On Thu, 13 Oct 2005 11:50:11 -0400, "Glenn Ashmore"
wrote:

OK, you asked for it. Prepare to be confused:

Mast design starts with the transverse righting moment. That is the force
in foot pounds required to overcome the initial stability and heel the boat.
It is usually measured at 30 degrees. 30 degrees is where the sail area
perpendicular to the wind starts to reduce faster than the wind speed
increases so it is about the point of maximum stress. The calculations
require finding the center of gravity and the center of buoyancy and the
metacenter at the heel angle. The Metacenter is the point at which a
vertical line through the COB crosses the centerline of the hull. The
horizontal distance between the COG and the COB is the lever arm. The
righting moment is the mass * the acceleration of gravity (32'/s/s)* the
lever arm.


That's pretty much exactly what I was after, thanks. I don't need to
work out the maths myself, I just wanted to understand the why and
wherefore.

The actual mast section depends on the righting moment at 1 degree and 30
degrees, the number of spreaders, baby stays, runners and several other
factors. I am not even going to try to get into that.


That I understand perfectly,

Gosh this newsgroup is useful isn't it?

Many thanks,

Pete