Thanks for the input Walt,
At first glance, I thought the author was ignoring the force of the wind on
the boat itself for simplicity's sake, and making a point about forces
developed by the sail. But then I realized that while the wind is
approaching the sail at the same angle in both diagrams, the sideways force
stayed relative to the boat's centerline and not the vertical plane of the
sail.
But from a practical standpoint, does total force = net force? And if so,
shouldn't the net force vector show the direction of the actual path, or
movement of the boat?
Scout

"Walt" wrote in message
...
Scout wrote:
Is sideways force always exactly perpendicular to the boat's centerline,
as
shown by the vectors in Sleight's Manual (link below)?
http://scout235.tripod.com/Sleight_p_31.jpg

The short answer is yes. Because sideways force is *defined* to be
perpindicular to the boat's centerline.

Think about it this way: there is a net force from the wind. It's a
vector (i.e. it has a magnitude and a direction.) You can always
express a vector in terms of it's components relative to a coordinate
system. In this case, the've chosen a coordinate system with axes
paralell to and perpindicular to the boat's centerline. So of course
sideways force is perpendicular to the boat's centerline - in the same
way that the x-component of any vector is parallel to the x-axis.

Can the camber of the
sail be forced to shift that force slightly forward?

You can definitely do things to make the net force more forward and
less sideways. i.e. make the forward component larger and the
sideways component smaller.


--
// Walt
//
// There is no Volkl Conspiracy