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Old 22-09-2013, 05:50   #1
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Running backstays question

Hello Cruisers,

I have a question about when to use the running backstays.

To set the scene, we have a cutter rig, with running backstays from the second set of spreaders, two thirds of the way up the mast, at the same point our staysail stay meets the mast.

The mast is supported by four 12mm lower shrouds from the bottom spreader, two 10mm intermediate shrouds from the upper spreader and two 12mm cap shrouds. We have solent style dual forestays, the inner forestay is 12mm and the forward forestay is 10mm.

We have a singe 12 mm rear stay.

I am including port and starboard shrouds in the count, so that's two lower shrouds per side, not four per side.

The inner stay for the staysail is detachable using a hyfield lever and is stowed to one side when not in use.

The running backstays are 10mm and are also on hyfield levers.

So, my question is, is there any advantage in using the running backstays when we are not using the staysail? Looking at the probable forces, it seems that their purpose is simply to counter the force exerted by the staysail, but am I missing something? I wonder if they might prevent pumping of the mast, though I have seen no evidence of this yet.

Thoughts?

Matt
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Old 22-09-2013, 06:24   #2
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Re: Running backstays question

You are correct they counter the pull of the staysail which can cause pumping. However, I keep mine on most of the time when I am using the genoa...

It is an extra support if your backstay breaks! I always run spare halyards to the weather side as backup support.

In 50,000 sea miles I have broken a shroud or stay every 10,000 miles.
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Old 22-09-2013, 08:34   #3
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Re: Running backstays question

Matt,if your mast is staying straight under load without the runners set and is not pumping (which is obvious when it happens) there is nothing to be gained by leaving them set when not using the staysail.

I don't know about your boat, but on mine the runners interfere with the mainsail, so leaving them set full time is a pita... but being fractional I need them except in light airs so I gotta deal with them. Surely wouldn't do it on your boat!

Finally, as far as being a back up for your backstay, well, my statistics are a bit different than the previous posters: circa 150,000 total miles and one broken forestay, one broken babystay (which proved to have hidden corrosion in the inner wires). I've not personally seen a broken backstay except for ones well past their useby dates. Your choice...

Cheers,

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Old 22-09-2013, 08:56   #4
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Re: Running backstays question

On my 44, without the inner forestay attached, I would sometimes set a runner if I was pounding into chop, that caused the mast to pump a little. I used a 4 part tackle rather than hyfield levers, so I could just put a little pressure on to steady it up. I dont know if the hyfield lever would put too much strain on the mast without the inner forestay attached to balance the pull. When you are pounding into the kind of chop that makes the boat feel like it is hitting one brick wall after another, if the mast doesnt pump, then dont worry about it. I never set the inner, unless I was going to be out for more than a day or two. _____My 2 cents worth._____Grant.
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Old 22-09-2013, 13:00   #5
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Re: Running backstays question

They are used not only to counter but also to stabilize the upper length of the mast (lower crosstrees to the top). So when the boat is working hard, better hook in that inner forestay and paired backstay(s).

Some very stiff masts can be sailed without the inner forestay and backstays - depending on how your rigger built the mast.

I always clip in whatever I can unless the conditions dictate otherwise.

b.
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Old 22-09-2013, 14:52   #6
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Re: Running backstays question

Given that many foul the boom and other bits and bobs, I see no point in leaving them attached under most normal conditions. Motor sailing in a seaway with the risk of pounding, its sometimes useful to connect up the inner stay and runners.

dave
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Old 22-09-2013, 16:59   #7
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Re: Running backstays question

A great range of idea here, thank you. Seems the jury is split pretty well down the middle on this one.

Hmmm... I guess it comes down to a trade off between the inconvenience of having them set vs the extra strength they may provide under heavier loads... the MPS comes to mind as putting a fair load on the top of the mast, had no considered that the running backstays might contribute here.

Grant, I did not completely describe the backstays correctly I realise now.. like yours, they have a four to one block set which the hyfield levers then attach to. This means you can preset your tension on each stay, but rapidly remove the downwind backstay when not in use. Not light, but convenient.

Thanks all again, I will take your ideas with me on the next trip and consider the application of each.


Matt
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Old 22-09-2013, 17:29   #8
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Re: Running backstays question

its worth bering in mind that the inner forestay and the running backs are designed to counter the load from the sail not really the stay. There is a danger you can pull the mast out of column using running backs and just an inner. The MPS is generating a load at the top of the mast that is being countered by the backstay.

dave
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Old 23-09-2013, 10:48   #9
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Re: Running backstays question

