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Old 26-07-2014, 12:27   #1
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Maintaining Tension on Running Backstays

Hello cruisers,

Our rig has running backstays to oppose the forces created by the staysail when it is in use. Our setup has some very robust highfield levers, one for each of the running backstays and one for the staysail stay itself.

I am experimenting with removing the highfield levers from the running backstays; although they work very well, they are very heavy and my reading on CF makes me think that we might be better off using dynema line and a 4:1 block arrangement instead of the levers.

The changeover is made easier for us as the running backstays were already fitted with 4:1 blocks with cam cleats. The setup (and I assume this is normal) was to get the tension right by adjusting the 4:1 block first, then putting on the tension using the highfield lever.

So today I removed one of the levers, grabbed some spare dynema line, threaded it all up and THEN discovered a problem.

I can easily run the line from the lower block (with the built in cam cleat) to a nearby spare winch, and the geometry suits the cam cleat on the block nicely with the line exiting through the middle of the cam to the winch, but then it all goes wrong. As I wind on the tension the backstay goes nice and tight, but as soon as I release tension from the winch, the small movement of the lower block, (which is being pulled sideways by the winch), combined with the movement in the line before the cams lock the line, contrived to release much of the tension I just put on, leaving the stay quite loose.

I was about to try it with more tension, but then it struck me that it might be very difficult to get the cam to release with that much tension on it, so I stopped the experiment and sought help.

So how do people solve this one? Is there a combination of blocks, cams, fairleads that work well? I actually wondered if I needed line with a bit of elasticity for this to work, but everyone seems to use dyneema line, which is pretty rigid. The distance between the blocks when the tension is on is about 12 inches... maybe this is too short, maybe more line is needed to provide some elasticity? Are cam cleats the wrong thing for the job, should I be stopping the line some other way? Does anyone have photos of their setup that might guide me?



Matt
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Old 26-07-2014, 12:43   #2
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Re: Maintaining tension on running backstays

What I think is going on is that your block with cam is too high above the attachment point and you are pulling it forward as you adjust the tension on the backstay. The easiest way to resolve this is to just move the block so it attached directly to the runner tang.

If that isn't possible or desirable then you need to add a cam somewhere between the block and the winch. This way it can be cleated under load, and will maintain the same geometry as it does while on the winch.

And yes the correct line for this is dyneema of some sort. Any line with spring in it will allow substantial amounts of mast flex as the line stretches under load. Or will require adding huge amounts of runner tension to pre-stretch the line.
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Old 26-07-2014, 13:09   #3
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Re: Maintaining tension on running backstays

it all begs the question... how tight does it need to be? Of course every rig is different, but as long as the runner tensions up when the staysail really starts to bend the mast a little.. all is good right? many boats do without runners and with staysails. Not that that is good, but the best test would be looking up the mast when it's blowing hard and you have the staysail up. The other thing of note is, when your main is reefed, it is counteracting the bend in the mast from the staysail.
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Old 26-07-2014, 13:20   #4
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Re: Maintaining tension on running backstays

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What I think is going on is that your block with cam is too high above the attachment point and you are pulling it forward as you adjust the tension on the backstay. The easiest way to resolve this is to just move the block so it attached directly to the runner tang.
Good point... I am using a snap shackle on the block as that is what was already fitted, I will try it with a short D shackle instead.

Ta,

Matt
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Old 26-07-2014, 13:29   #5
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Re: Maintaining tension on running backstays

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it all begs the question... how tight does it need to be? Of course every rig is different, but as long as the runner tensions up when the staysail really starts to bend the mast a little.. all is good right? many boats do without runners and with staysails. Not that that is good, but the best test would be looking up the mast when it's blowing hard and you have the staysail up. The other thing of note is, when your main is reefed, it is counteracting the bend in the mast from the staysail.
Our mast is pretty solid. I didn't realise how robust it was till we moved to a pen amongst the 50+ footers and saw that we still had a significantly thicker mast than anything around us, despite being the shortest mast in the row.

I am yet to see any deflection in the mast in any conditions, and in part because of this, I didn't understand the purpose of the running backstays till I read of their function here on CF.

I will try what you suggest though, and see if I can see any deflection with a strong wind and the staysail set without counter tension from the running backstays when the right conditions present themselves, a logical and interesting test.

Matt
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Old 26-07-2014, 14:46   #6
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Re: Maintaining Tension on Running Backstays

Matt, you will have some kind of a strong point where the Hyfield lever goes to. Our runners actually go to chain plates on the transom. Your set-up was meant to be secured with the Hyfield lever, then tensioned with your tackle, an arrangement seen in many forms on older boats. When you take it off, you will be able to pull the line hard enough to get it to come out of the cam cleat.

