New Tethers--Finally, a locking harness-end carabiner I can live with

rev. 3-13-2012, rev. 7-22-2024

I've always used locking carabiners on the jack line end; non-locking biners can lever off a fixed point or tight rope in any number of ways, and the jackline end gets dragged all over all sorts of edges and fittings. Ice climbers, wearing heavy winter gloves, take advantage of this very mechanism to clip gear in and out without fumbling with the gate. On our cat, we generally leave the tethers attached to the jackline anyway, so a screw-lock biner is safe, dependable, and snag-free. We use climbing biners rather than "marine" biners; their clunky stainless designs bang on the gel coat and their weight makes them more snag-prone, and to me, snags present a safety hazard. We keep them greased.

[On our F-24 the geometry is different and we switched to Kong biners on the jacklines and snap shackles on the tether end, though a Kong on the tether is also good. I considered removing the above text, but then decide that, in fact, it was right for the PDQ cat. Different boats, different long splices. Just make sure you consider all of the use factors.]

 

I'm not a fan of snap shackles on the harness end of  a tether. I've seen them break FAR below their rated strength and I've seen them open easily when not closed just right. Can you see or feel that they are fully closed , in the dark, with gloves on? Ask a climber--or a rigger or anyone with an ounce of common sense--to hang from one up the mast and they will look at you as though you have none. Use one in the mountains and no climber would join you again, convinced you are a complete safety menace and an idiot as well. Yet we're supposed to trust them in a storm, with the boat leaping about. No thanks.

Kong Tangos, Clog (right)  and Wichard Proline (left). The Wichard is a prototype that came out on the wake of the Clipper Race fatality.

I'm not a fan of the current crop of locking "marine" biners; the webbing loves to catch in the pesky grove at the gate, they don't slide over obstructions well when used on jacklines, and they're difficult to open when wet. I don't need glitchy hardware when things are going badly. The Kong biner does not have the grove (it's a key-lock style biner), is lighter and smother (not cut from plate) reducing snags, and has a much smoother gate action.

 

A Spinlock Race clip did this to a Dyneema jackline.  The nose and lock design is a serious snagging and rope damamge hazard.

 

 

 

Gibb hook snagged on webbing.

 

Wire gate biners are easy to use and unhooking at the harness end is very, very unlikely. The attachment isn't rigid isn't being dragged up and down the deck. But it could happen, and I think about that when working down the sugar scoops, landing a fish or fooling with the tender while underway, often single handed.

The Kong Trango seems to be the best of both worlds. Opening is effortless and instinctive; the same light squeeze that opens the gate releases the lock; as quick and dependable as any climbing carabiner. The gate opening is the widest of the bunch at 1.25 inches, enabling it to clip many railings and stanchions, and it's the strongest of the bunch. While it's heavier and bulkier than climbing biners, but it's aluminum and 1/2 the weight of the stainless alternatives. Some have expressed concern over corrosion, but Practical Sailor left one in saltwater until it grew a reef and it still worked, and I treat my safety gear a bit better than that. As usual, I will keep the pivots greased.

This style carabiner was invented for use in via ferrata systems, where climbers follow "iron ways" through the mountains. Frequent clipping and unclipping require a dependable locking carabiner suitable for one-handed use. Notice also that it is used with a 2-legged lanyard system, not unlike some sailing tethers, but with a shock absorbing section mandated by UIAA standards, because of the potential for high impact loading. I don't know.... It seems to me the marine deck harness, tether and jackline manufacturers are always following climbing innovation, a few steps behind.

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 Notes on lubricating biners:

• Waterproof grease is best on screw gates. very dependable.
• A good corrosion blocking spray should be applied to all pivots, and critically, to the spring inside the base of the gate. Be liberal there.
• Cor-Block and Bo-Shield did very well in Practical Sailor wire corrosion testing in a salt environment chamber/accelerated aging test. Many others, like WD-40, are basically useless. 

Rock climbers are generally advised not to lube biners. Lubricants attract grit when biners are thrown on the ground in dusty crag-side environment. Additionally and very importantly, there is a risk a climber will try to revive a bent carabiner with lubrication, which is an obvious risk; the biner may be weakened and there is a risk that the gate could hang open at a critical moment. These are good reasons, but they are less relevant in the marine environment. However, if a biner or other piece of climbing equipment does stick because it is bent or burred, discard it. Although I am a dedicated fix-it guy, I don't repair damaged biners.

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I have several other posts on jacklines, climbing gear for sailors, and the stresses involved. As a life-long sailor, rock climber, and engineer, it's a favorite topic.

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What about energy absorbing tethers, as  used rock climbing and construction? This study is the best I've found on survivable tether impact loads, and energy absorption.
IF the subject is well secured in a body harness it concludes g-forces over 10 Gs have significant injury potential and forces over 20 Gs are generally fatal. Since 20 Gs ~ 3500 pounds, it seems clear that the sailor will be dead before the harness breaks (cutting over sharp edges excluded) and probably seriously injured at 1,000 pounds, since he is only wearing a chest harness. Much depends on geometry, but the general conclusion is unarguable.

I found the discussion of variable arresting force depending on a persons weight (page 14-15) interesting. To me, this also suggests a sailing tether should have a lower arresting force, perhaps 600 pounds. A lesser total energy absorption capacity is needed, perhaps only 40% of the OSHA figure, so the required extension will not be excessive, perhaps 2 feet, based upon a comparison of industry figures and potential wave impact/falls on a boat (they are looking at a 12-foot fall, we are considering the wave force plus boat free board).

These are not just numbers on a table to me. I've taken thousands of roped falls rock climbing--most top-roping, but other sorts as well--and have a pretty well tuned gut feel for the issue. I have a strong feeling also, that non-climbers have no respect for how dangerous a fall on a chest harness, without shock absorption, really is.