Who Needs a Snubber, Anyway?

[Dockhead]

Originally Posted by sy_gilana

To answer Dockhead. I don't. Never have, never will, never had a problem. I will continue snubberless as long as I am sailing because that's the way I learned it on ships, and thats the way I have been doing it for, oh, 6000+ nights on anchor.

I have had my chain snatch up bar tight, and don't want it ever to happen again. It could wreak massive destruction with the snatch loads.

But it takes pretty strong conditions if I have a reasonable amount of chain out -- something like F7 and a bit of fetch.

So although I have been mostly snubberless for the last couple of years, I do certainly put it on if there seems to me to be any risk at all of something blowing up overnight.

I think the weight of the chain makes a very large difference in this. My previous boat with 8mm chain would snatch and bang terribly in even moderate conditions -- I would never anchor without a snubber in that. But with 12mm chain weighing 330kg/100m -- it does a really good job even in pretty brisk conditions. I'm sure that's why ships don't use snubbers.

[TheThunderbird]

@seehag

[TheThunderbird]

@seehag
When it comes to Alaskan hardships, i would not consider the actual size of your boat the main factor... this is ti say that a 22kg, or even a 55# thing, sounds like a toy for me, sorry.

Sicily offers deep anchoring sites too, around vulcanoes..

I had a main CQR of 75# with 230' of 7/16" (10mm) chain.

I spliced in 180' of 12 strand 7/8" rope line, and ordered a 100# Manson supreme (the maker claims it equal to a 120# CQR)

Btw, scope is less relevant, as far as you anchor in deeper waters

PS i keep 3 anchors on deck, two astern, one is spare, another for a light achoring in calm seas (bathing)

[thinwater]

Originally Posted by evm1024

..., Climbing ropes are designed to have individual fibers break as they absorb the energy of a fall. This is done to limit the impact force that the climber (faller?) is subject to. No need to break the climbers hips.

As such climbing ropes are rated in the number of falls they take before being retired. 4 to 8 is a normal range of falls. After that number of falls the ropes ability to limit the impact force is decreased with the UIAA tests actually showing the rope breaking.

The stretch comes from different construction methods and nothing in the above paragraphs makes any sense nor has any basis in fact. Additionally, I would add that a number of cruisers have sailed half way around the world with climbing rope snubbers. They last just fine.

Climbing ropes do have somewhat less abrasion resistance than marine ropes, but they hardly designed for a gentle environment. They are also less UV resistant.

[thinwater]

Originally Posted by seahag

I'm wondering if anyone has more information about anchoring in deeper water. In Peter Smith's nice essay he bordered on it, though the first graph regarding deep water was something like 30 feet. In Alaska where we cruise, there is no anchoring in 30 feet. We typically are setting anchor in 80-120 feet of water. It is so very different--we almost never have 3:1 scope out, and we get hammered by katabatic winds often, some with gusts up to 100 mph but MANY hitting 60. 40 MPH is possible on practically any night without warning. Our tides vary from significant (12+ feet) to Enormous, but we avoid anchoring in really big tidal areas and don't generally anchor in areas of much current. Many days we have unavoidable swells from exposure to the Gulf of Alaska, which can be pretty massive, and the holding ground is quite often very rocky.

With all of that, we have dragged twice in the last two seasons. The first was a brutal Katabatic wind that first blew a large fishing vessel past us, then a smaller sailboat. We held for another hour but when the wind hit (I am guessing 75 mph, possibly more, I was in the cabin) we started to take off. The second time was different. We were anchored facing the ocean swell in lighter winds but in the night, a powerful wind shifted to the opposite direction, coming down off of a glacier and ripping across about a mile of fetch, and blowing from different points on the bow, giving us a really unsteady and constantly changing angle to the wind and the waves as we sailed, pulling repeatedly on the anchor rode in a more jerky fashion.

During all this, our rode consisted of 125 feet of chain, backed by 200 feet of 3 strand nylon with a 22KG Bruce anchor. This year we switched to a 55 lb Mantus and have noticed a difference with no dragging and it gives us a feeling of confidence.

