Sam, like you said, the mast is more or less fixed, but not completely. As you
decrease backstay length the mast has two motions, bending and rotating from
the deck pivot point. As it rotates (pivots) backward it tightens the
forestay. That's about all I get with my tree trunk of a mast; no bending, but
more than an inch back and down. The thinner sections with multiple spreaders
and/or babystays will get more bending. Both motions move the tip of the mast
back and down since the forestay is mostly fixed (it does lengthen slightly
since it's a bit of a catenary and more tension takes some droop out). Since
systems seek an equilibrium which reduces overall tension, the babystay will
loosen slightly with the bending, but will assist the bending motion until
equilibrium.Frac rigs get a lot more bending of course by geometry alone. And
tuning them starts with lighting a candle by the hollow stump at midnight!
Those with multiple spreaders are the devils own design.RonWild CheriC&C 30-1STL
From: Sam Salter via CnC-List <cnc-list@cnc-list.com>
To: CNC-LIST <cnc-list@cnc-list.com>
Cc: Sam Salter <sam.c.sal...@gmail.com>
Sent: Friday, June 3, 2016 9:50 PM
Subject: Re: Stus-List Adjustable backstay?
Looking at this as an engineering problem (I don't have a 30-2) - explain what
I'm missing:
Top of the mast is more or less fixed (fore and aft) by the forestay. Sure, it
will move back an inch or two when it takes up slack in the forestay, but
mostly it's going to stay put.Baby stay puts pre bend into centre of mast or
at least fixes it in space, fore and aft.When backstay is tensioned won't the
top move mostly down and push the middle of the mast forward, slackening the
baby stay?Tensioning the forestay and taking draft out of the main.Do you guys
see the baby stay go slack or am I full of it???
sam :-)C&C 26 Liquorice Ghost Lake Alberta
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