Anchor snub lines

The only way Delfin's yacht would end up on the beach is if the chain failed and I am assuming the chain is sized for the vessel and has been mentioned chain failure is notable by its absence. Even if the primary snubber fails Delfin has a second snubber ready to come into play - which he implies is always part of his rode system. I do not recall if Delfin mentioned it but even when using snubber(s) the chain should be tied off to, another, strong point. If the snubber(s) fail the load is not then taken on the windlass. Snubbers are consumables which can be retired on a schedule or replaced when they fail (leaving it until they fail is not a good idea), except that in Delfin's case he always has that standby snubber. I am assuming he carries a spare snubber, in case of failure.

Most chain lifts off the seabed in winds over about 20 knots and by about 35 knots your chain is bar tight, and looks as straight as a die. Snubbers come into their own as soon as you put them on as they will stop any grinding on the bow roller, but start to use their elasticity immediately. They are obviously invaluable from around 25 knots and up. If you use Delfin's system of a snubber for winds to say 40 knots and one that'cuts in' at say 35 knots you should have a system that will stand you upto most windspeeds you are likely to encounter.

There is obviously no need to use snubbers for a lunchtime stop. But if you are out and the wind is not as forecast (how often does that not happen) then we would not leave home without them.

I do not know enough about the use of Dyneema in this application but Delfin's system seems belt and braces and it will be interesting to get feed back in a few months time, maybe at the end of a North West coast winter? The Dyneema is being asked to perform in roles endorsed by others, who use Dyneema in a similar way, though I have seen no history on how it actually performs long term. I recall when Dyneema was introduced the big phurphy was UV - that one got binned, but it took a long time - so there are things to learn.

I'm glad that people have the courage of their convictions and try new 'things'.

Jonathan
 
GHA said:
Doesn't it say the opposite? Use polyester where the may be chafe and nylon further down for the stretch.
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I understood it to say neither nylon or pe were ideally suited

"Polyester line may be more chafe-resistant than nylon but tests have found that it too builds up heat, although far less heat than nylon, and is subject to internal as well as external chafe under heavier storm loads. Is there a material that protects the line from abrasion while also keeping it cool internally? ....."

It then concludes that the budget way of doing is to use pe
 
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Storyline said:
I understood it to say neither nylon or pe were ideally suited

"Polyester line may be more chafe-resistant than nylon but tests have found that it too builds up heat, although far less heat than nylon, and is subject to internal as well as external chafe under heavier storm loads. Is there a material that protects the line from abrasion while also keeping it cool internally? ....."
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The reason for using something like Plasma or Dyneema Dux where it will be strained but will stay dry is because it won't heat up. This is because the heat in polyester or nylon is the result of the fibers rubbing up against each other as it elongates - slightly so with polyester but quite a lot with nylon. This generates friction that melts the line.. Since the Dux material essentially doesn't stretch at all, it is better for this application. That would be the only improvement I would argue for and have incorporated with my rig over Evans approach - the Dyneema he is using won't stretch much, but it will stretch more than the Dux.

The concern for Dyneema variants being weakened when making a sharp bend is also wrong. That is why they make soft shackles out of the material that have a 1:1 wrap, and they are stronger by far than a shackle.
 
Delfin said:
......The concern for Dyneema variants being weakened when making a sharp bend is also wrong. That is why they make soft shackles out of the material that have a 1:1 wrap, and they are stronger by far than a shackle.
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There is plenty of experience in the world of dinghies which confirms the lab results about bend radii.
I would always temper the advice of riggers with that from the manufacturer.
I have 4mm dyneema cored (a 4mm rope of which the 2.5mm ? core is dyneema) halyards on my dinghies, if I don't shorten them to move the pressure point every 6 months or so, they fail.
I suppose soft shackles are different because there is so little movement as they are so short. Although most racing people seem to use soft shackles with a very high safety factor.
 
