[MHml] Diamond shroud tension

[Will Moizer Flat4m Infusion]

For us, sailing Tennant GBE and T9 catamarans, the rig always reverts to a
two wire plus mainsheet rig when going in any direction except dead down;
the leeward shroud goes loose.  I set up my rigging tight enough so the rig
doesn't jerk around when we are motoring out of the harbour in a chop.  The
diamonds are key devices and I crank them up enough to induce a slight bend
to the mast really just to ensure they are doing their job.  We are fast
cruisers, not racers so I'm sure there is much more to it especially with a
bendy rig, but for us tight diamonds and snug shrouds have worked for ten
years of sailing including plenty of hull flying.

Will

-----Original Message-----
From: multihulls-bounces at steamradio.com
[mailto:multihulls-bounces at steamradio.com] On Behalf Of Clifford Bradford
Sent: January 5, 2010 5:10 PM
To: Informed discussion of multihull issues
Subject: [MHml] Diamond shroud tension

Hello all,
I have a question I'm trying to figure out and that is how much 
pretension to put into the diamond shrouds on a rig. I figure the 
diamonds serve two purposes (1) to help prevent transverse buckling by 
stabilising the rig where the spreader is located (I'm thinking a single 
diamond rig here for simplicity) (2) if any aft sweep is put into them 
to produce some amount of longitudinal prebend. I figure that the amount 
of preload is higher for (2) than for (1) because to prevent buckling 
the shrouds have to be just taut while a pretty fair amount of tension 
is needed to bend you typical wingmast. So then it'd just come down to 
how much prebend you want to put into the mast (?) or am I missing 
something else.

Cliff
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