On Oct 9, 3:05 am, wrote:
... Essentially the strength of rigging based on the effort to heel the
boat to its self-righting point times a safety factor.

Any boat design or professional rigging handbook should have the
calcs. ...

Yes, I think shrouds are typically sized to take about 3 times the
healing force at 30 degrees. Head stays are a little more
complicated. The NBS standard as described in the always useful
"Principles of Yacht Design", Larrson & Eliasson, does start from the
30 degree RM but the proper wire size uses a multiplier of 15.
However, I'm sure that IACC boats use much bigger multipliers and
little gaff rigged sloop could get away with a lot less. The loads on
the head stay are more properly functions of how stiff the boat is and
how effective the tensioning system is. You just can't have too much
headstay tension on a modern sloop. These days any reputable rig
designer (and there are specialists in this) will calculate the loads
from first principles. Since the static safety factor for the shrouds
is 2 to 3 times I'd expect a similar factor is built into the rules
for the headstay but I wouldn't bet a huge sum on that and it isn't
really easy to get there from transverse stability...

-- Tom.