Snubbers and climbing rope

[Cliffhanger]

I think it is worth remembering that the snubber performs two functions. Firstly to take the load off the anchor winch. Locking or lashing the anchor chain forward of the winch does the same thing.

The second is to absorb and level out the dynamic loads that come as the boat moves around at anchor. This is where stretch is important. If you take a piece of low stretch Dyneema (HDMWPE) and a piece of climbing rope (PA) with the same SWL (strength) the Dyneema will break well before the climbing rope does when used as a snubber. This is because the stretch gives it more toughness (ability to absorb load) than Dyneema. Also worth remembering is that Nylon (PA) is very hygroscopic and strength and stiffness decreases while impact and toughness increase in proportion the moisture content. In other words, when wet, climbing rope gets stretchier and tougher.

[thinwater]

Although I have not found fatigue data for climbing rope. I did find several studies by researchers developing high fatigue life ropes, and they all centered on parallel core constructions, with separate subropes. As you can see from the data, the parallel subrope construction is far more fatigue resistant. You can also see that high loads were used, so the Ferrari argument does not seem to apply.

black is parallel, green is DB.



The primary up-side seems to be the lack of yarn-to-yarn friction. The trade off is chafe and splicing.


Not sayin' which I prefer or which is better, just sharing data.



This is mine. I'd love to see more.

[LongRange]

Originally Posted by thinwater

Regarding chafe, yes, we all agree.
Do you have any data that suggests climbing rope behaves differently than, say, 3-strand rope under sustained load?

I have no such data, but the burden of proof lies with those suggesting that climbing rope is significantly better, thus presumably justifying the four-fold premium over 3-strand. Testimonials are useful, but not as useful as scientific testing and deductive reasoning.

Originally Posted by thinwater

Remember, that snubbers are designed to primarily operate below 12% BS, the normal SWL of nylon. I have load cell data to confirm that, up to about 50 knots is semi-protected waters, this is true (if properly sized). ANY rope load beyond that will eventually fail due to fatigue. The 12% figure is from ABYC table AP-1 for double braid and 3-strand.

Climbing ropes are not designed to be used as snubbers. There is no such thing as a "SWL" for a climbing rope, and no "SWL" statistic appears anywhere in UIAA or manufacturers' ratings. The very notion of subjecting a climbing rope to heavy continuous load is anathema to climbers' self-preservation instincts.

Originally Posted by thinwater

I don't understand where you are coming from. It sounds like you are suggesting that climbing rope construction is, in some way, sacrificial. If this is the case, explain exactly how the construction differences would make it weaker under sustained load, why, and point us to some data. So far, the available data do not point that direction... other than chafe.

All loading progressively weakens rope and reduces its energy absorption capacity. Polymer molecules exhibit a delayed reaction to mechanical internal stresses, and after the stress is removed they do not revert back quite to the same state.

There is a classic paper on the UIAA site whose main concept is graphed more succinctly in an image I presented already:



It can be observed that a typical modern <10mm, <10 fall rope loses more than 50% of its impact absorption capacity before it has seen 50 pitches worth of climbing. By that definition a pitch 30m up (very few falls) with 30 down (abseiling). A <10mm climbing rope thus loses more than half its capacity to absorb energy by the time it has done 1.5km of abseiling and a ew lead falls. That is say 1.5km of abseiling, with 30 small <factor1 falls.

A 10ton boat will cause the rope to plunge beneath that 50% absorption value in less than a day.

[thinwater]

There is truth in the data you present, but it doesn't mean what you think it means. The worth of a theory is whether it can predict real world performance, and we're not seeing that. Thus, the theory is missing something.

a. I did supply data. Look up. Parallel core construction does not just equal braided construction performance, it considerably excedes it.

b. The SWL concept is well understood. You can Google this.

c. Your arguments related to drop testing remain off the point. That is like testing football pads in the same way you would test a ballistic vest, by firing a gun at it. Yes, rope degrade over time. So do 3-strand and braided ropes. What we are interested in are measured differences between rope types.

Your closing statement is based on a false comparison (climbing with sailing). It does not compare parallel to braid core construction. It does not relate in anyway to the actual load on the snubber; no data is given. Combined with the fact that numerous sailors have done just what you suggest with 20,000-pound boats for a year or more, I'm not feeling it.

