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Old 26-10-2010, 12:10   #46
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Originally Posted by Stillraining View Post
What allows the mast head rig to come back is simply taking the belly out of the fore stay as much as you dare...This is where tweaking can be of great advantage from fully slacked for light wind performance allowing the head sail to power up, to bar tight for heavy weather pointing ability with as tight a luff and inboard sheeted as you can get.
Thanks for the explanation. Unlike a fractional boat, then, the ability to tension the backstay and bend the mast comes at the cost of a lot of slack in the forestay when the backstay is detensioned. If you had a tighter forestay the mast would not be able to bend as much. Is that correct?

On the OP's boat with single unraked shrouds and no inner forestay, it seems like the backstay will simply rake the mast backwards since it has nothing to act against to induce bend. On a keel stepped mast that doesn't sound like a great idea to me. He will not be able to flatten out the main with mast bend and will simply be tightening the forestay. Why not keep backstay and forestay well tensioned always. The only thing you lose is the ability to power up the jib in light airs (beyond what you can get from other sail trim like sheet tension and genoa track, or a headsail change).

It still sounds to me like this boat doesn't need a backstay adjuster for cruising, and I think that people recommending it may be basing that on experience with boats rigged differently from OP's to take better advantage of backstay adjustment.

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Old 26-10-2010, 12:20   #47
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Originally Posted by Sparohok View Post
Thanks for the explanation. Unlike a fractional boat, then, the ability to tension the backstay and bend the mast comes at the cost of a lot of slack in the forestay when the backstay is detensioned. If you had a tighter forestay the mast would not be able to bend as much. Is that correct?
no not at all

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On the OP's boat with single unraked shrouds and no inner forestay, it seems like the backstay will simply rake the mast backwards since it has nothing to act against to induce bend.
The rake is controlled by the headstay length.

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On a keel stepped mast that doesn't sound like a great idea to me. He will not be able to flatten out the main with mast bend and will simply be tightening the forestay.
Yes U will bend the stick flattening out the main.

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Why not keep backstay and forestay well tensioned always. The only thing you lose is the ability to power up the jib in light airs (beyond what you can get from other sail trim like sheet tension and genoa track, or a headsail change).
First of all you sacrifice light air ability sheet trim will not make up for it.

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It still sounds to me like this boat doesn't need a backstay adjuster for cruising, and I think that people recommending it may be basing that on experience with boats rigged differently from OP's to take better advantage of backstay adjustment.

Martin
Incorrect all boats need it.
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Old 26-10-2010, 13:36   #48
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Originally Posted by Sparohok View Post
Thanks for the explanation. Unlike a fractional boat, then, the ability to tension the backstay and bend the mast comes at the cost of a lot of slack in the forestay when the backstay is detensioned. If you had a tighter forestay the mast would not be able to bend as much. Is that correct?Martin
Sort of yes...but mast rake is determined by for-stay length its tightness is only determine by back stay tension the boat hull itself will bend as well acting as another dynamic in the equation...and that's why its hard on a boat to be tensioned to the max all the time...boats have literally broke in have due to to much tension.

On a frac rig there is this tendency as well as no shrouds alone can keep a fore stay taunt no mater where that fore stay is connected to the mast...there is just more movement in the upper portion of a frac riged mast so you have a lot more adjustment before the fore stay tension is affected as much as a mast heads is...This would be a complicated lever arm moment and My pee brain can not help you there.

Surfice to say that even mast head rigs can and do induce some tiny bit of mid section forward bend of the mast just from the nature of compression forces much like downward pressure leaning on a the end of a yard stick will induce a bend in it.

I am sorry but I have exhausted my ability to explain any further the benefits or lack there of with an adjustable back stay... so go with what suits your needs, desires and sailing preference...if not perhaps ignoring your boats.
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Old 26-10-2010, 13:46   #49
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Are you trying to say the designer of the boat that won the Americas cup off YOU just designs run of the mill non-radical boats?

Then it must have been the better sailors that won the Americas Cup!







