The 'original' question was:


Does anybody know how to go about calculating the stresses in
standing
rigging. I have an masthead sloop rigged 50 ' FRP boat. 4 lowers, 2
intermediates, 2 uppers, head & back stay. All inboard rigging. I'd
like to know the tensions in the various stays - vs the tensile
strength of the wires. Any ideas on how this is done?"

Please explain a bit further ... and/or answer the following:
1. Are you setting/tuning the original rigging you have ... based on
some % values of the existing wire?
2. Are you selecting / checking new wire rigging? thinking of
increasing or decreasing the wire diameter, etc.?
3. Do you intend to also 'prebend' the mast? if so how many spreaders
and is the rig mast headed or fractional (what % fractional)
4. Etc. ?

If you are looking for a 'plain vanilla' static tuning; then, set all
wire ar 12-15% tension (by use of a tension gauge) ... then go sailing
at a heel to see if these values of the lowers, intermediates are
correct to keep the mast straight. Otherwise, if you have a plan view
and deck view of the boat, or can post or list the URL of the plan,
etc, views AND if you can give me the relative shape (luff/leech/foot
dimensions) of each sail, I will calculate the approximate % loadings
in all the shrouds for you so that the rigging is 'perfectly tuned/
balanced' on a % of ultimate tensile strength for
you ..... if that is what you are looking
for. :-)