Collect some fatigue data. Test a climbing rope snubber 40 feet long and see how long it lasts. Measure the tension (buy a load cell) before and after one day, correcting for the difference in wind load. I doubt you could measure the difference unless there was a major storm. I couldn't.

In fact, the climbing rope I used for snubber testing probably had more than 100 pitches of vertical rock and ice climbing on it before years of boat testing started, though few leader falls. It was about 10 years old, one of several ropes in regular use. I didn't use a new rope.


I do the testing, in the field, with load cells, because I want to measure reality, not guess.

[LongRange]

Originally Posted by thinwater

There is truth in the data you present, but it doesn't mean what you think it means. The worth of a theory is whether it can predict real world performance, and we're not seeing that. Thus, the theory is missing something.

a. I did supply data. Look up. Parallel core construction does not just equal braided construction performance, it considerably excedes it.

b. The SWL concept is well understood. You can Google this.

c. Your arguments related to drop testing remain off the point. That is like testing football pads in the same way you would test a ballistic vest, by firing a gun at it. Yes, rope degrade over time. So do 3-strand and braided ropes. What we are interested in are measured differences between rope types.

Your closing statement is based on a false comparison (climbing with sailing). It does not compare parallel to braid core construction. It does not relate in anyway to the actual load on the snubber; no data is given. Combined with the fact that numerous sailors have done just what you suggest with 20,000-pound boats for a year or more, I'm not feeling it.

Collect some fatigue data. Test a climbing rope snubber 40 feet long and see how long it lasts. Measure the tension (buy a load cell) before and after one day, correcting for the difference in wind load. I doubt you could measure the difference unless there was a major storm. I couldn't.

In fact, the climbing rope I used for snubber testing probably had more than 100 pitches of vertical rock and ice climbing on it before years of boat testing started, though few leader falls. It was about 10 years old, one of several ropes in regular use. I didn't use a new rope.


I do the testing, in the field, with load cells, because I want to measure reality, not guess.

Thanks for an interesting discussion.

I respectfully disagree that the information as presented justifies spending about four times more on a climbing rope that is only available in a comparatively narrow range of diameters, all of them too thin for snubber use on average-sized or bigger cruising boats, designed for a completely different purpose which certainly does not include a "SWL", and expensive precisely because of the lead-fall testing which you seemingly believe to be irrelevant.

To put it in context, I LOVE climbing rope. Climbing is as close as it gets to religion for me, and I probably have a kilometer of retired climbing rope. I wouldn't recommend buying the stuff for use on boats though. That's the "Ferrari pulling a caravan" thing.

[Psy at SEA]

Quite a technical discussion here...however my take on this:

• Climbing rope is designed for climbing.
• Mooring rope is designed for mooring.

I will preferably utilise multistrand nylon 1 3/4 - 2'' spliced to a chain snubber with thimbles and seized shackles

see:

https://www.youtube.com/watch?v=rYfoki6vW-M

[thinwater]

Originally Posted by LongRange

Thanks for an interesting discussion.

I respectfully disagree that the information as presented justifies spending about four times more on a climbing rope that is only available in a comparatively narrow range of diameters, all of them too thin for snubber use on average-sized or bigger cruising boats, designed for a completely different purpose which certainly does not include a "SWL", and expensive precisely because of the lead-fall testing which you seemingly believe to be irrelevant.

To put it in context, I LOVE climbing rope. Climbing is as close as it gets to religion for me, and I probably have a kilometer of retired climbing rope. I wouldn't recommend buying the stuff for use on boats though. That's the "Ferrari pulling a caravan" thing.

Personally, I believe, and can support, that 3-strand offers the best value for snubbers and anchor rope. As for the rest, I was simple providing correct data.


