Often I post just to help order my thoughts. Some comments are posted and some come by e-mail and are not posted. They all help.
I've posted on tethers many times, always with caveat that my views were catamaran-specific. Now I have begun with actual drop testing, with an eye towards a published article, and solutions must be more universal. Or at least we need solutions for all boats and all uses.
A few of my notes. Scary if you can read them.
The crux is figuring out where sailors actually fall.
The bow, catamaran. On a cat the bow is wide and you should be on the windward jackline, even if it is long. If very rough and I need to lean out to add something to a clew, I've been known to clip both the leeward jackline with the short tether and something else with the windward line (the windward line will not allow me to lean out). If you do happen to go over, there is no bow wave trying to suck you under and drown you; the hulls are too fine for that. Upwind, waves can come over and wash you around, but a tight line to the weather jackline manages that, and falling on a tramp doesn't hurt. Getting thrown forward is the greater risk, as the boat stuffs a wave and slows suddenly; the cure is to terminate the jacklines some distance aft of the bow, just as they terminate forward of the transom. A clipping point in the center of the tramp is often handy, as many cats lack a forward lifeline, and on many boats the lacings are strong enough and serve very well. Lacking that, adding several strong sewn points 3-5 feet aft of the forestay can be logical and simple. Because the tethers are long, stretch is needed to reduce impacts, but only when clipped to a hard point; jacklines provide cushion. Falling off the weather side is managed by running the jacklines well inboard--we've got wide decks.
Getting lifted off the deck is also a problem. Catamarans commonly experience negative Gs up front, and the best answer is to have a jackline you can pull up against, keeping the feet on the deck. Again, the jackline should be well inboard, since the lift can throw you to windward or leeward. Again, a hard point on the tramp near the forestay is handy; when kneeling near the forestay it is common to float upwards. For the longer tether leg, shock absorption is nice; I've been thrown 12 feet before, airborne from the cabin roof, landing on the tramp. Between the give of the tramp, tether, and jacklines, not a bruise.
Clip toe rails from underneath--clipping from above can torque the carabiner.
Catamaran, aft. The risk here is simply falling off the back, and stumbling cause by a cat's quick motion. Since the tether is clipped to a hard point, there is no shock absorption, and the tethers are long. Getting swept by away by a wave is a minor risk on most cats; forward, yes, but not in the cockpit, not ever. The boats move over and away from waves. However, tethers are needed when working outside and aft.
Look at the corrosion in the stanchion socket.
Monohull, bow. The scary fall is to leeward, under the bow wave. Folks have drown there. And thus, a quick release is required, something of much less interest to a cat sailor. The answer there is a short working tether to a fixed point to weather, and a secure grip. It gets skinny up there, something cat sailors don't face.
Monohull, aft. All documented tether failures have been in the cockpit. The helmsman was stuck by a wave, thrown the width of the cockpit, and lacking any shock absorption (clipped to hard point by a static tether), overloaded the system. Broken ribs and other injuries due to tether impact forces were involved. There are 2 answers to this problem: clip short and use a dynamic tether.
Short, working tethers are important, particularly for boats racing in extreme conditions. Very few falls are documented while people are moving; they are holding on. It is when they get to the work station, take their hands off the rails and focus on the task, that they get thrown. Thus, there should be a good anchor for every station, located such that the sailor cannot get thrown. On boats prone to stuffing the bow--some cats and some sport boats--a tether from behind may be prudent.The new AC cup boats have a tether requirement, specifically
directed at stuffing a bow when bearing off. Keeping sailors on-station can prevent a capsize, since they can still do their job. The personal tether must have a short leg, or a fixed tether can be provided at each station.
Dynamic tethers are another part of the answer. ISO standards now required a drop test that should create nearly unbreakable tethers, but they may break the sailor in the process (unlike climbing drop tests, they did not specify a maximum impact force). I'm still using 8mm dynamic rope tethers, which are considerable lower in impact and tougher (can absorb more impact) than ISO tethers, but they have one drawback; the rope can roll under foot. I would love to find a webbing with required stretch properties, but I'm not certain it exists; the weave may prevent that.
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There are other issues.
The best quick release.
The quick releases must be accessible when the PFD is inflated (most are not).
Harness design. The ergonomics are terrible, but there is no practical test method, and short of a full body harness, no good way to transfer the load to a body without damage.
Where you you park the spare tether leg clip when not in use? Don't clip it to your harness, or you will have no release. But most tethers provide no alternative. My advice is to add something.
Folks don't like tethers, particularly if there is crew on board. But is the crew skilled enough to get the chute down and get back to you? Hmmm.
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So what are your MOB concerns? Where can you take a hard fall on your boat? What have you witnessed or read of? We need data to design solutions.
Yes, I am cheap. As much as I would love to lavish buckets of money on my sailing habit, there are 401-Ks, college funds, boat payments.... More to the point, I hate throwing money at West Marine or Lay Line for things that are not so well engineered and for things that are not inherently "marine" in nature. Climbing gear is an example: sailors know sailing, climbers know falling.
Example: a few years ago special rope-handling gloves for climbers became the rage. All sorts of designs came out, none as good as sailing gloves. Eventually, the designs morphed into re-branded sailing gloves, which had already been perfected. Example: a few years ago the marine outfitters all began selling climbing-style seat harnesses for work in the rigging. Harken rep at the Annapolis Boat Show had the cheek to tell me that they had engineered in additional abrasion protection, as though the deck non-skid was more abrasive than a granite boulder! They are easily twice the price of a top-quality big wall harness sold for rock climbing.
So often vendors pretended they've had invented something new, while simply marking-up something that has been perfected in a different application over many years. In the case of climbing gear, UIAA standards set the bar for all of the fall protection standards that followed:
Recently the sailing industry has started to catch-up, though only a few short years ago they were woefully behind, yet still charging premium prices.Safety at Sea Harness and Tether Testing
Finally, a few more relevant standards, for those who crave detail. and back-up documentation:
The point is this; much of the BEST equipment for jackline and harness systems is available from rock climbing equipment sources, not marine stores. The history is longer and and the QC is better. It's not all about price.
Multihull vs. Monohull Caveat: all of my comments are directed towards families with 27- to 40-foot cruising catamarans. I'm staying with what I know. Specifically regarding jacklines, some of what I will say is all wrong for other boats. You have been warned. Marine vs. Climbing gear Caveat: Not all climbing gear is appropriate in a marine environment. Not all marine gear is suitable for crew retention. This may be a matter of function or materials of construction. For example, rock climbing seat harnesses are not designed to serve as deck harnesses and are dangerous for that purpose (they'll drown you, dragging through the water), and conventional solid gate climbing carabiners are not corrosion resistant and will seize after repeated exposure to salt water. Some climbing gear--slings, wire gate carabiners, bolt hangers--is of superior design for either environment. We'll try to keep the distinction clear. Crewed Boat vs. Single Handing Caveat. If you are single handing in anything other than warm inshore waters, assume getting separated from the boat is certain death. Keep your tethers very short and don't plan to release under any foreseeable circumstance. If you are on a crewed boat in moderate conditions, you may want to release if you are dragged, may use a longer tether, and may do without a tether entirely. A PFD alone may be safer. But as night falls, the water temperature drops, and conditions become wild, even crewed sailors may feel falling in is a death sentence. So we must realize there are a continuum of situations and more than one right answer. Personal Testing Caveat. I have tested all of the theories presented here, either rock climbing or on the water. Be very careful if you take this approach. Personal Responsibility Caveat. My blog, my rant. I deviate from the conventional wisdom here and there, with reasoning that satisfies me. I have very extensive experience climbing and mountaineering, am very comfortable on-deck, and am very comfortable with this style equipment. But ANY equipment can be misused, and I've seen very good quality marine safety equipment rigged in an unsafe manner. Just because you bought the best from a catalog doesn't mean you know how to apply it. Read everything, learn the engineering, visualize the forces involved, and be careful. Capsize Caveat. A tether on a sailing dingy or beach cat would deserve a Darwin Award. What about a sport boat driven hard or a high performance multi-hull driven to the limit? Certainly a high priority needs to be placed on releaseablity. But be warned, recent testing suggests not all quick-release attachments work under load and that some are not accessible once PFD inflates. Practical SailorMagazine is investigating this one. For cruisers, I think this is minor concern.
