Mooring Snubber

Is snubbers needed when at anchor. What does it really do?

Kartracer, snubbers, when installed properly and used properly take up some of the shock that a boat would normally receive when riding at anchor in a wind or from waves.

With the line wrapped around it and kept snug, when there is a wave (or wind) that would jerk the boat, the snubber absorbs some of the shock.

Yes, they do work.

Snubbers are only needed with all-chain rode. A combination rode (nylon line with a short length of chain connecting the end of the nylon to the anchor) it it's own snubber (shock absorber). No separate shock absorbing device like a snubber is needed.

kartracer said:

Is snubbers needed when at anchor. What does it really do?

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Depends...if you are using mostly a nylon rode...probably not.

If using chain and expecting enough wind that the chain may straighten, definitely.

Most all chain rode users usually use a snubber.

A lot of ifs....so keep reading up on anchoring and you will get the idea.

Lots of people may tell you their way of doing it...but it isn't necessarily correct or the appropriate for any given situation or something that works for you.

Knowledge and practice will make your anchoring safe and a bit more relaxing.

An important reason for a snubber is to take the load off the windlass which is not intended to take heavy sharp loading. Internal damage, like expensive stripping and fracturing of gears, can result. The snubber line moves the load to another part of the boat, such as a sampson post or a mooring cleat.
While essential with an all chain rode, or when only using the chain section of a combination rode, I`m less sure about the position where a rope rode is in use, it may also be desirable to move that load off the windlass to a cleat or post.

BruceK said:

I`m less sure about the position where a rope rode is in use, it may also be desirable to move that load off the windlass to a cleat or post.

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It's a good idea to do this, but you don't need a snubber to do it. You can simply secure the rode itself to a solidly backed deck cleat or Sampson post.

Post #3.




Retrieving snubber attached to an anchor chain:





Use a nylon line when tied to a mooring (here fore and aft); no snubber needed:

I'm glad you guys responded. I was only thinking of a rubber snubber that would be used in an all-rope rode.

Thanks for setting the record straight.

GFC said:

I'm glad you guys responded. I was only thinking of a rubber snubber that would be used in an all-rope rode.

Thanks for setting the record straight.

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So was I !!!

kartracer said:

So was I !!!

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Between us, we found most of the merits of snubbers.
The snubber line I made up, using a bear claw for chain attachment, has one of those rubber block thingies you weave the line through, doubt it helps much if at all.

The simplest and most functional snuber rig is to attach 2 nylon lines to a low mounted bow eye with a proper backing plate.

The chain as always goes to a deck fitting a chain stopper, so the windlass has zero load.

The both lines have no metal at either end just whipped and tied on..

They are short enough not to engage the propeller if they go overboard.

The thinnest is simply tied with a bowline to a chain link as the chain is going overboard.

Should the wind get to the point the thin line goes taught and the chain jerks the boat hard , the thicker line with more chain is used .

The thin line (1/4 or 3/8) will simply snap, no big deal as it happens so rarely.

psneeld said:

Depends...if you are using mostly a nylon rode...probably not.
If using chain and expecting enough wind that the chain may straighten, definitely.

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Is there a boat size/weight where you would no longer use a combination chain, rope rode?

1/4" line as a snubber!?

One of the big, if not biggest, advantages of using a snubber line on a chain rode is its shock absorbing effect. The snatching forces that happen once a chain comes tight and the full load is put upon the anchor is one of the key reasons anchors break loose. So once the line breaks you no longer have the important shock absorbing effect of the line.

Hawgwash said:

Is there a boat size/weight where you would no longer use a combination chain, rope rode?

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Anchor size and weight probably has as much or more to do with that than the size of the boat alone. Once you reach the larger size and weight anchors it's not really practical to have a combination line and change rode.

Marin said:

Snubbers are only needed with all-chain rode. A combination rode (nylon line with a short length of chain connecting the end of the nylon to the anchor) it it's own snubber (shock absorber). No separate shock absorbing device like a snubber is needed.

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Marin, the question got me thinking that this really is a question that could be worthy of some serious investigation--the answer to which might be valuable to the entire boating community. True that the nylon line stretches x% and acts as a snubber. But the weight of the all chain rode also "snubs" the forces as it is straightened against gravity (is this the catenary effect?). I certainly don't have the time (and perhaps not the brain power) to figure it out, but perhaps you or one of your engineering contacts at Boeing could do the math for this hypothetical:

depth= 45 feet
7:1 scope (315 feet)
two scenarios: A=all chain 3/8" B= 25' 3/8" chain and 290' of 3-strand nylon rode (please specify typical diameter).
The question is, which arrangement, A or B, would take more force acting upon the boat to reach the full extension point of the anchoring system, and therefore benefit more from a snubber?

In other words, does it take more force to bring the weight of the chain to full extension or does it take more force to lift the short length of chain and then stretch the nylon rode to the x% (20% or?) of its limit? I have absolutely no idea what the answer is, but it would be great to have an analysis. Appreciate any help you or other TF members can provide...
I've probably not included some necessary facts to solve the equation (need weight per foot of both chain and line, etc)--can other TFers provide that?

Many with a combo rode only let out enough rode to only need the chain, so in effect, it acts as a chain-only rode. In those cases, combo rode owners are well served to use a snubber for shock absorption and noise reduction.

With 120 ft of chain then 240 ft of line rode, I often anchor in 15 ft of water with 80-100 ft of rode. I use a snubber in anything worse than benign conditions or if I'm spending the night.

