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Old 16-08-2014, 17:12   #1
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Staysail Stay Tension

Hello Cruisers,

After a bit of thought, I felt I should start a new thread, though this does follow on from the well answered thread I posed on maintaining tension on running backstays.

In that thread I asked about the effects of removing the very robust highfield levers on my running backstays and replacing them with a block and tackle setup.

Roll the clock forward and I have had a chance to put into practice SOME of the advice from that thread. But in doing so, I ran into a different question.

The old setup had highfield levers on both running backstays and the staysail stay. These were/are monstrous big things and allow a LOT of tension to be put on the stays. Much, much more tension than I can get out of anything I do with the four to one block and tackle arrangement that I am attempting to use instead, unless I bring the line from the block and tackle to the winch, and then I run into other problems, including an inability to easily release the line from the cam cleat on the lower block.

But from my other thread I think I understood that I should not need that much tension anyway, and that I had not completely understood the function of the running backstays. I felt they needed lots of tension whereas they were really just to prevent deflection of the mast from the staysail stay tension.

Well, applying Anne's advice, I sighted along the front of our "telephone pole" mast and discovered there is a slight, but noticeable bend in the mast being induced by the staysail stay, even before I attach and tension the staysail itself. This is hardly surprising when I think about it, as I still have one monster highfield lever on the staysail stay, and it makes the staysail stay super, super tight. If I release it, the mast comes back to shape nicely, but no matter what I do, I cannot counter that force with the running backstays without the highfield levers at the back.

So, at this point I am assuming I have too much tension on the staysail stay, and that I need to release it a little, but how much tension should I have? Should I be aiming for a similar sort of tension to that I can obtain from the 4:1 blocks that I have hauled on manually? Should the bulk of the tension really come from the luff of the staysail?

For what it is worth, the staysail stay comes to a point about 2/3 the way up our 50' mast and is parallel with our twin forestays. The "J" of the staysail is about 3/4 of the distance from the base of the mast to the mounting points of the running backstays, so in other words, the running backstays have a better effective angle to counter the forward pull of the staysail stay.

Confused, but feeling like I am closer to getting this one right...

Matt
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Old 16-08-2014, 17:39   #2
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Re: Staysail stay tension

OK a disclaimer first: I'm no rigger, just a DIYer who knows everything so please disregard the following once you better advice.

For starters; the bend you are experiencing is due (in part) to the backstay tension at the mast head and the "bendyness" of the upper part of the mast.

As you already know, it came be tamed by the lots of tension on the running backstays but it can be tamed (perhaps not as effectively) by making the upper section of the mast stiffer; say using baby diamond stays or such on the forward upper section.

So perhaps by adding such stays, you can get away with the lesser tension on the running backstays still using the block & tackle system.

Again, this may be hogwash but still worth thinking about
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Old 16-08-2014, 18:35   #3
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Re: Staysail stay tension

Added after edit time out:

I think you would want to maintain as much staysail tension as you can.

And first sentence in previous post should end with "once you get better advice"
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Old 16-08-2014, 18:54   #4
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Re: Staysail stay tension

Matt,

Pls., don't worry about it being tight: the runners are there to support the mast, and using their highfield levers will make it tight. It's all good. When the inner forestay stays really tight, you will not have the kind of staysail sag that we fought with our Solent rig and the old staysail.

I have yet to see a Swanson 42 whose owner added diamond jumper struts to its "telephone pole" mast, so I think that is most likely to be unnecessary in your case.

Ann [no "e"]
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Old 16-08-2014, 18:57   #5
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Re: Staysail stay tension

Hi Matt, and Wotname

Personally I like tight runners and tight staysail stays. Most staysails are high aspect sails that are very sensitive to stay sag, the top gets baggy very quickly with a slack inner forestay. And given that we use them in stronger winds for windward work is worth trying to keep them flat. A stiff full length batten near the top of the staysail helps flatten the top, but the middle still gets baggy...

Another benefit of tight runners is reduced pumping of the mast, and shock loads, fatigue and noise (as the mast moves in the partners and step), go forward on many boats with staysails in a breeze and you'll see the mast flexing fore and aft in gusts or over waves. Tighten up the runners and it stops.

I don't think a 4:1 tackle can get them tight enough myself. It works but you rely on the mast taking some of the load by bending slightly, this loads up the aft lowers and lets the stay go slack. If the sails cut for a slack stay it's not so bad, but most aren't. Another issue with the 4:1 and cam cleat is the amount of line and the fact that the cam cleat often jams under load, and can be hard to let go in a hurry, eg during a gybe with the main pressed against the runner. But the system does work on many boats including a 25 ton 62 foot cutter I work on sometimes.