Jacklines. On monohulls, where these must lay on the deck, webbing is the most popular choice since it won't roll underfoot. If that is where the lines must run, then there is little choice in the matter. However, in many ways webbing is exactly the wrong material.
Durability. Any outdoor rock climber has seen many examples of webbing that have been left on a cliff somewhere to back-up a rappel anchor; after 15 years of sun exposure, they can often be removed with a good yank, their strength reduced from over 4,000 pounds to a few hundred pounds. The general consensus is that blue tubular webbing looses about 15% of its strength per year in continuous exposure in temperate latitudes, and that lighter colors weaken more quickly. Rope is a far more durable material, since there is more thickness for the UV to penetrate. Numerous long term endurance tests have been performed on braid and core ropes; generally at least 55% of the strength of the line derives from the core, and even after 10 years of use and 10 years of sun exposure, at least 60% of the strength remains. Good Old Boat and Practical Sailor have both done this sort of testing on old docklines. Still, I wouldn't push it beyond 5 years in a safety-sensitive application.
Ease of clipping. Webbing can be fussy, hanging up on the gate when I least want it to. Rope is lightening fast, particularly when paired with climbing carabiners.
Hand hold. Webbing is poor by comparison.
I use jacklines as a single hander because I don't like the idea of my boat sailing to England on autopilot. A PFD is not going to bring help and I'm not sufficiently optimistic to think help will find me. In cold weather a PFD is little help unless someone actually sees you enter the water.
I don't understand the habit of rigging jacklines only when needed. "When needed" is pretty often:
When you go on deck alone, at night outside of the cockpit.
When the wind is over 15 knots.
When a thunderstorm blows up.
When something needs repair in an awkward position while underway.
When the chute is up.
In other words, nearly every day when cruising. Jacklines should be permanent, like seatbelts, and rope jacklines can be set permanently, like the rest of the boat's rigging. They should not be a temporary measure or an afterthought; they should be a designed part of the boat suitable for everyday use without getting in the way. You need to practice with them.
Once I watched a video of an ocean racing boat losing a man overboard (he was recovered, with some difficulty). It wasn't very rough; he simply was less than mindful of the action around him, was not clipped in, and simply slid across the cockpit and between the life lines (the center line had been removed in the quest to save weight). The main reason people don't clip in, right behind not taking the dangers seriously, is that it's a hindrance. That may have been a factor. Like many racing boats the cockpit was a cluttered mess of ropes and the jackline went over and under the many control lines. The jackline and tethers were a safety after thought, not a reality that the boat or sailing practices were designed around or a reality that the sailors trained with. Removing the center lifeline was just plain stupid. If you're going to use jacklines and tethers on your boat you need to practice with them, day after day, integrating them into the flow of lines and work so they are NOT a hindrance but rather a useful part of the rigging. Climbers are tied in all the time, and we spend years working out systems and routines that prevent us from getting caught up in our knitting.
Spare Halyard as Jackline--Don't Do It. I have heard of a spare halyard being used as a tether in fair weather only; nothing to add, nothing to trip over, and easy to get back on deck. I tried it. If there is enough slack in the halyard to reach the bow sitting down, then when standing on the cabin top there is enough slack to wrap the halyard around the spreaders. In a monohull, you will swing out over the water and drag until the boat tacks. This system is unsafe.
Location. Multihulls have a huge advantage when setting jacklines; they have a wide bow area. A common rational for having very tight jacklines is that the working area at the bow goes to zero and the sailor must to be held very tight to stay on the boat. He is safe from excessive jackline impact forces because he is not going to fall/slide far enough to generate them. Multihulls also have a disadvantage in that there is a lot more deck to cover, and that means longer tethers. Longer tethers mean longer falls and more fall energy. A tether of adjustable length, with multiple clipping points or 2 legs, is required. Mine have 2 clipping points: one very long where I can reach everything from either jackline, and one much shorter. I use the former in fair weather (when the only risk is tripping over my own feet) and the latter when it's nasty. both options are long enough to be remain clipped to the jacklines while re-entering the cockpit.
Even with adjustable tethers, this additional beam means the multi-hull sailor must design for greater impact energy.
The jackline in the photo is not rod-tight, though there is less slack than it appears. It can be moved about 12-inches side-to-side. They are 5/8-inch dock line and will retain sufficient strength through 5 years of continuous exposure. They are not underfoot and they can be clipped from the cockpit.
My jacklines are attached to the inboard edge of the tramp about 4 feet back from the beam, and to through-bolted hand holds on the hard top. The front beam could hold any load. I am certain the hard-top supports would distort at peak load, but not fail completely. This compromise makes sense to us, as it places the jackline in a safer position; we recognize this. The jacklines run above the deck, serving as a second railing, and we use these and the life lines as twin railings when going forward.; if you pull upwards against them, rather than lean on them, they add much stability. They are not under foot on the side decks as you walk around the side of the cabin. The side decks are also free of genoa tracks and sheets; these are farther aft, in a non-traffic area. Each boat will present its own challenges and solutions, so don't feel tied to convention. Experiment, but think it through from an engineer's view point. Do be certain that all attachments are through-bolted. Lifeline stanchions, for example, are too often only screwed into a rotted wooden block. Two 5/16-inch bolts or a single 3/8-inch bolt with a good backing are a conservative design basis to achieve 5,000-pound strength in shear (assuming a 1/4-inch solid glass deck--with cores or thinner decks consideration must be given to compression and shear).
Be certain the tethers will not allow a fallen sailor near a prop, a deadly hazard on any boat with a transom mounted outboard. This is not an issue on the PDQ because the engines are well forward and inboard, but it was a serious concern on any boat with a transom mounted outboard.
Be certain the tethers do not allow the sailor to go out of reach of the transom. Self rescue will be impossible. Better, see if you can go over the side, and if you can, see that you can get back on board with the boat moving.On boats with high freeboard, it is generally impossible, even for a fit individual.
A center jackline is another option; I've seen this on a Gemini and it looked practical. On one hand it would be impossible to fall over the side, but on the other, there is less security against being washed to leeward when on the windward side. I do not believe it is as safe on a monohull, which leans. Although there is a new fad, suggesting lifelines should be run down the middle, I have not heard any stories of folks falling of the boat uphill, to windward. It just doesn't happen. A windward jackline is safer because you are farther from the leeward rail. Just make sure you work from the windward line as much as possible.
Children. This generation grows up being belted into a car and wearing bike helmets. My daughter grew up, starting when she was crawling, wearing a harness and tether on-board. She liked it, and Daddy led by example. I much prefer tethers to PFDs for kids. They get more freedom, and Dad doesn't have a stroke every time a little one leans near the edge, gazing at the waves, or stumbles near an edge. Harnesses are much cooler on hot days--when it's 100F and humid, requiring a PFD means staying home. A parental eye is still required, and the harness must be fit so securely that Houdini couldn't escape. Yes, the law requires PFDs for small children. We very seldom did--they are so uncomfortable for small one--but we used the harness every time. However,harnesses often require some customization; this harness had an extra webbing adjustment added in the back, as the original design was insecure on a small child.
