anchor chain with rope and chain hook snubber - why?

A small warning on snubber hooks. My original one is shown in the upper photo. Although I had owned it for many trouble-free years, it gave way in a harbour in surging conditions, the two arms opened out, releasing the chain. The boat was thrown back and the stern platform was punched through the transom. I replaced it with the one shown lower in the photo, which seems a far stronger design.
snubberhooks.jpg


The main benefit of a snubber line is in stronger winds, F6 plus, when any catenary, and therefore 'elasticity', in the chain is effectively lost. As said above, the stretch in the line can be most impressive to observe. My line is 12 mm nylon, which in fresh to strong winds I will lead back to the centre cleat of the boat, extending the effective length. It needs good chafe resistance, which I do by passing it through a length of PVC tubing over the second bow roller.
 
I have never had that problem, using a substantial length of slack chain above the hook. A nice bonus of it is that invariably as soon as I begin hauling the chain in the hook falls off as soon as the snubber line is slack.
 
We have no choice and Must use rope and chain hook as well a bridle, it's the curse of owning a cat.

Without it she wants to wander from side to side be a blow or no wind, just the tide is enough.

Good luck and fair winds.
 
1) I don't think a chain should jam if cleated off properly. It shouldn't be cleated in the same way as a rope (don't use figure of eight and looped back on itself). I've never had a problem (though having smaller boats probably have smaller chain than most), and I'm mildly sure that my chain cleating off technique came from Admiralty Manual of Seamanship or somesuch.

2) Question: If one is using a snubber to take the weight off a winch, shouldn't one then attach the chain somewhere more secure (assuming not just a lunch stop) in case the snubber line chafes through, or is the winch adequate to take the load but best not holding it as a matter of routine? (I've little experience of winches, but would like to know in case Santa ever reads my list properly!)
 
vyv_cox said:
A small warning on snubber hooks. My original one is shown in the upper photo. Although I had owned it for many trouble-free years, it gave way in a harbour in surging conditions, the two arms opened out, releasing the chain. The boat was thrown back and the stern platform was punched through the transom. I replaced it with the one shown lower in the photo, which seems a far stronger design.
snubberhooks.jpg


The main benefit of a snubber line is in stronger winds, F6 plus, when any catenary, and therefore 'elasticity', in the chain is effectively lost. As said above, the stretch in the line can be most impressive to observe. My line is 12 mm nylon, which in fresh to strong winds I will lead back to the centre cleat of the boat, extending the effective length. It needs good chafe resistance, which I do by passing it through a length of PVC tubing over the second bow roller.
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Mr. Cox, I've gone over to a soft shackle made of dyneema that is stronger than the steel. Even the chain hooks as shown in your second picture end up being the weak link in the system, and as noted, do tend to fall off when unloaded.
 
LittleSister said:
1) I don't think a chain should jam if cleated off properly. It shouldn't be cleated in the same way as a rope (don't use figure of eight and looped back on itself). I've never had a problem (though having smaller boats probably have smaller chain than most), and I'm mildly sure that my chain cleating off technique came from Admiralty Manual of Seamanship or somesuch.

2) Question: If one is using a snubber to take the weight off a winch, shouldn't one then attach the chain somewhere more secure (assuming not just a lunch stop) in case the snubber line chafes through, or is the winch adequate to take the load but best not holding it as a matter of routine? (I've little experience of winches, but would like to know in case Santa ever reads my list properly!)
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Winches really are not designed to handle shock loading, so yes, it is desirable to secure the chain to a strong point if the snubber chaffs through. One practice is to overlay an everyday snubber (in our case 5/8", 30') with a stronger line that takes the load when 80% of the elasticity of the everyday snubber is reached (for us, 1", 38'). This was suggested by another poster elsewhere, who made up a length of dyneema for chafe resistance attached to the stronger backup snubber. Belt and suspenders, I suppose. But even in that case a length of dyneema attached to the chain with a Kleimheist hitch (or your preferred knot) is used to take the load off the windlass if need be. All of this is not necessary during mild conditions (except the snub line for quieting), but it seems prudent in really bad conditions.

Regarding cleating chain, the main problems are that it trashes or scratches whatever you cleat the chain to, it subjects the chain to loading that may reduce its strength, and it is a bugger to release under load if you have to let the whole thing go and flee the scene. As you say, smaller chain doesn't present quite the same degree of issues, although they would all still seem to pertain.
 
GHA said:
Not according to Yale's figures. Their 3 strand is quoted as breaking at 30%.

Worth noting as your wording suggests its OK to do so.
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Unless my math is wrong, I believe 30% of 15 feet is around 5 feet, but you are correct. If you want 5 feet of elasticity without reaching the breaking point to get it you should go with the generally recommended length of 30' for the snub line.
 
As a snubbing line I use climbing braid plenty streeetch.I've always taken turns round me post(chain wise) never had a prob.
 
Delfin said:
Unless my math is wrong, I believe 30% of 15 feet is around 5 feet, but you are correct. If you want 5 feet of elasticity without reaching the breaking point to get it you should go with the generally recommended length of 30' for the snub line.
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Picky and would probably get lost in the noise of the real world, but it's 33.33%. ;)

The 5' in 30' looks more like a figure to stay below the safe working load, as Yale and marinesaftey have it, of 20% elongation. Which looks just under 50% breaking strain from a Yale graph for 3 strand. Personally I'd like a higher swl ratio.
 