Since then I did some chafe testing (I've used the rig for a number of mag articles) to collect more data, and learned that the climbing rope I had was several times more abrasion resistant that the double braid I had. It turns out, and other published testing supports, that loose braids, suitable for splicing, are really quite poor for abrasion against rough surfaces. The fibers snag and cut. In fact, this is a considerable weakness of Amsteel for mooring lines; it resists abrasion well end to end, such as over a pulley, but not well at all side to side. This explains why failed spinnaker halyards are still common, unless the single braid is covered with a tightly woven abrasion cover. Webbing and tightly woven covers (climbing rope and also products like NER WR2 lifeline rope) fuzz and wear far more slowly. This is why chafe gear is always webbing. It's all about the weave, and standard double braid is optimized for splicing, not wear. Test it. [This will be published elsewhere.]

Just because a product is sold for a purpose, does not mean it is the best product. Take clothes line as an example; it's a good value, maybe, but it's not much. Just because something is expensive does not mean a sailor does not want it. Stainless anchors and chain come to mind. So whether some thing is "best at any price" is always a valid question. And maybe it is. So far no quantitative evidence has been presented that it is not.

Personally, my anchor rope is 3-strand and my last snubber was 3-strand, even though I have surplus climbing rope on the rack. I think grip when muddy is the main reason, for me. It is not a structural concern. I have used climbing rope for anchor rope and snubber line for years and structurally, it was unscathed.



As for the size question, climbing rope is well field proven to about 40-45 feet. Yup, that is a limit, but it covers a lot of people. Would I buy it for that purpose? No, not at full price. But I have a used boat. If I had a new carbon fiber speedster I'd have laminate sails, high mod running rigging, and climbing rope where that was best.

[Slovak]

Interesting information on rope construction and chafe Sail Delmarva: Chafe. Which Nylon Rope Weave Last Longest

[JimJohnston]

Originally Posted by thinwater

Personally, my anchor rope is 3-strand and my last snubber was 3-strand, even though I have surplus climbing rope on the rack.

Hi Thinwater. I've been following this thread and all the time thinking to myself "but these guys have a chain rode" and wondering how one goes about attaching a snubber to a rope rode which apparently is something that you do. May I ask how you do it?

As a secondary question, is not a snubber on a rope rode somewhat redundant?

Thanks for all the insight earlier presented.

[thinwater]

Originally Posted by JimJohnston

Hi Thinwater. I've been following this thread and all the time thinking to myself "but these guys have a chain rode" and wondering how one goes about attaching a snubber to a rope rode which apparently is something that you do. May I ask how you do it?

As a secondary question, is not a snubber on a rope rode somewhat redundant?

Thanks for all the insight earlier presented.

With a rope rode you do not need a snubber for shock absorption. The 3-strand rope will do that and is reasonably abrasion resistant. That said, there are the matters of chafe on the roller and bridles.


Multihulls use bridles. They sail all over the place without them and lie still with them. Perhaps the most common attachment is a prusik hitch, though a rolling hitch is common. For either, the attaching rope must be smaller than the main line but not slippery. Either Dyneema with a polyester cover or Dyneema/polyester blend. Dyneema climbing slings are good.


Some monos chafe. Either the bow roller is rough (fix it) or it sails at anchor too much (take the dinghy off the bow, use a V-riding sail, lift the rudder if applicable). I can make sense to rig a bridle for that reason.Again, a prusic hitch is good, as is a rolling hitch.


Note. Rolling hitches sometimes slide at high load, depending on the ropes. Many sailors have switched to either double rolling hitches or a camel hitch.


There's a good bit of anchoring stuff on my blog, below.

[pmagistro]

I've been following this with interest. I am a climber and a sailor, but a climber first. I climb for a living, as a mountain rescue professional. I have a god working knowledge of failure methods and appropriate loads for climbing ropes. And a growing understanding of those forces on a boat. I have a few thoughts to add to the discussion. I will try to minimize technical jargon but some will be required.

There are as many types of climbing rope as sailing ropes, but mainly we use two types of rope: "dynamic" ropes that generally elongate approximately 4-12% under the static load of an average human weight and elongate 30-40% under the dynamic loading that occurs when a climber falls, and low-elongation ropes (typically mistakenly referred to as "static") ropes that elongate 2-4% under any typical loads. Single dynamic ropes range from about 8.5mm at the low end to 11mm at the high end but are mostly around 9.5 or 9.8mm in diameter now. Static ropes are often 10 or 11mm in diameter. We use dynamics for leading, where a climber could fall, and statics for hauling loads on bigwalls, fixing lines to ascend later, and for rope rescue work. We generally worry about forces, measured in kilonewtons, rather than loads, measured in pounds. For the purpose of discussion we can approximate one kilonewton at 225lbs, however.