I think it all comes down to how your particular mast reacts when pounding. My own Peterson 44 was designed as a cutter, but spent its first 5 years in the bareboat trade. The charter companies did not order the boats with an inner forestay. Heaven forbid that a charter would have to tack around one. Mine did come with runners, but I doubt that they were ever used. I sailed the boat as a sloop for 4 years before I got around to installing an inner, and having a staysail cut. Even then I only set the inner a few times for practice and on a couple of passages. Other than passages, in the 8 years that I owned the boat, I think I only set a runner 3 or 4 times to stop a little pumping. I only set it snug enough to stop the motion, not putting any strain on anything. Different boats will react different, so looking up the mast the next time you are pounding into a nasty chop, will give you a good idea if you need the inner set or a runner. Good luck. _____Grant.
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Old 23-09-2013, 11:35   #10
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Re: Running backstays question

Hi. Sounds like our rig is similar to yours. We are cruising offshore in the Pacific Ocean. We set up our running backs when we have the staysail rigged. We almost almost always have the staysail stay rigged because we use that sail often and want the stay available. When the stay is rigged with no sail, we don't use runners.

I look at the mast often to make sure it is in column because the mast extrusion is not as stiff as it could be. Without the runners, with the staysail full, I will see a slight bend forward at the stay level. In other words, the running backs do make a difference. We have also been known to only rig the weather running back when we are on a constant long tack.

Annie
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Old 23-09-2013, 14:51   #11
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Re: Running backstays question

Can someone please give me a better definition of "pumping?"

I hear the term but am not exactly sure what is meant.

What does it look like, how does it feel, how does it sound?

Thanks.
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Old 23-09-2013, 18:09   #12
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Re: Running backstays question

Quote:
Originally Posted by gjordan View Post
Different boats will react different, so looking up the mast the next time you are pounding into a nasty chop, will give you a good idea if you need the inner set or a runner. Good luck. _____Grant.
Good point, and we got PLENTY of that coming home on Bass Strait. The mast was steady as a rock without the backstays, so I guess I am safe from that particular problem. But it is a very solid old mast, not some schmick racing item.
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Old 23-09-2013, 18:12   #13
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Re: Running backstays question

Quote:
Originally Posted by goboatingnow View Post
its worth bering in mind that the inner forestay and the running backs are designed to counter the load from the sail not really the stay. There is a danger you can pull the mast out of column using running backs and just an inner. The MPS is generating a load at the top of the mast that is being countered by the backstay.

dave
I see what you mean, basically there would be a fair bit or aft pressure from a point one third down the mast, with nothing to counter it thus translating to a force (30% thereof) to the aft at the foot of the mast....

Hmm... I THINK I'd be safe on this one, the lower shrouds probably have enough grunt to counter anything untoward in this matter. But that's just my rig, something racier might have problems as you suggest.

M
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Old 23-09-2013, 18:16   #14
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Re: Running backstays question

Quote:
Originally Posted by Annie in WA View Post
Hi. We almost almost always have the staysail stay rigged because we use that sail often and want the stay available. When the stay is rigged with no sail, we don't use runners.
Annie, it seems you are another advocate of the staysail. I confess to being a new convert, thanks to suggestions by CF members, and I am becoming more of a convert every day.

But from what you are saying, despite having a less robust mast than you might wish for, it seems you don't use the running backstays without the staysail... or is that BECAUSE you have a less robust mast... i.e. the running backstays need the force of the staysail to prevent the mast from deflecting aft in the middle?

Matt
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Old 23-09-2013, 19:02   #15
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Re: Running backstays question

Matt, this is how I see it:

In reality, you can not set up the inner forestay very hard without deflecting the mast forward when you don't have the runners set... there's nothing but the stiffness of the mast section resisting the forward pull of the stay. You don't want so much prebend in your stick, so you only bring the stay up tight enough that it is taught in static conditions (no sail set). When sail loads come on to it, the runners are set to keep the mast from bending forward and slacking the stay... undesirable in terms of sail shape.
Further, you certainly don't want to load up the runner(s) when the inner forestay is NOT set, for that could induce the dread mast inversion... a situation that can lead to collapse.

So, when you don't have the IFS set up, leave the runners off unless for some reason (like pounding hard to windward) you get forward mast deflection. If you do use them to counter that action, only set them up tight enough to stop the pumping, not nearly as hard as when you have a staysail set. It sounds like you have a big ole stiff mast section and don't have much to worry about there.

And for a scaling factor: on I-2 (fractional w/ swept-back spreaders) we set the runner with a 3:1 tackle lead to a Barient 28 winch, and grunt it up fairly hard. Not the same situation as your staysail for sure, but you should have the means of putting considerable tension on the runner when needed.

And for the poster who asked what "pumping" meant -- it is when the mast rhythmically oscillates in a for and aft direction with the vertical center of the mast moving, perhaps as much as a mast diameter. This action can be set up by pounding into waves or sometimes by vortex shedding off the spar when at anchor and no sail set. Frequency is on the order of 1-2 Hz in all the ones that I have experienced, and it can shake the whole boat. When sailing it can be observed by periodic slacking of the inner forestay or baby stay as the mast moves forward. Can be unnerving to watch!

Cheers,

Jim
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