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I would not use the winch as a primary securing point. In Watchet harbour, before the marina was built, I saw a winch casting shatter with the snatch load from the mooring in moderate conditions.

Paul
 
GHA said:
Picky and would probably get lost in the noise of the real world, but it's 33.33%. ;)
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Uh, thanks for that.....:confused:

GHA said:
The 5' in 30' looks more like a figure to stay below the safe working load, as Yale and marinesaftey have it, of 20% elongation. Which looks just under 50% breaking strain from a Yale graph for 3 strand. Personally I'd like a higher swl ratio.
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I'm not sure SWL has much bearing on selection of a snub line. If you want 4' of stretch, let out 4' more chain than the unstretched snub line. Want 6'? Let out 6' more chain. You could put out 1/8" nylon if it suits you snubbing 3/4" chain and it wouldn't break if you don't let it. The selection and length of a snub line should be the size needed to provide desired elasticity when subjected to an expected shock load. SWL is as important in the application as line color....
 
Bloody hell where are you guys anchoring? Bits of rope stretching 5' sounds to me like you're huddled down below with a full storm raging up on deck! Worst I've had was 38' boat in about 45 knots, the 10mm chain like a bar and the snubber stretched a few inches at most.
 
nimbusgb said:
Bloody hell where are you guys anchoring? Bits of rope stretching 5' sounds to me like you're huddled down below with a full storm raging up on deck! Worst I've had was 38' boat in about 45 knots, the 10mm chain like a bar and the snubber stretched a few inches at most.
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Does the fact that the chain was bar tight and the snubber had only stretched a few inches suggest that perhaps you're not using the snub line quite as intended? If you attach 30' snubber then let out 30'6" of chain, one expect to find the snub line had stretched 6" and the chain would now be tight in a 45 knot wind. Kind of defeats the point of a snub line.....
 
GHA said:
What a very strange viewpoint.

Do you not buy in to factors of safety then?? Just hope it doesn't break?
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I gather the use of a snub line is uncommon in your area.

The point of a snub line is to stretch. It isn't desirable for it to break, but you don't really give a rip what the SWL is because it is the breaking strength that matters. If you don't want it to break, then you limit the amount of additional chain over the length of the snub line to prevent it from ever reaching that breaking point. In truly bad conditions, you can provide an additional, stronger snubber that begins to take the load when the first snubber starts to reach its breaking point. Either way, the SWL of the line has zero bearing on anything. Besides, according to the ABYC, the SWL of a line shouldn't exceed 1/5th of the breaking load, and at 1/5th of the breaking load there is little to no elasticity. So by concentrating on that measurement, you may as well not bother to use a snub line at all.

Snub lines deteriorate rapidly because of how they're used (if used properly), so should be replaced regularly.
 
Delfin said:
Either way, the SWL of the line has zero bearing on anything. .
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Confusing.
You've already set a safe working load onboard by looking for 5' elongation in 30' of rope. Which is close to the figure from your marinesafety report of 120'/100'.
and then say it has zero bearing.
I don't think you understand the concept. A safe working load is arbitrary, what ever factor of safety you want it to be. You've already suggested a guideline of 5' in 30'.
 
GHA said:
Confusing.
You've already set a safe working load onboard by looking for 5' elongation in 30' of rope. Which is close to the figure from your marinesafety report of 120'/100'.
and then say it has zero bearing.
I don't think you understand the concept. A safe working load is arbitrary, what ever factor of safety you want it to be. You've already suggested a guideline of 5' in 30'.
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Actually, I couldn't care less about the SWL, which was a value you introduced, drawing concerns about SWL in mooring lines in the MarineSafety report and applying them to the topic at hand - anchor snubbers. The MarineSafety white paper is useful in the formula it provides that allows one to calculate the forces involved in bringing a vessel to a stop over a distance that is longer, rather than shorter. But that's about it.

Safety in a snub line means what exactly? Nothing. When a mooring line breaks, people sometimes die as described in the report. When a snub line breaks, you're on all chain, and the snub only broke because you sized it or used it incorrectly. If you don't want it to break, don't let out more chain over it than 25% of so of its length. However, if it makes you feel better calculating stretch to 2 decimals, or opining on the safe working load of snubbers based on the dynamics of mooring lines, please carry on.

p.s. Quiz time!

Question 1: What is the SWL of a nylon snub line backed by 1/2" chain? (Hint: what is the SWL of the chain??....)
Question 2: What is the SWL of a nylon mooring line not backed by anything?
 
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Delfin said:
Actually, I couldn't care less about the SWL, which was a value you introduced, drawing concerns about SWL in mooring lines in the MarineSafety report and applying them to the topic at hand - anchor snubbers. The MarineSafety white paper is useful in the formula it provides that allows one to calculate the forces involved in bringing a vessel to a stop over a distance that is longer, rather than shorter. But that's about it.

Safety in a snub line means what exactly? Nothing. When a mooring line breaks, people sometimes die as described in the report. When a snub line breaks, you're on all chain, and the snub only broke because you sized it or used it incorrectly. If you don't want it to break, don't let out more chain over it than 25% of so of its length. However, if it makes you feel better calculating stretch to 2 decimals, or opining on the safe working load of snubbers based on the dynamics of mooring lines, please carry on.
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You obviously don't understand the concept of how close to breaking strain you are happy to go to in a line so no point going any further, far too grumpy already.
 
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