Anonymous wrote:
[...] I suggest you make a test piece which is exactly to Arne's method B seam and batten pocket, but with straight edges. It need only be a foot or so long. Lay two pieces of cloth a foot square one on top of the other, and sew with straight stitch 3/4in from the edge (no more) to join them. Cut a piece of cloth a foot long, and wide enough to make a pocket 20% bigger than your batten diameter - I'm guessing 7in. Stitch this on according to method B, either straight or zigzag stitch. If you can do this, you can make a sail according to Arne's methods. [...]
Done. After making this mock up I have some confidence back. I understand the value of keeping the seam allowance (no idea what the sail making term would be, if there is one) for joining the panels smaller, 3/4", as you suggested. Thank you David, and Arne.
Now I need to get in the right state of mind to click 'order' and actually buy the cloth. The vendor does not seem interested in giving me any quantity breaks, so I think I may order 25 linear yards and then make a second order if (when?) I mess up a panel so bad that the cloth must be discarded.