Monday, September 19, 2016

Tether Shackles--No quick Release For Me

Before hoisting the spinnaker I inspected this shackle and double checked that it was latched. I remember staring at it, thinking I would never trust my life to a quick release mechanism so easily released as this.

The spinnaker flew perfectly for hours, and then while putting it away I realized the shackle had blown apart, the result of being dragged over the lifeline. No excessive force, just the the weight of the sail and sheet as I pulled it on board. Somehow the circle pin came off, allowing the pin to shoot out the other side. This is a common failure mode, one I have experienced before. No excessive force, just the the weight of the sail and sheet as I pulled it on board.


Today's experience simply reinforced my tether decisions:

1. Harness carabiner should be locking but with simple release. I like the Kong Tango because it is large enough to clip railings and is easy to unclip even with wet, cold-numbed hands. I really like the feel in my hands. I also like that I can clip in with one hand, something I cannot do with a snap shackle.

Kong Tango (Black)

2. Jackline carabiner's must be locking type. I like aluminum rockclimbing carabiner's", which seem to remain jamb free so long as I treat them with waterproof grease annually.  I like simple climbing carabiners, since I generally leave the tether on the jackline and unclip at the harness end when entering or leaving the cockpit.

Black Diamond Positron Screwgate Carabiner
This makes sense for us because our boat is center cockpit, but for most boats with aft cockpits, there are better choices. Some makers, including West Marine and Kong, use the Kong Tango on the jackline end of the tether. They like a snap shackle for the harness end, I don't.

3. Tether material is nominal 8 mm UIAA certified 1/2 or twin nylon climbing rope. It has the toughness and shock absorbing capacity to handle any conceivable fall or misstep without generating rib-breaking impact forces or overloading the jack lines or anchor points.

4. Custom tether lengths. I use two leg tethers. The short leg is 2 feet and the long leg is 8 feet. These lengths better suit my specific boat. The answer for yours could be different. However, I'm willing to bet that 3 feet is too long for the short leg on most boats.

Phase I: These were tied from 1-inch tubular nylon climbing webbing. I also inserted a Yates Screamer for testing, though it was later removed. These are the simplest to make and are quite safe, based on generations of rock climber experience.

Phase II: After many experiments, these are the tethers I use. 
  • 8mm climbing rope for shock absorption (easier on the ribs). 
  • Kong Tango at the harness end. 
  • Sewn ends (can be knotted--do not attempt sewing unless you have access to pull-testing equipment). 
  • 2'/8' lengths (fit my boat). The short leg just kept getting shorter.
  • Small "parking clip" so that I do not have 2 biners clipped to my harness (inhibits unclipping in an emergency).

Note that in both cases the middle carabiner is cow hitched and can be moved. This is important to getting the best fit. The cow hitch is secured with a seizing to prevent sliding (hidden).


  1. This is exactly how I have made up my tethers, thanks to your posts of a couple years back. Thanks again, Drew!

  2. I have added a second image showing the climbing rope tethers I use now. The webbing tethers are safe, but these are easier on the ribs.

    While testing drogues for Practical Sailor in near gale conditions, I fell against these dozens of times (I was using both hands and the transom lifeline was open. I was also single-handing. Without good tethers it would have been life threatening.

    1. please do not use a "shackle" that cannot be released under pressure.there are situations, rolling and sinking are just two that will get you killed if you cannot release

    2. Anonymous: I'm am sorry, but I cannot agree with you for me. I didn't say snap shackles were bad for everyone, just me, my catamaran, and the way I sail:

      a. As a practical matter, cruising catamarans do not flip and cruising monohulls do not roll over. This is a site for coastal cruisers, not racers or bluewater sailors. The primary risk is just falling off, and the risk of a snap shackle opening is simply orders of magnitude greater than my boat rolling. Yes, there is a trade off, but on my catamaran, the trade off does not favor snap shackles.

      b. A carabiner can be released under some load. I've done this many times. It's not as easy as pulling a string (thank goodness), but it can be done. In fact, in the case of an inverted boat, I believe releasing a carabiner may be easier and more instinctive. As a climber I have clipped and un-clipped carabiners hundreds of feet off the deck thousands of times.

      c. As a single hander you are very seldom better off unclipped. You'll just die more slowly. In cold water, hoping for rescue is naively optimistic.

      d. ISAF does not require a quick release shackle, or in fact, a shackle of any kind. The tether can be fixed to the harness. That is because there is substantial disagreement on this topic at the highest levels. [I disagree with tying the tether to the harness--every so often you may get tangles in the rigging and need to release and re-clip, in my experience]

      Yes, specifically on a monohull, it is possible to drown while trapped in the bow wave. My answer to that is to keep the tethers short, to end the jackline well short of the bow, and to stay low.

      Do you see that open shackle? That happened miles offshore and I'd have been swimming. I am not the only person who has expereinced this, some with tethers that rubbed across rails. Not acceptable.

  3. As a new sailor, I have enjoyed reading your blog for over a year, we seem to have similar sensibilities. My daughter was 3 when we started sailing and a tether/jackline system was paramount in my mind for her. After a lot of research and some kind consultations with Brion Toss i settled on precisely the same caribiners as you show in the same config. but with only one leg. I rig a line athwart the cockpit with a butterfly knot in the center of the jackline as the clipping in point. The tether is a flat webbing made with a daisy chain of loops every 10 inches. In this way i can adjust the amount of "runout" she has depending on the size of the cockpit and weather. It is attached to her harness with the kong clip. A drop of t-9 on all the pivots has kept them operatingly smoothly for two years. However, if it were me i think i should reverse the clips and have the kongs on the jackline ends as spinning that locking barrel while I'm crawling around the heaving deck with gloves on seems like it would be very cumbersome. If you needed to release from the harness end so badly wouldnt you just cut away anyway? Could you elaborate on you decision to do it the other way?

  4. When my daughter was small we had a Stiletto 27; open deck, no lifelines. We used single-leg tethers clipped to a central point, much as you describe. That wouldn't work on my PDQ, but it was perfect for the Stiletto. So yes, it is all about making the system fit the boat.

    Yes, the Kongs make a lot of sense on the jackline end. I do it the other way because I leave the harnesses on the jacklines and unclip at the harness end when I enter the cockpit. It is a deep center well and tethers are not needed there. If I had a monohull I would most likely use the Kongs on the jackline end, just as others do.

    I'm so used to locking biners from years of climbing they don't bother me. I like that they are very light. As for "cutting away," I don't believe that it is realistic to handle a knife in horrible conditions; I would either stab my self, drop it, or get tangled hopelessly if there was a lanyard. But I know from climbing that I can unclip in some pretty horrible conditions, hanging from one hand. I've done it a few times, caught up in my knitting way off the deck. I'm unconvinced it is any harder than fighting with a stuck snap shackle, and I've done both.