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Old 14-09-2019, 08:36   #1
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Custom Tether Design: Absorption & Reflectivity Questions

Thanks for everyoneís help with my previous question about custom tethers.

Iím still exploring ideas and possibilities, and Iím just wondering for those who clip into padeyes rather than onto jacklines, did you do any testing (or calculations as well if you made your own tethers) regarding shock absorption? I'm thinking about elongation ratings relative to safety and practicalities, etc. Obviously clipping into padeyes removes the shock absorption provided by jacklines, so an elasticated tether would be the obvious solution to absorb any shock in the event of a fall (on deck or overboard) when clipped into a padeye.


Also, has anyone added reflective or glow-in-the-dark material onto tethers, and if so did you choose thread/stitching or patches of tape/material?


Any thoughts are appreciated. Many thanks.
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Old 14-09-2019, 09:00   #2
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Re: Custom Tether Design: Absorption & Reflectivity Questions

I believe it was Sailing Uma who just uploaded a video of diy elastic tethers that we decided to copy (more or less)

We are fabricating ours to a length that prevents going overboard in most locations but specifically in the cockpit.

If we decide to use padeyes in the cockpit, placement and/or tether length fully stretched will be taken into consideration.
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Old 14-09-2019, 10:44   #3
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Re: Custom Tether Design: Absorption & Reflectivity Questions

Current World Sailing/ISO standards include a drop test that roughly simulates a person falling the length of the tether. This is about the same energy as a fast stumble or being slammed by a big wave. It is a tough test, and few older designs passed. There are documented cases of tether clipped to hard points failing, which was the reason for the rule change.



You are correct, that impact is a minor concern for the tether when clipped to a jackline. I've run the math and tested that.



Elastic inside the tether is for tangle reduction, not shock absorption. It does not really help with shock.


Could you fabricate a tether that would pass the drop test? Possibly. Use nylon webbing, not polyester.


Overall, though, I would advise against it. I'm all about DIY, and I built tethers for a cat I had (wide decks), but the prices of tethers have come way down, to not much more than the cost of materials if equivalent quality hooks are used. Look at the Kong prices.


Unless you have a specific reason and really needed different lengths, just go with standard tethers.
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Old 14-09-2019, 14:41   #4
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Re: Custom Tether Design: Absorption & Reflectivity Questions

We researched this last week. For the cost of one commercial tether I can purchase enough material to make 12 tethers, minus the hooks. Once hooks for 4 tethers are added, we have 4 tethers, each with 3 hooks, and material for roughly 8 more all for less than the cost of 2 commercial tethers. Pricing for identical milspec material.

Having done the drop test myself, maybe it's just me but it hurt alot more than any fall or wave has ever hit me. The force on the tether is huge. The force on your back and neck is hard to describe, surprised nothing broke inside.

It's a project that has to be done right.

My reason for diy is to have a shorter tether, and have an extra hook to clip to the booms or the masts when needed. The elastic I plan to use is for tangle management, but there are more expensive options that could allow some shock absorption.
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Old 14-09-2019, 16:26   #5
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Re: Custom Tether Design: Absorption & Reflectivity Questions

The standard practice is to sew in some stitching, such that it fails in a progression before the tether becomes taught.
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Old 15-09-2019, 11:15   #6
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Re: Custom Tether Design: Absorption & Reflectivity Questions

Which is better an elastic tether or a webbing or strap?
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Old 15-09-2019, 11:24   #7
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Re: Custom Tether Design: Absorption & Reflectivity Questions

Quote:
Originally Posted by S/V Adeline View Post
We researched this last week. For the cost of one commercial tether I can purchase enough material to make 12 tethers, minus the hooks. Once hooks for 4 tethers are added, we have 4 tethers, each with 3 hooks, and material for roughly 8 more all for less than the cost of 2 commercial tethers. Pricing for identical milspec material...
?
These safety lanyards are priced in Canadian dollars (1CAD ≈ 0.75USD)
https://simplifiedsafety.com/fall-pr...fety-lanyards/
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Old 15-09-2019, 11:47   #8
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Re: Custom Tether Design: Absorption & Reflectivity Questions

These proffesional tethers will have been tested before going to market , hence their price point to homemade tethers
For a safety point of view one would need to ask ,,, Do you trust your sewing or your placment to those that have been proffesionally tested
Perhaps why we do not see DIY lifejackets with their own gas cylinder being dragged along the boat with you in case you need Gas
As for a Utuber like sailing UMA endorsing their homemade tethers without being load tested ,( I do not count falling about your boat to mimic a wave hitting you with Force and putting you over the side as testing )
As a disgrace and should not be followed by anyone , A bit like those TV programs that say DO NOT TRY THIS AT HOME
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Old 15-09-2019, 11:54   #9
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Re: Custom Tether Design: Absorption & Reflectivity Questions