It beats the better legal team winning the cup...
Are we just going to let him poke like that?!?!?!?!?!?
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Old 26-10-2010, 13:47   #50
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The rake is controlled by the headstay length.
OK let's see if I've got this right. Rake is controlled by headstay length. Backstay tension takes out headstay sag. Thus backstay effectively lengthens the headstay while under sail. I'm going to stick with my assertion, backstay tension is raking the mast.

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Yes U will bend the stick flattening out the main.
In order to bend the mast something has to be counteracting the force of the backstay. No inner forestay, no forward shrouds on this boat. What force is acting on the mast to counteract backstay and induce bend?

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Incorrect all boats need it.
There's a hell of a lot of boats out there designed with fixed backstays (or no backstays at all) which might disagree with you.

Martin
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Old 26-10-2010, 13:53   #51
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Are we just going to let him poke like that?!?!?!?!?!?
Mark has a sharp stick...I know when to back off.......it hurts my ego not to...
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Old 26-10-2010, 14:28   #52
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Have a chat with Phil Bates at rigtech at RPAYC Newport, really knowledgable and nice guy to boot.

Never heard or had a complaint about his work.
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Old 26-10-2010, 16:13   #53
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How is the expense and trouble of a backstay tensioner justifiable for a CRUISING boat
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Old 26-10-2010, 16:51   #54
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I love how these threads start out with a simple question and wind up so far off the beaten path that I forget what I love how these threads start out with a simple question and wind up so far off the beaten path that I forget what the original intent was. On my measly little 26 foot boat I use the backstay tensioner to take the sag out of the headstay when hard on the wind. Works like a charm. I don't know much about any of the other stuff mentioned in the thread as I am still in the learning phase and enjoying every minute of it. Can't wait till next season so I can experiment some more. How come there is no mention of prebend in the mast?
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Old 26-10-2010, 17:18   #55
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no mention of prebend in the mast?
Pre bend depends on the rig design.

Usually there are two lower shrouds, so U can play those for pre bend, but you're putting the cart before the horse.

U only need pre-bend based on the way your main is designed/cut, it can be zero or many inches.

I think today the thinking is off the wind you don't want it.
So it more often than not no pre-bend set.
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Old 26-10-2010, 17:41   #56
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How is the expense and trouble of a backstay tensioner justifiable for a CRUISING boat
I gave one very justifiable real world on the water example...its up to others rather you except it for that yourselves or not...Thats all I own is a cruising boat....And thats what this whole thread has been about.
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Old 26-10-2010, 18:11   #57
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Ok, lets talk mast head, keel stepped, in line spreader mid 80's era rigs.

Number 1: Go get the cylinder serviced. It's not expensive and it's easy to use when sailing . You want it, you don't want a turnbuckle and you don't need to fiddle with it all the time.

Number 2: When you set the rig "or when you tune it" you add pre-bend to the mast for one main reason, to stablize the rig. How do you do this? You chock it forward in the partners using winches.

Number 3: How do you bow the rig? The mast crane is an eccentric that adds bow to the mast when you crank the backstay. Why do this, lots of reasons; one you depower the main, two you add tension to the headstay. Good stuff.

Number 4: Since we've gone this far you probably have checks. Use them, you want to stabilize the mast, they help.

None of this stuff is difficult to sail with or hard to maintain but for a non-tree trunk mast of that era it should be used.
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Old 26-10-2010, 18:17   #58
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Huh? Kind of depends on the rig that sits atop the boat doesn't it?

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How is the expense and trouble of a backstay tensioner justifiable for a CRUISING boat
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Old 26-10-2010, 20:10   #59
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I gave one very justifiable real world on the water example...its up to others rather you except it for that yourselves or not...Thats all I own is a cruising boat....And thats what this whole thread has been about.
It is what this thread is about....but most of the examples of how a tensioner work and it's application were refering to racing...I was hoping to give it a nudge back in the direction it was originally intended.
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Old 26-10-2010, 20:20   #60
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As my rig is pre-1950, came with a camber in it and no back-stay (the mast was actually recognized as an Atkin's style mast).
I wouldn't bother you any more.....It just bother's me when people are convinced that their cruising boats need racing equipment...it's a sales gimmick.
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