The Offshore Voyaging Reference Site

Flawed Jackline Systems, Part 2


In the last chapter we learned that being drowned by dragging on our tethers or badly hurt by fall-arrest shock loads (most likely a combination of both), is probably at least as big a threat as going overboard untethered and not being picked up.

In this chapter I’m going to apply a bit of simple arithmetic rigour, backed up by testing, to common jackline systems, and particularly the ones we have used on Morgan’s Cloud, and see if said systems will keep us out of the water—something I should have done years ago.

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Dick Stevenson

Hi John,
Nice analysis.
I have done the “hanging from the harness” exercise that you showed pictured and decided that if I went overboard, I would attempt to keep my arms down by my sides. Even my easily adjustable Lirakis harness is too loose when worn at a comfortable pressure and those I have observed in inflatable life vests that also serve as a harness were absurdly loose and very likely to be pulled over one’s head in a powerful snatch. or do serious bodily harm. I have been looking for a harness where there are 2 leg attachments going around the leg ( different from crotch straps) as well as a conventional chest arrangement. I am still looking, but variations from other professions/recreations come close.
Dick Stevenson, s/v Alchemy

Stein Varjord

Good post and an important one. My roots are firmly in racing, so I’ve been on boats where these topics were tested too, with similar judgements, but with no real good solution. The best we got to was that we made rules about moving on deck. They were about like this:
– Jackline can only by used on the windward side.
– Tether must be adjusted so it is about 1 foot too short to reach the lifeline, anywhere.
– Such attachment is ONLY for moving. At arrival, use fixed points and readjust tether length to same limits.
– Deck hands wear proper climbers harnesses strongly connected to a chest harness. When hanging fully on it, the tether attachment should be not much above belly button. This harness was also used when climbing the rig.

This worked, but I was never really happy with it and it was too slow sometimes, meaning one would frequently skip some steps and “just be careful”. Not good.

Stein Varjord

Hi John.

Exactly your point is why I was never happy with the solutions and rules. No matter how strong the rules were made, people would make potentially dangerous simplifications. I would even do it myself. Thus, the system might be much better than the average cruiser system, but the verdict must still be “Fail!”

Attaching to fixed points have the problems you describe, but if the tether is kept very short, so it’s already tight and even used to get support while working, shock loads should mostly be avoided, but then again comes the fact that we’ll use points that are not ideally placed, and adjust the tether way too long to reach something just a short moment, etc….. It will end up in too many risky situations.

Life jackets are slightly off topic, but I feel they still belong in the section describing the dangers of moving on deck and it’s definitely relevant in discussing why a good harness system is vital.

Countless times I’ve seen competent sailors step out of the cockpit intending to perform a task on deck. No harness and no life jacket. Then notice the task looks dangerous and immediately return to the cockpit. Then put on a life jacket but no harness and proceed doing what they just decided was dangerous.

In bad weather in the night, or even in daytime, the chance of finding a person over board is very close to zero, as probably all here will know. Even if found, getting onboard is very dangerous. If the vest gives you a feeling of safety, you are totally wrong. If that feeling makes you change your behaviour, the vest is directly responsible for increasing your risk of dying. Vests can give important additional safety in many situations, but in offshore sailing, life vests must kill much more people than they save.

Of course, a life jacket has no intention of its own. The real reason for its flawed effects is our own stupid emotions, but no matter how smart we are able to be, we’ll never stop being human. We’ll never stop acting according to our emotions at least as much as our knowledge and logic.

Our safety systems, whatever they are, must fit that reality.

I don’t know which good ideas will be revealed in the next chapters and discussions, but I’m very curious, since I’m certain that I’ll be wiser and safer after reading them. Coming from a wise ass like me, 🙂 that’s a pretty strong vote of respect and confidence in this site!

