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Old 10-07-2019, 18:07   #1
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Custom Tether Design

Hi everyone,

Im new on the forums.

Weve just got a new boat and are looking at changing the jacklines and padeyes and want to get new tethers while were at it. Weve read some articles on the web and found some great information (here, here, and here for example) and would like to know if anyone here has designed (or better yet made) their own tethers?

We know we want something different from the usual offerings from West Marine, Defender, etc, as they arent the right lengths for how were planning on laying out the jacklines and padeyes. Weve read some chilling reports about the weaknesses of some gear supposedly suitable and certified for marine use, and were keen to find/make something better. So far the only thing were sure of that we want double-ended (Y) tethers. Were actually thinking about a triple-ended tether if we can find parts light enough. Were looking around various options for parts and were wondering about the following questions:

Has anyone used climbing karabiners instead of gibb/snap hooks? If so, what have seen as the advantages and disadvantages?
Has anyone made tethers (or had them made) using climbspec webbing? If so, has it worked well?
Has anyone made elasticated tethers and if so, what sort of elastic did you use? Are there any useful guidelines we should follow when selecting elastic?

Thanks very much any input and/or ideas.
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Old 11-07-2019, 01:00   #2
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Re: Custom Tether Design

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You might like to read this rather sobering report:

https://www.gov.uk/maib-reports/man-...loss-of-1-life
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Old 11-07-2019, 03:23   #3
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Re: Custom Tether Design

Greetings and welcome aboard the CF, NPHiker.
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Old 11-07-2019, 03:33   #4
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Re: Custom Tether Design

Climbing gear is fine. Just keep an eye on the aluminum for pitting. I use a homemade "daisy chain" as a tether. I can't imagine why you'd want elastic tethers.
Read the many threads pro and con jacklines--you'll find them instructive. I'm anti-jackline, pro-central clip-in points.
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Old 11-07-2019, 04:03   #5
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Re: Custom Tether Design

First, I'd like to understand why you need something different. There are some fine products out there, and unless you really cannot work with them, it would be hard to make something better.


Second, scratch the Gibb-style hooks off the list, as well as non-locking hooks. Sail Delmarva: A Locking Carabiner... That Isn't


The main challenge with ordinary climbing carabiners is that they are not locking, and those that are, are not designed for one-hand use. I've climbed a lot, used tethers a lot, and I only use very specific climbing biners on tethers (type K).


I doubt you want 3 legs. Two is enough spagetti.



Sewn or tied, Climbspec webbing does not meet the ISO strength or toughness requirements. Remember, climbers use it as a loop. Close, but not quite.


I'd take a second look at tethers from Kong, WM, and Wichard. You'd be hard pressed to build something that was as good for the price. These arn't just slapped together from parts, they have to meet a pretty vicious drop test. I had some longer tethers I used on a cat I had with a large deck, but since then I went back to commercial tethers, because I like the and they are a good value.





The Sailrite link showed so many non-conformities with ISO standards, I would not consider that an information source (you really can't use non-locking hooks).
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Old 11-07-2019, 04:13   #6
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Re: Custom Tether Design

You may have trouble imagining using the tether in zero visibility, driving rain and pitching seas. It's better to have some experience than just using google. For example, a triple end tether will be pretty difficult to use in blackout conditions.

There is good advice on this subject on Attainable Adventures (https://www.morganscloud.com/). It has a pay wall but well worth the small cost.

Climbing and industrial tether solutions will work on a boat. But a boat is a different and much more variable environment. Once you have learned what works and what doesn't making your own tethers is a good idea. Just remember that a tether is also a fall arresting device. Coming up short against an inelastic tether can cause internal injuries. But a tether should not grow much in length lest you risk falling over the side of the boat. That's why commercial products have sewn in "fuses" that break at a certain point. Many believe this is better than an elastic tether material.
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Old 11-07-2019, 05:39   #7
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Re: Custom Tether Design

The climbing gear is more widely available better tested and better quality than most boat terhers. In fact some marine manufacturers like Spinlock are now using Kong carabiners.

