Tether Clip Update

Posted by Drew Frye with Darrell Nicholson at 11:14AM - Comments: (10)

A Spinlock Race Safety Clip for sailing tethers with labeled parts. Testers found that webbing jacklines could get snagged on the pin groove and that when this occurred the clip opened to the point of failure at loads of less than 300 pounds.

As promised, here’s an update of what we know about the recent failure of a safety tether during the Clipper Round the World Race. This is latest in several accidents in which the use, misuse, or failure of tethers have been linked to fatalities.

Ten days after our first report on the tether failure, the race founder and noted offshore sailor Robin Knox Johnston has revealed more details about the accident, and is cautioning Clipper sailors regarding the proper use of certain tether clips. Although we are not in full agreement with all that has been reported, we are glad to see the race organizers are recognizing the importance of sharing this information with the sailing public. This month, the Marine Accident Investigation Board issued a Safety Bulletin on the topic. Certainly, when the full Marine Accident Investigation Board report (likely to to take months) is released we will have more answers to the many questions that still remain.

Testers deliberately loaded the pin hook to simulate failure. The clip opened at relatively modest loads, illustrating the importance of making sure you are fully clipped in—especially when using a webbing jackline. It is also possible that the tip can snag on metal or lines on deck.

One of the videos posted on Facebook demonstrates the risk using a Wichard original double-action locking clip, which as we understand was NOT the clip being used by Simon Speirs at the time of his fatal accident. Based on what we've been told, the snap-hook was a Spinlock Deckware Race Safety Clip (# DWSTRCLIP), a double-action, locking snap-hook used in Spinlock Deckware Safety Tethers (# DWSTR). Introduced in 2009, the Deckware snap-hook is based on the Gibb safety snap-hook—a design that has been used in a variety of sailing tethers for more than three decades. In past tests, Practical Sailor has noted it is one of the easiest locking snap hooks for people with weak hands to operate. The chief difference between the Deckware clip and the original Gibb version is that Deckware clip is lighter and has a black plastic locking latch, while the locking latch in the original Gibb snap-hook is made of stainless steel.

The jackline frequently snagged on the Gibb latch during testing. Once this occurred and load was applied, the latch punctured the jackline and became fully embedded in the weave, eventually cutting the jackline. The smoother, round-edged latch on the Spinlock Deckware Race Safety Clip resisted snagging.

We’ve completed a fairly comprehensive round of testing on various tether snap-hooks. Although some of our findings conflict with public statements regarding the accident ("it could have happened to any tether," for example), we are generally on the same page regarding the need for a closer look at safety tether snap-hooks. For some background on the accident and several links to related Practical Sailor tests, please read my first post on this topic as well.

The Marine Accident Investigation Board Safety Bulletin cautions against jackline arrangements that induce side loading on the tether snap-hook. Having a jackline terminate at a cleat is one arrangement which might induce side-loading.

The following points are particularly relevant if you continue to use these flat-plate style tether clips—including the Wichard original (not the Wichard Proline, which we have not yet tested) and any Gibb-style hooks (from Spinlock and others). According to our testing so far, only one of the popular locking tether snap hooks on the marine market—the Kong Tango double-action safety hook (formerly used in West Marine tethers)—is built to withstand eccentric loads (loads that do not align with the anticipated load paths) that can induce this type of failure. (We’ve not yet tested the clip used on the Wichard Proline tether, which, like the Kong, is based on climbing via ferrata clips used by climbers and is tested to a higher standard than sailing clips—see Final Observations below).

Tether snap hooks (Gibb on left, Spinlock on right), when hooked on the the pin-groove, failed in a manner nearly identical to the failure reported in the Clipper fatality.

  1. Our testers found carabiners with grooves in the nose to capture the gate pin (Gibb, Gibb-style Spinlock, Wichard orginal and others) very frustrating to clip on and --especially--off webbing. They caught almost all the time. Watch out for nose-hooking, in which the jackline slips under the gate. If you clip directly into a jackline, make absolutely certain that you are properly clipped in by giving the tether a hard tug. (This does not guarantee you can’t get nose-hooked in an accident, but will help avoid it.) Most locking carabiners have evolved away from this mechanism, most going to key lock gates, where a bulge on the gate fits into a slot in the nose, making for smoother clipping. Additionally, even though climbers use many webbing slings to rig anchors, they avoid clipping directly to the webbing by pre-rigging carabiners on the slings before climbing. Doing this on your boat may be inconvenient, but it will avoid snags.
  2. Modify any jackline arrangements that terminates in a cleat or other anchor that the hook can wedge under and twist. Aboard the Clipper boat that Mr. Speirs sailed, the jackline terminated at a large cleat in the bow. As Knox-Johnston describes in the Facebook video link above, racers are now wrapping line around the cleats making it impossible for the tether clip to wedge under the cleat.
  3. For fixed clip in points, use only well-reinforced pad-eyes or u-bolts that leave no opportunity for the clip to bend under or around. The snap-hook can bend and fail if you are clipped into the bail of a stanchion, aluminum toe-rail, cleat, or similar piece of hardware that can become a fulcrum when the the snap-hook is misaligned and the tether is under load.
  4. Keep jacklines taught and ensure that the jacklines do not run near hardware that can snag the hook. Twisting the jackline can make it easier for you to clip into (more jackline tips are in last week’s post.) Also see our May 2017 article, "Reassessing Clip-in Location Points," for ways to improve your jackstay system.