Quote:
Originally Posted by GordMay View Post
?
These safety lanyards are priced in Canadian dollars (1CAD ≈ 0.75USD)
https://simplifiedsafety.com/fall-pr...fety-lanyards/
Not bad pricing, but this site doesn't offer what I want. Closest I could get would be $38 for the lanyard and $40 for the extension with hook. And that is for hooks I don't particularly like the design of.
We have commercial units at work (standard issue for scaffolding crew) those guys have a short tether to clip directly in front of them (fall arrest tether clips above you if possible) This allows them to lean against the tether and work securely. In the event of a fall, the shorter tether is capable of holding you, but if whatever it is attached to fails the main tether and jackline comes into play. This is what I am looking for.
For me it makes more sense to make what I need, and it will be cheaper.
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Old 15-09-2019, 12:15   #10
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Re: Custom Tether Design: Absorption & Reflectivity Questions

Quote:
Originally Posted by tarian View Post
These proffesional tethers will have been tested before going to market , hence their price point to homemade tethers
For a safety point of view one would need to ask ,,, Do you trust your sewing or your placment to those that have been proffesionally tested
Perhaps why we do not see DIY lifejackets with their own gas cylinder being dragged along the boat with you in case you need Gas
As for a Utuber like sailing UMA endorsing their homemade tethers without being load tested ,( I do not count falling about your boat to mimic a wave hitting you with Force and putting you over the side as testing )
As a disgrace and should not be followed by anyone , A bit like those TV programs that say DO NOT TRY THIS AT HOME
Do I trust my sewing? Yes (not a first time venture) The material has already passed safety testing, and I tend to overkill the safety aspect.

Using the same materials does a commercial manufacturer have a magic potion that makes their's work better? No, but they paid for testing allowing them to mass produce and sell to the public. Mine are for my personal use and I accept that responsibility.

I don't have access to the tooling required to make the many parts of a diy self inflating life vest, but you could bet your last dollar if I did, I would and standard CO2 bottles would hook up to it, just like commercial units.
I am not suggesting anyone who isn't comfortable making their own. My design is patterned after a proven commercial design and will be made using materials at least equal to, if not better than the original.
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Old 15-09-2019, 12:24   #11
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Re: Custom Tether Design: Absorption & Reflectivity Questions

As a climber and a sailor I have developed some preferences for tethers. The variety of commercially available tethers tells us something about how different people and different circumstances produce a variety of products.

On our boat when on a passage we have a very strong rule - everybody clips in to a padeye at the top of the companionway before entering the cockpit. Then, we clip into a wire jackline that runs the length of the cockpit or low-stretch, professionally made fibre jacklines that run mostly down the centre of the boat to the bow.

To do this safely so that there is never a moment when we are unclipped we use bifurcated tethers with a long and a short arm. We have also set up the jacklines and use a tether protocol that makes it nearly impossible to leave the boat over or through the lifelines. It took several full-time days and a lot of trial and error to accomplish this arrangement. Previously we used the standard "jacklines running up both side decks" approach. This makes it easy to accidentally exit the boat and even if tethered, prospects for getting back on the boat are slim under some conditions. There is a lot of literature on this situation, including post-mortem analyses.

The choice of clips is very important. My first boat tether used a Wichard clip and was not bifurcated. The clip was terrible - very hard to use with cold hands and I often didn't use it as a result. A single line also means that there may be times, at least on our boat, where we were untethered. So we don't use that kind anymore. We also have some Plastimo single tethers which we use for very specific purposes usually to transfer from one jackline to another. The clips are not the best but they work and are easy to use. Like non-locking standard carabiners there is some risk of an accidental opening.

The above Wichard-clipped tether was replaced with a bifurcated, elasticized tether, with Kong clips at the bifurcated ends and a quick release snap shackle at the other end. These work well most of the time. Being tethered is a pain but falling overboard in a big sea is much worse. Sailing off the coast of Oregon/California, 150nm offshore provided us with the opportunity to experience lots of wind (40-50kts) and big seas (20-30 feet). We would not have been able to turn the boat around in those circumstances to retrieve a COB. Hence the mandatory tether rule.

Lastly, sewing a tether with stitching designed "to fail" under load is tricky. I would prefer to leave it to professionals who are required to demonstrate the efficacy of their products for certification purposes, rather than try to do it myself. It costs more but it is a good investment. I prefer to invest more in the things that may save my life or the lives of others (or prevent injury), and cheapskate on the things that don't matter that much. Unfortunately, on a sailboat there are very few things in the latter category. It is an expensive sport even when we do our best to DIY as much as possible.
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Old 15-09-2019, 12:33   #12
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Re: Custom Tether Design: Absorption & Reflectivity Questions

Quote:
Originally Posted by S/V Adeline View Post
Do I trust my sewing? Yes (not a first time venture) The material has already passed safety testing, and I tend to overkill the safety aspect.

Using the same materials does a commercial manufacturer have a magic potion that makes their's work better? No, but they paid for testing allowing them to mass produce and sell to the public. Mine are for my personal use and I accept that responsibility.