We don't generally worry about a breaking strength or SWL on climbing ropes. The rope is not the weak link, it is the human attached to it. The American Society of Civil Engineering states that the human body can take 6 kilonewton forces and still go to work the next day. So, in rope rescue (where we use large mechanical advantage systems to raise loads, usually a rescuer or two, patient, and litter and can create massive forces with enough haulers or by making a mistake and subjecting a package to a fall with acceleration) we try very hard to avoid forces larger than 6kn. (Which approximates to 1,350lbs.) Depending on who you learned from, there are various approaches in rescue but generally we built our systems with a large safety margin, often around 20kn for the system. Ropes are not the weak link, so I feel safe assuming that any modern climbing rope in good condition, dynamic or static, can likely accept a force of up to 20kn without breaking in the absence of chafe. Again, approximating 1kn at 225lbs, that's 4,500lbs.

Impact forces can be largely mitigated when using either dynamic or static climbing ropes by putting more rope in service, that is, a longer length to absorb a given impact. In other words, falling a bit further onto a longer strand or rope generally puts less force on the climber/rescuer than a short fall onto a short piece of rope.

The main issue related to climbing rope failure is when you combine dynamic loading with sharp edges. Ropes subject to a 4+kn load over a sharp edge fail in a type of chain reaction where a few fibers chafe through and spring back, releasing heat energy that melts the next fibers, which release their stored energy and so on until the rope parts. Search YouTube for Basecamp Innovations drop testing for more on this. In climbing or rescue, it is virtually impossible to create forces that can simply break a rope. Chafe/sharp edges and dynamic loading are the main issues.

How does this relate to use on a boat? Well, the forces are different. A 5 or 10 ton vessel sailing around on the anchor or bucking up and down on breaking waves in an stormy anchorage present a vastly different load profile than a 80kg climber falling 7 feet or whatever the scenario. Without putting load cells between the anchor chain and snubber, and the snubber and deck cleat, it is virtually impossible to know what those loads truly look like. The ABYC data shows that my 30 footer in a 60 knot wind will generate 2,800 lbs of load on the anchor rode. That falls well within the forces I would expect my climbing ropes to handle.

As to the question of elongation, dynamic kernmantle climbing ropes are wound and braided to stretch under dynamic loading. Continuous loading beyond the weight of a person or two isn't really a factor, and certainly could be on a boat at anchor in a big wind/sea....although the likelihood of most cruising boats being subjected to worst case scenarios is probably low, and some research (see link at end) shows that the ABYC data is dramatically conservative.

Ok, for those of you who stuck with me thus far, we'll leave the objective and move on to my opinions based on understanding the above. Without direct testing that is beyond my skill and experience, it is impossible for me to say definitively that climbing ropes are appropriate or superior for use as snubbers. That said, I feel strongly that for a sailing vessel of moderate size, say 30-40 feet, climbing rope would be perfectly appropriate for use as a snubber especially if those snubber are made long (30 or 50ft rather than 5 or 10ft) and protected adequately from sharp edges and chafe (by well rounded fairleads, not canvas or firehouse "chafe protection" that is, in my opinion, of dubious value except to pad a rough area, like a concrete dock). I think that either dynamic or static rope would provide similar benefits, that is, elongation to gently absorb and release impact forces.

In climbing, we tie in with one rope, or two in rope rescue or specialized situations, to minimize weight. Failure is catastrophic. On a boat, there is no reason not to use two snubbers or more. A concerned captain could conceivable run four or six or more snubbers to every available hard point on deck (mooring cleats, mods hip cleats, sheet winches, etc). While this would increase forces by reducing the amount elongation present, or would also spread those forces over more snubbers and hard points, which I think would improve survival of the system. In other words, failure of a single retired climbing rope snubber wouldn't result in the immediate death of everyone aboard, but rather a challenge for the captain and crew who I would expect to be awake and alert in the type of situation that could result in such a failure.