Shock Absorption. Rock climbers rely on both climbing rope stretch to prevent a very short fall from generating impact loads well into the thousands of pounds. The body can absorb only so much, and the anchor points can only withstand so much. I once had this conversation with the gentleman who was fitting tight stainless steel cable jacklines to his 45-foot yacht, in preparation for a trip to Bermuda. I explained to him that because his cables were strung guitar string tight, it would take only a modest force to pull the anchors right out of the deck. He assured me that all components could take a 5,000-pound strain. I asked him, would he mind if I gave the cable a good strong yank, just with my hands, as a test. He said "knock yourself out--don't hurt yourself. Those fittings can hold a car." I wrapped a rag around my hand, gave a sharp tug, and snapped the 1/4-inch high-strength shackle holding the cable to the aft pad eye. He couldn't decide whether to be mad at me or embarrassed. I apologized anyway, but for a few dollars it was a cheap lesson. He grumbled something about "defective parts." (The 1/4" shackle had a rated breaking strain of 4,400 pounds and a SWL of 1,450 pounds, I was told. After muttering something about "defective equipment" he replaced the 1/4-inch shackle and turnbuckle with a high tech lashing. I'm still not sure he got the point, since the entire system had been strained to the very limit by a weakling.)
A jackline should never be made from material with no stretch (OK monohull guys--breath deep. This is catamaran advice, and the rules are a bit different. The jacklines are inboard and there is no skinny bow.). A jackline should never be rigged absolutely tight. Think of it this way; a jackline is like a tight rope, and the less deflection that is permitted the greater the initial tension of the rope must be. If only a 5% deflection is achieved, then the applied force is multiplied by about 10 times. You can slice the data many ways with engineering calculations (Sample Calculations for Jacklines); it becomes clear that 200-pound sailor that is propelled across the deck by a breaking wave or loses his balance falling off a wave in just the right way will cross the deck at a modest running speed. His body must have at least 2 feet to decelerate or the stress on the jackline will exceed 5,000 pounds and something will break. That stretch must come from the jackline or from a special shock absorbing tether. Not one of those self-retracting tethers sold at the marine store with a shock cord down the middle and not one of the new tethers with an over-stress indicator; a tether designed with sacrificial stitching for use in climbing or the construction trade. These sacrificial tethers were invented by rock climbers (see Yates Ice Screamer to the left above) and grafted into the construction trade. Most of these begin absorbing force in the 400-800 pound range and extend several feet when fully expended; about right for this application. I wouldn't be at all surprised to see marine tethers adopting this feature in a few more seasons, implying through advertising literature that it's a new invention and not just a new application. The new marine tethers have one row of expendable stitching that indicates over stress but does nothing to reduce the stress. A poor and confusing design choice, in the eyes of OSHA and the climbing community. Rather like closing the barn door after the horses have left; "Oh, see here, your harness nearly failed", rather than preventing the failure.
The longer the jackline, the less stretch is needed, the short the the line the more stretch is needed, within limits. A steel cable or even polyester braid, if employed as a rock climbing rope, would be fatal to the climber; the impact force is too great. A bungee cord would be fatal too; the excessive stretch increases the probability of a ground or ledge fall. For the sailor, the strain on the jackline system must be kept below 5,000 pounds. The strain on the tether must stay below 1,000 pounds to achieve that, which indicates a side deflection of 2-3 feet, which equates to a stretch of about 2-3% at 5,000 pounds of strain. This rules out wire and most high-tech lines if they are conservatively sized. 1/2-inch polyester yacht braid seems about right for catamarans with 30-foot long jacklines. 7/16-inch line would be strong enough, but the extra size allows for aging losses and reduces is stretch into the optimum range. Mine are 1/2-inch nylon dock line and are only 22 feet long--it's what I had on-hand and the math works out the same. Given their size, they will be safe for 7-8 years or until they chafe. For jacklines 40-50 feet long, the math changes and high tech lines should be spot-on with regard to stretch, but the strength requirement goes up to 7,000 to 9,000 pounds. Amazing, but easy to achieve with the new materials. The range of calculated answers is broad, because of difference in geometries. One size never seems to fit all. I suggest you have an engineer friend take a look at your arraignment with these shock absorption concepts in mind.
Tethers--Construction.Why webbing instead of rope? Rope tethers look a lot like running rigging. Webbing is less prone to rolling under foot. Unlike the jacklines, it won't likely be in the sun enough for UV damage to matter. This is the conventional choice.
Don't use Spectra webbing for tethers; it has too little stretch. Yes, climbers use it for anchors but NEVER where it will be required to absorb the energy of a fall without some rope in the system for cushioning. Used as a cockpit tether, it would be equivalent to steel cable and would damage either the anchor or the sailor. Nylon webbing tethers have a small amount of give.
If you opt for 2-leg tethers--and you should--the lengths should suit your boat. The standard 3'/6' split is really too long for most boats. I use 2' for the short tether (including carabiners), which suits work at the bow and on the side decks, and 8' for the long tether (catamarans have broad bows).
We pre-rig tethers to each side, clipped port and starboard. Thus, if we need to go forward quickly and even if we have tacked since the last tether use, there is always a tether rigged on the required side. As I have stated earlier, we leave the tethers clipped to the jackline when we come off the deck. I should clarify that I very seldom harness in the cockpit; ours is very deep, is surrounded by hard-top supports an winches, and falling out would be very nearly impossible. Consider your individual situation.
What about climbing rope for tethers? In fact, that is my preferred solution, as the shock absorption is much have discussed this at length. However, the downsides are that knotted tethers are bulky and sewing climbing rope is only properly done by people that specialize in climbing rope. It is easy to do wrong. I tested many samples of my work.
The best option is to buy a 2-leg tether from Kong. The price is reasonable, the Tango clips are the best available, the long leg is elasticized, and the price is not much more than the hardware bought separately.
Tethers--Length and Getting Back On-board. In the best of all worlds tether length and jackline position are such that falling off is not possible. That must be addressed on a boat-by-boat basis due to geometry differences. Often having 2 length options on a tether will help. But let's assume for the moment you can fall over.
Can you get back aboard? With a full crew, someone may be able to man-haul you aboard. Let's disregard that option for the typical cruising family; they lack the horsepower, depending on who went over. There is always the option of cranking them up with the spinnaker halyard. Again, not dependable with a family crew. Not enough hands and not enough horsepower.
I suggest trying to reboard without assistance, with you crew slowly motoring ahead. Don't strain yourself either; this must be easy or it will not work if you are injured or unconscious. Gently--there is no point in risking injury--lower yourself easily over the side and see what works. It will be very difficult. Realistically, the victim is likely to be Dad, as he goes forward to wrestle with the jib in terrible conditions. Poor old Dad. Logically, the answer is to combine this with your MOB hoisting practice, as we have. Fun on a hot day. After this sobering exercise you will probably shorten your tethers.
Tethers--2 Legs are Better Than One. For most boats tethers really need to be adjustable in length; a short leg for the bow and getting past the cabin trunk, and a longer length for use around the mast, and in the case of catamarans, on the foredeck. Being able to clip two points, so that you never unhook, can also be vital. My two-leg tethers are described here.
Carabiners. Wire gate aluminum carabiners hold up very well, and the anodized ones do best. Conventional climbing carabiners rapidly seize-up due to corrosion--avoid them. Locking carabiners must be religiously lubricated or they will also freeze up, though I have had good luck with screw gate locking biners on the jackline end--I am very careful to keep them greased several times each year. Even if they only last 4-8 seasons--I retire them to other uses if there are any signs of wear--I prefer them as they are much cheaper and three times lighter than their stainless steel cousins, which means they are easy on the gel coat. I prefer non-auto-locking biners; those are sometimes fussy and occationally fail to lock in ice climbing and dusty climbing environments. However, many have reported that they are very happy with auto-locking biners on jacklines if kept lubricated. Locking biners are required on the jackline or u-bolt end since there are many obstructions that can force the gate open and un-clip the biner.
