Graeme: "And do not go much below 33% or there is no point in SJR , but that's just my opinion".

Indeed - my Galion 22 SJR (as discussed on my conversion thread) might be a living example of this. Basically I am very satisfied, but the lack of jib power is evident, at least this is what i feel. Might be some other thing, of course.

(Anyone interested in trying themselves and buying the sail? I would prefer - but can't afford the cloth - making a new sail rather than start playing with extending the battens for longer jib chord. I bet the mains would also make a nice, very high-AR sail without the jibs...)

Thanks Maxime

I have a feeling you are probably correct in the first point you make, in regard to halyard and other control line forces - if only because when  it all boils down,  this is the angle of the halyard force vector (when all the other forces are in play it may vary slightly from what is shown on the plan). However, the CoE offset demonstrated by Arne does help one to form an understanding of what is going on, and is particularly illuminating in regard to sheeting forces - and the heavy helm which tends to develop with most cat rigs going down wind (of which, Amiina 2 or any highly mast-balanced rig will likely be among the best behaved).

Your second point concerns me a bit, and here is why: what you wrote is perfectly correct (in the static situation). Below: same outline, different moment of force about the mast.

But you are attempting to explain the (static) balance forces, whereas explanation is not the purpose of the definition. The purpose is of the definition is purely to be unambiguous in the design of a SJR sail, so that lofting mistakes are avoided. The slot won't vary much - it is specified, perhaps a little arbitrarily, as being equal to the diameter of the mast, and I would regard it as a constant, not a variable.

Within the bounds of what is reasonable and likely, I think the definition we have been using, is appropriate and can be made to unify (sort of) with the standard definition of mast balance for contiguous sails, and allow (sort of) apples-with-apples comparisons.

A definition can be quite quite arbitrary, and it does not matter what it is, provided everyone understands and uses the same definition when bandying numbers around.

The definition I gave (and Arne used) for mast balance - the proportion of a lower batten which is ahead of the mast centre line - is in accordance with what Slieve intended when he described his SJR sail as having, say, 33% "balance". This high mast balance is thought to be close to the limit of what will work safely, and anyone fooling around with different definitions of their own will create ambiguity and might risk failure in the making of a SJR. You can call it what you like, and leave out the word "balance" altogether if you prefer, but this is the rule to use when lofting a McGalliard SJR sail: Keep the slot width about equal to mast diameter, and do not go much above 33% of the sail outline ahead of the mast centre line - unless you want to be a pioneer. There is reason to believe 35% may be possible.

Measuring along the length of a lower batten is near enough and good enough, and less likely to lead to error.

(And do not go much below 33% or there is no point in SJR , but that's just my opinion).

[If you start analysing width of slot, area of jibs etc etc someone is going to get it wrong, and over-balance, and then others come along and blame the rig for the failure (or blame the very principle of higher than normal balance, as happened before). Call it a rule of thumb, if you prefer. At this early stage in the development of the rig, perhaps one can be forgiven for being a bit "touchy" about it. Remember, this "definition" is for amateurs (like me) not for aerodynamicists.]

Arne wrote: Hasler and McLeod mention the option of having downhaul spans. These are meant to help reefing when sailing downwind (without needing to round up first).

To avoid confusion here, the spanned parrel-downhauls used on a SJR (here and here) may not be of much assistance in lowering the sail when reefing down wind. I've never had to try (I mean, never needed  their assistance for that), so I don't know. I suppose they would help?

Above: two forms of a spanned parrel-downhaul pair. (McGalliard). Serendipity has a third variation, which I prefer.

I must point out, anyway, that reefing downwind is easy with spanned parrel downhauls because as soon as the halyard is released they go slack, allowing battens to fall down easily. If down-wind pressure on the panels were to make it impossible to lower the sail, then you might have to round up, because pulling on the parrel-downhauls and tightening them doesn't actually give you a direct downward pull.  I just don't know, can anyone help?. If a conventional set of control lines is used together with a set of downhauls which are solely downhauls - that is maybe what Arne is talking about - then you perhaps get the best of all worlds, but what I have been trying to suggest all along is: this would mean an awful lot of control lines which, with SJR anyway, would all need to be adjusted at every reefing event.

Arne - it seems to me you have opened up a new development pathway for SJR which is worth trialling. I am very tempted to pull the top triangle off Serendipity's sail and give it a new (longer) yard and new upper section, like your HM style, just to see what happens - with a view to examining the control lines necessary, rather than performance. Next winter maybe. Thanks for your creative input Arne.

Here are four more non-McGalliard SJR variants: 

The catamaran sail is a crude Amiina look-alike, with six lower panels. Its not my cup of tea, but David likes the look of it. The ketch scow (Wayward) has a split mainsail - interestingly in this photo the mains panels comprise centre panels only, the shelfs have not yet been made and the camber is achieved by differing-length temporary "Thai lashings". (Its a "shelf-foot" sail with the shelfs missing). It has five lower panels. The single upper panel is a polynesian crabclaw (negative roach). I believe Dave Z is very happy with it. The schooner (Fly) has a heavily forward raked foremast carrying a 32 sq m split sail to the owner's design, with two upper panels, five lowers, and a rather shortish yard. The sloop (Hihi) appears to be an unraked (vertical mast) version of Fly's fore sail, with one less lower panel. It would be interesting to know the sheeting and control lines used on these rigs, and what their owners have to say about their performance.

