Anonymous wrote:

Still, have a look at the photo of the Chinese junk below, nicked from PJR. The sails, in particular the mainsail, show quite some fullness in their panels. 

Hmm, and not much twist... Though, to be fair, the junk is running downwind (being wing on wing) and perhaps flatter because of that.  The foresail shows the camber/bagginess in the aft third but the main shows about half the sail is running more like a crab claw. That top panel is one serious chunk of sail cloth (or rice mat) and the panel below is at quite a high angle too.

And didn't Vincent Reddish add bagginess to his fanned sails as well?

From the outset, because I did not know any other way, I used twin sheeting on Serendipity. (Upper and lower panels – not port/starboard). It worked perfectly and I never wanted to change it.  Low friction, low sheeting forces, sheets handled together as if a single sheet, perfect control over twist while very little need ever to adjust one sheet relative to the other, less spaghetti if you ask me – works perfectly on that particular sail (single upper triangle, cambered sail, zero twist). Maybe other types of sail have other requirements.

Slight change of subject: Jan W:  “Arne's … diminutive Halibut dinghy rig … only known example of this sail has a little barrel cut in the panels to make up for non-stretchy modern material, really does fly like a kite and powers up when twisted” Can we learn more about this sail Jan? A new thread?

Anonymous wrote:

It has to be remembered, and I'm going to keep repeating it, that Arne's sails (Arne's very good sails, it must be said) and traditional flat-cut fanned sails are different beasts. Arne and his sails do not like twist, the camber comes from the sewing. Flat-cut fanned sails develop camber and power when twisted and de-power and behave themselves impeccably when not twisted. I feel like this knowledge is being lost in the junk community which is a shame as I don't think the phenomenon has been explored to its full potential in the "western" rig.

Absolutely right. Hasler and McLeod devote a great deal of attention in PJR to developing sheeting systems which try to eliminate twist. Since then, Vincent Reddish looked at Chinese junks and recognised that twist gives flat sails their power. And anyone who hasn't yet read Kurt Jon Ulmer's excellent article "The Merits of Flat-cut Junk Rig Sails" should do so. 

In pursuing added complexity by trying to add camber to junk sails, we could lose sight of their essential simplicity, together with an understanding of the subtle manner in which traditional Chinese sails work.

Anonymous wrote:

John, your posting is very interesting.

Your reasoning behind your choice of sheet makes quite some sense. However, different boats have different sailplans and very varying space for the sheets, so I don’t think there is such a thing as a generally ’best’ sheeting. The sheeting angle you get when close-hauled, is about the one I get in my Ingeborg when broad-reaching. At that angle, the sheet forces are quite light on my sheet too (3-part purchase, 35sqm sail).
As I round up for close-hauled sailing, the last bit of sheeting gets heavy. I can still manage by hand, but tend to rather make a couple of turns with the (1-speed) winch. Still, no show-stopper. Only if the sheeting space gets very narrow, as on foresails on schooners, would I completely rule out using central sheets.

As you say, the sail is prone to get creases (diagonal I guess) when close-hauled with central sheeting. I too got that, until I set up the Hong Kong parrels just taut enough to remove those creases  -  while still avoiding new creases in the opposite direction when squaring out the sail. 

http://goo.gl/r0fwCf

I generally divide my sails up in seven panels, which result in smaller panels. This lets me fit HK parrels without them intruding too far aft in the sail. I guess that your 5-panel sail would not like HK parrels that well, so your port-stb. sheets make sense. Actually, in the 80-es and 90-es, many British junks had the single sheet attached to a rail-to-rail sheet track. You get some of the same benefits that way.

Frankly, I guess we end up sticking with the sheets we have become used to, whether it is ‘the best’ or not.

If I were to try a two-tail sheet for a (large) Johanna-style sail, I would let one tail control the upper section and the other the lower one. This gives great twist control. I stress that keeping the twist right (= almost none) is an important performance factor. With telltales attached to the leech of each panel, you can see if the twist is right.

Cheers,
Arne

Thanks Arne! Regarding sail twist. It was obvious from old pictures (see attached) that the junk sail was divided into upper and lower sections, as observed from the arrangement of sheetlets and euphroe. I have been wondering how the old masters adjust the twist, until I saw one holding two sheets in his hand last year. There were simply 2 sheets, one from a upper euphroe another from the lower one. He fly the sail like a kite and tie the 2 sheets together onto a common single cleat.

In about 50 years of JR sailing, I've probably tried most of the sheeting options. Two sheets, port and starboard, sometimes makes sense for the after sail of a ketch or schooner, which must be sheeted in further than the forward sail. Two sheets, upper and lower, often makes sense in a high AR rig, for better control of twist.

But one sheet will always be easier to live with. Back in JR NL 21, in 1990, I wrote about a way of making the upper part of a single sheet "think" it was being hauled from the weather side, which was quite effective. The only downside was that after one or two reefs, the bridle needed shortening for further reefs to be taken.