Standard for tethers

[zoidberg]

I spent some time this week in an 'arborist trade supplier' with an international clientele and a huge range of safety equipment, and I was able to inspect the PPE available. It struck me that the personal tethers available to pro tree climbers were rather more capable than those I'd noticed in chandlers.

They're also rather less expensive.

Arborists' tethers ( and access ropes ) are tightly regulated and are required to conform to ISO EN 566 2017, EN354 and EN795b. One priced at £10.50 was rated at 30Kn. Corresponding two-stage snaplinks conformed to EN362, and cost £8.

Yottie tethers sold with snaplinks attached should all conform to ISO 12401 of 2009.
One major UK chandler is still selling 'Scandi' tethers made to the obsolete ISO 1095 standard - revoked and superceded in mid 2009 - and shouldn't.

Many tethers have overload indicators fitted to indicate 'when the item needs replacing'. They do NOT indicate if the webbing has been weakened by salt, solvents or UV radiation.... just like webbing jackstays.

The chandlery-sold items inspected all seem rated to 22Kn, while the arborist items are rated at 25Kn or 30Kn.

 

[thinwater]

Please show links. Your thought process is good. The most common clip now used on most yacht tethers, for example, is the Kong Tango (sold under other names) and was developed for via ferrata climbing, not sailing.

Yup, many chandleries sell unsafe old stock.

 

[Neeves]

Without focussing on the chandlers - the manufacturers should have made a recall. The manufacturers know the problems, know how many units they sold to the chandlers, they should have been on the phone, personal contact:

"Please remove the offending items from display. We will replace the offending items for any sold...."

If this was about anchors - there would be a furore.

Sad.


Even more sad, the issues was uncovered by an 'amateur' (no disrespect intended) contributor to the printed media, minimal acknowledgement.... but people enjoy disrespecting 'the gifted amateur'.

Jonathan

 

[Sandy]

As an ancient mountaineer I'm somewhat surprised that tethers don't have a 'locking clip' at the harness end, but suspect that this is because somebody in the standards world wants to be able to unclip from either end in the event of needing to exit a vessel while under water. Personally, I think there is more of a risk of somebody unclippling the wrong end when being called up on deck from their pit to sort something out on a dark and stormy night.

I wonder how often people change the deck safety lines?

 

[lustyd]

I don’t think the breaking load is an issue. HowNot2 on YouTube tests this stuff very thoroughly and he said you’re unlikely to see even a few kN on a big fall. Given the biggest fall on a yacht is 2m not an issue at all.

 

[Stemar]

I wonder how often people change the deck safety lines?

Mine were tapes. I got black, and figured it would be time to change them when they faded to dark grey, but since I only fitted them when we went out and kept them out of the sun, they were still good after five years. On Jazzcat, the grabrail on the cabin top is a track with a slider in it that I can clip to, so no change needed.

As for strength, I doubt I'll be in very good shape after a 20KN force is applied to me. As Lustyd says, 2m is a long way to fall on a boat. You might manage 4m on a big boat, but you'll be tumbling down a slope, rather than falling like a climber

 

[Sandy]

I don’t think the breaking load is an issue. HowNot2 on YouTube tests this stuff very thoroughly and he said you’re unlikely to see even a few kN on a big fall. Given the biggest fall on a yacht is 2m not an issue at all.

It is the wall of green water over the deck that worries me.

 

[Sandy]

Mine were tapes. I got black, and figured it would be time to change them when they faded to dark grey, but since I only fitted them when we went out and kept them out of the sun, they were still good after five years. On Jazzcat, the grabrail on the cabin top is a track with a slider in it that I can clip to, so no change needed.

I have bright yellow tapes, kept in a cool dry place out of the sun when not underway.

 

[jamie N]

I worked with a Thai diving company which had a rope access dept. for offshore NDT. After each contract all pieces of lifting/climbing kit were cut up and thrown away. For each and every contract, all kit was brand new, which added to the safety and regulational efficiency. I was told it's an obvious step, given the overall price of a job against the safety factor and costs involved.
Thailand (of course) does have a bit more of a UV issue than say the Northern North Sea, but it's a good point.
On my boat, I made and sewed the jackstays myself, and they get inspected each and every day that I use them: it takes 10 seconds and I'm there anyway. Over winter they're exposed to fewer than 200 hours of 'dusk' a month.

