I've ordered some of Antal's low friction rings, for use in the sheet spans. They are, in fact, a modern day euphroe, and rather lighter and less expensive than using small blocks.

And I've ordered  an Easymatic block for the lower end of the sheet. That's the type with a double jammer, so that you can haul on both parts at once, if the load is light, or on just one part if the load is heavy. I think I'll be rigging a four part sheet to five battens, with an equal power three point span for the lower three battens, and an anti-twist two point span for the upper two battens. So I've chosen the 93101 model, which is the one used for a bermudan 4:1 mainsheet. And then, if I work out how to jam the sheet as it passes around the upper sheave in the block, I will have an independent upper and a lower sheet. That covers the options, and I can amuse myself by seeing whether an upper and lower sheet are really worthwhile, on a small rig. I know they are on a large rig.

David,

I do like the look of your new sail design, sure it will be pretty powerful - most interested to see how it performs against a pointy sail. 

With such a short section between the double cones, it hardly seems worthwhile - is the reason that single cones cannot give enough articulation?

Cheers Mark

ps when are you planning to be sailing?

Finally, I think I've finished changing my mind about how I want the sail to look, and how I want to make it. I've uploaded pictures of the sailplan, the sail sections and the lower panels.

Sailplan

I've tried to make the maximum use of the materials that I've bought, increasing the batten length to 3.375m, which brings the sail area to 22.1 sq m/238 sq ft, and the SA/D ration to a very generous 20.4 - she ought to sail quite fast. I like to keep the yard shorter than the battens, to keep it lighter and more easily managed, and so that the after end will stay aft of the topping lifts, the diagonals of the upper two panels are quite short, introducing an appreciable amount of positive stagger.

Sail sections

In the lower five battens, I'm using two double-cone hinges, with each cone having a half angle of 4 degrees, spaced apart by a tube that's 375mm long. Thus, the total angle of articulation is 16 degrees, but not all in one place - the change of direction is softened somewhat and a hard spot is avoided. The hinges account for about 60% of the total camber of about 10% of the chord, with some camber built into the panels to account for the remainder. I dislike using hinges alone to achieve this much camber, as they are reluctant to articulate in light airs, and I dislike using deeply-cambered panels alone, as they are difficult to set without creasing, and are unpleasant to live with in light going combined with a swell. The combination of two methods of adding camber is one way of getting the best of all worlds.

Lower panels

The picture shows how I propose to use a turned tabling at the luff and leech, as the clipper canvas is wide enough to cut the panels with a very minimal bias, only 3.5 degrees, which will be within acceptable limits. I wouldn't use a turned tabling where the threads make more of an angle with the edge of the sail. To join the panels, I propose to use, not the amateur method B or C, nor the sailmaker's method of a lap joint, but the canvas worker's method of a run-and-fell seam. I suspect that this canvas will be best treated like cotton canvas, with all cut edges turned under, no edges exposed. I don't mind at all having to pass a rolled panel under the arm of the machine, in a sail this small and with minimal cambering allowance added to the panel edges, and there is no need for me use the amateur methods B or C. I found with my first wingsails that the batten pockets are better sewn on flat against the sail than raised on the starboard side, so that there is symmetry, with the hinged batten on the same vertical line as the panels, which is another reason not to use the amateur methods. Using a batten pocket that consists of a length of cloth folded lengthways, so as to make a patch in the same operation, protects the seam stitching from abrasion by the battens, and the edge can be turned under.

David, many thanks for the hints on seaming allowance and leech hollow versus panel rounding.

I've now cut out most of the panels, but before I sew anything please could you advise whether it's better to add any leech, luff, yard and foot tablings as short lengths to the individual panels prior to assembly, or to wait until the panels are stitched together and  joined to their neighbours before adding the tablings as long continuous strips?

The photos of Tystie seem to show short lengths of leech tabling overlapped at the batten joins rather than full length strips added to the assembled sail.

Malcolm Duckett wrote:

David Tyler wrote:

David Tyler wrote:

The tapered mast tube, 9.2m x 165mm dia x 3mm wall, is on order with the Aluminium Lighting Company, and I'm awaiting a delivery date.

I now have a delivery date of May 13th.

David, can you give us an idea of the cost of this - I am trying to figure out if I can afford an alloy mast or need to make a birdsmouth one....

The carriage for one off is a whopping £250 + VAT, but I couldn't see a way to avoid it, as it takes a specialised trailer or a big truck to transport this length.