The Kong Tango is a popular tether carabiner, suitable for either the harness or jackline end. However, they do require seasonal lubrication.
The text below is from the ISO standard. All conventional (non-locking) carabiners will fail this test. Why is this not deadly to rock climbers? They do not go in circles around the anchors. The weight of the rope generally holds the biner in a fixed orientation. They clip either to runners (short slings) or purpose-designed bolt hangers that resist this action. And they use locking carabiners where there is some risk or redundancy is lacking.
5.4 Accidental hook opening testing
5.4.1 The tendency of the hook to accidentally become detached from its attachment point shall be tested using the following three styles of attachment point, made from 8 mm diameter rod: a) a straight rod; b) an eye bolt of internal radius 10 mm; c) U-bolts of internal radius 15 mm and 20 mm.
5.4.2 Move the hook by hand as far as is possible in the following directions with the attachment point mounted vertically: a) move forward and backward, right and left without any rotation, movement being in the horizontal plane; b) rotate in the horizontal plane by up to 360° using the attachment point as the axis, rotating both clockwise and anticlockwise; c) rotate in the vertical plane by up to 360° about the axis of the hook, rotating both clockwise and anticlockwise; d) rotate in the vertical plane by up to 360° about an axis running through the attachment point, rotating both clockwise and anticlockwise.
The hook fails the test if it releases from the attachment point. If the hook closure mechanism is shown to open but not release, this will also constitute a failure, as release would probably occur with geometry of different dimensions.
No hook will fail a test on an attachment point where its use is clearly and permanently warned against in accordance with 6 g).
Not Spinlock Race Tethers. They can rotate off a U-bolt ...
.. Or if pressed against a railing.
This is not so clear on the harness end, so I formerly used ordinary wire gate biners there, though now I use the Kong Tango and like it better. There, I've said it, counter to the "new" conventional wisdom that spinnaker shackles should be used on the harness end so that a sailor can free himself in the event of a roll-over or knock down. I don't care for spinnaker shackles--I've seen too many spinnakers fly away when the lanyard hooked on something or because the locking pin was not fully inserted. My thoughts:
I am not concerned about a carabiner unclipping from a harness; in 25 years of climbing, I never heard of it. Unclip from fixed anchors, certainly, but not from the harness end. However, we have switched to the Kong Tango carabiners, for a little added security.
I can clip a conventional biner 100 times, in the dark hanging from a cliff, with gloves on, and never get it wrong; I've done it. Same with the Tango. I'm sure I can't get a spinnaker shackle right 100 times in a row on a nice day on a bouncing foredeck; I've done that too and seen a few sails kite away.
Clipping a wire gate or Tango carabiner is a one-hand job. A spinnaker shackle takes 2 hands.
I believe the chance of a capsize on a cruising cat, compared to a knock down on a monohull is much lower. Possible, but remote compared to all other risks.
I have a great deal of confidence that I can un-hook a conventional biner under load in adverse circumstances; after 30 years of climbing, I am very familiar with the tricks and don't have to think about them. I've unclipped while being dragged beside the boat at 5 knots; not easy, but it took only seconds. I am not prone to panic. Better than risking accidental release.
Most sailors leave the harness end clipped and unclip the jackline end off when going below. We do the opposite; the harness end is clipped off and the tether remains in place on the jackline for the next user. Otherwise, the sailor would have to go on-deck to clip in. For our boat configuration, this is safer and more convenient. It is also a reason why a carabiner works for us at the harness end. The jackline end is ALWAYS a locking biner.
It has been suggested that a sailor should always carry a sheath knife to cut a tether loose. My personal guess is that I am more likely to inadvertently stab myself than to benefit from the knife's close proximity. My choice. I do keep a folding knife in my pocket and there is always a knife at the helm.
What does the ISAF have to say about carabiners? "Warning: it is possible for a for a plain snap hook to disengage from a u-bolt if the hook is rotated under load at right angles to the axis of the u-bolt. For this reason the use of snaphooks with positive locking devises is strongly recommended." Very true. In fact, even a locking carabiner or snap hook will fail at a small fraction of its rated strength in that circumstance, since the gate is intended to retain the rope but not to carry cross-loading strain. I have seen gates collapse under little more than body weight. Rock climbers discovered this in the late 40s and it became common practice to connect to fixed points with a flexible sling. If you are going to attach to a fixed point, consider extending the hard point with a short strong sling, allowing the carabiner to ride away from the deck and hardware. In fact, this is much easier to arrange at the mast, helm, or bow pulpit, as often no new hardware is required; only a strong loop, easily rigged and easily removed.
On the other hand, this from a sailor with releasable snap shackles on his tether: "The replacement tether I bought from West Marine (ISAF Specification Safety Tether, No. 9553504) has a new toggle on the snap-shackle release lanyard that consists of an open triangle of plastic.This is dangerous, in my opinion! In my first few hours of using the new tether, in moderate sea conditions, I managed to
snag the triangular loop on something and release the snap shackle. I am now replacing all triangular loop pulls with bead pulls that I have crafted myself."
This is apparently the reason West Marine now uses the Kong Tango carabiner. I suspect we are going to see a general move away from spinnaker shackles on tethers. We'll see. Everything is a compromise.
There is also this counter point, from Andrew evans, one of the world's most expereinced singlehanders, excerpted from his free on-line book on singlehanding:
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Some boaters insist on locking carabiners. I have no problem with this concept as long as they can be quickly and easily fastened and unfastened blindly with one hand. In nine years of running all over my boat dragging my tether, I have never had a carabiner detach from the jack lines or my harness, so I don’t feel that a locking mechanism is necessary. I have heard of situations where the jack line runs parallel to a sheet and the carabiner runs onto the sheet. My suggestion is to move the jack line to a new position where this can not happen. Some races insist on a quick release mechanism for the clip. I disagree with this concept. First, I have never seen a quick release mechanism that can be easily fastened with one hand. If this can’t be done, it won’t be used for the reasons mentioned above. Second, I can not imagine the circumstances were I would want to be detached from the boat. Even if I am thrown overboard and dragging injured beside the boat, this is a much better situation than watching the boat sail away. I can see the safety advantage of a quick release on a crewed boat, but not singlehanding. The tether must be long enough so that the skipper can move from rail to rail without unclipping during normal tacking or gybing. After a tack, it will be necessary to unclip from the leeward jack line and clip to the windward jack line in order to walk up the windward side of the boat.
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And thus, even with ISAF, the carabiner at the harness end is not required to be locking. Locking is a very good idea--I like the Kong Tango--but it remains a choice. At the jackline or u-bolt end, I repeat, a locking biner is required by rule, experience, and common sense.
I have heard it suggested that aluminum carabiners are subject to cracking if dropped. There is some minor truth in that, but the caution applies to drops from great heights onto rocks. I've abused biners of many designs on weekly climbing trips, some for 30 years. Two have been retired due to hairline cracks in the gate mechanism; it was a design error that was retired 25 years ago. However, I did pull one of the cracked biners to destruction on a test rig, just to see; it made it to 3,800 pounds. There are no rocks to drop them against on your boat.
Never use a non-locking carabiner as a shackle substitute up in the rigging, for example as a halyard shackle. You'll be hating life when it clips on to the upper shrouds and won't come down! I didn't do it, but I heard the swearing from down the dock. They are nice for hoisting the dingy, securing the boom, and a host of minor conveniences.