Jeff Bander

The working principle here is to stay onboard at all costs. Nothing good comes from reaching the water so that possibility has to be eliminated. In addition to the key practices of staying low, holding on (gloves help) and wearing grippy shoes, I think a little mental preparation can help. 1. Even if you decide to wear a PFD act as if you’re not; the darn thing can give you a sense of security that’s wildly inaccurate. 2. Even if you’re tethered when moving forward act as if you’re not; again the belief of protection may exceed the actuality 3. See the lifelines as protecting you not from the water but from the edge of a 100 foot cliff with sharp rocks at the base. Thinking this way may help avoid ever having to put the whole “safety” system to the test.

Keep those posts comings….we’re making progress.

Henrik Johnsen

An adjustable lanyard like the Petzl Grillon, which we use in our rescue service, will make it possible to always have the right (read: short enough) length on the lanyard.


“That’s an interesting alternative, but would we really adjust the length of our tether continuously as we moved around? I fear not.”

I’m also a huge fan of GriGri’s (grillion) onboard, but very hesitant to recommend them as a good idea for everyone. After decades working in the air adjusting the length is instinctive and automatic, not something which even gets thought about. For others with no experience it may well be a very different ball game and more intrusive than helpful. Personally single handing I never use a PFD but a lightweight climbing harness which might never be taken off for days on end offshore, combined with a GriGri it works well, lanyard is always as short as practical. Great at the mast as well, clip off and lean back so both hands are free.

Henrik Johnsen

I don´t think it´s possible to make a system that covers all aspects, and that one just can put on and be safe and sound. My experience from over 30 years in the rescue service has taught me that you constantly need to adjust your gear, and always take into consideration whatever the environment throw at you.
On board we put on at climbing harness in addition to the life vest, and attach the lifeline to the harness when the weather gets rough. That way we take the load of the life vest, should we fall in. This way we don´t have to think about the crotch straps breaking, and we´re lowering the attachment point of the lifeline with a good 50 cm, compared to when it´s connected to the life vest, which is of great importunes.
When the weather is on the mild side though, we trust the lifeline attached to the life vest.
Yes, this means we have to adjust the gear quite often, but that´s the way it has to be, and are of no concern to us. We do the same again and again without thinking about it when climbing in the mountain or moving around on glaciers.


My professional background is in climbing/rescue/work at height. So I recognize the potential value of a device like the Petzl Grillon in this application. I should point out that although the Grillon does have some load limiting capabilities, it is not intended to be used a shock absorber so without proper testing, I would caution against its use as such. I do believe however, these technologies (load limiting camming devices and tear away shock absorbers) could be applied to this problem with good results. Very much worth looking at for sure.

Dick Stevenson

Hi John and all,
Crotch straps as seen in the recreational marine environment are designed so lightly that they will likely only suffice to hold an inflated vest down so it does not ride up. Any kind of “harness” contribution seems illusory at best.
I went back to some past researches and found:
Harnesses w/ flotation and leg attachments such as I was referring to in my last email.
And shock absorbing harness tethers.
There are likely reasons these products are not readily applicable to the recreational marine area, but they reflect much more the way my thinking is going, especially the harness/flotation rig with its substantial leg attachments. I also suspect these products are well vetted by their professional users.
My best, Dick Stevenson, s/v Alchemy


Hi John
I’m working as light rigger. we work same time’s At an height of 15 meters +.
We have a safety harness with two short arms, Each has a handle that can be attached to the Rig.
So we basically moving slowly but safely, when the rule is: always one of the arms is connected to the rig,
and the other arm is ready to connect to the next step.
I think it’s a great way to move on deck. the only thing you need is to worry about is the connection point.
Best regards

Martin Loxton

I would think that rescuing someone after they have gone over the side into the water on their tether, gets a whole lot harder, if the life jacket inflates.
Best regards
Martin Loxton


Applying logic and probability:

1- The worst case is that in which you fall overboard and are dragged while underweigh. Probability of death is extremely high.
Therefore the first priority of any restraint system must be to avoid going overboard.

2- Second level risk is that of injury by falling against the restraint system.
—Loads and resultant injuries are highly variable depending upon the angle and length of the fall.
—Not all falls will result in injury.
—Most injuries will be survivable.