 

[Neeves]

Anchors failed, there was a witch hunt. Forum, world wide, had field day. But, I don't recall, no-one died. Similarly I don't recall yachts actually being lost.

Tethers don't engender the same passion.

If you are on the bow you do not fall 2m - you fall overboard until you reach the end of the jackstay The average speed of the yacht might be 8 knots, down a wave it will be much, much faster. As you are going overboard you have no input on how the securement device is loaded, nor does any one else. But the securement device, lets call it a hook, needs to accept and not deform, at all.

If the hook fails - you die (and your relatives are lucky if your body is recovered)

The jackstay, your tether, the hook should not fail - ever.

If the tether, jackstay design, hook is found wanting it should be retired immediately. If the hook is found wanting - there should be a recall and a forum witch hunt. If similar devices, especially from the same manufacturer are still on the shelf, years later, - the manufacturer should, at best, be black balled. There are alternatives, they are demonstrably better.

A man died, an investigation was made:

Safety Tether Clip-in Caution - Practical Sailor

The death may have been preventable.

But it was the 'media', one of us here, that made the investigation.


Stop dreaming - a 2m fall, maximum ? Get real. Stop shooting the messengers.


I, skipper and owner, had a girl fall overboard - I would never live with myself if we had not found her and plucked her to safety. The weather was daylight, warm and sunny, big seas - I'm still chilled at how lucky I am, or was.

The jackstays and tether are susceptible to UV and have finite lifespan. Hooks should last for ever - if they are fit for purpose. As the PS investigation clearly demonstrates - the protocols for hook testing for the marine environment are not fit for purpose - and when shown to be wanting...?


I'll stick to anchors - worrying about tethers would reduce life expendency

I am well, very well, aware - complacency come to mind.

Zoidberg, good timing - hopefully a wake up call - that should have been unnecessary.

Sad, very sad.

Jonathan

 

[zoidberg]

Gosh! Something close to a compliment! I'm blushing....
( maybe someone could tell the Mods I'm not just a PITA. Well, not all the time.... )

As for "Even more sad, the issues was uncovered by an 'amateur' ....contributor to the printed media"
Not the first time. The highlighting of 'failure of several PSS face-seals causing flooding' was an earlier example of Joining The Dots on/in here.

That led to some peeps increasing their inspection regime, some changing their installation, some sourcing and fitting a solution, and some others bleating predictably "It'll never happen to me!"

 

[thinwater]

As an ancient mountaineer I'm somewhat surprised that tethers don't have a 'locking clip' at the harness end, but suspect that this is because somebody in the standards world wants to be able to unclip from either end in the event of needing to exit a vessel while under water. Personally, I think there is more of a risk of somebody unclippling the wrong end when being called up on deck from their pit to sort something out on a dark and stormy night.

I wonder how often people change the deck safety lines?

World Sailing and ISO do not have a requirement for quick release at the harness end. US Sailing requires that it be releasable. I don't know the history. However, I know of one fatality after a capsize (monohull that did not roll back up) that resulted not from have a locking harness end, but because the sailor clipped the spare tether back to the harness, defeating the quick release option.

The other notion is that you might want to unclip if you found yourself in the water being roughly dragged under the bow wave. But I've not heard of a sailor that was able to do so, and it would take nerves of steel to release yourself in mid-ocean, since you might not be found again.

I've released at the harness end a few times to facilitate some change or foul up, but quick release or no would not have mattered. I recall the tether was non-quick-release at the time.

Personally, I agree with Sandy, that the greater risk is accidental unclipping, which happens occasionally. As a practical matter, I suspect it does not matter. Tethers are to keep you on deck.

 

[lustyd]

It is the wall of green water over the deck that worries me.

Doesn’t significantly add to required tether strength though so irrelevant here.

 

[thinwater]

I don’t think the breaking load is an issue. HowNot2 on YouTube tests this stuff very thoroughly and he said you’re unlikely to see even a few kN on a big fall. Given the biggest fall on a yacht is 2m not an issue at all.

