Build 2

Now take both halve and lie them one on top of each other so the front surfaces are together.  Line both sides of the sail up perfectly.  Now sew along the center line of the sail.  Use a straight stitch

Now unfold the sail and place the back surface up.  Then take the extra material left over from the seam and fold it inward to one side or the other.  Sew down the side with another straight stich.