Since our windlass setup is really a pain in the butt to use with the nylon (I have to feed it foot by foot as it comes through the windlass into the locker or it binds up due to some missing parts on the windlass) I have been considering going with all chain, as I'm not too concerned about adding the weight of another say hundred feet of chain to the bow in this case.

When we bought the anchor I had intended that, so we ordered a 25' snubber from Mantus which is still in the bag because we've never been in shallow enough water to use it with our chain setup.

Alternatively, we have an extra length of 150' of the nylon line we could add to what is on there now. In either case, I would be concerned about the connection--I am just "okay" with my splicing skills and when I've done three stand splicing, I have had decent results and can make it look "okay" but not professional. That concerns me. I have also read on this forum about a particular chain splicing bit that is far and away the best (chain is 5/16") but I don't recall what that type was.

Anyone with some advice especially tied in with real deep water anchoring experience that could help with some further direction would get my sincere appreciation as to me, the shallow water anchoring most people are doing does not really seem congruent to what we experience here.

Thanks!

First, lets introduce some numbers.

Catenary. An on-line catenary calulator will let you figure out when the cable is getting straight.Cable Sag Error (Catenary Curve Effect) Calculator

Wind load. Our boats should have similar wind load (32' catamaran). I have measured this at lower speeds and estimate 425 pounds at 40 knots and 885 pounds at 60 knots.

Force to lift chain off the bottom. While the chain does not need to be right on the bottom, a 3:1 scope is not going to hold either. At about 600 pounds the angle will be similar to 7:1 scope in shallow water in very high winds. Of course, this is a static figure, and it will drop in the lulls and rise in the gusts.

Energy absorption. While I am strongly in favor of snubbers for shallow water, with that much chain out, the chain is going to absorb as much energy as the snubber can. Snatching tight, unless exposed to waves, is pretty unlikely. This is why folks have different experiences and can both be right. I would run a snubber anyway, if I was on all chain. Some of those winds are extreme.

For me, the greater concern at very short scope is lifting the chain. Thus you add rope, and thus your concern about the splice. If you were using 1/4" high tensile chain you would probably need to use an irony spice to get 1/2" rope to feed through the windlass, but with 5/16 chain and 1/2-inch rope, a conventional backsplice should do. If you can make an eye splice you can do this, and pretty does not really matter that much, so long as you taper (the line always breaks at the start of the taper).

IF you decide to use 5/8-inch rope, you will need the irony splice. Brian Toss has instructions in his book. Figure on making 2-3 and cutting them off before you get one you like. But you can do it. It isn't looks so much as even tension on the strands going through the link.

[evm1024]

Originally Posted by thinwater

The stretch comes from different construction methods and nothing in the above paragraphs makes any sense nor has any basis in fact. Additionally, I would add that a number of cruisers have sailed half way around the world with climbing rope snubbers. They last just fine.

Climbing ropes do have somewhat less abrasion resistance than marine ropes, but they hardly designed for a gentle environment. They are also less UV resistant.

Glad you set me straight. The parallel fiber info came straight from a Mammut brochure circa 1985. The breaking of fibers info cane from analysis of rope failures in the same time era.

Rope construction has changes no doubt in the decades past.

Take a look here for some current climbing rope physics:

http://www.sigmadewe.com/fileadmin/u...bing_ropes.pdf

Any fiber be it steel or nylon has a strain/stress relation. See:

Steps to Analyzing a Material's Properties from its Stress/Strain Curve

In a climbing rope the rope the stress increases as the strain is increased. Elongation happens. So long as the strain does not exceed the yield strength the rope will "rebound" without damage (or very little damage).

Should any fibers strain exceed the fibers yield strength then strain hardining sets in which decreases the fibers yield strength and leads to eventual fracture (breaking of the fiber). Should the strain be large enough then many fibers reach breaking. The whole process (elongation, hardining, fracture) contributes to dissipating of the energy of a fall.

If there was one 'big' error in my posting that you took objection to was the implication that breaking was the only way the energy was dissipated. So sorry.