Seat Harnesses. For use on deck, climbing seat harnesses are completely inappropriate; in the water they will hold your head under, whereas a chest harness will hold your head-up... sort of. For use up the mast, big wall seat harnesses are best. They were designed for days spent on the big vertical walls in Yosemite. Yates Mountaineering makes some of the best. A few minutes or an hour up the mast is a piece of cake. The so-called "marine" versions and "riggers" harnesses are just watered down wall harnesses. Also, a harness should fit the individual just as a shoe fits the foot. Go to a store and try the harness on. Any good climbing store will have a rope that you can hang from for a little while, so your backside can tell you how it fits and your legs can try to go to sleep. Important cautions, marked on the harness:
The accessory loops on the waist belt are for hanging tools, NOT attaching safety lines.
Buckling the waist correctly is VERY important; 20 years ago I watched a teenager fall out of a harness from 200 feet up and land 30 feet from me, all because the belt was not buckled properly. It must be snug to the smallest part of the waste in such a way that it cannot be pulled down in the event of an inverted fall. The webbing must double back through the buckle in the require manner and have a minimum free tail length, typically 3 inches (6 inches is better, in case you gain weight or are wearing more clothes).
Chest Harness Fit. I see many worn low and loose at the lower edge of the rib cage. I see this on round-the-world race sailors, but that doesn't make them right, not in this one case. Does it feel safer, like a life jacket? I think so, and it makes it easier to move and more comfortable with foul weather gear. I understand. Still, it's enough to make a climber cringe. Climbers have been killed that way, back in the days when climbers wore chest harnesses. Falls caused a broken ribs and the sharp ends punctured lungs. They need to be worn up higher, nearer the arm pits and certainly above the edge of the ribs. It's likely that if I were sailing the southern oceans for weeks, showered in near-freezing water I would change my tune. I would be a world class sailor and very confident of my abilities. I also have done a good bit of easier (for me) rock and ice climbing without a rope, because it was faster, because it was safe enough for me, and for the thrill of it. That doesn't make it smart; it is a poor habit that experienced climbers can get away with, and it sets a terrible example for new comers.
This poses a challenge for women, something learned as my daughter grew. A full vest of some sort would help, but that is impractical in warm weather and not comfortable the rest. It seems all that can be done if to watch tether length and to wear the harness as high as possible. After I took the above photos I realized the problem and made some adjustments to the fit.
Slings. A staple of the rock climber's anchor inventory, these are sewn loops of various high-tech materials, ranging in length from 6 inches to 48 inches. They can be used for everything from sail tack extensions, to anchors for securing yourself while working at the masthead, to secondary anchor attachment points (prusik hitch them to the rode, and clip the secondary rode to that--it makes untangling after tide swings easier. A hundred uses that you will only discover over time and perhaps by reading a book on rock climbing. Cheap compared to "marine" alternatives and very strong.
Acmeclimbing - Stainless Bolt Hanger
I'm not generally suggesting these for direct jackline attachments; they present a cutting hazard to webbing (sharp edge--attach the jackline using a shackle or other smooth hardware). On our boat, they work well for cabin-top attachments. Not for use as cockpit tether anchors: they are designed to take load in one direction and parallel to the surface; cockpit tether loads are more variable. Any application would need to considered the above factors.
Some Thoughts from Charles Kanter. A guru of catamaran sailing. Jack Lines. We seem to agree on most everything, for catamarans, except my desire to keep jacklines rigged at all times. He too promotes inboard lines using dockline. I guess we've kicked the same rocks.
I hope you have enjoyed my ramblings; they were just a few ideas I wanted to share. I've been involved in roped climbing and mountaineering for over 30 years, been on thousands of routes all over the country on both rock and ice, and fallen on a rope thousands of times. I have tested my ideas and never had a major gear failure. In other words, I have had gear failures and learned from them, and always had backup systems in place that were adequate. Just as every sailor should be a solid swimmer, I believe every sailor should learn the basics of climbing and fall protection in order to understand the systems involved. I have not provided that knowledge here. Take a class - you may like it enough to give up sailing. Think of all the money you'll save.
There's nothing like a nice frosty icefall! Sizing-up a New Hampshire waterfall a few years ago.
Via ferrata trails, literally iron ways in Italian, are climbing trails equipped with rungs and safety wires that allow fit but unskilled personnel to move quickly and safely over difficult terrain. Though they date back into the 19th century, they are best know from their use during World War I, moving troops through the mountains. Since then they have expanded to thousands of tourist routes in Europe and the United States. Since tether technology is the focus of this post, I'll leave history research to the reader; the internet is great for that.
The climber is protected falling all the way by a pair of tethers that follow a safety wire to the side of the rungs. Periodically, the wire is fixed to the face, and this is the challenge; these points are generally 10-20 feet apart, allowing for serious falls before the tether takes, and requiring the tether to absorb a great amount of energy, more than a dynamic rope alone can handle. Dynamic ropes are rated for a fall factor of 1.8, whereas a via ferrata fall can be fall factor 5 or more.
The solution is a more extensive energy absorption system, including either friction through an aluminum plate or a tear-type energy absorber, like a Screamer.
Why wouldn't these make useful sailing tethers?
The allowable impact force is much greater, since the load is taken on a seat harness rather than a chest harness; the human tail can take a lot more force than the ribs. Sailors need a softer catch.
The falls are really much greater. A sailor will never see an impact beyond fall factor 1; the ISO drop testing required by the ISAF rules is based on a FF1 with a 100Kg mass.
The end clips on via ferrata tethers are applicable and gaining popularity. The West Marine tethers are now Kong Tango via ferrata biners (pictured on tethers to right), and I like them very much. Fast on and off, one-handed even when cold and wet, locking, light, and fit over most handrails too. Because they are aluminum, they do require periodic lube and rinse. Mine have held up very well, like new after 2 seasons.
Harness attachment. Sailors like a quick release on the tether, something that can be removed under load. Climbers opt for a locking biner, since no possibility of accidental release is acceptable. Most often the tether is cow-hitched to the harness.
Length. Sailors like dual lengths (2-3 feet and 4-8 feet) while climbers are restricted to 2 matching arm's length tethers; they never want the clip to move out of reach (if it snags below you this is a real drag).
Certainly there are some ideas here, some worth adapting, but the application is different.
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Note on recalls. Because of the extreme nature of the falls and untrained nature of many users, there is some history of failures, most often fatal. In general, the causes have been:
Fall too great. Anything of 10 feet is trouble and over 15 feet is beyond the equipment rating. The via ferrata trails generally recognize this, placing tie points ever 10-15 feet, but risk is often part of climbing; if it looks too scary, go down.
Worn friction rope. Some designs rely on a rope slipping through a plate with many holes. If the rope wears through use--tour groups use them daily--the rope slides more easily and insufficient energy is absorbed. This type has gone out of production because they are too difficult to inspect.
Poor or worn stitching, or any other construction fault, though this type of failure can result from too long a fall.
ALL via ferrata falls are bad, far more dangerous than falls on a climbing rope. They feel safer but are not. The impact forces are high and there is much to hit on the way down.
Stitched Splice Warning. Based on limited testing we have found that nylon rope is much different to sew than polyester rope. Because of the extreme elongation prior to break, the stitching at the tail must carry nearly all of the load, while the stitching near the throat carries no load. It is rather like tug-of-war with a bungee cord; only the 2 men nearest the center can do any work. Because of this difficulty, I strongly suggest all dynamic tethers be knotted rather than sewn. Climbing ropes have very high knot strength and are drop-tested with a figure-8 to attach the mass. A double overhand noose has also been drop tested.
[Since this article I switched to a webbing retracting Proline tether by Wichard. I don't like the clips quite as well as the Kong Tangos, but once you get used to them they are very good. The webbing has a bit more stretch than the prior polyester webbing and can pass the ISO drop test, but with a terrible jolt. After 5 years, the elastic is about shot, so the long tether droops dangerously. It has a quick release on the harness end, but I have mixed feeling about something that can release when I don't want it to. This winter I will either buy a new tether or build a new dynamic tether with Kong Tangos on for all three clips (On my F-24 we detatch the rope end as well, rather than leaving the tethers on the jacklines.]
