Rolling Hitch on Snubber

[jim_thomsen]

Transmitterdan,

Regarding climbing ropes:

A dynamic rope is a specially constructed, stretchable rope. This 'stretch' is what makes it 'dynamic', in contrast to a static rope that doesn't have any give when under load. By stretching under load, a dynamic rope will soften the impact of extreme stresses on it, such as falls, and lessens the likelihood of failure. This is particularly useful in rock climbing, where it can absorb much of the energy of a fall

[AnchorageGuy]

Lots of good info, but my thoughts on the original posting question. I see 3 issues that may have contributed to the failure. Number one is the use of dacron, a snubber needs to stretch to prevent the shock loads of the chain. Nylon would be a better choice IMO. Using braid instead of 3 strand, braid will build up heat in the core as it tries to stretch and the inner core will "melt" causing it to fail. The outer braid does not have the strength to take the load. Number 3, the line does look to me to be a bit small to be used as a snubber based on Evans advertised boat size and type. I'm no expert but I did sleep in a Holiday Inn Express last week. Chuck

[Kettlewell]

A few comments on various things. I use a 3/8" 3-strand snubber on a 38-foot, 20000 lb. boat, and I have never had one break. So far, the highest it has seen was 56-60 knots, did not slip, did not break, appeared fine, kept using it for a long time afterwards. On my previous boat, a 32-foot cat, we went through Hurricane Bob with a 3/8" snubber on there, and nothing broke. I have had a chain hook fall off numerous times, but always in light winds when it is not a big deal--I can hear the chain rumbling which lets me know. I keep the deck end of the snubber cleated off so it can just be let go in an emergency. I have had to do that a few times in very high winds, but later pulled the snubber back onboard because the rolling hitch kept it on the chain. I do slap on a few extra half hitches to keep the hitch tight, and I use extra turns around the chain--never slips, and never jams when you want it undone. I've also used it around line in order to take the strain and chafe off the main rope rode, and it works well for that too.

I also use a chain hook, particularly in normal light air anchoring, or for short stops, or for backing down the anchor when I don't put out a long snubber. I have had the line break right where it goes into the eye of the chain hook, but due to old age--should have been replaced long before.

[mbianka]

I'm trying to picture what I do for the snubber line. I think it's just using two or three half hitches that secure it to the chain. Never had it slip or chafe at the knot/chain area. Comes up easily through the chain roller and is untied on deck.

[Kettlewell]

One other thing on the reports of cyclic loading causing 3-strand nylon to overheat and melt. Obviously, it can do so based on a few reports from reliable folks, but it takes some very extreme conditions to get to that point--we're talking over 100 knots and exposed conditions creating big waves. It has never happened to me, and I have never seen an example of it in the real world, and I looked at a lot of broken lines after Hurricane Bob--they all were due to ordinary chafe problems. Lots of moorings--I would guess the majority, still use ordinary 3-strand in fairly hefty sizes. So, yes, if you are expecting a hurricane in an exposed location, it might be something worth considering, but short of that I don't think you have to worry about it.

[noelex 77]

I think a must of offended the god of snubbers in a previous life because a well as my rolling hitches slipping, I break a least one snubber a year, usually a couple.

I am hoping its its the lousy nylon that sold here. The local fisherman buy more on price than quality.
I have just received some octiplat from the UK and I have my fingers crossed for no more broken snubbers.

[thinwater]

Originally Posted by estarzinger

...........

Climbing rope for snubber. Yes, I thought about you when I switched from polyester to Dyneema (free as part of a test group). Big mistake, dynamic climbing rope would CERTAINLY be better, but too large for my application.

Energy absorption and climbing rope. For a limited number of impacts over the sorts of turns knots make, climbing ropes are rated for about 200 ft-pounds/foot of absorption, but over a longer term, let us say 1/2 of that. So with 20 feet out it should handle about 2000 ft-pound surges.

Assuming your boat weighs 25,000 pounds (wild guess--no idea) and a surge has you moving 3 ft/sec, the energy is 3500 ft-pounds. The chain will absorb a good part of that, but still we can see that the rope is going to be operating in the range where it will eventually fail from fatigue. If it had been spliced around a thimble, probably not.

It seems that the lesson may simply be to trim the last 2 feet off every 40-80 nights (guessing), depending on how bad the exposure has been.

I'm following this with interest because I am thinking of going to a 8.5 mm climbing rope bridle on a 8000 pound cat; I have something heavier now and could benefit from the increased shock absorption, since my rode is now all-chain. I use a chain plate, so the knot bit does not concern me.