Tests along those lines have been done. And they have shown that snatch loads are the most significant cause of anchors braking loose. As well as showing that a combination line and chain rode makes for the best rode as far as dealing with snatch loads goes.

I've got a book that talks about this at home but not with me. I don't recall its title off hand. As I recall the author is French. Perhaps someone else knows what book I'm talking about.

Thanks Capt Bill. After I posed the question I was curious and did a little on-line research--agrees with what you said. facts seem to support idea that weight of chain (catenary effect) doesn't help nearly as much as scope and absorbing the "snatch loads." Thanks for response.

I think the title is "The Complete Book of Anchoring".

sounds like that could lead to a serious hijacking of the snubber question and get us all back into anchoring!
Let's let sleeping dogs lie....
Best to you, Capt Bill
curtis

Capt.Bill11 said:

I think the title is "The Complete Book of Anchoring".

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Could it be "The Complete Book of Anchoring and Mooring" by Earl R Hinz ( American,not French). At p.115, Revised Second Edition, he deals with what he calls "Chain Riding Stoppers". P117 depicts a range of chain attachment devices, of which the "common grab hook" ( bearclaw) is described as "not recommended" as it "weakens the chain to about 80% of normal strength because of the eccentric grasp". He shows other commercially available attachment plates.
My copy came from Amazon. If we confine discussion to the relevant part, the thread should be safe enough.

It's an excellent book. We bought a copy not long after acquiring our PNW cabin cruiser and learned a lot, like the fact we had our swivel on backwards.

Dawdler said:

sounds like that could lead to a serious hijacking of the snubber question and get us all back into anchoring!
Let's let sleeping dogs lie....
Best to you, Capt Bill
curtis

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And to you.

BruceK said:

Could it be "The Complete Book of Anchoring and Mooring" by Earl R Hinz ( American,not French). At p.115, Revised Second Edition, he deals with what he calls "Chain Riding Stoppers". P117 depicts a range of chain attachment devices, of which the "common grab hook" ( bearclaw) is described as "not recommended" as it "weakens the chain to about 80% of normal strength because of the eccentric grasp". He shows other commercially available attachment plates.
My copy came from Amazon. If we confine discussion to the relevant part, the thread should be safe enough.

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No it's not Hinz's book. I'm fairly certain of that.

Im pretty sure it's this book http://www.amazon.com/The-Complete-Anchoring-Handbook-Weather/dp/0071475087

Capt.Bill11 said:

Anchor size and weight probably has as much or more to do with that than the size of the boat alone. Once you reach the larger size and weight anchors it's not really practical to have a combination line and change rode.

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Ok, but;
Aren't anchor size and weight mostly determined by boat size and weight?
So, put another way then, is there generally an anchor size/weight when you would not use a combination?

I'd say once you get close to and over a 100 lb anchor your going to be using all chain. Or perhaps cable.

I think three strand nylon rode provides considerable streach for shock load reduction but braided line not so much.


It does not seem to take extreme winds to remove the catenary from chain, at least as far as I could tell from on deck.


I often thought about setting up a spare anchor on a big shackle to slide down the chain to act as a kettle With a small line for retrieval.Never tried it though just relied on the my anchoring adage, when in doubt let it out. More chain gives more catenary..

Hawgwash said:

Ok, but;
Aren't anchor size and weight mostly determined by boat size and weight?
So, put another way then, is there generally an anchor size/weight when you would not use a combination?

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I'd say it's broader than that. Boat size (length, volume), and weight (displacement) are biggies, but there's also windage (profile), normal anchoring areas (typical weather, wind, etc.), normal holding grounds (sand, rock, mud, grass, whatever), and anchor design (which in turn influences anchor weight, windlass sizing, etc.). I've probably forgotten to include something or other, but it's all one big system of systems.

And then... yes, there comes a time when all that together influences rode make-up... but the actual "where" is most likely an "it depends" -- with obviously huge boats using all chain and/or cable, and obviously small boat being fine with all (or mostly all) rope... and a whole bunch of boats in the middle somewhere.

I can add that I'd use all chain if it weren't for the mud here; takes me too long as it is to wash all the mud out of the links... so we only use about 25' of chain leading the rode. That's not particularly a factor of boat weight/size (and all that other stuff) in our case; it was easy enough to properly size our combo rode.

-Chris

Hawgwash said:

Ok, but;
Aren't anchor size and weight mostly determined by boat size and weight?
So, put another way then, is there generally an anchor size/weight when you would not use a combination?

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I do not think there is a firm point where all chain becomes more practical.

The issue is the windlass more than anything.

Small boat windlass's seem to work with combo rodes very well. All my previous boats had a combo rode and the windlass was able to work with the line, the transition, and then the chain.

Above a certain pulling capability you run into a situation where the windlass manufacturers quit offering a windlass gypsy that will work effectivly with both line and chain. Their solution is to add a capstan to the windlass either on the side or the top for the line, and a regular gypsy for the chain.

If you anchor allot, especially at any depth you will find that using a capstan is not all that much fun. That is what drove my decision to go to an all chain rode this spring.

Hawgwash said:

Is there a boat size/weight where you would no longer use a combination chain, rope rode?

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Just my opinion, so it's only worth what you paid for it, is that if a boats big enough to have a windlass, it gets chain.

Therefore, dinghy's, tenders, speedboats etc, with no windlass, loose anchor with short chain and coiled rode in locker.

Anything larger, with fixed windlass and permanent anchor chock/mount/storage gets chain.

And let the flaming begin, lol.