I suspect the "one" refers to your original note of the equation being for
one lb per sf wind force (correlating to 16 mph wind speed). The formula
would still work for different wind forces.

One comment - the resulting angle is an approximation that is good for only
small angles of heel. The 57.3 and GM are related in that if you plot GM at
57.3 degrees (one radian) on a GZ curve (righting arm curve) and scribe a
line back to the origin, this line reflects the slope of the GZ curve at
small angles of heel. There is also a cosine factor which gets introduced to
both the sail area and heeling arm (h), so the applied heeling moment is
reduced as the boat heels. Fortunately, in all but a few rare cases, the
angle you get with the simplified formula will suggest a heeling angle
higher than you'd actually get on the boat.

Regards,

Don

Donald M. MacPherson
VP Technical Director
HydroComp, Inc.
http://www.hydrocompinc.com
tel (603)868-3344
fax (603)868-3366



"William R. Watt" wrote in message
...
"Aniculapeter" ) writes:

thanks for the additional info.
I can get the value for GM now.

l is one ?

mulitplying by unity doesn't make sense.
it does not change anything.


57.3 x SA x h x l
-----------------
D x GM

I know SA = sail area (sq ft)
D = displacement (pounds)

I don't know what h, l, and GM are.
Anybody know?

I think "h" is the height of the centre of effort of the sail. a note
says
"from designed sail plan center to LWL plus 40% draft" it doesn't say
if
the centerboard is up or down. I think it would be in feet.

"l" is "lpsf" in one location. I think that might be "lateral plane in
sq
ft"
but not sure. Waterline plane?

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