[Kettlewell]

I think a must of offended the god of snubbers in a previous life because a well as my rolling hitches slipping, I break a least one snubber a year, usually a couple.

Where do they break?

[thinwater]

Originally Posted by Kettlewell

One other thing on the reports of cyclic loading causing 3-strand nylon to overheat and melt. Obviously, it can do so based on a few reports from reliable folks, but it takes some very extreme conditions to get to that point--we're talking over 100 knots and exposed conditions creating big waves. It has never happened to me, and I have never seen an example of it in the real world, and I looked at a lot of broken lines after Hurricane Bob--they all were due to ordinary chafe problems. Lots of moorings--I would guess the majority, still use ordinary 3-strand in fairly hefty sizes. So, yes, if you are expecting a hurricane in an exposed location, it might be something worth considering, but short of that I don't think you have to worry about it.

I posted some calculations on that topic.
Sail Delmarva: Can Nylon Anchor Rope be Melted by a Severe Cycling Load ? Myth Plausible.
I've actually broken ropes on test rigs and looked at the ends. It seems to be about rope diameter and heat dissipation; the rope has to be fat to build heat. Certainly possible and I believe the stories. A risk anytime rope over 3/4-inch is needed.

"Below 5/8-inch rope heating due to cycling is probably not an important factor; failure will be due to something else. Beginning at 3/4-inch moving upwards, it can be very important, since the larger rope can not cool as easily. The myth seems plausible."

[s/v Jedi]

It's getting pretty messed up in this thread

Originally Posted by Dockhead

It's not the snubber we're worrying about releasing -- it's the chain strop or whatever is used to belay the chain ahead of the windlass. I presume you use something like this? Maybe you have a chain lock, which some people use for this purpose? I sure hope you have something besides your snubber between your chain and your windlass . . .

Sure I have and would guess you know that: a chain stopper. It's made for the job. There is no drama or releasing tension or anything like that; the snubber has the tension, the chain is laying slack through the chain stopper and I only need to lift the pawl and that's it. It is the people who do not use proper gear and thus start using shackles (with spanners and all!) or ropes tied to chains to make up for lack of a chain stopper that get in trouble on that front. For many, the thought about how to deal with emergencies doesn't even come up and they will be clueless when that time comes... and it will one day.

Originally Posted by transmitterdan

Exactly right! Many people are "afraid" to use the correct snubber because it is small nylon 3-strand. We use New England 1/2" nylon 3-strand snubber on a Valiant 42. Jedi's snubber looks too big but may be right for his boat too. Depending on windage Hawk might want 5/8" nylon but probably not bigger than that. Our 1/2" nylon line breaking strength is more than the chain safe working load. This is a key parameter to consider in choosing a snubber. It should be the smallest line with breaking strength that exceeds the chain's safe working load.

For calm the snubber is 25 feet. For difficult conditions it is 50 feet with another 75 feet snubber behind it as backup. For hurricanes you need multiple anchor points anyway so we are ignoring that scenario in this discussion.

Nylon line will stretch to nearly twice it's normal length before breaking so I never put out enough loop of chain. We set the brake on the windlass somewhat so if the snubber stretches more than the chain loop then more chain will pay out of the windlass but stop when the snubber finally comes up short. Hearing the chain pay out will make me want to go up on deck and check things.

After a serious blow discard the snubber and use a new one. They are cheap and work perfectly.

There is no way I would use high tech climbing line as a snubber as it only serves to defeat the purpose of the snubber. A proper snubber has to stretch...a lot...to do its job.

Oh my, I'm afraid you got some things backwards... it is your snubber that is too big at 1/2". Mine is 5/8" which is only 1/8" more while my boat weighs 4 times yours I guess... Also, the climbers rope is designed to stretch while 3-strand does so because they couldn't make it better. Next it the length of your snubbers which is just way off. 125', really?? that means it will stretch to 250', you don't even have that much extra chain to spare, reducing it's usefulness. The diameter of the snubber should be reduced until it breaks during a 50 knot or so squall and then you go up one size and that's it. 30' is enough.
I have seen lots of people using snubbers that are too long and overthinking it all... I remember that many always had trouble with dragging anchors and try to make up for inadequate anchors. All IMHO of-course.

Originally Posted by noelex 77

I think a must of offended the god of snubbers in a previous life because a well as my rolling hitches slipping, I break a least one snubber a year, usually a couple.

I am hoping its its the lousy nylon that sold here. The local fisherman buy more on price than quality.
I have just received some octiplat from the UK and I have my fingers crossed for no more broken snubbers.