lw395 said:
There is plenty of experience in the world of dinghies which confirms the lab results about bend radii.
I would always temper the advice of riggers with that from the manufacturer.
I have 4mm dyneema cored (a 4mm rope of which the 2.5mm ? core is dyneema) halyards on my dinghies, if I don't shorten them to move the pressure point every 6 months or so, they fail.
I suppose soft shackles are different because there is so little movement as they are so short. Although most racing people seem to use soft shackles with a very high safety factor.
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In dynamic situations the bend radius ratio is most definitely important, in the entertainments business Hi tech rope has almost completely taken over from steel wire rope for high speed winch stunt work. for that you need to size the sheaves correctly. As for static when anchoring I don't know, as the factor of safety is so high probably something else would go first. the Dynex site says the annealing process is to get rid of constructional creep, not stretch, but even so sk-75 is even stiffer than wire so any movement would be minimal.
But it is amazing stuff, dyneema isn't used for high speed winches, it's predominantly tech12 which is a bit tougher with little constructional creep, I get offcuts of that free and it's slowly working it's way all over the boat. :cool:
 
GHA said:
In dynamic situations the bend radius ratio is most definitely important, in the entertainments business Hi tech rope has almost completely taken over from steel wire rope for high speed winch stunt work. for that you need to size the sheaves correctly. As for static when anchoring.........:
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With that rubber dog bone thingy on deck, the anchoring situation is not going to be static.
Anchoring in other than a millpond and gust-free wind is not static anyway.
It is dynamic, which is why we have snubbers and so forth.
tech-12 is technora, which is more like Kevlar? Again needs to be used cannily as most dingy sailors have seen a few broken Kevlar halyards in their time.
Anyway, to be more constructive, what peak loading should an anchor rode be designed to?
Unfortunately that is a circular question, as the peak load will very much depend on the elasticity and damping of the rode, as well as the wind and waves.
 
I have found this thread fascinating and am going to update our snubber using the information gleaned. It is good to have something to put on the 'to do' list that is not too expensive :)

I have learned that we need a longer snubber (going to be anchorplait) but am not sure whether to add a pennant (or pendant, which is right ?). To be honest we are unlikely to anchor in storm conditions, to date we have only experienced 40-50 knots once but winds over 30 knots are encountered once or twice a season on average. I do fancy having one that could cope in a severe gale but am worried that a narrow diameter piece of dyneema will cut through our bow roller which is made of natural acetal h. I have experimented with two different profiles of roller (I got a long length of acetal) and reckon for dyneema I could make one with a pronounced V which would stop it wandering around from side to side but even so, would the dyneema cut through quickly ? A metal bush in the middle of the roller would stop the problem but I cannot think of a way of doing it. The roller we use for the snubber is also used for our mooring (heavy chain) so if I went down this route I would have to design a way for the rollers to be swopped easily - starting to sound a bit over complicated.

Also, another problem. I want to run the snubber down the side deck to a midships cleat so dyneema woukd defeat the advantage ofnthe extra length so i would have to have anchorplait to chain, then dyneema for the roller, then octoplait again to cleat.
 
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Storyline said:
I have found this thread fascinating and am going to update our snubber using the information gleaned. It is good to have something to put on the 'to do' list that is not too expensive :)

I have learned that we need a longer snubber (going to be anchorplait) but am not sure whether to add a pennant (or pendant, which is right ?). To be honest we are unlikely to anchor in storm conditions, to date we have only experienced 40-50 knots once but winds over 30 knots are encountered once or twice a season on average. I do fanûcy having one that could cope in a severe gale but am worried that a narrow diameter piece of dyneema will cut through our bow roller which is made of natural acetal h. I have experimented with two different profiles of roller (I got a long length of acetal) and reckon for dyneema I could make one with a pronounced V which would stop it wandering around from side to side but even so, would the dyneema cut through quickly ? A metal bush in the middle of the roller would stop the problem but I cannot think of a way of doing it. The roller we use for the snubber is also used for our mooring (heavy chain) so if I went down this route I would have to design a way for the rollers to be swopped easily - starting to sound a bit over complicated.

Also, another problem. I want to run the snubber down the side deck to a midships cleat so dyneema woukd defeat the advantage ofnthe extra length so i would have to have anchorplait to chain, then dyneema for the roller, then octoplait again to cleat.
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Mountains and molehills come to mind:D

You could always have the complete snubber outboard of your bow roller. Would that not be a lot simpler?
 
