MAIB harness report.

[Impaler]

https://www.gov.uk/maib-reports/saf...e-of-safety-harness-tethers-on-sailing-yachts

 

[Tim O]

Thanjs for this.....i have been following discussion of this incident, and discussions around jackline, tether and attachment design and materials with keen interest, particularly in Practical Sailor and Attainable Adventure Cruising

 

[prv]

Have to say, it didn't seem like a particularly useful advisory to me.

"When you fall overboard, make sure your tether clip doesn't fetch up under a cleat and get bent."

I don't think I'm really going to be in a position to make sure of that in the split-second as the tether tightens and slides down the jackstay.

Pete

 

[pvb]

Have to say, it didn't seem like a particularly useful advisory to me.

"When you fall overboard, make sure your tether clip doesn't fetch up under a cleat and get bent."

I don't think I'm really going to be in a position to make sure of that in the split-second as the tether tightens and slides down the jackstay.

Yes, a bit of an odd advisory; I imagine they felt they ought to issue something.

I'd have thought that most people would install taut jacklines as far inboard from the edge of the deck as possible, making it less likely that a clip could get near a cleat.

 

[RupertW]

Have to say, it didn't seem like a particularly useful advisory to me.

"When you fall overboard, make sure your tether clip doesn't fetch up under a cleat and get bent."

I don't think I'm really going to be in a position to make sure of that in the split-second as the tether tightens and slides down the jackstay.

Pete

I read it as guidance to look at your attachment points including jackstays to ensure that a pull can't make a hook reach a cleat and/or consider those cleat attachments that stop them catching rope.

 

[pcatterall]

Have to say, it didn't seem like a particularly useful advisory to me.

"When you fall overboard, make sure your tether clip doesn't fetch up under a cleat and get bent."

I don't think I'm really going to be in a position to make sure of that in the split-second as the tether tightens and slides down the jackstay.

Pete

+1 ...that was my first thought Though I suppose some obvious danger points could be made safe? For instance unused cleats on long passages could have 'anti catch' inserts
Useful in any case to avoid snagging loose lines?

 

[thinwater]

It is an important builtin, but I think they left it a little thin on information. I can see why you found it hard to use.

One point they skipped over (pending further testing I imagine) is that it took only 300 pounds to cause that distortion! Other carabiner options are as much as 6 times that strong in a side load. Have you ever seen a climbing carabiner only a few mm thick? You won't. But you can bend a Gibb-style hook with your bare hands if it is clamped. PS will be reporting on this next month (still collecting facts).

The second point, which they did not make clear, is that it probably did NOT catch on the bow cleat. There is a second cleat ~ 30 inches farther back that was the hazard. Thus, the point is to examine your deck for things the clip could catch on as it slides. In the case of the Clipper yachts, they are now wrapping the offending cleat in rope. A good battle field fix. Perhaps your boats can benefit from similar simple fixes. Maybe. A corollary is to mindful of the hardpoints you clip to; toe rails and stanchion bases can be trouble.

 

[penberth3]

..."When you fall overboard, make sure your tether clip doesn't fetch up under a cleat and get bent."

I don't think I'm really going to be in a position to make sure of that in the split-second as the tether tightens and slides down the jackstay.

Pete

Of course not, you're supposed to think about that before you go to sea and arrange your protection so it can't happen.

Thinwater's last paragraph in Post #7 explains it very well.

 

[prv]

Of course not, you're supposed to think about that before you go to sea and arrange your protection so it can't happen.

Cover the cleat and on a busy deck I'm sure it can still find somewhere else to jam into.

The point about those flat hooks bending relatively easily is a good one, though. On the square riggers I used to sail on, the tethers for working aloft used that style when I started. After a few years, I joined the ship for a voyage and found they'd all been changed to a different design closer to that of a climbing carabiner. I wonder if this was part of the reason.

