Interesting stuff David, I look forward to hearing about your further results.  I do see how you need to limit the amount of vertical articulation.  Although maybe the rule could be more like:  the amount of vertical articulation allowed must be kept significantly less than the amount of horizontal articulation??  Also, you need a catchier name.  Perhaps "Tyler's Limit", short for Tyler's rule on the limit of vertical articulation (also known as the axis of evil).  

Darren Bos wrote:

The sail looks great David.  Are the bolts shown in the batten joints photo temporary or were they left in place when the battens are mounted in the sail?  I can't see them in the photos with the battens mounted on the sail.  If they're left in place, do you need elongate holes in the battens to achieve the vertical articulation you mention?

One thing I've learned, in a 2-reef breeze two days ago, is that the battens still tend to cling to the mast when the sail is loaded, as happened with the wingsail. This means that they try to find the easiest way of articulating again, which means that they try to turn through 90 degrees. This doesn't seem too harmful. But it does lead me to formulate "Tyler's Hypothesis" - A hinged batten ought to articulate equally in both the vertical and horizontal directions, so that it is not inclined to rotate about its axis. Clearly, round tubes with a conical hinge are a convenient way to achieve this, but I have rectangular section battens, as a leftover form the wingsail. I can, if there's a problem, relieve the hinges so as to permit 20 degrees of horizontsal and 10 degrees of vertical movement. But I'll watch and wait for the time being.

The sail looks great David.  Are the bolts shown in the batten joints photo temporary or were they left in place when the battens are mounted in the sail?  I can't see them in the photos with the battens mounted on the sail.  If they're left in place, do you need elongate holes in the battens to achieve the vertical articulation you mention?

Well, the first couple of short sails, in 5 - 10 knots of wind, went well, and everything is working. I took some photos as I sailed, but then forgot to get them out of the camera and into the computer. Soon. 

interestingly, because the yard is at a low angle, with the halyard in its centre and therefore pulling forward under full sail, and because I have short batten parrels that stop the sail going forward, I don't need to belay the YHP, and I don't need to touch the LHP either. Everything just sets well, just by hoisting until the tackline stops me. Helm balance is good, as it was for the wing sail. 

The double sheets, upper and lower, are good too, as with 3:1 in each, rather than a single 6:1, they overhaul more readily, and in effect, you only have to haul in half the sail at a time. I think double sheets are a must for tall, narrow sails.

one thought I've had is that if I tension the sail along the after battens, but give it some slack along the forward battens, I might get some camber in the forward section without having to do any more sailmaking.

Yes, Darren, there's a strong wind warning - and at the moment, I'm sitting outside the Saturna pub ( for the free wifi) in about 5 knots of wind. Maybe later.

Good luck for the trial. I guess satisfaction for being able to make ones own sail is compensating the lack of wind.

Antoine (WaterBear)