Im sure @Thinwater will be along shortly with some data or info on what he has tested.
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Old 11-07-2019, 14:32   #8
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Re: Custom Tether Design

Quote:
Originally Posted by transmitterdan View Post
...That's why commercial products have sewn in "fuses" that break at a certain point. Many believe this is better than an elastic tether material.

However, these commercial units are designed for used with a full body harness, which can withstand 3-10 more impact than a chest harness, depending on the direction. You will be injured first. Thus, the design basis is not directly transferable, although people have tried to do just that.


Climbing gear is "different" from marine gear. There are some products (Kong Tangos are one example) that are very good, but I would NOT say that climbing carabiners in general are suitable for tethers. Not at all.


I do use wire gate climbing carabiners on my boat for many things. They are very light, very strong, far easier to clip than an marine product, and inexpensive. But I use them for utility purposes, not fall arrest or climbing.
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Old 12-07-2019, 02:24   #9
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Re: Custom Tether Design

Quote:
Originally Posted by thinwater View Post
However, these commercial units are designed for used with a full body harness, which can withstand 3-10 more impact than a chest harness, depending on the direction. You will be injured first. Thus, the design basis is not directly transferable, although people have tried to do just that.


Climbing gear is "different" from marine gear. There are some products (Kong Tangos are one example) that are very good, but I would NOT say that climbing carabiners in general are suitable for tethers. Not at all.


I do use wire gate climbing carabiners on my boat for many things. They are very light, very strong, far easier to clip than an marine product, and inexpensive. But I use them for utility purposes, not fall arrest or climbing.
But you can't believe that something like this first tether with this clips is better than a fully tested kong carabiners. After all aren't climbing carabiners actually tested for falls? Many of these 'marine' tethers show no testing processes or certification whatsoever.



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Old 12-07-2019, 03:45   #10
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Re: Custom Tether Design

Quote:
Originally Posted by mikedefieslife View Post
But you can't believe that something like this first tether with this clips is better than a fully tested kong carabiners. After all aren't climbing carabiners actually tested for falls? Many of these 'marine' tethers show no testing processes or certification whatsoever.



I'm with you on this one. After climbing for many years, I'm far more comfortable with a wiregate biner (what I use for my tether) than with the gimcrack gizmos they sell as marine tethers. The fall potential on a boat is far less than on a crag; the potential to catastrophically shockload even the most indifferently spec'd webbing is about nil. (how much force can a body generate sliding down a deck for the entire three feet of the tether?).
This is another place where people go way overboard trying to re-invent the wheel. A snug waist belt (chest harnesses are dumb); a daisy chain a little longer than your arm; a wiregate 'biner--you're all set. I find that setup enough of a burden without imagining two or three 20-pound double-locking clips with an--of all things!--quick release shackle at the harness end (someone had one of these, couldn't tell why).
Efficiency requires simplicity, especially in bad conditions, which is the only time you need a tether anyway.
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Old 12-07-2019, 19:17   #11
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Re: Custom Tether Design

Quote:
Originally Posted by Benz View Post
I'm with you on this one. After climbing for many years, I'm far more comfortable with a wiregate biner (what I use for my tether) than with the gimcrack gizmos they sell as marine tethers. The fall potential on a boat is far less than on a crag; the potential to catastrophically shockload even the most indifferently spec'd webbing is about nil. (how much force can a body generate sliding down a deck for the entire three feet of the tether?).
This is another place where people go way overboard trying to re-invent the wheel. A snug waist belt (chest harnesses are dumb); a daisy chain a little longer than your arm; a wiregate 'biner--you're all set. I find that setup enough of a burden without imagining two or three 20-pound double-locking clips with an--of all things!--quick release shackle at the harness end (someone had one of these, couldn't tell why).
Efficiency requires simplicity, especially in bad conditions, which is the only time you need a tether anyway.

A non-locking carabiner can:
a. Twist off a u-bolt or similar fixed point. In fact, this is something climbers must guard against.
b. Non-locking biners can clip to control lines when they drag across them. I've had this happen and it is REALLY annoying.