Pete

 

[Tim O]

i reccommend everyone to read the recent articles in Practical Sailor regarding this issue. i'm going to change my tethers to dynamic climbing rope and climbing hardware, or other hardware designed for greater lateral loads, and with quick release at harness end.

the points about location of jackline relative to possible snags is critical too i think. what i cant understand is why there isnt a design yet for an attachment that slides along the jackline when you want it to but locks in place when shock loaded.....something exists that could do that im sure

 

[thinwater]

... What i cant understand is why there isn't a design yet for an attachment that slides along the jackline when you want it to but locks in place when shock loaded..... Something exists that could do that I'm sure.

An interesting question with several possible answers.

1. If you clip with the second leg you won't get washed along the jackline. This is probably simpler and is good practice for other reasons. For example, on the Clipper boat the other crewman that was washed off was clipped short and was quickly recovered, unharmed.

2. Sailors very seldom slip when traveling along the line. It is when they are working, not holding on and focused on something else, that they fall. Thus, travel along the jackline has proven quite safe.

3. There are locking mechanisms. They are either one-way, which requires the user to slide them. This means you are not holding on with that hand. Others require a freefall. A slide on deck would not be quick enough to trigger them.

4. They tend to be clunky.

5. Another options, seldom discussed, are work station tethers. Common on race boats at the mast, helm, and grinders.

A devise could be design that simply locked with a lever, but if it takes a user action, you are probably better off clipping to a hard point. That is generally more positive.

These are the alternatives, as I understand them.

 

[zoidberg]

what i cant understand is why there isnt a design yet for an attachment that slides along the jackline when you want it to but locks in place when shock loaded.....

There is.... it's commercial... it's costly.

 

[prv]

There is.... it's commercial... it's costly.

All the ones I've seen assume you've fallen off a ladder or similar, and are travelling, rapidly, parallel to the rope.

Slipping on the deck of a heeling yacht, you initially slide perpendicular to the jackline, and then possibly get washed aft along it by the boat's motion. But the movement aft is not rapid enough to lock many of these self-acting brakes.

In most cases, the fact that you slide aft along the stay is neither here nor there anyway; if anything it might make you easier to retrieve, being near the cockpit rather than the foredeck. It's just not worth adding the complexity of a sliding lock against the small probability of your hook happening to jam at just the wrong angle against some deck fitting and then deforming.

Pete

 

[thinwater]

... Slipping on the deck of a heeling yacht, you initially slide perpendicular to the jackline, and then possibly get washed aft along it by the boat's motion. But the movement aft is not rapid enough to lock many of these self-acting brakes....

The key, I suppose is identifying what it is that should cause the devise to grab. You hit on one possibility; instead of triggering based on speed, trigger based on side force. Interesting mental exersize. and probably not to hard to engineer, but still clunky and prone to catching on stuff. A tube with two spring loaded cams, one facing forward, one aft. A side pull lowers them, a spring retracts them, sort of like a Powercleat or jammer.

I would rather see people use hard points and a second leg. For example, the sailor is still over the side being beaten to death and drown.

I have long used screw-locking carabiners on the 6' jackline leg. They are strong, utterly reliable, very light, and slide easily. I can easily lock and unlock with one hand, taking only an added two seconds, but I don't detach the long tether very often anyway. Side loading is not a factor in a sailing fall because they are 6 times stronger laterally. I use something faster for the 3' and harness connectors. But this is just my practice, suited to the multihulls I have sailed.

 

[Neeves]

The focus appears to be exclusively on the jackstays, not the hook. I've hardly looked at every yacht but the few I look at have jackstay arrangements like those on the Clipper yachts. The suggestion is that any jackstays that are near a cleat, chain plate etc will be prone to this type of failure. The idea that hooks that can be bent by hand, as suggested by Thinwater, are acceptable does not instil me with too much confidence. The report does mention that the standard does not envisage a side load, that the hooks met the standard - but ignored the idea that stronger hooks (that can accept high side loads) might exist.

A simpler immediate solution would appear to be stronger hooks, which can be bought off the shelf, immediately - without the need to alter existing jackstay patterns and practice.