Adding Jumpers as per wotnames post works well as a good backup/alternative to runners if you have a fixed inner forestay, but can't be used if you want to drop the inner stay for short tacking in light airs, as without the inner forestays support the jumpers will try to bend the mast the wrong way with potential for mast inversion (very bad).

So IMHO the best system is runners led to a winch in the cockpit. Easy to tension properly, strong, easy to release. Probably cheaper than the extra rope and blocks. With this system you can get the runners set exactly right, to a mark each time. In light conditions you don't even need a handle. Practically every racing boat has this system on it's runners for good reason. A small winch would do it if you had a 3:1 and on the windward side you normally have at least one spare winch that can be used. I think those new textile clutches would be perfect as a way to secure the runners if you wanted to free up the winch before tacking.

With regard to the bend in the mast, you should have a slight bend forward (maybe 1/4 to 1/2 a mast diameter?) with the inner forestay attached to prevent inversion and stop the main from becoming too baggy. This bend should be even from top to bottom of the mast. Not just a wobble in the upper panels. The runners shouldn't pull the mast back to straight, but should stop the mast bending too much more as the staysail is loaded up.

Saying all this with your tree trunk mast its all pretty academic. The mast will put up with a world of abuse and come back for more, so I wouldn't get to paraniod. Take a few photos and video of the mast and staysail when bashing into a decent chop and you can anaylise the amount of sag, bend and pumping. Try tighning the runner and see what happens. I would also look at the shape of the staysail. Too flat and you need to slacken the inner forestay, too baggy and you need to tighten it. Whether you do this with the runners or by adjusting the inner forestay will depend on the bend in the mast and the mainsail shape. Basic rules are to not let the mast invert and bow aft in the middle, or bow foward by more than about a 3/4 to 1? mast diameter for you tree trunk, and make sure the bend is smooth and even over the whole mast.

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Old 16-08-2014, 19:03   #6
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Re: Staysail stay tension

Ann, I believe Matt has already removed his highfield levers and replaced them with a 4 part block and tackle. Now he can't get enough tension on them to keep the staysail tight.

Are you suggesting he refit the highfield levers or accept lesser staysail tension or something else?

I concur the original Swanson 42 setup does not need changing but Matt has already modified his AFAIK.
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Old 16-08-2014, 19:03   #7
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Re: Staysail stay tension

^^ I guess thats the long answer, the short is that you don't need to completly straighten the mast with the runners, a small amount of bend forward is ideal. Set up the runners and go sailing in a stiff sea breeze with what you have. Take some pics, try it, and modify if you aren't happy with the amount of pumping, bend or sag or set of teh staysail. Take the runner tail to a winch and see if it helps any. You will learn alot really quickly. Cheers

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Old 16-08-2014, 19:09   #8
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Re: Staysail stay tension

Long answers are good .

Especially helps folk like me and hopefully the PO
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Old 16-08-2014, 19:29   #9
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Re: Staysail stay tension

Yes, Wottie,

I am suggesting he re-install his humongous hyfield levers. This is the situation as I see it presently: Matt is not able to get a good sheeting angle from his block and tackle runner arrangement to his winches, and the tackle is probably not man enough for the job. He might actually have to make a new strong point further aft that would lead clear to the winch, and then, with the cam cleat, he's not going to be able to un-do the block and tackle without putting it back on the winch, which he needs to be accessible for other jobs.

Just my two cents.

Snowpetrel: Great answer.

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Old 16-08-2014, 22:03   #10
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Re: Staysail stay tension

Well, ask and ye shall learn. First, Ann, sorry for the extra e, brain fart moment there.

Just to clarify things, nothing I have done so far is irreversible, and so far I am simply swapping existing fittings around to see what works best. The monster highfields are still keepings us lower in the water, they are safely stowed below.

Snowpetrel, thank you for the concise explanation of mast bend. I had to re-read it all a few times, but I from your description the small amount of forward deflection in the mast that I currently observe is ok. BUT, I am a little confused about sail shape here. I would have thought a forward deflection in the middle of the mast would cause the sail to become MORE baggy, since it has been cut for a straight mast, at least I ASSUME it was cut for a straight mast... what am I missing here please?