The right-hand failure is typical of what happens when the snap-hook twists over a hard point (such as a cleat) used for a jackline anchor. Clipper race officials suggested this might have caused the failure linked to Simon Speirs' death, since boat's the jacklines terminated at a cleat. From what we understand, the recovered snap-hook in the Clipper fatality did not have significant damage to the plastic sheath, and more closely resemble the failure our testers induced when the pin groove snagged on the jackline (left hand photo).



Since this main body of this report was first published in December 2018, Practical Sailor tester Drew Frye has been hard at work examining various tether clips. A more comprehensive summary of his work appears in the March 2018 issue, now available to subscribers online. Since that report was published he's conducted some additional tests and videos of those tests appear below. 

The above video replicates the accidentally opening test used check that a tether clip or snap-hook will not self-release. This is one of the requirements to meet ISO Standard 12401. World Sailing, the governing body of sailing, requires all race tethers to meet this standard. The tether Mr. Speirs was wearing at the time of his accident was certified as meeting the standard (an excerpt describing the required test appears below). Our tester was able to easily replicate the self-release shown in the video applying very little pressure (less than 25 pounds).

The above video illustrates a possible mode of failure for Mr. Speirs' tether, or any tether connected to a jackline that connects to or passes adjacent to a large cleat. In this test, the tether hook is attached to a taught jackline and the gate of the tether is pressed open with very little weight upon it (about 25 pounds). The nose hook of the open tether snap hook then slides up the basket snags on the tether, and the body (spine) of the hook, under loads of as little as 350 pounds, straightens before fully releasing. The gates on sailing tether snap hooks are not required to be tested for resistance to direct pressure in this way. However, climbing carabiners and ANSI (industrial) snap hooks are tested for this. The UIAA-121 Type K tests for climbing carabiners, for example, must resist at least 1KN (about 225 pounds) of direct pressure. Our testers noted that some older versions of the Gibb design better resisted opening under direct pressure because the locking latch met the basket at a right angle. In current designs, the locking latch meets the basket at a slightly more acute angle, presumably to make them easier to open.  

Final observations

In our view, the sailing community needs to implement more stringent testing of safety tethers required for World Sailing sanctioned events. Strength testing of carabiners is not required by ISO 12401, the standard that sailing tethers must meet. We think this is a mistake. Sailing tethers are required to survive the drop test, but the forces involved are lower than can be encountered and the test is performed in a manner that minimizes leverage. For example, no test properly simulates clipping into a padyeye, and off-axis loads and open gate strength are not tested at all, resulting in flimsy designs. The remedy—applying the same test required for via ferrata climbing tethers (UIAA-121 type K testing)–has been plainly available for years. It is something we here at Practical Sailor should have looked at sooner ourselves. It is devastating that a sailor had to die to initiate more in-depth testing, but we are hopeful the sailing community and gear manufacturers will respond swiftly with equipment improvements and more clearly stated cautions regarding the proper use of safety tethers.  

Our full report on tether clips will appear in the March issue of Practical Sailor. For more on tether, jackline, and harness safety, Practical Sailor also publishes a report on Man Overboard Prevention and Recovery, which details the gear and tactics that can keep you alive. 


[Editor's note 12.31.17: Images and captions have been updated to correct an error. Since this article was published Clipper Venture boat Invictus Games Down Under lost a crew overboard during the Sydney Hobart Race, the crew member was recovered unharmed by another race boat after approximately 15 minutes in the water. The crew of Invictus Games Down Under included eight wounded, injured, and ill defence personnel and veterans. Paul Atwood was at the helm with six other crew members aboard. The crew member who went overboard was not identified.]

[Editor's note 1.9.18: A link to the Marine Accident Investigation Board's safety bulletin, and illustrations from the bulletin have been added.]

[Editor's note 2.21.18: Videos and description have been added.


Comments (10)

Then what Tethers have passed the Stringent Testing , to avoid Failures ?

Posted by: Golden Nugget | January 11, 2018 9:44 AM    Report this comment

I've followed the debate of flat webbing versus wire jackstays, for some years, and have used both, on several boats. The solitary argument against wire seems to be that 'it rolls underfoot'. My take on that is 'Don't stand on it' and 'Run it higher, up off the deck' - and that works for me.