But then again climbing ropes to have a design to limit the peak impact forces. This is achieved by balancing the fibers use, the fibers size and weave and about a dozen other factors.

This is born out by the limits in the number of "falls" that climbing ropes are rated for. At some point when you exceed the number of UIAA falls the rope is rated for it will FAIL.

If you put a climbing rope in an anchor setup and subject it surges where a boat hits a rope much like a UIAA fall the climbing rope will fail in short order. Say, 10 UIAA scale surges.

Sure you can double up the climbing rope and get more life out of it. Sure you can only use it on "normal" days. THe biggest diameter climbing rope is around 11mm (7/16th") or so. Not even a half inch.

If you have a heavy boat you should be using a snubber greater than 1/2" and if you are expecting heavy surge (or not but want to protect for it) then you will use a bigger and longer snubber.

The Mantus bridle (for example) comes in 3 sizes. 5/8" (15.9mm) is the smallest and speced for boats 30 to 40 feet. Next is 3/4" (40-50') and then 1" (50-70')

Even their smallest is larger than a climbing rope (15.9mm vs 11mm)....

As for none of this being delicate - well, no. But don't you ever step on my climbing rope. Ropes fail at the weakest point and stepping on one creates a weak place. I charge a beer if you step on my rope (a "beer fine").

And just as a side note - I've got 45 years climbing experience that runs the range to 5.11s in Smith Rock and Yosemite, Cascade volcanos to Aconcagua and Gasherbrum 1. Toss in running the climbing activities for perhaps the oldest climbing club in America. And thus I do have an opinion that is not so humble.

[thinwater]

Originally Posted by evm1024

Glad you set me straight. The parallel fiber info came straight from a Mammut brochure circa 1985. The breaking of fibers info cane from analysis of rope failures in the same time era.

Rope construction has changes no doubt in the decades past.

Take a look here for some current climbing rope physics:

http://www.sigmadewe.com/fileadmin/u...bing_ropes.pdf

Any fiber be it steel or nylon has a strain/stress relation. See:

Steps to Analyzing a Material's Properties from its Stress/Strain Curve

In a climbing rope the rope the stress increases as the strain is increased. Elongation happens. So long as the strain does not exceed the yield strength the rope will "rebound" without damage (or very little damage).

Should any fibers strain exceed the fibers yield strength then strain hardining sets in which decreases the fibers yield strength and leads to eventual fracture (breaking of the fiber). Should the strain be large enough then many fibers reach breaking. The whole process (elongation, hardining, fracture) contributes to dissipating of the energy of a fall.

If there was one 'big' error in my posting that you took objection to was the implication that breaking was the only way the energy was dissipated. So sorry.

But then again climbing ropes to have a design to limit the peak impact forces. This is achieved by balancing the fibers use, the fibers size and weave and about a dozen other factors.

This is born out by the limits in the number of "falls" that climbing ropes are rated for. At some point when you exceed the number of UIAA falls the rope is rated for it will FAIL.

If you put a climbing rope in an anchor setup and subject it surges where a boat hits a rope much like a UIAA fall the climbing rope will fail in short order. Say, 10 UIAA scale surges.

Sure you can double up the climbing rope and get more life out of it. Sure you can only use it on "normal" days. THe biggest diameter climbing rope is around 11mm (7/16th") or so. Not even a half inch.

If you have a heavy boat you should be using a snubber greater than 1/2" and if you are expecting heavy surge (or not but want to protect for it) then you will use a bigger and longer snubber.

The Mantus bridle (for example) comes in 3 sizes. 5/8" (15.9mm) is the smallest and speced for boats 30 to 40 feet. Next is 3/4" (40-50') and then 1" (50-70')

Even their smallest is larger than a climbing rope (15.9mm vs 11mm)....

As for none of this being delicate - well, no. But don't you ever step on my climbing rope. Ropes fail at the weakest point and stepping on one creates a weak place. I charge a beer if you step on my rope (a "beer fine").

