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Old 03-10-2013, 22:13   #1
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Tensioning jacklines

One of my upcoming projects is a set of jacklines. I will make them of 1" wide nylon. One end (bow) will get a loop sewn into the line to fit over a cleat. The other end seems to traditionally be left straight so you can tie it off at a stern cleat. With a fair amount of stretch in nylon, I am wondering how people pre-load the jacklines. Is pre-loading done at all or am I looking to make my life harder for no reason ?
My idea of pre-load comes about because even with a short tether between the jackline and the harness there is considerable stretch that would probably allow being tossed over the life lines. Pre-loading would likely reduce the amount of stretch. Obviously the pre-load can't be too much but it would seem that it should be more than what I can do by just pulling the jackline tight as I cleat it off.
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Old 03-10-2013, 23:49   #2
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Re: Tensioning jacklines

What are you asking? A jackline is any line that Jack clips onto to hold himself on board. Nylon webbing seems okay to me, as does steel rod, woven cable, rope, or whatever. Jacklines are preferably run inboard of the ways, and above Jack's center of gravity where possible. Jacklines aloft should be positioned high to minimize any fall. I can't think of any good reason to leave a jackline less than taught. Any snubbing should probably be done with a "screamer" on Jack's lanyard, if needed.
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Old 03-10-2013, 23:59   #3
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Re: Tensioning jacklines

Trucker's hitch?
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Old 04-10-2013, 00:02   #4
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Re: Tensioning jacklines

I also use a 1" webbing (fluorescent yellow) and keep it as tight as possible by hand. It stretches a bit under load. It's attached center forward on a pad eye and runs back inside the shrouds on both sides, back to the aft cleats.

So it's basically on the deck. That way it's out of the way of any lines or rigging, of which I have a lot. So far it's worked out very well.
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Old 04-10-2013, 00:11   #5
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Re: Tensioning jacklines

I've found jacklines made of webbing or nylon tubing to stretch a great deal when they get wet so I would wash them down and then get them as tight as possible on a cleat using a cleat hitch.
My personal preference is old standing rigging wire that will not stretch. Rig as close to the centerline as possible and as tight as possible.
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Old 04-10-2013, 01:43   #6
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Re: Tensioning jacklines

Nylon webbing is great, it doesn't roll under your feet like wire...it doesn't need to be really taught....short tether on your harness is good...
On Diva we installed Wichard U-bolts with backing plates..ends had loops...one end looped through and back on itself, other end secured with small dia line loops...lots.
On Elyse similar system but run between forward and aft cleats.
If you're getting loops sewn in make sure whoever does it uses UV resistant thread.
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Old 04-10-2013, 01:48   #7
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Quote:
Originally Posted by Albro359 View Post
Nylon webbing is great, it doesn't roll under your feet like wire...it doesn't need to be really taught....short tether on your harness is good...
On Diva we installed Wichard U-bolts with backing plates..ends had loops...one end looped through and back on itself, other end secured with small dia line loops...lots.
On Elyse similar system but run between forward and aft cleats.
If you're getting loops sewn in make sure whoever does it uses UV resistant thread.
" doesn't need to be taught ". Well for an experiment heave you frame over the side connected up and see how much it stretches in the middle. Nylon web along the side deck as jack lines are an exercise in self delusion

Dave
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Old 04-10-2013, 03:16   #8
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Re: Tensioning jacklines

Quote:
Originally Posted by goboatingnow View Post
" doesn't need to be taught ". Well for an experiment heave you frame over the side connected up and see how much it stretches in the middle. Nylon web along the side deck as jack lines are an exercise in self delusion

Dave
I said "really taught"...meaning bar tight
OK...maybe I should have said they shouldn't be loose.....but self delusion, I don't think so
I've had nylon webbing jack lines for years on different boats and had crew nearly over the side...it hasn't been an issue...with short tethers.
Its long tethers that are a large part of the problem....in my humble opinion....even with wire jack lines.
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Old 04-10-2013, 04:09   #9
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On the Navy 44s we use webbing jack lines on the side decks, drum-tight and twisted a few times along the length to make them easier to pick up for clipping in. They are girth-hitched to a bow padeye, and lashed with 1/4" line to a stern padeye. Tensioning comes from first pre-soaking in a bucket, then stretching them in place while lashing at the stern. I like to use the tail of a sheet run through the padeye, the the jack line loop, the. back through the padeye, then to a cockpit winch to tension (and hold the tension) while lashing the back. Experiment with the tension--using a winch you can easily tension them enough to break something. Having them tensioned allows you to pull up on your tether for support as you move.

On my own boat I'm still experimenting--I think I would prefer jack lines on the cabin top, and using modern low-stretch lines seems like a good option. Having them super-tight puts a lot of stress on fittings, and I don't have dedicated padeyes for this like on the 44s. I also don't have the need to go forward so much in heavy weather.

