Hello Bertrand,

Thank you for admitting that the true wind is deflected. That's all we need to know. Now please don't confuse this with the apparent wind. the apparent wind is the resultant of true wind and forward speed of the yacht (over ground). This leads, by the way, to the interesting phenomenon that you can sail at 5 knots dead against a tidal stream of 5 knots, not gaining and losing any ground, so that true and apparent wind are the same.

The resultant means that there is a (momentary) balance between the forces exerted on the sail (or the wing, no difference). A curved sail will generate more power, a flat one less. So in low wind you need a curved sail, while in high wind you need a flat sail. Normally the junk sail cannot cope with this demand. So you reef. Another option is to reef from the top, binding two battens together (including the panel sail cloth), to make the sail stiffer also.

Just remember. You need sail area to drive the boat in moderate winds. In storm conditions, you will not need any sails. Bare poles and the boat structure are enough to send you down wind at a speed that you might want to control.

I have changed the original concept by balancing all sails fully, so that the mast is roughly in the center of the sail. Like this, there is very little stress on the sheets. For an illustration of the idea, check out Maltese Falcon