Hi all, I live on the west coast of Canada, and I have been following the development of the junk rig for decades, lurking and reading, hopefully benefitting from all your expertise.  I was very excited about the split junk rig, although it looked complicated in its execution, so when I saw the simplicity Paul McKay's Origami rig, I knew I would have to give it a go. I improved my time last winter during the 'covid response insanity'

by working on the design and construction aspects of the Origami rig for a folding inflatable dinghy that I am also working on, as a test bed for junk rig design (I am going to junk-rig my pointy top trailer sailer Mac 25 this coming winter), and I have settled on the Origami rig, or variation thereof, for the FIB (Folding Inflatable Boat based on the Fliptail 9- but that is for another thread...).  Looking at a dinghy sail, it needs certain compromises in order to be functional (I am lazy, or efficiency expert, you choose!) the sail needs to be easy to reef, easy to set up and strike, stow-able without much fuss, efficient upwind, easy and cheap to build and look cool... At least it must look esthetically pleasing to both my engineering and artistic soul, which requires it to have form follow function...  I also want the sail to be balanced as it is reefed, requiring each jiblet/main pair to have the mast at 33% of the length of the battens framing it, for ease of sheeting and better balance on all points of sail.  I have been pondering the mast-meets-the-batten conundrum at length, as I also wish the sail bundle/mast/sailcatcher to be one when stowed.  I planned on having this possible by having a ring of webbing with a rivet/chicago screw holding the webbing ring and webbing stretcher (I am experimenting with attaching the ring of webbing to the strip of webbing the sail will attach to in order for the mast ring/batten to be able to twist when the mast is folded into the sail catcher). the msat must be able to pivot 90* for each batten, allowing them to stay flat as they settle around the mast in the sail catcher when stowed to keep the whole thing un-stressed at rest (like me!). I am starting again this fall with the onset of the west coast 'pineapple express' that keeps the greater Vancouver area wet and snow free most of the winter.  I made a test sail, but my construction set-up needs rethinking, I was not happy with the cut of the jib, the set of the sail, so to speak. I think that 35% of batten length was too much, I will settle out at 33% next time.  The masts, one for each of the dinghies I am going to build, as I am making two, comprise of 8' + 4' of 1-1/16" aluminum tube with a 12" length of aluminum tube to make an inner sleeve , giving a total length of 12' for the assembled mast.  I riveted the sleeve to the 4' top section, to which I added two webbing loops at 90* to each other secured with two 'jubilee clips' or pipe screw clamps for the running rigging attachment, an idea that I 'borrowed' from another fellow junk aficionado. Sorry, not sure who came up with that one! I bungeed the two sections together so they will stay together when folded.  The top of the mast will stay in the sail catcher beside the top of the bottom section of the mast, (along with the sail bundle) and part of the base portion of the bottom section that sticks through the sail catcherwill be strapped to the bottom of the sail catcher with added strap + buckle for ease of stowing.

I like the esthetics of the Chinese junk sail, and although the identical panel sails of Sleive and Paul in their respective styles of split junk are designed for ease of construction, I wanted something that was closer to the esthetics of the traditional Chinese junk sails.  With the Origami rig, this is possible.  I laid out the sail panels on a piece of plywood, the largest one first, and it turned out, that each sail panel as I went up the sail, was the same front edge shape as the one below, only a consistent length shorter each time.   As the sail panels are sewn flat and it is the location of the attachment points that creates the 3D shape, they are extremely simple to build.  I tapered the leading and trailing edges (luff and leach) to both keep the overall shape of the sail tapered from bottom to top, but the proportion of the whole sail before the mast stays the same, only the aspect ration diminishes when reefed.  The whole thing has a 5* rise, and 5* slope in the leach and the luff from the vertical.  As I said, the set of the sail was a lot to be desired, although, to be fair, I didn't test it in a stiff breeze. That is all for now, more this fall...  Anyone else with experience building origami junk sails for a dinghy?  My balcony is about to set sail...  Didn't get as far as sheeting yet...  :-{}

Dave J

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.)

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!

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. 

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?