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Old 26-07-2014, 15:01   #7
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Re: Maintaining Tension on Running Backstays

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Matt, you will have some kind of a strong point where the Hyfield lever goes to. Our runners actually go to chain plates on the transom. Your set-up was meant to be secured with the Hyfield lever, then tensioned with your tackle, an arrangement seen in many forms on older boats. When you take it off, you will be able to pull the line hard enough to get it to come out of the cam cleat.

Ann
Ann,

That doesn't make sense to me, if the tensioning was to be done with the tackle, the highfield becomes redundant in the face of the snap shackles... I thought the purpose of the highfield was to get the tension with the advantage of great leverage?

But yes, there are seriously beefy chain plates in a line just aft of the wheel for the running backstays, again, like the rest of the smaller chainplates on the Swanson they are a big inverted T bar glassed into the hull.

Your comment about releasing the cam has made me think a bit, and I know one problem I have, the cam exits downwards, so it will be very hard to pull down and out of the cam. I guess I could use my foot to push the line down... but I will see if the cam can be flipped over on the plate.

Matt
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Old 26-07-2014, 15:16   #8
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Re: Maintaining Tension on Running Backstays

The tension on the runner doesn't need to be all that great. All you are trying to do is keep the mast in column. All we did on our boat is set he runner up snug but not super tight with a 4 part tackle on the opposite tack before we tacked. Once we fopped over on the opposite tack, it was set up nicely. OPnour boat, unless the boom was way out, the lee runner didn't foul boom when set up. If we didn't set it up before hand, snugged up the runner with the tackle while in irons.

Not understanding what the problem is with the Highfield levers. They are basically there to give you a repeatable tension on the runners. You don't have to fiddle with the proper tension, just release the old and set the new as you go through the wind if you can't set it before the tack.
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Old 26-07-2014, 15:28   #9
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Re: Maintaining Tension on Running Backstays

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The tension on the runner doesn't need to be all that great. All you are trying to do is keep the mast in column. All we did on our boat is set he runner up snug but not super tight with a 4 part tackle on the opposite tack before we tacked. Once we fopped over on the opposite tack, it was set up nicely. OPnour boat, unless the boom was way out, the lee runner didn't foul boom when set up. If we didn't set it up before hand, snugged up the runner with the tackle while in irons.

Not understanding what the problem is with the Highfield levers. They are basically there to give you a repeatable tension on the runners. You don't have to fiddle with the proper tension, just release the old and set the new as you go through the wind if you can't set it before the tack.
OK, so now I am confused...

From the sound of it I have been missing the point by assuming the highfield was there to put on lots of tension. If that is not the case, then I can't see them being much help to us.

Sure they are quick to set the repeatable tension as you say, but since they are set so far aft they (unlike your boat) foul the boom and main on just about any heading relative to the wind, even pinching. This means they have to be completely detached and brought forward to the babystays on each tack, so they don't save any time. My thought was that with just blocks and line I could release lots of line on the downwind running backstay to clear the main and boom.

But I read of people using winches with their running backstays... are you saying this is overkill and that simple hand tension should be adequate?

Matt
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Old 26-07-2014, 17:15   #10
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Re: Maintaining Tension on Running Backstays

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OK, so now I am confused...

From the sound of it I have been missing the point by assuming the highfield was there to put on lots of tension. If that is not the case, then I can't see them being much help to us.

Sure they are quick to set the repeatable tension as you say, but since they are set so far aft they (unlike your boat) foul the boom and main on just about any heading relative to the wind, even pinching. This means they have to be completely detached and brought forward to the babystays on each tack, so they don't save any time. My thought was that with just blocks and line I could release lots of line on the downwind running backstay to clear the main and boom.

But I read of people using winches with their running backstays... are you saying this is overkill and that simple hand tension should be adequate?

Matt
Running backs are a PITA. And yes, it sounds like you are misinterpreting how to use them.

All boats I've been on with running backs you release the upwind on the tack and attach the downwind.

They are used predominantly when there is not an option to attach permanent stay because they would foul the boom.

There may be adjustable running backs for when tuning mast bend underway is desired but that just adds to the PITA factor.