And just as a side note - I've got 45 years climbing experience that runs the range to 5.11s in Smith Rock and Yosemite, Cascade volcanos to Aconcagua and Gasherbrum 1. Toss in running the climbing activities for perhaps the oldest climbing club in America. And thus I do have an opinion that is not so humble.

Fair enough. Sounds like we've fallen of some of the same routes for just about as long. A Mazama, I presume. I have a few friends there.
I still think you are missing 2 very important points.

• Properly specified, the climbing rope snubber is not operating beyond the WLL (about 10% BS) and the fatigue life is very long. I've done a bunch or instrumented testing of snubbers, so I have a good feel for this. Somewhere about 45 feet they become too small. In my case, I use a bridle made of retired 8.2 mm 1/2 rope; it is enough. If the rope is operating above the fatigue limit, it is the design that is flawed, not the concept of climbing rope.
• These have been in use as snubbers for many years. Not theory but actual practice.

As for Mantus, that is a design choice for them. That does not make it a data point. Additionally, they are shorter than optimum, so the forces are higher and they must be fatter. So different.

[evm1024]

Mazama, yes.

10% of the breaking strength of a 11mm climbing rope is around 450# (I'll stipulate any WLL you like). Double the rope and I'll give you 900# (we do need to factor the actual angle of the bridle halves in but we can skip it for now)

If we look at the PS anchor test of 2012 this comes to mind:

The Peak Load

The maximum load we experienced in our tests was 1,400 pound but this was at a scope slightly less than 3:1. The impact is a bit like driving your boat into a brick wall. It was not pleasant, and the tests were rapidly terminated when this occurred. It is also unlikely that anyone would, like we did, anchor using a 3:1 scope when 20-knot gusts are forecast. Interestingly, our test anchor, a 36-pound Australian Anchor Right Excel, did not move, and it is this lack of movement that makes the impact feel as if you have hit a brick wall. Maybe a less efficient anchor would burrow some, or even “drag” slightly, to cushion the impact.

Anchor Testing and Rode Loads - Practical Sailor Print Edition Article

So for sake of argument let's say that we have sustained 35 kt winds that have more or less eliminated your catenary (and its shock absorbing qualities) and that there are now 6' to 8' storm surge that gives 1400# shock loads. What happens then? WLL is exceed, some portions of the rope do exceed the yield strength, some fibers harder and some break. This goes on overnight and this is the 3rd storm that this snubber has been used for....

https://www.youtube.com/watch?v=_J_Eu6IO6DE

I happen to be in the long, large diameter snubber camp. Others may have different ideas.

The question is why use a climbing rope? Are there not other ropes that are better suited for snubber duty? Climbing ropes are specifically designed to withstand a lead fall while limiting impact force. With a trade-off for the number of falls that can be withstood. Surely there are better choices.

Of course you could adjust the snubber design to get the results you want with most any rope. But why a climbing rope.



I am sure there are many boats that are using climbing ropes. And not to beg the issue I wonder how many have gone through major storms with that climbing rope snubber. As a side note this is positive feedback. Positive feedback >>can<< lead to false conclusions.

You spoke of some data or testing that you have. Care to share?

[evm1024]

There was a navy study that took a look at the failure rate of nylon. The findings were that (from memory Don't shoot me) below 5% elongation nylon could be cycled many many times (>10,000) but as the % elongation rose the number of cycles before failure dropped dramatically. At some point (was it 20% elongation?) the number of cycles was less than 100.

I don't remember where the paper is (perhaps in this thread even).

Here is an article that sums up one cruises thoughts on snubbers. It aligns with my own.

Sizing the Capable Snubber | | PassageMaker

[thinwater]

Originally Posted by evm1024

There was a navy study that took a look at the failure rate of nylon. The findings were that (from memory Don't shoot me) below 5% elongation nylon could be cycled many many times (>10,000) but as the % elongation rose the number of cycles before failure dropped dramatically. At some point (was it 20% elongation?) the number of cycles was less than 100.

I don't remember where the paper is (perhaps in this thread even).