Secondly, I am increasingly feeling like I should re-evaluate the paths for the lines from the running backstays to see if I can find a way of getting round the binding cam problem. I do have ideal winches on both sides of the cockpit for winding tension onto the running backstays, so at least that part of the problem is solved, but before I go about re-routing lines etc, it would really help if Snowpetrel could maybe spell out his recipe for the running backstays again, as I am now confused as to whether he/you are recommending any blocks in the equation at all.

Sort of less confused than before, but still scratching my head a bit...

P.S. The whole aim of the exercise here is to test the feasibility of decommissioning the highfields, as they are really heavy and nasty things to have crashing around the deck. Ann, I am sure you would agree with at least that bit of the logic of the process.

Matt
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Old 16-08-2014, 22:26   #11
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Re: Staysail stay tension

Matt, this is really FWIW, because our rig is so different (fractional, a little bendy, swept back spreaders). Our runners go to the same part of the mast that both forestays attach to. We can avoid using the runners up to some mythical wind loading (Sayer won't tell us just how much, so we tend to be a bit conservative here), but when we do set them we have a three part tackle lead to a Barient 27 winch, and we load them up in low gear. To be honest, it doesn't seem to make a hell of a lot of difference in mast bend or forestay tension, probably because the caps have a lot of tension in them. We never get either forestay as tight as one can with a masthead rig (a problem endemic to Solent rigs), so we have sails cut with that in mind. Seems to work ok.

So, how does this apply to you? Well, first, the 4:1 tackle without winching won't get much load on the runners... perhaps 2-300 lbs. We likely get on the order of 5 to 10 times that ( Barient says that with 100 lbs pull on a 10 inch handle, the line tension should be around 2700 lbs including frictional losses. We don't pull that hard, but say with 50 lbs force the winch puts ~1350 lbs into the 3:1 giving maybe 3000 lbs tension on the runner). These, I think, are sorta typical runner loads on fractional rigs of this size. So, I reckon that you will need to use a winch, mate! One hates to have a winch occupied full time, so some sort of clutch would be nice. We use Lewmars, and they have done fine, allowing one to simply pull up the handle to dump the runner when needed... very quick. I don't like cam cleats in such applications, for if much loaded you must winch on the line to get it released, and with it winched, you can't pull the line out of the jaws of the cleat. Buggered!

Finally, bending the mast forward in the middle pulls some cloth forward along the luff of the sail. It has to come from somewhere, and that is out of the draft cut into the sail, so it flattens it out. Works the same as when you tension the halyard or cunningham, again pulling material forward out of the draft and flattening the sail. Both of these are common techniques to de-power a sail. This might prove useful to you in the wind strengths where you use the staysail.

All this makes the levers seem a good compromise, despite their weight and awkwardness!

Cheers,

Jim
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Old 16-08-2014, 22:57   #12
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Re: Staysail stay tension

^^edit, thanks Jim, (and Ann), good writeups, cheers

Quote:
Originally Posted by GILow View Post

Snowpetrel, thank you for the concise explanation of mast bend. I had to re-read it all a few times, but I from your description the small amount of forward deflection in the mast that I currently observe is ok. BUT, I am a little confused about sail shape here. I would have thought a forward deflection in the middle of the mast would cause the sail to become MORE baggy, since it has been cut for a straight mast, at least I ASSUME it was cut for a straight mast... what am I missing here please?
As the middle of the mast bends forward it pulls extra cloth out of the middle of the mainsail, this flattens the mainsail, but if the mast bending causes the inner forestay to slacken it will then bow aft in the middle from the staysail loads and the staysail will become fuller (more baggy) as the cloth is pushed into the middle of the sail.

Quote:
Secondly, I am increasingly feeling like I should re-evaluate the paths for the lines from the running backstays to see if I can find a way of getting round the binding cam problem. I do have ideal winches on both sides of the cockpit for winding tension onto the running backstays, so at least that part of the problem is solved, but before I go about re-routing lines etc, it would really help if Snowpetrel could maybe spell out his recipe for the running backstays again, as I am now confused as to whether he/you are recommending any blocks in the equation...
For now I would just try the system with the 4:1 tackle and see how you like it. If you can run it directly to the winches from the bottom of the tackle then give it a go that way, otherwise add a temporary lead block someplace, making sure it's strong enough. Compare led to the winches vs locked into the cam and hand tight. If it's led to the winches the cam cleat becomes redundant, it just gets in the way, just leave it cleated off at the winch. 4:1 plus a winch is way overkill, for your boat, but this way you can compare both methods in the same conditions and see what you think before commiting resources. There really are pros and cons to both systems, so like all things boat wise it's a compromise.

