! Jami? Edward? Dave D? James? Any fan-ups yet?



    Last modified: 29 Mar 2021 10:32 | Anonymous member
  • 26 Mar 2021 23:53
    Message # 10239242

    Hello, I'm a new member, wanna-be cruiser with just about zero hands-on experience in sailing other than a few rides on charter boats, but a seasoned engineer in aerospace (lots of rocket propulsion design and flight testing, including six flights in the right seat of the XCOR Xracer).

    I'm fascinated with the simplicity and modularity of Paul McKay's Origami Rig. A sail of arbitrary height could be assembled from as many jib and main panels as the mast could support, along with a batten assembly for each panel. Obviously the panel height can be selected to juuust fit within the width of a standard bolt of cloth, and the overall sail plan would be designed by the batten count and the jib + main panel lengths, producing an admittedly boring hershey-bar sail- but color patterns can be cheerfully individualized. All the sail's parts can be made by essentially assembly-line methods and built up as needed, and those D-shaped formers (issue 85, p5, fig 3) make the sail's performance consistent and improved on both tacks. On a cruise, any damaged parts could easily be swapped out with spares.

    Heck, panels and battens/D-formers could be built from local materials pretty much anywhere in the world, with no need for finicky sail pattern layout and large scale precision sewing. "Field expedient repairs" seems like a rallying cry for the DIY cruiser.

    Won't most of the various parrels and parrel hauls be eliminated by the D-formers? It seems that the luff, tack, and yard hauling parrels would be unneeded since the sail's fore-aft position is fixed- no need to monkey with it if the jib keeps it balanced and holds the helm forces near zero. Hong Kong parrels also vanish due to the split, too- at least it appears that McKay's Miranda doesn't need them. The function of the batten parrels is subsumed in the D-formers, of course.

    Arne Kverneland's Fan-up preventer Mk1 might be the only other non-standing rigging needed. Dreaming of going cruising and being as lazy as I can get away with, I like the idea of deleting most of the strings, and I feel fortunate to be arriving on the scene after a lot of smart people have solved the big problems.


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

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