I don't have access to the tooling required to make the many parts of a diy self inflating life vest, but you could bet your last dollar if I did, I would and standard CO2 bottles would hook up to it, just like commercial units.
I am not suggesting anyone who isn't comfortable making their own. My design is patterned after a proven commercial design and will be made using materials at least equal to, if not better than the original.
Thankgoodness I live in the EU were standards and EU directives for saftey equipment are tested , their is a reason why those work on tall buildings and bridges do not make their own tethers , I wonder , why, YOU do not have the ability to test your equipment that proffesional tethers have to go through to be sold to Joe Public therefore it should not be used , endorsed or otherwise told to others that it works , if you want to use it, good for you I am Happy your are feeling confident in your sewing machine I do hope it is industrial quality or one would guess its a Winchrite do they give you warnings that should not be used for life saving equuipmemt, one would suspect in the US were litigation is the national hobby , one would expect a saftey warning.
Then there is the old argument that its my life keep you nose out , to a point I agree but when you go overboard and your tether fails brave men and women from the CG and rescue operations have to come out and save your sorry arse and put their lifes at risk for the sack of 30 more bucks
Ah I do feel better now.
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Old 15-09-2019, 12:46   #13
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Re: Custom Tether Design: Absorption & Reflectivity Questions

Quote:
Originally Posted by Marathon1150 View Post
As a climber and a sailor I have developed some preferences for tethers. The variety of commercially available tethers tells us something about how different people and different circumstances produce a variety of products.

On our boat when on a passage we have a very strong rule - everybody clips in to a padeye at the top of the companionway before entering the cockpit. Then, we clip into a wire jackline that runs the length of the cockpit or low-stretch, professionally made fibre jacklines that run mostly down the centre of the boat to the bow.

To do this safely so that there is never a moment when we are unclipped we use bifurcated tethers with a long and a short arm. We have also set up the jacklines and use a tether protocol that makes it nearly impossible to leave the boat over or through the lifelines. It took several full-time days and a lot of trial and error to accomplish this arrangement. Previously we used the standard "jacklines running up both side decks" approach. This makes it easy to accidentally exit the boat and even if tethered, prospects for getting back on the boat are slim under some conditions. There is a lot of literature on this situation, including post-mortem analyses.

The choice of clips is very important. My first boat tether used a Wichard clip and was not bifurcated. The clip was terrible - very hard to use with cold hands and I often didn't use it as a result. A single line also means that there may be times, at least on our boat, where we were untethered. So we don't use that kind anymore. We also have some Plastimo single tethers which we use for very specific purposes usually to transfer from one jackline to another. The clips are not the best but they work and are easy to use. Like non-locking standard carabiners there is some risk of an accidental opening.

The above Wichard-clipped tether was replaced with a bifurcated, elasticized tether, with Kong clips at the bifurcated ends and a quick release snap shackle at the other end. These work well most of the time. Being tethered is a pain but falling overboard in a big sea is much worse. Sailing off the coast of Oregon/California, 150nm offshore provided us with the opportunity to experience lots of wind (40-50kts) and big seas (20-30 feet). We would not have been able to turn the boat around in those circumstances to retrieve a COB. Hence the mandatory tether rule.

Lastly, sewing a tether with stitching designed "to fail" under load is tricky. I would prefer to leave it to professionals who are required to demonstrate the efficacy of their products for certification purposes, rather than try to do it myself. It costs more but it is a good investment. I prefer to invest more in the things that may save my life or the lives of others (or prevent injury), and cheapskate on the things that don't matter that much. Unfortunately, on a sailboat there are very few things in the latter category. It is an expensive sport even when we do our best to DIY as much as possible.
A well written and though challenging post
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Old 15-09-2019, 12:49   #14
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Re: Custom Tether Design: Absorption & Reflectivity Questions

Marathon1150,
If you don't mind my asking, how much did the long arm/short arm tether set you back?
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Old 15-09-2019, 13:51   #15
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Re: Custom Tether Design: Absorption & Reflectivity Questions

Quote:
Originally Posted by S/V Adeline View Post
We researched this last week. For the cost of one commercial tether I can purchase enough material to make 12 tethers, minus the hooks. Once hooks for 4 tethers are added, we have 4 tethers, each with 3 hooks, and material for roughly 8 more all for less than the cost of 2 commercial tethers. Pricing for identical milspec material.

Having done the drop test myself, maybe it's just me but it hurt alot more than any fall or wave has ever hit me. The force on the tether is huge. The force on your back and neck is hard to describe, surprised nothing broke inside.

It's a project that has to be done right.

My reason for diy is to have a shorter tether, and have an extra hook to clip to the booms or the masts when needed. The elastic I plan to use is for tangle management, but there are more expensive options that could allow some shock absorption.

Tell us what hooks you are using. (All prices from Amazon)



Kong double tether = $112


2 Kong Tangos = $60
Spinnaker shackle, 5500# breaking strength = $35
Webbing (15' to allow for sewing) = about $8 (1" climbing webbing will not meet the spec after sewing)
Elastic = $5

materials total = $115, without labor or thread.



Yes, I could sew something with 1-climbing webbing and carabiners for less. But it is not apples to apples.



3 locking carabiners = $36. Can you work these in the dark, while going through waves?

climbing webbing = $5 (mil-spec is ~ 3600 pounds after sewing, vs. the standard of 5000 pounds)
no elastic (makes it prone to tripping)
materials total = $41



It could even be safish. But it would not be comparing apples with apples. You will have to give up features.
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