The babystay doesn't go slack. The whole mast moves back, but more at the top than at the middle. If you want to see the effect of tightening the backstay, look at the forestay, and sight up the mast from the side while the backstay is not tensioned too tight. Then run a weighted line (or even your main halyard if the main is down) from the top of the mast to the boom. When you tension the backstay, the top of the mast moves back; the middle of the mast moves back (less than at the top); the weighted line will move aft along the boom; the forestay will be straighter and you'll see the bend of the mast when sighting from the side from the boom to the top of the mast.
Alan Bergen 35 Mk III Thirsty Rose City YC Portland, OR On Sat, Jun 4, 2016 at 10:14 AM, Ronald B. Frerker via CnC-List < cnc-list@cnc-list.com> wrote: > 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. > Ron > Wild Cheri > C&C 30-1 > STL > > > > > ------------------------------ > *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 > > > > _______________________________________________ > > This list is supported by the generous donations of our members. If you > like what we do, please help us pay for our costs by donating. All > Contributions are greatly appreciated! > >
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