1. That seems true, but it is not. These were bent at 2-4 kN. I ran the tests. The trick is that they were side loaded over a tether near a cleat, which the old standard did not test. A man died because of this failure. The failure begins are 1 kN, not even body weight for some blokes.

2. There have been multiple documented cases of webbing failures at over 6-8 kN. A knockdown with some green water will reliably do that.

3. A tether that will hold 20 kN may only hold the very minimal 8 kN after 5-10 years of use. An important purpose of the standard is to provide durability.

4. Tethers have very little stretch and chest harness do not spread loads properly. If you fall 2 M fall with a chest harness you will break most of your ribs and sufocate--this is why they are banned in construction by OSHA and EN. Try 8-12 inches and see how it feels. Just try hanging free for more than 30 seconds and see how it feels.

Finally, watch this. The tension on the tether was less than 0.05 kN. This is an astonishing failure to meet the standard.
Video of clip rotating off

 

[Sandy]

Doesn’t significantly add to required tether strength though so irrelevant here.

I wonder if I did not describe what I was thing about. Let's consider this scenario.

What force is involved if

A vessel with a water speed of six knots in a F7 and rough seas is hit by a big wave over the bow while I am working on the foredeck? The big green one knocks me over and my life jacket, as designed inflates, significantly increasing my surface area. The tether is clipped into to the eye at the bow. Once I am forced back to the end of the tether what is the shock load? I suspect it is far greater force than me falling off the deck and plunging two metres into the oggin.

 

[lustyd]

That seems true, but it is not

Nothing you said suggests a higher breaking load than 22kN is required.

 

[lustyd]

I wonder if I did not describe what I was thing about. Let's consider this scenario.

What force is involved if

A vessel with a water speed of six knots in a F7 and rough seas is hit by a big wave over the bow while I am working on the foredeck? The big green one knocks me over and my life jacket, as designed inflates, significantly increasing my surface area. The tether is clipped into to the eye at the bow. Once I am forced back to the end of the tether what is the shock load? I suspect it is far greater force than me falling off the deck and plunging two metres into the oggin.

Not even close to 22kN. Most of the factors you mention don’t add to strain on the tether line. A bit of drag might double the load but still only maybe 2kN. As said above side loading is an issue, but ultimate breaking strain is not.

 

[thinwater]

Doesn’t significantly add to required tether strength though so irrelevant here.

. What?

• Boat is now leaning
• Wall of water starts fall and adds to acceleration of sailor to 2-3 M/s downhill.
• Adds push when the tether catches.
• The sailor was accelerated at ~ 1 G for 2 M, but was stopped in 0.2 meters or less when the tether catches, so 10X body weight is very possible.

Pretty basic school math, which matches the gear failures we have seen. Remember, climbing ropes stretch, tethers, not so much.

In fact, known failures relate to a wall of water leading to webbing failures of cockpit tethers.

 

[Sandy]

World Sailing and ISO do not have a requirement for quick release at the harness end. US Sailing requires that it be releasable. I don't know the history. However, I know of one fatality after a capsize (monohull that did not roll back up) that resulted not from have a locking harness end, but because the sailor clipped the spare tether back to the harness, defeating the quick release option.

The other notion is that you might want to unclip if you found yourself in the water being roughly dragged under the bow wave. But I've not heard of a sailor that was able to do so, and it would take nerves of steel to release yourself in mid-ocean, since you might not be found again.

I've released at the harness end a few times to facilitate some change or foul up, but quick release or no would not have mattered. I recall the tether was non-quick-release at the time.

Personally, I agree with Sandy, that the greater risk is accidental unclipping, which happens occasionally. As a practical matter, I suspect it does not matter. Tethers are to keep you on deck.

That is interesting. I contacted SpinLock in the UK asking if they did a tether with a locking clip and the response was we manufacture to the standard. Perhaps time to get the next set of tethers custom made.

Having a locking clip might mean that inspections would take longer and a small amount of lubricant would need to be used in the mechanism from time to time.

 

[Sandy]

Not even close to 22kN. Most of the factors you mention don’t add to strain on the tether line. A bit of drag might double the load but still only maybe 2kN. As said above side loading is an issue, but ultimate breaking strain is not.

Do you have the maths to demonstrate that?