Most of the information I used for designing the drifter came from Emiliano Marino's Sailmaker's Apprentice, and a few threads on the web.
The sail has a modest foot length because in very light airs a low aspect, long footed, sail will just collapse under its own weight even cut from light nylon. The draft is designed to be shallow and forward, because nylon is stretchy and the draft will blow aft as the wind picks up above a few knots. And supposedly in the lightest of winds, a flat foil will keep flow attached and provide some drive where a fuller sail may just stall.
The cloth is 1oz nylon which is pretty light, but the sail has robust corner patches so I am hopeful it will hold up in 10knots or so. For its winter test flight seen above, there was probably only 1-2knots which was enough to fill it.
It is set free flying on an internal Dyneema luff rope which can be tensioned for a straight luff going upwind, and then eased off to add more draft when desirable. This setup should be easier to handle than the asymmetric spinnaker with its soft leading edge which loves to collapse and send the whole sail thrashing about.
For a sheeting angle, the rule of thumb is that if you extend the line of the sheet through the clew into the sail it should bisect the length of the luff. I picked the midships mooring cleat as a convenient sheeting point which gave about the foot length and height I was looking for and went from there.
I'm not too concerned about helm balance, as the SB provided a-spin is a larger and more powerful sail set in the same location and has never pushed the bow off the wind too hard.
It is hard to accurately shape any nylon sail, and my broadseaming was certainly amateur-ish. But I liked the shape when hoisted so I am curious to see how it performs. It was a fun learning experience, and a pretty cheap project in any case.