Jackline systems MUST be designed so that falling overboard is nearly impossible. This means that at full extension the combined tether length and jackline stretch are such that the harness attachment point reaches no more than 1′ beyond the top lifeline. (or less)

— The best way to achieve this is to locate the jackline on the centerline of the vessel. In the case of typical cruising boat foredecks the mast base and the windlass provide hard points capable of sustaining any load. The midship jackline(s) can be raised slightly over whatever deck mounted line spaghetti that exists. Because this is the beamiest part of the vessel two cabin top jacklines can be used while still maintaining the same tether distance to the deck edge.

—Cockpit and exit attachment points should be custom designed around individual vessel characteristics.

— Tethers should be designed to progressively absorb as much shock as possible while limiting maxim extension to 2′ or less. If I were designing an improved tether it would incorporate multiple small strands of very high stretch line inside of flat webbing, sewed in place so that the energy absorption gradually increases as the tether reaches it’s limit of extension. They should have two different attachment points to allow length reduction when working the very bow in extreme conditions.

Bill Wakefield

Hi John,
Thorough and sobering, as always…

In case it is of interest and appropriate here, Practical Boat Owner published what I perceive as a companion article on 23-Nov-2015. It not only reinforces the current direction of your online book, but also supplements with some testing I suspect you would rather not perform- at least until your rib mends: photographing the POB while being dragged in the water at various speeds…

Thank you for this effort. It is timely for us all.



What is often lost in the PBO article referenced above is the the video of the follow-up test that was done, using the Team O Life jacket where the tether attaches on the top of your back instead of the front. The risk of drowning while being pulled by the boat is greatly reduced. I believe that the Team O Life jacket is not available anymore. I wonder why…?

Anton P.
Anton P.

Thanks bill for the read on PBO.
Here is a summary:

  • Staying on board in the first place has to be the number one priority.
  • A short tether: if you go overboard there’s a better chance of being held clear of the water than if you are wearing a longer tether. The shorter the tether, the better.
  • Consider clipping on near the boat’s centreline
  • If someone does go overboard while clipped on, the crew’s first reaction must be to STOP the boat as soon as possible, before attempting recovery.
  • The whole crew need to be fully trained and ready to react instantly. Even a minute’s delay could kill the MOB

The key point: Use the shortest tether available that still lets you move around in safety


Hi John,
Sorry, I don’t understand how the topic of flawed jackline (and tether) designs can be logically separated from a discussion of alternatives or improvements. Looks like I should just be an observer on this topic as my suggestions are going to be discarded.

That said, I do understand your need to pare the editorial work load into manageable size.

Rusty Gesner

On our catamaran, the jacklines are rigged far enough inboard to keep you from going over the toerail, with versatile dual length tethers, and heel isn’t an issue.

Ramon Rodriguez

Thank you. My first season of big boat sailing just completed. I’m glad I can reflect on your evaluation of jack lines and tethering systems. I look forward to your next chapter on options to make it possible to have a safer alternative. On my part, I look to evaluate your recommendations in the context of my short handling coastal cruising. I bought all the gear you could need for jacklines and harness with skepticism but believing others know better then me. Now coming to realize that crawling and being like a snake on deck when I need to leave the cockpit should always be how I operate when making changes on deck. Staying low at all times. As a beginner, usually in awe of your activities and those of your readers, thank you for tackling this important subject.

Drew Frye

I would like to read discussion on how to recover a POB that is still tethered. Man hauling over the side has generally been unsuccessful, even on fully crewed boat, and for the short handed is nearly hopeless.

What I have tested, but only once and in mild weather, was slowing the boat, clipping a 40-foot utility line to the harness, and cutting the tether away. The swimmer then drifts aft, away from the dangerous bow wave and to places near the cockpit where recovery is simpler. In our case, boarding via the sugar scoops is pretty easy even if the boat is moving slowly. It is a place where a tethered crewman could render aid without risk or having to lift the swimmer up the side. But I have only tested this once and would like to read other opinions.

