DC> RR> Thus, the tension in the windward shrouds is the same in both
DC> RR> boats (becasue the same amount of wind is pushing the mast sideways)
DC>However, you still have to take in the account the pre-load.  If
DC>the pre-load is set as if for 10 knots and you are getting less,
DC>you are creating more of a strain on the hull.  When the wind
DC>excedes that rate, it blances out, to an extent.  However, the
DC>bend in the mast head will be less, thus creating more of a
DC>sidewards force on the mast, due to the lack of bend that
DC>would spill wind.
Nope, spilling the wind makes no difference to the shroud tension.  I
know that this seems wrong, but let me go through the arguement.
First, there are two ways to look at the forces.  You can look at the
forces in the mast and sails that are trying to heel the boat.  Or, you
can look at the forces of the buoancy, crew weight and keel weight that
are trying to keep the boat level.  These must be EQUAL and opposite.
If one was greater that the other the boat would heel more and more
until it flips or it would heel less and less until it tips to windward.
Since the boat stays at a steady angle of heel (for this arguement) the
two are equal.  So, to determine the tension on the shrouds, we can look
at the righting forces on the hull.
It is easier to look at the forces righting the boat and then accepting
that the forces heeling the boat will be equal and oppsite, reguardless
of how they are created in the rig.
Let's say that the rig is tuned so that the leeward shrouds are just
going slack at 10 knots of wind on the beat.  You are sailing close
hauled, heeled at 15 degrees.  You will have three major forces that are
keeping the boat upright:
1) the centre of buoancy has moved to leeward becasue the hull is
heeled.
2) the centre of mass of the keel has moved to windward due to the heel.
3) you have a couple of bodies on the rail.
These forces are providing a torque that is trying to flatten the boat.
The forces trying to heel the boat come from only TWO places:
1) the windward shrouds pulling up.
2) the compression of the mast pushing down.
Thus, if the boat is heeled 15 degrees with the two people of the rail
you will have the exact same force trying to right the hull REGARDLESS
OF THE SAIL SHAPE!!!!!  It doesn't even matter if you reef!  The
forces in the windward shroud and the compression forces of the mast are
the only forces trying to heel the boat.  Thus, they must be the same
regardless of sail shape.
DC>Only until the point where the wind begins to spill...
Makes no difference.....
DC>It may be different on different boats.  Mine is designed to
DC>allow quite a bit of lee bend to the mast.
The type of boat makes no difference!
DC>That could be the difference in your view, as I only have single
DC>stays, as well as no backstay.
Dan,
I have kinna lost track of what type of boat you have.  It has a single
set of shrouds - or do you mean that it has a single set of spreaders
(i.e. two sets of shrouds; uppers and lowers)? Is it a fractional rig or
masthead?  What type of keel does it have?  etc?
If your shrouds are aft of the centerline of the mast (as mine are),
the shroud tension determines, in part, the tension on your forestay.
Tighter shrouds will produce less forestay sag - giving a flatter jib.
The ratio of the tension in the lowers and uppers will determine how
much bend you get in the mast, thus how flat the mainsail is.  You have
to mess aroung 'til you get the combination that you like...  Mainsheet
tension affects the forestay sag and some jibs are cut to have the
desired shape with more sag than others.
DC>We have a 135 that we'd like to bring in closer, but the spreaders
DC>get in the way.  The 100 allows us to sheet closer.  (Those are
DC>on the boat I sail on Thurs.)
DC>Hmmm, noticed you are from Toronto..., yet:
I and hooked up to a "sailing only" bulletin board network called
Ship-to-Shore.  There are about 10 nodes in North America.  In the
middle of the night, when phone rates are cheap, all messages get
transfered to Vancouver, which, I guess, is the main node.  Vancouver
does the hookup into the internet.  Thus, I get an internet hookup, with
a one day delay in messages, for $1.25 per month!  (Many, many
conferences in UseNet and FidoNet etc are monitered but this is NOT an
area that I know anything about!)  A real deal for $15 per YEAR!!!!
 * S2S Toronto, Ontario  (416) 975-1547
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