YMMV.
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Old 04-10-2013, 06:00   #10
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Re: Tensioning jacklines

First, webbing jacklines should be polyester rather than Dacron, because polyester is less UV sensitive and because it stretches less.

Second the webbing should be 4500lb minimum breaking strength. That's the OSR specification. The reason it needs to be so strong is that the angle on it's ends is 'acute' and those has high leverage. That's 'high strength' webbing and not walmart sort of stuff.

Third, The jacklines should be run as close to the center line as possible. Minimizing the potential for going overboard while clipped on to the jack line is a high priority when setting up the system.

Fourth, to the OP's specific question, the typical way to tension is to have loops at both ends and use multi part lashings to the strong points (cleats or padeyes) to get the tension. (or you can cow hitch the loop directly to the strong point at one end and only have the lashing at the other end. The tension usually needs to be adjusted after the jackline gets wet.
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Old 04-10-2013, 07:00   #11
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Re: Tensioning jacklines

Aside from Evans' typo, I agree with him 100%...
Quote:
Originally Posted by estarzinger View Post
First, webbing jacklines should be polyester rather than Dacron, because polyester is less UV sensitive and because it stretches less.
Since others were referring to "nylon" rather than "Dacron", and "Dacron" is polyester...I assume that Evans' meant the jacklines should be polyester (i.e. Dacron), rather than nylon...



BTW, I use polyester webbing, tensioned from the bow cleats to the aft cleats....and they work very well for me...
(I can't imagine the stretch some of you might have using nylon...)


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Old 04-10-2013, 07:18   #12
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Re: Tensioning jacklines

Take a look at sling calculations. You'll soon realise it is a big mistake to have the jackstays bar tight. My boat has the usual aluminum toerail. I shackle both ends of the jackstays. It's the work of a moment to rig or stow.

Incidentally, I use double jackstays and a very large shackle as a runner. Almost never gets snagged up.
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Old 04-10-2013, 07:51   #13
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Re: Tensioning jacklines

Quote:
Originally Posted by SV Sea Monkey View Post
On the Navy 44s we use webbing jack lines on the side decks, drum-tight and twisted a few times along the length to make them easier to pick up for clipping in. They are girth-hitched to a bow padeye, and lashed with 1/4" line to a stern padeye. Tensioning comes from first pre-soaking in a bucket, then stretching them in place while lashing at the stern. I like to use the tail of a sheet run through the padeye, the the jack line loop, the. back through the padeye, then to a cockpit winch to tension (and hold the tension) while lashing the back. Experiment with the tension--using a winch you can easily tension them enough to break something. Having them tensioned allows you to pull up on your tether for support as you move.
This is great information...I particularly like the idea of putting in twists and tensioning with a winch. Good tips that I will employ on my own rig.

BTW, I have to say watching Navy 44s dueling at the start of a race, and then going off is a pretty awesome sight. Ran right behind the start of a race the other week (Hospice Cup weekend) on our way to our own start. Some impressive teamwork on gorgeous boats in a stiff breeze. Too bad you can't buy one of those boats. I think they're just about the prettiest thing on the water.

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Old 04-10-2013, 07:51   #14
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Re: Tensioning jacklines

Nylon webbing cannot be left rigged; UV is tough on it and a few monts exposure causes measurable degradation. They must be removed after sailing.

Several have suggested multi-step tensioning methods. Sounds like they take a little time.

Jacklines are needed at night, in squals and when the weather gets worse. Are we planning to run around as night aproaches, as the sky turns black or as the wind increases to 3rd reef, crawling along the rail, rigging lines? Sounds contrived or like something done when the rules call for it, not something practical for a cruiser.

Why aren't your jacklines an engineered part of the boat, like seat belts are of your car?

Rant over.
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Old 04-10-2013, 09:14   #15
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Re: Tensioning jacklines

Quote:
Originally Posted by thinwater View Post
Nylon webbing cannot be left rigged; UV is tough on it and a few monts exposure causes measurable degradation. They must be removed after sailing.

Several have suggested multi-step tensioning methods. Sounds like they take a little time.

Jacklines are needed at night, in squals and when the weather gets worse. Are we planning to run around as night aproaches, as the sky turns black or as the wind increases to 3rd reef, crawling along the rail, rigging lines? Sounds contrived or like something done when the rules call for it, not something practical for a cruiser.

Why aren't your jacklines an engineered part of the boat, like seat belts are of your car?

Rant over.
Thanks everybody for your comments!
To answer a few points - I am using nylon because that's all I could get from Sailrite. They are rated at 5500 lbs,
I would prefer rigging them once but yes, I am aware that they are affected by UV and can't be left rigged. It would be marvelous to see a boat pre-rigged with something (like seat belts in a car) but alas, I have not seen such a boat and as a single hander I would kinda like to stay with my boat and as such, jacklines are 'it'.
On the positive side, up here in the PNW, UV isn't as bad as in Florida or Mexico or other warm southerly destinations.
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