Bill Balme

If I may be so bold and play Devil’s advocate, your conclusions that you’ll be 7, 5 or 3 ft under water due to the geometry of the system doesn’t hold much water for me. The POB will drag towards the rear of the boat, therefore elevating to the surface – as far as I can tell in all circumstances unless stationary.
Not getting dunked in the first place would be good, but perhaps the easier solution is to find a method that will allow someone to be dragged in such a manner that their face is kept above water. However, your second photo in this article seems to indicate that indeed, most harnesses will end up around your neck, in front of your face – thus keeping your face above water.
We’ve all read recently of people being dragged and drowning as a consequence – terrible. I’m a little baffled as to how this occurred – unless it was due to exhaustion while trying to get back aboard. I wonder, are there any tales of people who have gone over with the traditional jackline layout that have survived?? I’m sure there must be, but perhaps the stories of them are not as common since the outcome is rather dull – survival!
I am eager to read your next installment with a solution to a problem that I believe may be less serious than perhaps you’re indicating – as I am sure I will learn something helpful!

Dick Stevenson

Hi Bill,
I pay casual attention in this area and the rescues from being dragged alongside that I recall seem to be executed on racing boats where 2 or more burly young fellows reach down and snatch the POB onto the deck.
My best, Dick Stevenson, s/v Alchemy

Stein Varjord

Hi Bill.
It’s certainly possible to survive going overboard and dragging on a harness. It’s way better than having no harness, when your already out there. The point is that it’s still a quite bad situation. So it would be good to have a safety system that didn’t put you in that type of trouble.

A bad harness system will give you a false sense of security and make you take risks without being aware of it. Much like life jackets do. Instead of reducing risk, they probably increase your risk of dying. The topic here is to become aware of these shortcomings and maybe explore smarter systems.

Another side of this discussion is that all this talk of danger gives the impression that ocean sailing is dangerous. It’s NOT! The ocean is an environment normal people see as exotic and hostile. It’s kinda like sharks and wolves. People are very scared of them. Each species kill less than ten people a year. Most people are way less scared about dogs and mosquitos, even though they kill 25 000 and 75 000 humans every year. Humans are emotional, much more than logical.

Even though ocean sailing is safer than most bus trips and restaurant evenings, there are dangers. Falling overboard is clearly the dominant one. If we can improve our systems significantly, which I’m convinced we can, our already very safe passion will be much safer. That’s worth quite a bit of interest and discussion.

Dick Stevenson

Hi Stein,
Nicely stated.
Dick Stevenson, s/v Alchemy

Victor Raymond


Thank you for the insightful post. I started to write inciteful which maybe fitting since I am sure your hope is that your insights will incite us to think and take positive steps to improve our chances of avoiding going overboard to begin in the first place.

I have a tendency to go overboard in many ways so last year we installed a 1 1/2″ welded hand rail at 37″ with new stanchions. The previous lifelines were repurposed approximately 12 inches apart between the toe rail and the bottom of the hand rail. Although very strong, there is the possibility to rely on one’s hand grip too much going forward so a highline with tethers will used in bigger seas and heavy weather.

Beyond that I am counting the luck of the Irish in me. After a while believer that when you time is up, nothing will save you. When it is not nothing, will kill you.

Victor Raymond

Often I will go forward with a tether and just attache myself to the inside handrails going forward. The thing I don’t like about jacklines even highlines is it just one other line that can trip you up or help kill you.

I like the idea of just being more careful and aware. That is key. You nailed it.

Colin Farrar

Thanks for these sobering insights.

Not an argument but on honest question: isn’t the shorter, 3′ length on the two-tether products the one that should be used for moving along the side decks while clipped to a jack line? That’s what I do, assuming that others do the same. I use the 6′ tether to clip to the center of the cockpit or the mast.

Marc Dacey

That last point is key: Personal habits of mind count for a lot. The best system can’t save you if you take shortcuts and/or use it improperly. Look at “GPS-aided accidents in the absence of a proper watch”.

