While waiting for the fabric to arrive I ordered that book "The art and science of sails" from amazon.
I feel I'm opening a bag of worms and will want to buils more sails.

My Bobie 18 is the family boat I have three boys 9,11,12
All want to sail, none understand how sailboats work. I want to set the boat up so I can single hand and the boys can trap. WIth the new square top main the I want to add a self tacking jib. This will be smaller than the original.

On the 18sx main I'm going to try placing the battens in the seams. I've enlarged the seams to 145mm. My battens are 1 in. cedar tapered strips. I have lots of carbon sleaving to cover the wood with. I plan to play with the taper to get the bend in the right place then cover with carbon to make stiffer. The top batten pocket will glued on cause there is no seam to hide it in.

I got the fabric direct from contender. Enough material for main and jib less than $200. The monofilm material won't last as long as other sail fabrics, but will allow a not so expensive learing curve.