I would not use a wire gate on a tether, just as I would not use one to secure a belay or rig a repel device. I have used locking biners for situation where a tether was more or less permanently attached to a jackline, which I have done on certain boats, but not in general.
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Old 13-07-2019, 03:49   #12
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Re: Custom Tether Design

Quote:
Originally Posted by thinwater View Post
A non-locking carabiner can:
a. Twist off a u-bolt or similar fixed point. In fact, this is something climbers must guard against.
b. Non-locking biners can clip to control lines when they drag across them. I've had this happen and it is REALLY annoying.



I would not use a wire gate on a tether, just as I would not use one to secure a belay or rig a repel device. I have used locking biners for situation where a tether was more or less permanently attached to a jackline, which I have done on certain boats, but not in general.
Twisting off a fixed point is rare in my experience, especially if attention is paid to which way the gate faces with respect to where one is going. This becomes second nature after a while. The danger of it can be much reduced by having a soft loop at all your clipping points.
Accidentally clipping control lines is a small risk to accept over the weight and bother of locking 'biners, IMO. Again, situational awareness is your friend.
Not to drift the thread into rappelling, but since you brought it up: don't you think that 2 biners with gates opposed is better than 1 single biner, even if the gate locks? I set up all rappels and topropes and belays with 2 biners, using a single locker only when the situation demands(like if a grigri is in play)--in fact, I've climbed quite a lot without a single locking biner anywhere.
But back to the thread: since in fact the tether is loaded only in the event of being washed off your feet or toppled by a lurch, which has never happened to me in all my miles at sea, I find it perfectly acceptable to have a tether that is just going to save my life in an unlikely event, not one I plan to be hurling myself constantly against.
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Old 13-07-2019, 04:49   #13
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Re: Custom Tether Design

This is a question, not an opinion. I use two industrial (OSHA compliant) safety belts and a 3/4" diameter mooring line running stern cleat to bow cleat. So far I have not real-life tested that, thankfully. Is this an adequate arrangement, in your opinion? I'm not a climber, but do use a locking carabiner as the master link in my electric hoist, which includes a life ring, and which would lift me on board if I ever went MOB. Again, your opinion?
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Old 13-07-2019, 07:34   #14
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Re: Custom Tether Design

Thanks for all the welcomes and replies.

We've definitely turned away from any type of tether with gibb hooks - the Morgan's Cloud article we linked to was enough to know they're a pretty sub-standard design! Also, we'd like tethers which are the right lengths for us and the boat and will not allow anyone to go overboard - therefore the lengths are important. So far most tethers we've seen either have the wrong hooks or the wrong length.

We've contacted some climbing gear manufacturers (DMM, ISC Wales) and they've been great in providing specifications on the various Karabiners we've asked about (we're only looking at locking and one-handed versions, and we got some great help about the type of aluminum or alloy used, major/minor axis loading limits, etc.), so we've got a few good solid choices for those.

We understand the Sailrite article doesn't take into account the ISO standards, but we did find their stitching analyses pretty useful. Does anyone have any doubts about their findings? We certainly aren't going to follow blindly, but it seemed pretty thorough.

We're looking at climbspec webbing because while we know it doesn't meet ISO standards, it does seem like a solid option for tethers which are short - which is what we're looking to have made. The Practical Sailor article where we read about the webbing and rope types seemed pretty in-depth and sensible.

To clarify about the elastic - we were thinking about inserting elastic inside the tubular webbing so the tether could be more compact when not taught - in no way would the elastic be relied upon to provide safety!

We're thinking about how to address visibility and obviously using a high-visibility webbing is the first solution. Moreover, we're wondering if there is a way to add reflective patches or stitching to the tethers? We're still working this out as we're not sure how this could be achieved if we go for the tubular webbing with internal elastic design, and if it would actually be a bad idea as the reflective material may constantly catch the light at random and could be annoying/unsafe.

Has anyone has added reflective/high-visibility stitching or patches to their tethers? If so, what was your approach?

Lastly, for those who have made their own tethers, how have you tested them?

Many thanks again.
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Old 13-07-2019, 08:13   #15
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Re: Custom Tether Design

Twisting off a non-locking spring gate carabiner clipped to a pad eye is really easy to do. Its why no standard body recommends them for tethers.

The Kong locking clips are designed to open easily with one hand wearing big wet gloves in the dark. Other types dont hit all those requirements.
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