Jonathan

 

[Tim O]

I tink there is lots of research going on now into designing the perfect tether and jackline system.....for example: https://www.practical-sailor.com/bl...e36477:2335658a:&st=email&s=p_Waypoints121717 https://www.practical-sailor.com/bl...ilor:e36462:2335658a:&st=email&s=p_Blog121417

I think there is a lot to learn from the climbing community, where falling on a regular basis is expected, and gear is designed accordingly to reduce the consequences

Attainable Adventure Cruising advcate a mixture of fixed points plus a central jackline with custom made tethers (of dynamic limbing rope i believe) of the correct length for each area left attached to the points/jacklines so that you clip into one before unclipping from the other

 

[lw395]

The focus appears to be exclusively on the jackstays, not the hook. I've hardly looked at every yacht but the few I look at have jackstay arrangements like those on the Clipper yachts. The suggestion is that any jackstays that are near a cleat, chain plate etc will be prone to this type of failure. The idea that hooks that can be bent by hand, as suggested by Thinwater, are acceptable does not instil me with too much confidence. The report does mention that the standard does not envisage a side load, that the hooks met the standard - but ignored the idea that stronger hooks (that can accept high side loads) might exist.

A simpler immediate solution would appear to be stronger hooks, which can be bought off the shelf, immediately - without the need to alter existing jackstay patterns and practice.

Jonathan

Talk of bending clips by hand relies on the clip being held in a vice.
The failure in question is basically about leverage. The 300lb force on the clip exerts a greater force at the other end of the clip, given a fulcrum in the right/wrong place.
It pays to remember that the jackline has to survive that 'greater force'.
It might not be a great step forwards to simply make the clip strong enough to break the jackline.
Much better remove the fulcrum. Or perhaps use a shorter clip to reduce the potential leverage.

Also there is a lot of airy talk about clipping on to hard points.
This is about moving along a moving deck, carrying a share of a genoa.
You really need one hand for yourself, so you don't inevitably fall on your harness.
I don't see a free hand for repeated clipping and unclipping.

When we see rock climbers carrying an acreage of genoa up the hill, then they will be more relevant to the discussion.

 

[pcatterall]

It seems we could take several actions
Stronger in side force clips. I like the suggestion of Carabiner type for the long line and a quick clip type for the short one.
use the short one whenever possible when working on tasks-consider fitting clip on points at strategic places
identify possible snagging points and make ( temporary - at sea ) modifications.

So the report has 'done good' in getting us to think about this aspect of safety?

 

[KellysEye]

The best safety for harness and tethers is to have one short and one short and one long. The short one should be used when going forward on deck so you can't go over the life line and I used the long one around the mast to stop me falling back when adjusting the mainsail. In bad weather I went forward my knees. We always clipped on in bad weather and at night.

 

[TLouth7]

Talk of bending clips by hand relies on the clip being held in a vice.
The failure in question is basically about leverage. The 300lb force on the clip exerts a greater force at the other end of the clip, given a fulcrum in the right/wrong place.
It pays to remember that the jackline has to survive that 'greater force'
.....
When we see rock climbers carrying an acreage of genoa up the hill, then they will be more relevant to the discussion.

In fact in the situation shown in the MAIB bulletin (figure 1) the jackline is taking no load, the amplified loads are acting on the underside of the cleat and on the deck.

The situations encountered in climbing (or roped access, caving etc) may not be directly applicable, but there is a wealth of knowledge/testing from those fields that should not be ignored. For example in caving it is standard to use dynamic cow's-tails (basically tethers) to minimise shock loads on anchor points.

UIAA standards for normal climbing karabiners (UIAA121) have minimum strengths for straight pull , side pull and straight pull with the gate open. For via ferrata karabiners there is an additional test under load conditions almost identical to those described in the bulletin. This suggests that such a requirement could reasonably be added to the marine standard (ISO12401).

If you are concerned about adverse loading then via ferrata karabiners might be a good alternative to standard marine tether clips. NB I have no idea whether the locking mechanisms used in these would work well in a sailing environment.

http://www.theuiaa.org/wp-content/uploads/2016/08/UIAA121-Connectors_2.jpg