This subject is a little too esoteric--for most sailors--and so magazines aren't much interested. Fatalities due
to tethers breaking are rare. On the other hand, bruised ribs and back injuries are more common, but wrongly accepted as a part of rough weather sailing. However, if we simply apply what we know from climbing about falling--lots or real world experience and lots of lab testing--it just doesn't need to be that way. Let's see if I can sweep away a few bits of conventional wisdom that are just plain wrong. Though you may never sail the Sydney/Hobart, capsize your boat and test the limits of the human body, routine bumps against tethers don't need to hurt either. We can make our sailing experience more comfortable and safer at the same time. My tethers don't hurt.
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Dynamic tethers spliced from 8mm ice climbing rope. Knots would serve just as well. 10mm climbing rope works, but it is heavier and a little rolly if you step on it.
I started my investigation into soft tethers and impact forces years ago, but honestly, my boat is not the ideal
test bed; catamarans don't heel, I don't sail in big waves, and I'm not as willing to risk physical trauma as I used to be. I hold on and I don't fall. However, I've let myself slam into tethers intentionally a few times, just for testing, and I'm not happy with the current state of design. My back is too old.
Let's step back for a moment, before we charge forward, and state the limits of our investigation. We're not discussing jackline and energy absorption. I've covered that before and common experience indicates that a jackline will absorb enough energy to safely slow the sailor. I am discussing only the case of a sailor clipped to a rigid point.
While the Screamer/webbing combination is a huge safety improvement over the typical non-elastic tether, it is really engineered for a different purpose; to catch severe impacts in a survivable way for climbers and workers wearing hip or full body harnesses. Sailors, on the other hand, have a chest harness, which is lousy at distributing force. The screamer is just too hard.
A little backyard testing
I do NOT suggest this as you can easily hurt your spine. I've climbed enough to know what I was getting into.
Anchor one end of the tether to an immovable object, in this case a large tree wrapped with non-stretch line.
Create several tethers, 6 feet long from test materials: 1-inch nylon webbing, 1-inch webbing with Yates screamer, 10.4 mm dynamic rope (UIAA single), 8.2 mm dynamic rope (UIAA double).
With increasing amounts of slack in the line, run at the end of the tether as hard as you can back first.
Results:
1-nylon webbing with Screamer. A very tough stop. With about 3 feet of slack I was able to just get the Screamer to trigger and it hurt. My back will complain for a few days. 10.4 mm rope. Firm stop. I didn't go further than 4 feet, not wanting injury. I'm sure I could have run from 6 feet with no harm, though it would be a jolt. 8.2 mm rope. Even at 6 feet and with a sore back, the stop was practically fun. It might take you off your feet, but was no harder than hitting a well padded couch. At 2-3 feet it was only amusing, with about 1-foot of stretch. 1/4-inch Amsteel. I was smart enough not to try. It would be worse than webbing without a Screamer.
General Observation. I wear my harness high, nearly in the armpits and definitely on my lats. If the harness had been worn lower, where catalogs show them or where combo PFDs fit, I would have injured my ribs. Whiplash is also a problem. Wearing a harness down near the solar plexus and lower ribs, where so many are located, is plainly dangerous.
In the end, only the 8.2 mm rope felt good, thought the 10.4 mm was livable.
Data and Calculation
Is it strong enough? 8.2 mm line is not 5000-pound rated, but as we will see, it is far tougher (can absorb more energy) than 1-inch webbing.
What do we know from laboratory and real-world fall data? For new products....
Webbing tethers are just adequate: They occasionally fail at
forces near 4000 pounds. Rare, but we can use that as a design point.
1-inch
webbing can just manage a 6-foot fall with a 185-pound rigid mass; this
is generally considered as equivalent to a 200-pound person, since the
harness and body absorb some energy by deforming (data from DMM, a climbing equipment manufacturer).
10.4 mm UIAA single rope can manage more than 10 falls from nearly twice this distance.
8.2 mm UIAA double rope can manage more than 10 falls from nearly twice this distance with a 242 pound rigid mass (261-pound person) using 2 strands.
8.2 mm UIAA double rope can manage more than 10 falls from 6 feet with a 242 pound rigid mass (261-pound person) using 1 strand. Thus, it is more than 50% tougher than 1-inch webbing.
8.2 mm UIAA double rope can manage one fall from nearly twice this distance feet with a 242 pound rigid mass (261-pound person) using 1 strand. Again, it is more than 50% tougher than 1-inch webbing.
1/4-inch Amsteel is the worst material that could be used. While strong, its energy absorption capability is negligible. Its only advantage over chain or cable is light weight.
I created data using well-used products. Why used? Because they will become so, obviously. Less documentable and less repeatable by others--science is all about reproducible results, be they real-world or not--but ultimately more practical.
Percent Elongation (left) vs. Pounds Stress, pounds (bottom)
Webbing is 3-5 times stiffer than dynamic rope. Amsteel is very stiff.
I took the samples and pull tested them up to 2500 pounds; I didn't feel like destroying my tether just yet. I used on-line data to extrapolate out to the breaking point of each material. In dynamic situation, the breaking strength and the elongation to break is typically 30% less and energy absorption about 3 times less, but for blog post purposes, the above data at least allows comparison on an equal basis.
What matters is the area under the curve.
Static Energy Absorption, 6-foot tether, ft-pounds (left) vs. Stress, pounds (bottom)
Static calculated energy values are greater than fall values for 3 reasons:
Ropes are tested with figure-8 knot, weakening rope by ~ 40%.
Dynamic testing does not allow for heat dissipation and reorientation of fibers.
Dynamic ropes survive 8-12 falls, the webbing only 1 fall in our test data. Dyneema survived zero test falls.
Dynamic Energy Absorption, 6-tether, ft-pounds (left) vs. Stress, pounds (bottom)
At lower stress, 8.2 mm rope absorbs more energy for a given impact force, but eventually 10.4 mm rope has greater capacity. Both dynamic ropes have greater energy storage capacity than webbing. 8.2 mm rope is more than twice as tough as 1-inch webbing.
Both this data and UIAA drop data thus confirm the following:
11mm rope can absorb many fall factor 2 drops.
8.2 mm rope can absorb 1 fall factor 2 drop.
1" webbing can absorb 1 fall factor 1 drop.
What happens in a 6-foot test fall?
1-inch webbing: At 4000 pounds impact, 1100 ft-pounds energy. We know from fall testing, however, that 1-inch webbing can only absorb about 1100 ft-pounds (sometimes passes, sometimes fails), so we will use 1100 ft-pounds as the design point.
10.4 mm rope: If we accept the design point only 1100 ft-pounds of energy, impact force is about 1400 pounds. New rope fall data indicated significantly less.
8.2 mm rope: If we accept the design point only 1100 ft-pounds of energy, impact force is about 1100 pounds. New rope fall data indicated significantly less.
1/4-inch Amsteel: Only 236 ft-pounds of energy were absorbed by the point 5000 pounds of stress were reached, and only 677 ft-pounds of energy were absorbed at the break strength of 8600 pounds. Amsteel will kill the sailor and pull the harness apart before surviving a 6-foot fall. This has been duplicated in real-world fall testing with spectra products; Dyneema is worse.
If we limit the fall to something more reasonable--a 2-foot fall is similar to wave strike and 6 knot stumble, and more severe than my backyard testing--the energy for me is only165# x 2' = 330 ft-pounds, which can be absorbed by a 500-pound impact; you'll feel it but not get bruises. With a webbing lanyard it would be 3 times that pressure and you will be injured. A Screamer will trigger but not be fully spent (though they are single-use).