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Paddydog`1 said:
that's a neat solution. How would you lead it back from anchor chain at or above waterline to mid cleat though
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Ideally the snubber would be attached to the chain with rolling hitches, with a bight of slack chain, and it would all be overboard, but to be honest, it would be difficult to rig. It's not what I do, but some people worry about the internal friction in a line stretching back and forward over the bow roller. To my mind, this is made a lot worse by taking the line further aft.

I use a climbing rope, which is fed through a bit of plastic hose in way of the roller or fairlead.
 
NormanS said:
.....

You could always have the complete snubber outboard of your bow roller. Would that not be a lot simpler?
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I would prefer if the snubber went over the bow roller then in the event of a catastrophic failure the load would be passed onto the chain which would be aligned in the same direction.. I am also not sure how I could lead it aft to the cleat, possibly through a fairlead but it seems that the bow roller/stem head fitting is the ideal place as it is over engineered and if that failed then we would really be in trouble.

Of course I could not lead it directly to the midships cleat as the boat would present too much windage and it would just be wrong.

Edit: I said earlier this is for storm conditions which we hopefully will never encounter but if it is low cost, why not have it ? I like anchoring and the snug feeling when everything is set up nicely and it is blowing a hooley outside ;)
 
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Storyline said:
I have found this thread fascinating and am going to update our snubber using the information gleaned. It is good to have something to put on the 'to do' list that is not too expensive :)

I have learned that we need a longer snubber (going to be anchorplait) but am not sure whether to add a pennant (or pendant, which is right ?). To be honest we are unlikely to anchor in storm conditions, to date we have only experienced 40-50 knots once but winds over 30 knots are encountered once or twice a season on average. I do fancy having one that could cope in a severe gale but am worried that a narrow diameter piece of dyneema will cut through our bow roller which is made of natural acetal h. I have experimented with two different profiles of roller (I got a long length of acetal) and reckon for dyneema I could make one with a pronounced V which would stop it wandering around from side to side but even so, would the dyneema cut through quickly ? A metal bush in the middle of the roller would stop the problem but I cannot think of a way of doing it. The roller we use for the snubber is also used for our mooring (heavy chain) so if I went down this route I would have to design a way for the rollers to be swopped easily - starting to sound a bit over complicated.

Also, another problem. I want to run the snubber down the side deck to a midships cleat so dyneema woukd defeat the advantage ofnthe extra length so i would have to have anchorplait to chain, then dyneema for the roller, then octoplait again to cleat.
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I have three rollers, with the top used for the snubber. I had it turned out of high density plastic, with a 'U' groove for the line. If your's rolls, I can't see it sawing through, but I guess that would be something to watch. There is virtually no movement under load for the Dux, so it will perform pretty much like a piece of wire, only easier to work with. Since this stuff is used by loggers in place of chain, as well as tight wrapped soft shackles I doubt you need to worry about breakage if you size it right. Mine is good for up to around 19,000# and the 5/8 plait will give up long before then.

Seems to me the right design is to have the stretchy bit overboard outside the roller, with the Dux inboard for chafe resistance. With the nylon overboard, spray should keep any part of it above the water coo, or you can rig the Dux so it makes it to the water. I guess I'm not sure what you'd gain with Dux or whatever you use sandwiched between plait as you suggest.
 
Storyline said:
I said earlier this is for storm conditions which we hopefully will never encounter but if it is low cost, why not have it ? I like anchoring and the snug feeling when everything is set up nicely and it is blowing a hooley outside ;)
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Not everyone agrees, but I rather like noodling through design to suit extreme conditions even if I never encounter them. We carried a para anchor around for years (never took it out of the bag), and I spent many happy hours thinking through deployment in a hurricane (which we never saw.) So I'm with you.
 
Roberto said:
What if you need to increase scope while under load ? Do you have to pull the chain in untils you can free the snubber, then let go the chain and attach the snubber a second time at a lower point along the chain ? Or have you devised another method ?

