**Asmat wrote:**
** The fact remains that boats with cambered sails heel more than those with flat ones. They are also less close - winded, but I concede that cambered sails are more powerful and make better progress to windward.**

I am not so sure about that. My first, flat junksail on my Albin Viggen, Malena, did never let me sail as closely to the wind as later cambered sails. Even when the wind was strong enough to be on the edge of needing a reef, we still pointed lower, although the performance gap was smaller in strong winds than in light wind-conditions.

My conclusion was therefore that the flat sail could never produce as high lift-to-drag ratio as the cambered sails. That is still my view.

Arne

PS:

The simplest place to spot the lift and drag angles is at the Windex. The lift of the sail will by definition have to be at 90° of the arrow's pointing direction, while the drag by definition points the opposite direction of what the arrow does.

Now, if we manage to point and sail the boat as closely as 30° from the apparent wind, then we can decompose the lift and drag force vectors (Fl and Fd) into two sets of force components running along the ship’s CL, and at 90° to it (I cheat a little, disregarding the little leeway angle of the boat)

The sail’s lift, Fl, will produce

a *boat* *driving force* of Fl x sin30° = 0.5 Fl

It will also produce

a *boat heeling force* of Fl x cos 30° = 0.87 Fl

The sail’s drag, Fd, will produce

a *boat braking force* of Fd x cos 30° = 0.87Fd.

It will also produce

a *boat heeling force* of Fd x sin 30° = 0.5 Fd.

Only if the lift is sufficiently stronger, (say 3 or 4 times) than the drag, will this result in the boat going forward.

If I get my sums right, and I guess that

the sail’s lift/drag = 3.0, then..

The resulting *net driving force* will be

0.21 Fl - that is only 21% of the lift,

and the *total heeling force* will be

1.04 Fl - that is 104% of the sail’s lift.

It’s a wonder we can sail to windward at all...