DC> RR> I wonder, however, is:  If the structure cannot take the shroud 
orces
DC> RR> when the boat is at the dock, how can it take them when it is 
ailing.
DC> RR> Just feel how tight the windward shrouds are when you are sailing!!!!
Hi, Dan  (who said...)
DC>You have to look at the whole picture.  Too tight to begin with
DC>puts even more strain on the shrouds when stressed in a wind
DC>situation.
Not true!!!!  Imagine two boats sailing to windward in 12 knots of wind.
Boat A has the tight shrouds, and boat B has the looser shrouds.
On boat A the leeward shrouds are just barely begining to go slack;
there is no tension on them; you might as well cut them off and toss
them overboard to save weight unless you think you may tack in the
future.
On boat B the leeward shrouds are flapping like overcooked spaghetti in
an earthquake; there is no tension on them; you might as well cut them
off and toss them overboard to save weight unless you think that you may
tack in the future.
Thus, the tension in the windward shrouds is the same in both
boats (becasue the same amount of wind is pushing the mast sideways)
and the tension in the leeward shrouds is the same. In otherwords, in a
medium wind the sailing tension in the shrouds is the same even though,
at the dock, the shroud tension in boat A is much greater than that of
boat B.
In fact, the actual tension would be higher in the boat B with the
looser shrouds because the mast would have moved farther off centre and
the moment arm would be less.
I appologize for the dreadful English above, but the physics is correct.
DC>Also, the distance of the spreaders from the centerline changes
DC>the loading forces.  This is apparent in inboard shrouding where
DC>the side loads that would be fine for an outboard shroud are
DC>magnified into heavy pulling forces on the shrounds and
DC>subsequnetly higher down forces on the mast as the shrouds are
DC>moved towards the center of the boat.
Yup, the farther that that chain plate is from the mast the less tension
is need in the lowers to prevent the mast from falling.  For the uppers,
a greater spreader length reduces the tension needed to stop the mast
from falling to leeward.  Surprizingly, the location of the chainplate
isn't very important, though is does make a little difference.
DC>To further complicate the issue, inboard shrouds have either less
DC>stout material to use for their support, or, in the case of a
DC>cruising boat, require a loss of interior space to beef up the
DC>area of the chainplates.
Also true.  My boat has the chainplates all the way out to the toerail,
and the boat is fairly wide.  Thus, the shroud loads are low (thus
the compression loads in the mast are low) and I can use a nice
lightweight bendy mast with tons of sail area.  (This makes up for the
fact that I can't have a jib bigger that 119% becasue I must sheet
inboard of the shrouds to get the correct sheeting angle.)  Further, I
don't require the extra weight of the structure require to support the
shroud loads and the extra compression in the mast.  So, my boat is
light.
DC>... Don't stand up under a gibing boom!
OK.
Cheers, r
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