roll your own tethers - Page 3 - SailNet Community
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post #21 of 34 Old 04-30-2008
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Yup. Check this at Wichard for more info: Wichard Product Bulletins

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post #22 of 34 Old 04-30-2008
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Quote:
Originally Posted by Plumper View Post
Using a piece of rope for the tether is fine in my opinion. They key thing is to be able to undo it, under load, at the person end in case you get trapped somewhere where you don't want to be.
Couldn't agree more. A length of line will work just fine, but make sure you can detach from it quickly under ALL your body weight. Litterally hang youself by your tether, and try and release yourself. A large snap shackle is a great investment.

Merit 25 # 764 "Audrey"
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post #23 of 34 Old 04-30-2008
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You can buy a harness for a hang-glider, you can buy a harness for rappelling from a helicopter, you can buy a proper harness with lights and whistles.
A sail maker can sew up anything you could dream of and the materials are extremely strong. Your possibilities are endless.
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post #24 of 34 Old 08-18-2008
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Just remember to put a snap shackle on the end attached to YOU!
Do NOT use a carabiner to attach the line to your harness. You must be able to release yourself even under load.

And I wouldn't use a climbing carabiner to clip onto the jackline either. They are NOT SS and not made for a marine environment.
That said, no reason you can't make up something just as good as store bought.
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post #25 of 34 Old 08-18-2008
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I have been a caver for almost 30 years. I've made my own harnesses and gear and trusted my life to it many, many times. I have no problem with making my own jacklines and tethers. As already pointed out, just use the proper gear for attachments.

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post #26 of 34 Old 08-19-2008
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I find this thread funny.

On one end, there are people that will buy the best and sue if it fails.

On the other end, there are ones that hook it up and use it.

I lean more towards the latter. You hook a line up to pull your 20,000 lb sailboat upwind without worrying about it, so what’s the big deal about hooking a line to your body. Sure I’d test it, at the dock. Do a couple of falls, see how it feels. adjust the lengths.

I do admit, I’m an engineer, so I take this stuff for granted, but if you want to buy or build a tether, go for it. It’s better than not using one.

BTW: This is my next project, so let’s keep talking about it.

If a man must be obsessed by something, I suppose a boat is as good as anything, perhaps better than most. A small sailing craft is not only beautiful, it is seductive and full of strange promise and the hint of trouble.

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post #27 of 34 Old 08-19-2008
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Alright, great thread, but I have to weigh in also. Yes, I am fairly new to sailing, but I am not new to using webbing, ropes and carabiners in lifesaving conditions. I also bought a pair of 40' jacklines on ebay. Very well stitched with good quality hardware and top-quality webbing. People, these materials are so strong that they will never feel your weight if/when you fall and are restrained by them. The 1" webbing is rated for well over 1000 lbs breaking strength. The same holds for well-tied knots in quality rope. When you go up the mast using your good condition halyard (tied with a bowline), it is so much stronger than the load that you are applying that the safety factor is probaly more than 10:1.

Check the knots and stitching of any sewn loops in any safety gear, no matter the brand name or the amount of $ spent. That is just prudent.

Keep up the great threads. I am learning so much from you all.

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post #28 of 34 Old 08-19-2008
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If you did a bit of research, you'd realize that the breaking strength of tethers and jacklines needs to be far higher than what you might expect. The momentary shock loads on a jackline can be very, very high. A person falling across the boat and getting stopped by the tether may generate upwards of 20 G's of force on the tether. If they weigh 180 lbs., which isn't all that heavy, that means the shock loading is 3600+ lbs. Then add in the mechanical advantage caused by pulling at a near-perpendicular angle to the jackline... and you've got some really serious forces involved.

Also, on a typical small sailboat, where the halyards are 3/8" polyester double braid, the breaking load of the line is about 4400 lbs. If tying a bowline only has at best 60% of the breaking strength of the line, you're now looking at 2600 lbs... Which isn't much more than 10:1 for a lot of the sailors I know—and that assumes the line is in perfect condition, without chafe or UV damage—not generally the case.

Also, consider that the shock loading caused by falling may be an order of magnitude more than what you actually weigh, the safety margins aren't all that large.

BTW, this is one reason I upgraded my halyards to spectra cored lines of the same diameter...to get a greater safety margin even with some wear and tear on the lines.

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Alright, great thread, but I have to weigh in also. Yes, I am fairly new to sailing, but I am not new to using webbing, ropes and carabiners in lifesaving conditions. I also bought a pair of 40' jacklines on ebay. Very well stitched with good quality hardware and top-quality webbing. People, these materials are so strong that they will never feel your weight if/when you fall and are restrained by them. The 1" webbing is rated for well over 1000 lbs breaking strength. The same holds for well-tied knots in quality rope. When you go up the mast using your good condition halyard (tied with a bowline), it is so much stronger than the load that you are applying that the safety factor is probaly more than 10:1.

Check the knots and stitching of any sewn loops in any safety gear, no matter the brand name or the amount of $ spent. That is just prudent.

Keep up the great threads. I am learning so much from you all.

Sailingdog

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post #29 of 34 Old 08-19-2008
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Quote:
Originally Posted by montenido View Post
The 1" webbing is rated for well over 1000 lbs breaking strength.
1000 lbs is only a bit over 20% of the ORC recommendation (kindly provided by SailorMitch).

Jim
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post #30 of 34 Old 08-19-2008
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The other factor, stretch, will spread the decelleration over a longer time lowering the peak force.

Of course if you stretch to far, you might go half way over.

If a man must be obsessed by something, I suppose a boat is as good as anything, perhaps better than most. A small sailing craft is not only beautiful, it is seductive and full of strange promise and the hint of trouble.

- E.B. White
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