How much energy can a Screamer absorb? About 270 foot-pounds according to several testing sources, or about 25% of a 6-foot fall; in combination with the stretch of the webbing, enough to reduce the impact force below 2000 pounds. And then you bottom out and the force goes up, though less so.
Other Factors. Does the extra stretch bother you? Probably personal. Is stepping on rope a greater hazard than webbing? For 8.2 mm rope, not much, but on a monohull (sloping decks) that may be more of an issue. Construction? Either knots (testing assumed figure-8 knots) or sewn eyes are practical.
A critical biometric factor, not easily relayed by a machine or simple data, is that a force that comes on gradually (the dynamic rope) allows the muscles time to tighten and resist. A sudden 500-pound kick before a screamer gives is painful and damaging, like a blindside blow, even at the same force level. You truly feel the difference.
Dynamic rope or a screamer--The best solution? For smaller, more routine falls on the deck, the rope is
kinder. For that once in 100 sailors' lifetimes, torn from the cockpit by a rogue wave impact, the screamer/webbing combination is competitive, though the climbing rope tethers are still survivable without serious harness impact injury; both could have impact forces of 1000-1500 pounds depending on the force of the wave, and it would hurt, but not break ribs or vertebrate. A climbing rope, even 8.2 mm, has greater energy absorption capacity than a webbing/Screamer combination. Thus few climbers use Screamers, but they ALL use dynamic ropes.
The only disadvantage of rope over webbing is the potential for rolling under foot. A dynamic webbing would be nice, but I could not find any. On a catamaran this is a limited problem (level decks), and the roll-under-foot potential is reduced by the small size of 8.2 mm line (5/16-inch).
What have I done? I've switched to 8.2 mm dynamic tethers. It is kinder on the back for minor falls and even over the edge. It is lighter than the webbing/Screamer combination and easier to hold on to.
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Where to get limited quantities of dynamic (climbing) rope? MEC sells both single and half rope off spools, by the foot. Half Rope, Single Rope.
The old conventional wisdom was windward and leeward lines, in as far as the cabin and shrouds would allow. Now the new mantra is centerline, and that anything else is unsafe and the user uninformed. They blithely ignore facts suggest something different:
You can't slide uphill.
Every case of injury by dragging along side was to leeward. They were caught in the bow wave.
It is farther to leeward if the jackline is to windward.
Waves and gusts come from windward.
The new internet forum wisdom feels more like group think than change based in evidence and experience. By all means move the jacklines in as far as practical, but I believe the physics of falling limit windward overboard incidents. If you know of a documented case, please comment.
[note: The Cal June Jim Buoy model 9225 harness that I am wearing does not pass ISAF or ISO standards and I am not recommending it.It is lightweight, comfortable, and I believe that it is adequate with the shock absorbing tethers that I use. The failures occurred at forces 3 to 4 times greater than my engineering design allows.]
7-24-2024. I have long since replaced this with a better harness, but still home-made (I have experience fabricating rock climbing gear--don't try this at home. The reasons I fabricated my own are:
Wider chest band. Testing suggested that anything less than 3 inches is asking for a rib injury.
Fleece lining.Much more comfortable if wearing a thin shirt or no shirt.
Easier on-off. The new harness closes with a non-load bearing 1.5 inch Fastex buckle. The closure is maintained in use by the tether clip.
Non-adjustable for lightweight and simplicity. One for summer, one for winter, to allow for layers.
For me, windward lines and short tethers are the best bet. And my boat doesn't even lean!
Quick Release vs. Locking Carabiner at Chest End of Tether
As a single hander, I'm fairly certain that cutting myself free is seldom better.
Cold water. Today, for example, I was sailing on the Chesapeake with 34F water temperatures. I did not see a single boat over a 4 hour period. Unless we all take to wearing drysuits, the only ending is slowly freezing in your PFD.
Accidental opening. Ever have a spinnaker shackle release unexpectedly? Granted, it was generally because the shackle was not closed properly, but that is only proof accidents happen. A locking biner is more secure.
Offshore. Same as cold water. Yeah, someone could be coming for you. Probably not.
I don't fancy the idea of dragging, so I keep my tether short when near the rail, and crawl when I need to.
Not a screw-lock on the tether end (Kong Tango). That would be silly.
rev. 7-24-2024. I now have tethers with snap shackles on the harness end and tethers with a Kong Tango. I feel like the snap shackle makes sense in-shore and if the water is warm or I am wearing a dry suit. Swimming is better than dragging. But I still feel it is situation specific and that US Sailing is wrong (require snap shackles) and World Sailing is right (leaves the choice to the user). For example, if I were single handing across and ocean , I still don't see how releasing is going to be much better, and I still feel that accidental release is the greater risk.
As for multihulls, just keep the jacklines well in the from the edge. You've got lots of room. Also, because multihulls can stuff and stop fast, terminated the jacklines 4-5 feet back from the front edge of the tramp.
Rev.1-2-2014 (Since the original post we have moved to dynamic rope tethers (softer catch), but I have left this as there is still good information and it is still valid. However, in reviewing a number of accidents, where multiple impacts would have been poorly served by a single use energy absorber, I now recommend dynamic materials [elastic, like climbing rope].)
As an experiment, hang in your safety harness for 1 minute. Go on. We'll wait for you.
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Hurt pretty good after a few minutes, didn't it? Imagine falling a few feet on a 6-foot tether with no real shock absorption. The impact would over 10 Gs, or over 10 times what you experienced just hanging there. The maximum, in lab testing, is over 20 Gs. Can you feel you ribs cracking and spine shattering? Of course, this is an exaggeration of anything likely to happen on a boat. How far can you fall? Over the railing, of course. But there will also be some attenuation as the lifeline stretches and stanchions bend. The length of the fall will be lengthened about 2 feet (1 foot of give). YOu probably didn't really fall 6 feet; the jackline is inboard and if you fall more than 5 feet you'll hit water, depending on whether you went head or feet first. It.s going to hurt, but the actuall fall distance is only 4 feet and the was ~ 2 feet of breaking. The harness impact should be perhaps 3 Gs. Survivable with bruising, and probably no the worst case scenario. Thrown from the cockpit. There have been a few cases where a sailor was washed out of the cockpit, the tether broke, and the sailor lost. How could the impact force have reached 4000-5000 pounds? Lets assume the sailor was thrown at 19 feet per second-- 11 knots, a good wave strike, only a fast jogging pace. He is clipped to a hard point--no give-- so the only attenuation will be the tether stretch, plus the wave is still pushing. In the case of the above 6-foot fall the time is about 0.61 seconds and the final velocity is 19 ft/second. Ouch.
It will save me a lot of typing if you visit this post about fall energy first. The long and the short of it is that falls on jacklines are less severe because the jackline stretches and the sailor also slides along during the line. Falls against a fixed anchor point are brutal. This is where we take up the thread.
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I've made some effort to research sailing chest harnesses and injuries, with very little luck. Clearly, if a sailor takes a 4,000 to 5,000-pound hit in the ribs there will be serious injuries; OSHA and military studies support this. Yet, because of the circumstances of these accidents, the actual injuries are usually unknown. The sailor is lost. Other times there are injuries, but the assumption--right or wrong--is that the sailor hit something, other than the end of his leash.
The harness or tether is typically blamed, though there are 2 falsies in this logic: the harness should never have seen a 5,000-pound load because there should have been shock absorption in the system; the sailor would have very likely died from his injuries anyway.
