This pictorial shows the methods I use to actually sew the sail described in Designing a 76sqft Lug Sail. There are lots of ways to do this - please don't think I am telling anyone what to do, I'm just showing how I have done it.

I have my tarp, some wet erase markers (wet erase is WAY easier to clean up than dry erase) and the layout plan of the sail.

You'll also need a batten that is at least 13ft long. I bought a 14' 2x4 and ripped it into a long, whippy batten about 3/8 thick. Don't have a tablesaw? You should be able to pick up some bendy molding or baseboard in lengths longer than 13ft.