That's what you get for trying to keep it cheap cheap cheap Test for minimum diameter with one solid brand and then stay with that brand. A snubber lasts for a year or more and only needs 30' of line to make, so once you know which line, buy 120' of it, splice 4 snubbers from it and you're done for a decade

Octoplait is better than 3-strand; it is the eye splice that keeps me away from it. I hate to spend that much time on it for piece that I consider chafing gear. I did an eye splice in my 1.25" octoplait secondary anchor rode and it took me the better part of a day... within a year I had to cut it off during an emergency

[Dockhead]

Originally Posted by noelex 77

I think a must of offended the god of snubbers in a previous life because a well as my rolling hitches slipping, I break a least one snubber a year, usually a couple.

I am hoping its its the lousy nylon that sold here. The local fisherman buy more on price than quality.
I have just received some octiplat from the UK and I have my fingers crossed for no more broken snubbers.

If your rolling hitch slips -- a very unusual problem -- try tying an extra turn in it, and/or tying off the the tail with a clove hitch or a couple of half-hitches. It should form into the chain and be absolutely secure. You could also try some of the other knots suggested, but keep in mind that few knots compromise the strength of the rope less than a rolling hitch, which is almost as good as a splice for strength (n.b. that strength and security are completely different qualities in a knot; the rolling hitch is not particularly secure), about 60%.

If your snubbers are breaking, then something is wrong. Is the size ok? Are they breaking somewhere where they might be chafing on something?

I've only ever broken one, and that was my own d*mn fault. It was when I first acquired my boat, and was still using a ridiculously skinny (probably 12mm or at most 14mm) and short snubber inherited from the PO. I was anchored in Studland Bay in a gale which decided to veer 180 degrees during the night, removing all shelter, putting us off a lee shore in the surf, and buffeting us with big waves, some of them actually breaking. The snubber broke. Thank God I had belayed the chain with a stout strop, which saved my boat and possibly my life. Unaware that the snubber was broken (I should have checked), and not wanting to work on the heaving foredeck in the stormy dark, I waited until morning to do anything. Yikes. I would do it all differently today.

[noelex 77]

Originally Posted by Kettlewell

Where do they break?

No consistent spot.
The last one broke only a couple of feet from the Samson post where it is secured. At this point it was inside some water water hose that I use for chafe protection. There may have been some extra heating and friction, but the one before broke at the other end.
It is a nusance but not a big problem. They go with a tremendous bang, so it is easy to tell what has happened. I have second very thick metre long "snubber" attached to the Samson post that transfers the shock load of the boat surging backwards to the strongest part of the boat.

[Dockhead]

Originally Posted by s/v Jedi

Sure I have and would guess you know that: a chain stopper. It's made for the job. There is no drama or releasing tension or anything like that; the snubber has the tension, the chain is laying slack through the chain stopper and I only need to lift the pawl and that's it. It is the people who do not use proper gear and thus start using shackles (with spanners and all!) or ropes tied to chains to make up for lack of a chain stopper that get in trouble on that front. For many, the thought about how to deal with emergencies doesn't even come up and they will be clueless when that time comes... and it will one day.

A chain stopper is a great solution, of course, provided, however, that you are able to install it in a strong enough spot. I have not yet figured that out on my boat, which has a balsa-cored deck, which is why I use a devil's-claw like technique like on a ship (my arrangement looks quite like the deck of the Royal Navy frigate in the drawing I posted a few pages back). The downside of a chain stopper is that it is probably not possible to make it as strong as a proper chain strop on a boat with a fiberglass deck; the upside is that it is extremely convenient and a cinch to release in an emergency. My father's boat has one.

I would disagree, however, that belaying the chain other than by using a stopper is "improper gear". A chain strop is a traditional and proper technique, as is a devil's claw, both used on large ships as well as on yachts for centuries. You are correct, however, that one must think about how to quickly release whatever it is you're using, and I confess to not having thought that through adequately until now.

[Cotemar]

I think Evans Starzinger “Get a Grip!” article in BoatUS may help here.
It covers the Rolling Hitch, Modified Rolling Hitch (Camel Hitch) and the Icicle Hitch

http://www.boatus.com/magazine/2013/June/get-a-grip.asp

[foolishsailor]

Any method of belaying that involves line is inherently quick release and a proper method - even if not as "efficient" as a chain stop. All one has to do with line in an emergency is to apply something with a sharp edge.

I still prefer a loop and prusik knot for my chain as I can pull the chain over my bow roller with the loop in. Maybe just lazy I guess.