--- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@...> wrote:
> The aim with the canted bi-directional rig is to get better
> alignment of drive and drag forces in 3D.

The effective angle of attack of a sail depends on its cant angle. If you start off with a vertical sail, and the boat heels to lee, the effective angle of attack decreases. If you lean the rig to weather, but you fail to sort out the force vectors to prevent heeling to lee, you increase the angle of attack. Windsurfers demonstrate that, with quick enough control, this can be dealt with. However, the bidirectional sail will have its centre of effort forward of the axis around which the sail rotates. You can't depower by sheeting out, you have to depower by hauling in a brace at the forward end of the boom. That will take more time.

> the mast could be canted to the windward side rather than being
> vertical to give more vertical component to counter healing.

That would also move the vertical component more to windward. You would be better off moving the foot of the sail leeward rather than the head windward.

If you want benign behaviour in a gust, you need to go all the way to non-heeling or heeling to weather. Sailrocket demonstrates how wide a boat you need to achieve that, at least if you want your sail upright enough to produce reasonable drive for its area.

Regards

Robert Biegler