Here is an article that sums up one cruises thoughts on snubbers. It aligns with my own.

Sizing the Capable Snubber | | PassageMaker

At 20% BS it is closer to 3000 cycles. Still not very long.

This characteristic of nylon is greatly misunderstood. It can absorb incredible shocks. It can last a very long time at light load. But it can't do both. There is a sweet spot between 5-10% BS that works for many applications.

The only problem with the article is agreeing on what the forces are. It's not like climbing where people are similar in size and falls are well defined. In this case, the depth of the water and geometry of dock tie-up make a big difference. I've tried low-stretch/high strength docklines, and while probably works on a heavy trawler, it's a failure on a light catamaran. Regarding anchoring, higher stretch lines dramatically reduce forces in shallower water (I often anchor in 5-6 feet) compared to a fatter nylon line, the end result being that the fatigue life is not very different.

Finally, there is the anchor itself. If a thin snubber can reduce the load 20-35% below a fatter snubber, the hook may stand a better chance of staying in.

It's all about compromise. My boat has significant windage but weighs only 10,000 pounds (8.2 mm climbing rope bridle). I've known a number of folks with mid-weight 45' boats use long 11 mm single line snubbers. Certainly a heavier boat needs something heavier and longer. How long do you expect it to last before preventative replacement? I also have a second 1/2" bridle I might use if I expected sustained horrible weather.

One size does not fit all.

[Hudson Force]

Well, call me simple-minded, but this seems to be another thread where the presentation and analysis of data far exceeds the needs for simple function and application choices of a snubber.

Those away from the computer and out on their bow setting an anchor can make some fairly easy choices with the length and type of snubber with a little trial and error, learning by doing.

The presentation of the first posts in this thread promoted the idea that there are successful choices that can be made with the use or not the use of a snubber.

Account for the wind, fetch, depth, current, wave action, rode and choose by your observations of the natural world.

The analysis and research of data can be interesting, but nothing surpasses direct observation of your boat in the natural world.

[Cadence]

Originally Posted by Hudson Force

Well, call me simple-minded, but this seems to be another thread where the presentation and analysis of data far exceeds the needs for simple function and application choices of a snubber.

Those away from the computer and out on their bow setting an anchor can make some fairly easy choices with the length and type of snubber with a little trial and error, learning by doing.

The presentation of the first posts in this thread promoted the idea that there are successful choices that can be made with the use or not the use of a snubber.

Account for the wind, fetch, depth, current, wave action, rode and choose by your observations of the natural world.

The analysis and research of data can be interesting, but nothing surpasses direct observation of your boat in the natural world.

[Cotemar]

Originally Posted by Hudson Force

Well, call me simple-minded, but this seems to be another thread where the presentation and analysis of data far exceeds the needs for simple function and application choices of a snubber.

Those away from the computer and out on their bow setting an anchor can make some fairly easy choices with the length and type of snubber with a little trial and error, learning by doing.

The presentation of the first posts in this thread promoted the idea that there are successful choices that can be made with the use or not the use of a snubber.

Account for the wind, fetch, depth, current, wave action, rode and choose by your observations of the natural world.

The analysis and research of data can be interesting, but nothing surpasses direct observation of your boat in the natural world.

Yes, but how would all of us CF'ers sleep at night knowing that a few CF'ers like to calculate the Zinciod Cravistat velocity of a piece of 3 strand line.

This is NyQuil at its finest before bedtime.

[seahag]

Thanks- good information! currently it's 5/8" with the 5/16 chain, seems like splicing the additional line is the best approach and we can save the snubber for shallower anchoring. Yeah I guess it's about time to get that book, been hearing about it for years.

[Zephyrcat229]

I have no test data or the like, however I have used "retired" climbing ropes to pull logs out of the woods for 20 years of use.These ropes are used ROUGH, logs get caught upon stumps, rocks, and such like, the truck bounces to a halt before it pops over, or you stop and go sort it. Anyway nothing scientific at all but good quality climbing rope is amazingly strong. Hard to break with a pickup truck and 1000# log anyway. Even used season after season.