"A lesson in harness and tether construction can be learned from Tami Ashcraft, who along with a sailor friend was making a sailboat delivery to Hawaii when they ran into a powerful storm. Ashcraft was knocked unconscious. When she came to more than 24 hours later, she climbed to the cockpit where a single tether dangled over the side. The D-ring had snapped where it was connected to her friend's PFD. He was gone. Ashcraft was convinced a round ring might have held, like those on Mustang vests." Ashcroft, in my opinion, was wrong in her conclusions.
1998 Sydney-Hobart Race Accident. Glyn Charles was never found, after his tether parted. But the force of dragging his body through the water could not have generated that kind of force, only a sudden impact. The inquest stated that he was attached to a "fixed point" and thus would not have benefited from jack line shock absorption. The lanyard may have also been defective, though I can't locate the testing information. http://www.parliament.nsw.gov.au/Prod/parlment/hansart.nsf/V3Key/LA20010307027. http://www.telegraph.co.uk/sport/othersports/snooker/2994528/Yachting-Charles-died-after-safety-harness-failed.html.
(I now believe dynamic tethers make more sense, in terms of energy absorption and multiple impacts. It seems that several or even most of the fatal MOBs that were related to tether failure involved multiple high impacts, and this need would be poorly served by a single use devise such as a Screamer. I have left this article as food for thought, but please refer to this more resent post for more up-to-date information.)
And this leads to a very interesting conclusion: the shock absorption device (Screamer) doesn't really need to be on the the tether, it could be on the u-bolt. It is the fixed-point anchor that is the hazard. If the sailor is on the jackline, the system will stretch and slide and nothing will break. Some sailors have expressed concern about the elongation of the Screamer on-deck, and this removes that concern. No one wants more clutter on the tether. Up front, the real hazard is being dragged in the water, as many have said. Only if the sailor is attached to a u-bolt in the cockpit is the impact force extreme! Thus, if we clip Screamers only to the cockpit u-bolts, the force is absorbed where it needs to be and no new hardware needs to be invented! While this adds a little cockpit clutter, it could save lives very cheaply. In fact, the mere presence of shock absorbers on construction lanyards has been credited with safer work practices, as it reminds the workers of the incredible forces involved. The presence of Screamers in the cockpit might even encourage sailors to shorten their tethers.
Well, at least that's one possible answer, something very simple that would only need be deployed in extreme conditions. This is much how climbers originally use Screamers; other applications came later.
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So I made up some new tethers a few weeks ago, for my own use on a catamaran. These are my best yet, and I like them both, though for reasons I will explain below--multihull reasons--I like the one on the left better. They both have features I like, though they will not be for everyone. (I have since switched to dynamic tethers.)
Knots instead of sewn loops. I'm still playing with the lengths and years of climbing experience tell us that the knots are not a real risk. But years of climbing, industrial and marine experience also tell us that sewn joints are stronger, reliable, and durable. They would be sewn if I were not still experimenting. (These knots weaken the webbing about 30%). Tails must be 3 inches and knots must be tightened by bouncing on them with body weight to prevent loosening or slippage--standard climbing practice.)
Attaching the snap to the center of a 2-leg tether with a larks head is quite convenient. It is a simple matter to adjust the legs without re-sewing or re-tying the ends. The larks head will not slip appreciably during a fall and could also be secured with a lashing, though that is not needed. This also simplifies the construction if sewn and probably results in very little net loss over time; several fewer joins, it can be moved if worn, and there is no UV vulnerable stitching. It also takes the load equally well from either leg or from end-to-end.
We like screw gate biners on the jackline because we do not often unhook from the jacklines. They are light and snag-free. We unhook from the harness end. This is because we have a deep center cockpit and never harness in the cockpit. If you clip on-and-off the jackline, the Kong Tango is a better choice.
Rope jacklines. Rope is stronger and withstands UV better than webbing. It offers controlled stretch, absorbing fall energy. It gives a better hand grip and clips more easily. On the down side, it can be mistaken for running rigging; on our boat this is no problem because of location and because we leave the jackline end attached. It is worse underfoot, rolling and making for poor footing; ours are not under foot because they are run on the cabin roof--cats are wide. If I had a monohull I would still strive to get the jacklines up against the cabin trunck and out from under foot. I might be forced to use webbing, which I would replace frequently (6-months?) and not like. I believe jacklines and harnesses are for everyday use, that practice with equipment breeds competence, and that rigging jacklines only when "needed" is a big mistake. Even more than reefing too late, who wants to be rigging jacklines too late, in a thunderstorm or at dusk? On a narrower boat, non-stretch rope is required.
Quick release on harness end. We don't, since getting washed off a cruising cat by a wave is very unlikely and capsize even less so. We prefer the security of a locking biner and the Tango is a quick-open compromise. However, there have been a number of drownings of sailors dragged by tethers or on boats that capsized; monohull, sport boat, and performance catamaran sailors should have quick release snaps at the harness end. However, be warned that most tether quick releases have failed in testing and in the real world to release under load . Test by hanging before you buy! Practical Sailor is investigating this issue. If your boat can capsize or is narrow and washing off a possibility, use a quick-release shackle.
One leg vs. two. Vital, as most boats need a short leg on the side decks and at the bow, and a longer leg around the mast. Though I played with 2 versions for some years (the conventional 2-leg version; a 1-leg version with an intermediate clipping eye at about 65% length) we have settled on the 2-leg version as handier. Do NOT clip the unused leg to you harness; clip it to the eye below the harness shackle. In the event of a capsize you will find that releasing the harness tether has left you clipped to the boat via the unused leg!
Shock absorption: Screamer. Notice the Screamer at the harness end. A simple $18.00 gadget that ensures the impact force cannot pass 600 pounds. I've broken ribs snowboarding and don't fancy doing it again. Climbers have been using these for many years, and ALL industrial and military tethers use them. Because they are easily replaceable (larks head to the 2-leg tether and overhand loop on the end of the 1-leg tether), triggering one is a minor expense (they are still full strength after triggering but will no longer absorb impact). I thought about only using the Screamers on the fixed-point anchors, but decided a fall over the side could be rough for me and that they were not in the way. This feature is NOT yet commercially available, though prototypes are being field tested.
Shock absorption: Dynamic Rope. 8-10 mm dynamic rope is another excellent option. Read this later post. The advantage of dynamic rope is that it can withstand multiple impacts.
Fit to boat. I think it is a mistake that all tethers are 6 feet or 3-6 feet; there are sound engineering reasons why falls over 6-feet are very serious, but honestly, boats are not one size. Most boats should have a short leg less than 3 feet. Multihulls need more than 6 feet to work effectively on the tramp. This is one reason I make my own. If you feel the need to modify your tether lengths, just be careful. This post may help.
There does seem to be one potential weakness to having shock absorption installed in the tether; when it triggers the entire tether must be replaced. With a commercial tether, this will be about $200.00. There are 2 things I've asked the manufactures to consider:
The Screamer section should be replaceable. Then it is only a $20.00 fuse.
If the Screamer is non-replaceable, it must be protected from wear with a single bar tack. I have already learned that repeated non-critical impacts tend to loosen the stitching. This is not a safety concern, but in heavy duty use (Volvo?) it will reduce the effective life.
If this is something you would like to see on the market, call Yates and ask for them! They've built prototypes, but demand is required for an idea to make it to market.
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Another option is making the tether from a more dynamic material, such as nylon dock line or climbing rope. Let's consider climbing rope. A single rope meeting UIAA standards cannot have an impact force of greater than 1650 pounds (187-pound climber), while a typical modern rope gives a fall factor 1 impact force of more like 1000 pounds. These ropes are rated for twice this fall distance. How does this compare to the Screamer? The elongation is similar; about 2 -2.5 feet. The peak impact force is about double because the Screamer gives steady braking instead of graduated braking. The climbing rope gives lighter weight and greater simplicity.