I use retired 8.4mm climbing rope to tow my dinghy, and as tethers for our PFD/harnesses. I currently use a nylon/chain combo rode (for the elongation advantages of nylon) but will likely be adding an all chain option to the boat and intend to use retired climbing ropes as snubbers. I will use two 30-50 foot snubbers of retired 9.8mm dynamic or 10mm static (as that is what I have access to). If we get into a major blow, I'll consider running additional snubbers as conditions warrant.

Climbers are conservative in general and retire ropes from lead climbing typically well before they are damaged beyond use for a boat. Also, climbers need continuous 60+meter strands of rope in excellent condition . We frequently retire ropes with damage at the ends only, or at a specific point (a "core-shot"), leaving behind many meters of perfectly fine rope that can't be used for climbing, but are only 10 or 20 or 30 meters in length. Those retired ropes get woven into rope rugs, used for projects around the house, or go into the trash.

If you go on the Mountain Project forum (climbing equivalent to Cruisers Forum) and post a request for retired rope, explain your purpose and that life is not on the line, I bet there are hordes of folks who would happily unload miles of useable nylon rope to sailors for the cost of shipping plus a few bucks for their trouble.

Finally, I came across this article which is very detailed but seems to support my argument:

http://northpacificresearch.com/down...d_revealed.pdf


Happy sailing!
Phil

[thinwater]

^^ great post.

Regarding anchor loads, I have spent many hours with a load cell, as have others, some included in the article you liked to. With a rope rode or a long snubber, the load is about 3-5 times less than the ABYC Table 1, which assumes all-chain and shallow water. In fact, the ABYC numbers are correct in a worst case situation (all chain, not much out, strong wind, steep chop)--I've seen numbers that high.

You are right about the limited effectiveness of chafe gear at very high load. It is only a patch and it was good to hear someone else say it. In fact, I have melted chafe gear to climbing rope during drop tests. A well-rounded bend is better, and the smaller the angle of the bend is better.


Most of my ropes have been retired due to localized damage near the end, where a rope either dropped into a crack during a fall or was kicked by a crampon. Once or twice you just trim the rope, but soon it is too short.

[nhschneider]

We use a bridle made of 18mm 3-strand nylon with stainless steel thimbles spliced into one end and eye splices into the other end. I recently replaced the chafe guard, using fire hose material which I stitched into place with a heavy whipping twine. We were anchored off of the southern Baja California coast in some northerly winds of about 25 knots and the rope bridle stretched so much that stitching that held the chafe gear in place snapped on each side of the bridle (the chafe guard remains in place as it’s secured still on one end). The bridle is almost 4 years old and has seen hundreds of days in use.

Fair winds and calm seas.

[JimJohnston]

Originally Posted by thinwater

With a rope rode you do not need a snubber for shock absorption. The 3-strand rope will do that and is reasonably abrasion resistant. That said, there are the matters of chafe on the roller and bridles.


Multihulls use bridles. They sail all over the place without them and lie still with them. Perhaps the most common attachment is a prusik hitch, though a rolling hitch is common. For either, the attaching rope must be smaller than the main line but not slippery. Either Dyneema with a polyester cover or Dyneema/polyester blend. Dyneema climbing slings are good.


Some monos chafe. Either the bow roller is rough (fix it) or it sails at anchor too much (take the dinghy off the bow, use a V-riding sail, lift the rudder if applicable). I can make sense to rig a bridle for that reason.Again, a prusic hitch is good, as is a rolling hitch.


Note. Rolling hitches sometimes slide at high load, depending on the ropes. Many sailors have switched to either double rolling hitches or a camel hitch.


There's a good bit of anchoring stuff on my blog, below.

Thanks for this. A youtube video demonstrates how to tie the prusic hitch which I did not know about until now. And I've also believed that an all rope rode works well on its own, but I nevertheless will consider a bridle this summer, using a prusic hitch. cheers

[NorthCoastJoe]

Climbing rope strands are twisted and straighten out to provide the energy absorbing. Rescue rope is the same materials but the strands are not twisted and provide no give.
I have used old climbing rope for directing the fall large of trees with a 4000 pound tractor on one end. They stretch like crazy and don't break. Sounds like a good use for a retired climbing rope.