I'm a lazy sailor - I would avoid running backs like the plague.
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Old 26-07-2014, 17:57   #11
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Re: Maintaining Tension on Running Backstays

On a boat with a staysail stay, you are primarily just trying to keep the mast in column. Some, but not great, tension is nice because of stretch. With Dyneema, etc there is precious little stretch so it's not a big thing. If you can set them up with little or no side load on the mast, all should be well. FWIW, one of the first Westsail 32's to do much voyaging made a circumnavigation of the Pacific. On the final leg home to California, they had some nasty weather off the Oregun Coast. The skipper just happened to go forward and look up the mast under storm conditions for the first time. The mast was being pulled out of column so much by the staysail that it scared the hell out of him. Even though it was a scary sight, the mast had held up for many thousands of miles without running backs and survived that storm. One of the first things he did when he got home was install running backs, however.

On fractional rigged boats, the running backs are there to maintain forestay tension. The racer types want their headstay razor straight so you need a good deal of pressure on the runners to do that ands to be able to adjust tension for different conditions. Not such a factor on cutter rigged cruisers.
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Old 26-07-2014, 20:11   #12
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Re: Maintaining Tension on Running Backstays

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Running backs are a PITA. And yes, it sounds like you are misinterpreting how to use them.

All boats I've been on with running backs you release the upwind on the tack and attach the downwind.

They are used predominantly when there is not an option to attach permanent stay because they would foul the boom.

There may be adjustable running backs for when tuning mast bend underway is desired but that just adds to the PITA factor.

I'm a lazy sailor - I would avoid running backs like the plague.
I think I understand their purpose very well, they are there to balance the pull of the staysail stay, which would otherwise be unbalanced and pull the mast out of shape. If I were to avoid them on my boat I would be ignoring the wisdom of Ron Swanson, who designed the boat, and I reckon knows a bit more about the boat than me.

What I DON'T understand, clearly, is how much tension is appropriate.

Given the significant tension on the staysail stay, even before it is loaded up with a staysail, I would have expected an equal tension on the running backstay, particularly given it terminates on the deck a similar distance from the mast as the staysail stay.

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Old 26-07-2014, 20:19   #13
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Re: Maintaining Tension on Running Backstays

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...
On fractional rigged boats, the running backs are there to maintain forestay tension. The racer types want their headstay razor straight so you need a good deal of pressure on the runners to do that ands to be able to adjust tension for different conditions. Not such a factor on cutter rigged cruisers.
Peter, I think you might have explained something for me. The threads I found on applying lots of tension to the running backstays were probably fractional rigged boats. And now that I think of it, some of the photos I found were from fractional rigs. (Including Insatiable II)

Still, I do feel there should be at least equal tension to that applied by the staysail, though your point about a lack of stretch in the system alleviates some of that concern....

The problem is, I guess, a bit like your Westsail 32 skipper, the problem, if it exists, is likely to manifest itself at an inopportune moment. I don't want to be in 30+ knots (when, by all reports, the staysail really serves a useful function) to find out my modifications to an otherwise perfectly functional system were a bad idea.

But then, like was also pointed out, by that stage the reefed main would be providing some counter pull to the staysail stay.

Anyone got a wind tunnel that will fit a 42 foot boat?

Matt
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Old 26-07-2014, 23:43   #14
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Re: Maintaining Tension on Running Backstays

Tension on running backs really depends on boat. Generally you don't need much, but some rigs are different. A good rule of thumb is to look up the mast while it is pumping, and put on just enough runner to stop it. On the J-130 I raced on it probably came out to about 150lbs, on the Andrews 70 more like 1000lbs. Lumpy wave conditions generally require more than flat water and high winds, but again it does somewhat depend.

And ONLY tension the windward runner. Never the leeward. You also need to check backstay tension as you apply more runner, since the runner can pull the bend out of the mast and increase backstay tension.
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Old 27-07-2014, 01:05   #15
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Re: Maintaining Tension on Running Backstays

Stumble,

The Swanson 42 is an extremely conservatively designed cutter. She has double inline spreaders, a telephone pole style mast, and all Matt needs the runners for is to support the inner forestay.

Matt: Go out in 24-35 using the staysail and appropriate for the boat amount of mainsail. Go stand right next to the mast and put your eyes as close to the mainsail track as you can, and sight up it. You will probably see a "wow" to leeward. Now, put on the running back, and pull it snug. Go look at the mast again. Is it in column? Great! If not, put some more grunt into tightening the runner. If necessary, pinch up to do it. Continue process till you can see the mast column is straight. Now take some red yarn and make a whipping around the tail of the tackle to show you where to set it! The yarn will have to be replaced from time to time, but gives a quick visual indication of where it needs to go to. Also can be done with fabric dye marking pens, or thread sewn through.

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