I've sailed on boats where the webbing had lain on deck, year after year, summer and winter, together with thin cord lacings used to secure the ends. Same thing found when scrutineering big French multis in the recent Bakerley Transat... How on earth does someone determine such UV-degraded straps are still capable of doing the job? How often should one replace these webbing straps, and why? No-one knows.....

Posted by: oldbilbo | January 2, 2018 5:11 AM    Report this comment

To clarify, all but the last image were straight pull, with webbing hooked on the nose as in the first image. No twisting force was applied. Once the hook was loaded to about 300 pounds, the thin plate buckles to one side, resulting in the spiral result you see. Side loading can produce a similar, but subtly different failure.

Posted by: Drew Frye | January 1, 2018 3:41 PM    Report this comment

This post has been corrected to eliminate errors in the images and captions. 12.27.31.

Posted by: sailordn | December 30, 2017 3:30 PM    Report this comment

As Allen Rees I consider the KONG # 283.set.e tether a valuable one (22kN)

Posted by: albatrosbis | December 29, 2017 8:12 AM    Report this comment

As a climber and a sailor, I can say without reservation that I would not trust my life, nor the life of my crew, to that which the sailing manufacturing community has to offer. No climber in his or her right mind would use the hardware that sailors trust their lives to, whether top-roping or multi-pitch climbing. I would never consider using any of the hardware tested by PS, regardless of the manufacturer, in a climbing situation; I would, however, use climbing hardware in all boating situations. Consider this - a lockable carabiner is rated at 22KN; only when the sailing safety hardware manufacturing community replicates what Black Diamond and Petzl, et al, produce, will I consider switching.

Posted by: Allen Rees | December 28, 2017 11:00 AM    Report this comment

Problems with tethers:
The sharpish edges on the flat SS stock on most carabiners will snag and drag on nylon jacklines. Unless the jack line is very tight, this will cause it to twist around the carabiner, impeding progress along the deck. Round staock such as used in some tether carabiners from West marine eliminates this problem.
From the pictures in the article, it appears that part of the failures in those carabiners were caused by the locking catch.
The locking catch is awkward at best to use without a lot of practice and even then is often impossible to use in a hurry and certainly not one-handed in a hurry.
Most sailors going offshore are not terribly practiced in using harnesses and tethers; anything that makes it more difficult is a safety hazard.
On my tether I have eliminated the safety catch. In my opinion, based on more than 350,000 offshore miles sailed as a delivery skipper, I am safer without the locking mechanism as it makes it easier to clip in and hence I am more likely to clip in earlier, even in benign conditions.
To the person who suggested that stainless wire would be a good alternative to webbing; you have a good point, but two factors come into play, 1, the wire will roll underfoot when stepped on, and 2, the stretch from nylon webbing is an added safety factor in the shock loading when you come up suddenly at the end of your tether.

Practically speaking, it is worth remembering that the jackline and harness are there to keep you on the boat. Once you're over the side, you're going to release yourself to prevent drowning from being towed.

Posted by: ABurton | December 28, 2017 10:42 AM    Report this comment

Here are two thoughts: The first is that, of course, all safety hardware needs to be above reproach in regards to its strength and integrity, over many years of use, and when used basically correctly. Secondly, it appears from the photos of twisted metal, that some forces other than basically linear stretching were at play in the failures that you induced, and perhaps happened to the lost sailor. I would like to see the test conditions of the failures so that I could compare them to the way that I use my clips and what I clip into. Perhaps one of the valuable takeaway lessons here is that you cannot just clip into anything, as some attachment points can present high side-loads to the clip that will cause a failure.

I would never use a composite spinnaker pole as a lever on a gunwale to lift something out of the water. It is simply not designed to handle those kinds of forces, and would snap like a toothpick. Likewise, if there are inappropriate attachment points for these clips, perhaps an attachment loop could be added to them to make the clip forces appropriate. To condemn tens of thousands of clips that otherwise have fine quality (if they do) would seem rash if what is needed is better education of usage.

Posted by: JSROOKS | December 28, 2017 10:18 AM    Report this comment

For years I struggled with Wichard tethers (difficult to work with one hand, silly hook on the end, etc.) and finally switched out all of them to true manual-locking (screw down) Petzl Am-D's... The only thing that can go wrong with these is me being in too much of a hurry to lock down. So, my second mantra (first is 'don't get off the boat) is 'screw down before you screw up'. We can learn a lot from mountain/rock climbers (smile).

Posted by: jwinkelhake | December 28, 2017 10:12 AM    Report this comment

Instead of using flat strap for the jackline why not a SS wire? Seems like that would eliminate many of the snagging issues.

Posted by: skipmac | December 28, 2017 9:52 AM    Report this comment

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