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Old 06-02-2014, 06:47   #1
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Easing the backstay in light air?

Some say when in light air one should ease the backstay right off to reduce pre-bend in the mast and increase sag in the forestay and then trim the sails accordingly.

Others say trim the sails first and if that doesn't work, then ease the backstay.

Anyone have a preference?
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Old 06-02-2014, 07:15   #2
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Re: Easing the backstay in light air?

I don't mess with the backstay at all on my boat, which has a masthead rig with three aft-swept spreaders. All the more since I have in-mast furling, which wants a perfectly straight mast.

I think these techniques are more relevant to fractional rigs, where the backstay can really change the bend in the mast.
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Old 06-02-2014, 07:38   #3
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Re: Easing the backstay in light air?

Quote:
Originally Posted by OldFrog75 View Post
Some say when in light air one should ease the backstay right off to reduce pre-bend in the mast and increase sag in the forestay and then trim the sails accordingly.

Others say trim the sails first and if that doesn't work, then ease the backstay.

Anyone have a preference?
Not sure it makes much of a difference. I ease the backstay first, because this will induce sag in the forestay and deepen the mainsail. The I adjust the main halyard and the genua halyard. Doing it the other way would mean having to adjust the halyards again perhaps
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Old 06-02-2014, 07:52   #4
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Re: Easing the backstay in light air?

Quote:
Originally Posted by OldFrog75 View Post
Some say when in light air one should ease the backstay right off to reduce pre-bend in the mast and increase sag in the forestay and then trim the sails accordingly.

Others say trim the sails first and if that doesn't work, then ease the backstay.

Anyone have a preference?
If you are looking for more power in lighter air basically every adjustment is eased. Backstay, downhaul, sheeting etc.........you are wanting more draft/camber in the sail for more power.

Folks (racers) usually crank in on the backstay for more mast rake/prebend in heavier air for better pointing on the upwind legs which should also help flatten the main. It heavy air the main will be sheeted in hard also. They will then ease the backstay to power up for the downwind legs.

This in combination with the forward lower shroud tension amount will control the amount of prebend you get.
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Old 09-02-2014, 16:17   #5
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Re: Easing the backstay in light air?

What Thomm said.
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Old 09-02-2014, 17:32   #6
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Re: Easing the backstay in light air?

This depends on the condition of the sails also, if they are new and flat it may be needed but if older and fuller not needed as much
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Old 09-02-2014, 23:39   #7
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Re: Easing the backstay in light air?

Well if you like picking fly **** from pepper in really light air (drifters) you want your sails to be quite flat. This allows the air to stay attached. As the breeze gets up a couple of knots then you deepen the cambers etc etc
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Old 10-02-2014, 11:42   #8
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Re: Easing the backstay in light air?

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Well if you like picking fly **** from pepper in really light air (drifters) you want your sails to be quite flat. This allows the air to stay attached. As the breeze gets up a couple of knots then you deepen the cambers etc etc
I'd think you'd want flat sails in high wind and more camber in light wind.

I'm just starting to play with headstay tension since I don't have a back stay. A looser headstay in light winds, tighter in high winds. Adjust in the morning depending on expected conditions.
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Old 10-02-2014, 12:22   #9
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Re: Easing the backstay in light air?

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Originally Posted by robert sailor View Post
Well if you like picking fly **** from pepper in really light air (drifters) you want your sails to be quite flat. This allows the air to stay attached. As the breeze gets up a couple of knots then you deepen the cambers etc etc
???????????????????????????????????????
I always thought that sails should be flat as possible in heavy winds, and allowed to go "baggy" in light airs.
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Old 10-02-2014, 12:45   #10
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Re: Easing the backstay in light air?

what Robert Sailor stated is absolutely correct.
in the real light stuff flat sails are faster because of attached flow.
also you do not change mast rake by putting on the backstay as others have stated. Rake is set by your headstay length weather you are a frac or masthead! It becomes more complicated if you have runners.
as you increase mast bend on frac boats you SAG the headstay as power is applied. By bending the mast with the backstay you simply flatten the main on both frac and masthead boats.
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Old 10-02-2014, 12:53   #11
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Re: Easing the backstay in light air?

This is really a racing question. I used to trim main on both fractional and mast head race boats. If you are going to constantly watch the trim it is a good idea to make those adjustments and I agree that in real light air you need a flat sail so that the laminar flow attaches. in light air a baggy sail gives you more power and in heavy air you need to decrease the power by flattening the sails. Depending on the complexity of the rig you can have headstay sag and no prebend. It really is alot of work and needs to be adjusted near constantly to get the most speed.
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Old 11-02-2014, 11:39   #12
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Re: Easing the backstay in light air?

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....I agree that in real light air you need a flat sail so that the laminar flow attaches. in light air a baggy sail gives you more power and in heavy air you need to decrease the power by flattening the sails...
I'm confused. These two sentences seem to directly contradict each other.
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Old 11-02-2014, 11:57   #13
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Re: Easing the backstay in light air?

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Originally Posted by gamayun View Post
I'm confused. These two sentences seem to directly contradict each other.
I think it reads like this:

really light air = flat sails probably 3 knots or less
light air = eased sails 3-6 knots
medium air, etc...
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Old 11-02-2014, 11:59   #14
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Re: Easing the backstay in light air?

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I'm confused. These two sentences seem to directly contradict each other.
It's in the books. It says that a flatter sail is really best for really light air say under 5 knots because the air will attach better, but it has never worked for me and I've tried it while reacing. I always had better results with the big ole rounded deep draft sail for light winds.

Then as the wind increases start sheeting in and flattening out. In really heavy air, we used to use two hands from the trapeze and all our might on an 8 to 1 block to tighten the main sheet while racing catamarans. (there's no reefing on small catamarans) We'd also crank in max prebend on the diamond wires and would have setup for quite a bit of rake before leaving the beach.

Last step would be traveling out some on the main traveller. Some folks will derotate their mast to breakup the smooth airflow over their mainsail also. On a sloop rig, folks will feather their jib.
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Old 11-02-2014, 22:01   #15
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Re: Easing the backstay in light air?

Flat sails in very light air works on racing boats, easily driven, with clean bottoms, and nicely cut sails in good condition (or the very rare cruising boat which meets these requirements).

But it doesn't work even on these boats in any sort of sloppy seastate.

So I wouldn't read too much into reports that it doesn't work for most cruising sailors.

The single thing which I personally think helps most, for most boats, in REALLY light air, is to find some way to get the boat to heel to leeward.
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