My own prefered system is a 2:1 or 1:1 led directly to a winch. Simple, powerful, strong and quick (Edit: similar to Jims except the 3:1 isn't needed for a smaller staysail due to the shorter luff) . Normally this ties up a winch, its very hard to find a clutch that can take the dynamic runner load to free up a winch, but the new textile ones show some promise. (edit, interesting Jim, that your lewmar clutches work fine. Cheers) But if the secondary winch is spare it's not really an issue. The downsides are the need for handles and such, it's quicker to just pull on the 4:1 and lock it into a cam cleat. You also need blocks that can take the load and some way to take it all forward, like a tricing line.

The 4:1+ built in cam cleat means the whole lot can be taken forward if it has a snapshackle on the lower block and tightened up without much clutter, it quick to use and simple, but often has long tails of rope or you need to unclip it and shift it forward to ease the main right out. Tension is limited to about 3.5x what you can pull (friction), and strength in extreme scenarios, like backstay breaking or capsize is not certain. Due to the cam cleat being a weak link.

It may be that a good compromise is to use the 4:1 with its cleat most of the time in light stuff, and when it gets nasty if you need more tension take the tail to the winch. By then the genoa will likely be rolled up and the primarys will be free for the runners. With this you could possibly get away with 3:1 + cam cleat for the light, and 3:1 + winch for stronger conditions.

Any photo's? Would help to see if i've missed anything obvious.


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Old 16-08-2014, 23:33   #13
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Re: Staysail stay tension

OK.

Right....

Er... that's kind of embarrassing. I had the whole sail shape thing totally ar*e-backwards in my head. Well there was a lesson for me for the future, and I have added understanding sail shaping to my list of things to go and read about.

You've all given me a much better understanding thank you. As it turns out, this could all have stayed under my original thread about maintaining tension on the running backstays after all, since is seems the one thing not in contention is the tension on the staysail stay. So the highfield stays attached to that stay, and maybe I will end up with two levers in my spares kit yet...

Now to the stern again. For clarity, the running backstays on the Swanson attach to very sturdy chain plates which are glassed into the hull, just about parallel with, or a little aft of, the wheel. So from an ergonomics point of view, they are as handy as you can get and are useful in my "grand plan" which is to be able to do as much of the "normal" sailing as possible without needing to leave the cockpit. I figure this is a logical aspiration, even if getting around our decks is pretty straight forward.

So, I will now look at ways of running the line from the 4:1 block including the discussed options of either cleating off after the winch (we have a spare so this idea is feasible) and also a lewmar clutch, which I was also already investigating as part of my process of converting from our wire halyards to rope. I will try the clutch on the running backstays first, and if successful will leave it in place and buy another for the halyard, if not, it goes to the mast for one of the halyards. Also, I will try different ratios on the blocks, 3:1 and maybe even 2:1, I have plenty of spare blocks of adequate strength which came with the boat.

Point taken about long runs of line to manage when the stays are tensioned, but I think the merits of not leaving the cockpit to tack outweigh the extra bit of mess to manage. As it is we have snap shackles to release and take the blocks and levers forward to stow the lazy stay, and it's not good.

Overall, I think the biggest take home I get here is (aside from the sail shaping thing) that the cam cleats on the current arrangement are a hindrance not a help at all.

Thanks all again, I knew you'd all clarify it for me.

Matt.

P.S. Maybe jumping straight from a 20 footer to a 42 footer was a bit ambitious after all...
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Old 17-08-2014, 02:51   #14
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Re: Staysail stay tension

Quote:
Originally Posted by GILow View Post
OK.
...........................
P.S. Maybe jumping straight from a 20 footer to a 42 footer was a bit ambitious after all...
No, no, no and no
If I could jump from a 14' tinny to 30' steely, you can easily cope .

Mind you, I've never been able to get past the 31' mark .

I reckon you will have it nicely sorted soon(ish) .
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Old 17-08-2014, 03:21   #15
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Re: Staysail stay tension

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No, no, no and no
If I could jump from a 14' tinny to 30' steely, you can easily cope .

Mind you, I've never been able to get past the 31' mark .

I reckon you will have it nicely sorted soon(ish) .
Actually, based on my theory of the cube of the length, we have both increased complexity by the same amount, i.e. 8 times more complicated.

Eeek!
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