For now, I still prefer the Amina mk2 sail. And I do think the raked Poppy sail would look lovely on a SibLim 10m, if it could be made to work without too many control lines (which, I have my doubts. David - what about just setting the mast plumb?).

Here is a familiar photo of Amiina, slicing through a short chop and smoking along under her old Mk 1 sail

Thanks those who chimed in. I was hoping a lot of people would add to this thread, with descriptions of their own hands-on experiences of SJR . Please do.

Currently the discussion seems to have settled on panel size (and number), control lines- and upper sections, as introduced by Arne.

There is a lot more to be discussed in the New Year.

I hope everyone following this thread will have a safe and happy Christmas.

To drape or not to drape...

I don’t want to draw any firm conclusion about the need for control lines on the HM-style SJRs. After all, these sails are only armchair ideas, so far.

However, if I were to rig such a sail, I would start with making the top section set well.

• ·         I would give batten one from top  an ordinary batten parrel, short enough to prevent the sail from moving forward of the working position on the sail plan.
• ·         I would fit an ordinary YHP to counter the forces from the sheet.
• ·         There is probably no need for a THP or any other running or standing parrels near the throat end of the yard. The very short luffs of the top panels have proved to prevent the battens from moving forward or aft (at least in my HM style sails).
• ·         Further down I am sure Slieve’s combined batten parrels and downhaul spans will do the job.

Hasler and McLeod mention the option of having downhaul spans. These are meant to help reefing when sailing downwind (without needing to round up first). Since I only sail inshore, I have had no need for these. If the sail is a bit reluctant to come down, a light tug on the THP is enough to bring it down. However, for offshore use, downhauls could be useful. I think Slieve’s version could work fine on ordinary one-piece HM sails. When spring comes, I must remember to fit one such span to Ingeborg’s sail, just to see how it works.

I rest my case  -  time for preparing just a little for Christmas...

Cheers, Arne

PS:
Graeme, seven battens need not weigh 40% more than five battens. Remember, each of them will only take roughly 5/7 of the load, so may be built lighter.

You don't have to remind me, Arne, I am well aware that all of this is in a second language for you, though reading your posts, one would hardly guess. Your mastery of English is outstanding and I am constantly noticing and admiring that. 

I wanted to reduce the halyard angle of the Amiina SJR to make the sail hoist easily and drape nicely.

That's a loaded sentence Arne. In fact I think you might have made a typing error. The fact of the matter is, the Amiina SJR already hoists easily and drapes nicely.  (as long as it is not given too short a mast).

Perhaps what you mean is, you wanted to retain its good quality of draping nicely, and still be able to hoist easily, yet do so with a with a shorter mast. I think that is what you really mean - and provided it will work with a system of parrels which is simple, and also incorporates a light downhaul of each panel, then you have surely suceeded, and well done.

To be honest, I have my doubt if a SJR does perform that much better (speedwise) than a properly made one-piece JR. Me too. I feel that it ought to perform a little better up wind, but have no idea whether it really does, or not - all I know is, it works well. A badly designed SJR could quite possibly be not as good as a contiguous sail, which is why I think your "tongue in cheek" hybrid ought to be tested on a smaller size, though on paper, with my limited knowledge,  I can see no reason why it would not be just fine.

I feel that the Amiina2 sail is very efficient when sailing to windward, but I will say one thing, it needs careful helming. If you lose concentration it very quickly falls back to ordinary. That's what I found, anyway. I wonder if Edward has found that.? I believe this is called low "alpha tolerance"? (I'm a bit out of my depth here). I believe that in the carefully calibrated trials which have been recently carried out, the most tolerant was David's Weaverbird wingsail. That's an important factor to consider in the "which sail is best" question.

[ I always wished that one day at a tall ships regatta, I might be able to enter Serendipity and persuade Lynda (Fantail) to take the helm. I think then, that sail might punch above its weight and surprise a few people. Anyway, for an ordinary helmsman, it probably doesn't matter what sort of sail as long as it is well cambered, well proportioned and simple and safe to operate. (And proven robust, as I can hear David say). 

And another thing, on the day of Annie's first sailing of Fanshi I repeatedly went to the back of the fleet to do filming (here and here) and Serendipity with her little Amiina 2 sail, and 15' of waterline length, caught up with the fleet again each time easily and was overtaking Zebedee as we went into the bay. Nobody noticed I think, or nobody mentioned it anyway. Oh well - sigh - one sometimes has to blow one's own trumpet].

edit: (..time for swinging the casseroles here, Edit  -  play with the casseroles, i.e cook dinner...)  Oh, is that all you meant - time to cook dinner - I was expecting a more colourful Norwegian colloquialism!