Drew Frye

A few years ago I added two vertical lines (front edge of mast just below the spreaders to a pad eye on deck about 1 foot forward and 4 feet outboard) lines to help with some sheet hang-up problems.; no matter how good my line management, when I tacked in over 15 knots there was a 30% chance of wrapping a sheet around one of the mast mounted winches or snagging the luff on the jumper. The lines solved the problem 100%. I used a piece of Dyneema core line that had been installed on the main traveler; strong, small, and low stretch. (I replaced it with high-stretch 7.5 mm climbing rope—MUCH smoother jibes.)

And soon I realized I was using it as a hand hold on the exposed cabin top. And eventually, I learned it made a handy local clipping point when working at the mast, better than a hard point at deck level, and because I could clip the windward side, better than clipping anything at the mast.

Just an idea, probably boat specific but perhaps worth sharing.

a. My other tether is still on the jackline.
b. Notice how short the one leg is. It works because the jackline is high (the white rope coming of the cabin top in the foreground).
c. Someone is bound to notice the rather light duty harness. I can put it on in 5 seconds, don’t notice I’m wearing it, and with the dynamic tethers, I am not concerned about loading it past its actual strength. I also have a sturdier harness that I wear when it is violent. This one is just for bumble feet and fishing solo.

Ramon Rodriguez

Thank you for all your comments on this important safety issue. Is there a way as commentators describe their solutions to share a picture, either a photo or drawing, of what each looks like. Maybe it’s just me but I’m having a difficult time understanding the descriptions.


A wild, contrarian idea: what about very long tethers? That would avoid most of the shock loads discussed while keeping the person attached to the boat. This would allow “safely” falling in and if in a life preserver designed for dragging, there would be some chance of being winched back to the boat before dead. Maybe a retractible, seatbelt like inertial reel with winching capabilities mounted in the cockpit with a boat-length tether that adjusted its length automatically.

Patrick Genovese

The PBO article is certainly sobering have a look at the comments this is an interesting concept for a harness:

Drew Frye

I saw that a few years ago and liked the innovative thinking. On the other hand, I’ve used rear-clip harness in industry….
* Because of the extension, he is going to fall ~ 3′ farther. In other words, it is like having a tether that is always 3′ longer.
* With a conventional harness (look at where the clip point is by the side of the boat) he would have been able to reach the toe rail and lifelines and roll on deck. They did NOT use the same tether length! I see a 3-4′ difference!
* Take a deck stumble and get caught, and it is going to flip you so you hit the rail face first. Really not good for work station use. This is why OSHA tower harnesses attach on the front; back clips are no good for positioning.
* It is better if you are fully in the water. However, if you are only just over the rail a back tether makes you utterly helpless. Been there, And you fall 3′ farther.

But I do hope folks keep trying.

Victor Raymond

Maybe it is better to forget about the harness and tether and something akin to this:
It could be towed behind the boat when offshore. Just thinking out loud here.

David Nutt

These posts are great and thought provoking as intended. One thing that is clear to me is what works on one boat may well not work on another.
When headed offshore we run a line from the mizzen shrouds to the main shrouds about 2 feet above the lifeline. This fills a 20 foot section of territory that always seems like a scary place giving one more chance to grab a secure handhold. Rule is to stay on the windward side and sometimes this line works as a guide. We run two midship jacklines from the mast to the bow (two because we are cutter rigged ketch) and use the 3′ part of the tether to minimize fall distance. We actually have had very little reason to go forward as both the jib and staysail are roller furling systems. We have a jackline that runs the length of the main boom that keeps us centered when tying or untying reef points. And there is a jackline that runs from the foward end of the cockpit to the bow.
I do think use of netting, at least up forward, may help keep a flailing body aboard. We used netting during a six year, 42,000 mile circumnavigation as our 4 kids were ages 4 to 12 when we left. We always joked that by the time the kids did not need them Judy and I would. Turns out that is not a joke and I will put them on again before heading north this summer. If it saves one of us from going over board just once, just one tiny little time, they will have been worth it. BTW they did save a lot of bits and pieces of gear from going over board including one of our 20′ spinnaker poles that untied itself at night in a gale.
I am going to experiment with connecting a climbing harness to my lifejacket/harness as I find the attachment point of the lifejacket system too high in the event of a fall. Has anyone played around with this idea?