Thanks
r
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Nope, you're pretty much committed on the scope you lay out as it would be a bitch to haul in 30' of chain in a blow to redeploy with greater scope. As a practical matter, we generally lay out 3:1 and because our anchor weighs what it does, we never budge. If winds greater than 30 knots are forecast, then we will haul in the snub line and lay out more scope with the snubber reattached to accommodate. In the event I had to lay out more scope in a blow, I would have to rely on the 3/4" backup snubber (200' long) after cutting loose the primary snubber. The whole point is, as noted, to increase the distance traveled by the vessel before she brings the chain up hard. This geometrically reduces the load on the ground tackle, so in my mind, it is important never to have a direct chain to the vessel connection when the wind howls unless your snub line precautions have failed. Which raises another detail I didn't mention and that is to only overlay a loose bight of chain equal in length to whatever stretch you have designed your system to handle, plus a couple of feet. The point is to have the load taken first by the snubber, then by the chain without allowing the vessel to get up a head of steam if the snubber(s) gives way. The force to stop the vessel is determined by the square of the velocity she's moving, so you can see why this is important.
 
Delfin said:
Nope, you're pretty much committed on the scope you lay out as it would be a bitch to haul in 30' of chain in a blow to redeploy with greater scope. As a practical matter, we generally lay out 3:1 and because our anchor weighs what it does, we never budge. If winds greater than 30 knots are forecast, then we will haul in the snub line and lay out more scope with the snubber reattached to accommodate. In the event I had to lay out more scope in a blow, I would have to rely on the 3/4" backup snubber (200' long) after cutting loose the primary snubber. The whole point is, as noted, to increase the distance traveled by the vessel before she brings the chain up hard. This geometrically reduces the load on the ground tackle, so in my mind, it is important never to have a direct chain to the vessel connection when the wind howls unless your snub line precautions have failed. Which raises another detail I didn't mention and that is to only overlay a loose bight of chain equal in length to whatever stretch you have designed your system to handle, plus a couple of feet. The point is to have the load taken first by the snubber, then by the chain without allowing the vessel to get up a head of steam if the snubber(s) gives way. The force to stop the vessel is determined by the square of the velocity she's moving, so you can see why this is important.
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Thanks for your comments Delfin

r
 
Sorry, I went off for 24 hours on the water.

We attach our snubbers (cat so snubbers replace a bridle) to the stern cleats. They then run up the outside of the side decks through the stanchion bases (so outside deck area). On the bow we have a padeye (suitably reinforced below deck) to which is attached a turning block. The snubber goes through the block to a common chain hook. The run along the side decks is almost straight, I'm not concerned with friction but if I was I'd run through fairleads - but that seems unnecessary. We have been running our furling lines through the stanchion bases for years -with out wear.

We could also attach dedicated padeyes on the transom, but attaching to the aft horn cleats works well.

The reason for 'starting' at the aft cleat is to keep as much of the snubber out of the water, or not have the snubber able to touch the seabed. We are using a chain hook, just a simple hook, and find that it it has the chain weight on it all the time its fine allow any slack (say if it and the chain sit on the seabed) and the hook falls off. An advantage of our long snubbers are - they are really long, so lots of elasticity. Many have a snubber attached near the windlass which results in them shortening the snubber (or the slack chain is huge) so they have a short (less effective snubber). If you have a 10m snubber and only 1m is on the boat the other end inevitably rubs on the seabed. We tried a Witchard chain hook with spring retaining pin, lovely piece of kit - but needs 2 hands which is not so easy with restricted space.

You could arrange the same system on a mono-hull all you need is a turning block perhaps attached by a soft shackle on the toe rail so as to pull the snubber into the centre line and then over the bow roller (through plastic hosepipe (maybe). It is, after all, not much different to barber hauling a genoa sheet.. Its an ideal project to hone up your ingenuity and practice making soft shackles.

With regard to the question as to how to deploy more chain. If we know the weather is to be bad - we deploy it all in the first place but then we are shallow drafted (1m) and only carry 50m of chain (we will increase this to 70m when we get our G7, 6mm chain - but only so that we can use deeper anchorages). But if the weather was to be really bad, we'ed deploy a second anchor 30m of chain, 40m of 3 strand nylon (or find a nice tree (we carry warp for trees). The choice is: motor up, take in chain, remove snubber, deploy more chain re-attach snubber - that should be possible. Or Delfin's route, ditch snubber, deploy more chain attach spare (or storm) snubber. If most of the snubber is on the yacht, when deployed, you will not need to ditch very much. Or, take in slack on chain + 1', release snubber (which now has no load) off aft horn cleats and reattach to bow horn cleats. On a 10m yacht, deploy 10 more metres of chain, plus slack.

Its all about tinkering.

Jonathan
 
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