Anchor snub lines

[Delfin]

Dyneema is good on chafe when it's not highly loaded.
So hollow tape sleeve protecting a snubber would work well.
The dyneema is not carrying the load.
A 10mm dyneema snubber/(pendant? not sure of the correct term TBH) with 65T of Yacht bouncing around on the end of it is a very different set up.
High modulus ropes like dyneema do not share the load across the whole rope very well when bent.
That can magnify the effect of chafe, as some individual fibres are highly loaded, therefore more easily cut.
I would be concerned about the point load at the bow roller.
If the rubber thingy is one the deck, that will mean the rope at the bow roller is constantly moving, a recipe for chafe.
10mm seems small string for 65T?

Interesting comment on the rubber inducing movement over the roller, which might be a good reason to move it outboards. Thanks. That said, it is my impression that the pre-stretched product is far more resistant to chafe than the standard issue. As near as I can tell from the Interweb, this seems to be the case.

Incidentally, the Dyneema I am using is 16 mm, not 10.

 

[Storyline]

To our resident anchor gurus
Of these affects of a snubber, which is the best reason to use one or in which order should they be ?

1. To reduce the likelyhood of a snatch load causing the anchor to let go
2. To save wear and tear and stress to the bow roller/cleats
3. To provide a more comfortable experience at anchor
4. To reduce the chance of the chain breaking
5. Any other reason .....

 

[NormanS]

To our resident anchor gurus
Of these affects of a snubber, which is the best reason to use one or in which order should they be ?

1. To reduce the likelyhood of a snatch load causing the anchor to let go
2. To save wear and tear and stress to the bow roller/cleats
3. To provide a more comfortable experience at anchor
4. To reduce the chance of the chain breaking
5. Any other reason .....

I would think it's a bit like looking both ways before crossing the road. It doesn't matter whether it's a bus or a lorry that knocks you down. Either would spoil your day.

 

[GHA]

To our resident anchor gurus
Of these affects of a snubber, which is the best reason to use one or in which order should they be ?

1. To reduce the likelyhood of a snatch load causing the anchor to let go
2. To save wear and tear and stress to the bow roller/cleats
3. To provide a more comfortable experience at anchor
4. To reduce the chance of the chain breaking
5. Any other reason .....

I would say all of the above

Once the boat gets moving in a gust the snubber decreases the force going down the anchor chain by increasing the distance over which the boat decelerates as it stretches. Which is a good thing

 

[Storyline]

I would think it's a bit like looking both ways before crossing the road. It doesn't matter whether it's a bus or a lorry that knocks you down. Either would spoil your day.

Yes, I realised after posting it that it applies to all and was a bit of a stupid post . The reason I posted it was that I wanted to know if the use of a snubber significantly reduces the chance of the anchor breaking out as I sometimes think that a snatch load will dig the Rocna in even deeper (within reason).

 

[vyv_cox]

To our resident anchor gurus
Of these affects of a snubber, which is the best reason to use one or in which order should they be ?

1. To reduce the likelyhood of a snatch load causing the anchor to let go
2. To save wear and tear and stress to the bow roller/cleats
3. To provide a more comfortable experience at anchor
4. To reduce the chance of the chain breaking
5. Any other reason .....

It seems to me that:
1. Snatch loads can be considerable when the boat is yawing in gusting winds, particularly behind high ground that causes gusting from various directions. A snubber certainly helps, although I favour a second anchor laid at about 90 degrees to the bower. I have anchorplait on the kedge, so effectively a snubber on both anchors. We have sat out some big blows like this, where boats visibly yawing through twice the angle we were have dragged.
2. Almost negligible. I take the snubber through a length of hose that fits the bow roller quite snugly, which reduces the noise a bit and cuts out slamming from one side of the jaws to the other.
3. Definitely a big plus. After several nights of noisy chain dragging constantly across the bottom the quieting effect of a snubber is most welcome.
4. In theory yes but chain fracture is extremely rare. Test the weld strength using the method on my website, inspect annually for corrosion, wear or other damage and it is doubtful that this will ever occur.
5. Don't forget shackles, connectors, C-links etc, all of which merit careful inspection from time to time.

 

[Storyline]

In have found the yawing effect is to some extent, boat dependant. Our last boat was a narrow beamed bilge keeler and she behaved very well at anchor. I can remember our worst gale (steady winds over a low lying island) when some boats were veering wildly and indeed several dragged. In contrast, whilst we did veer it was a much more slow motion effect. I was bit disappointed when we got Storyline to discover that she is not quite as well behaved. She is of modest beam, quite heavy, fin keeled and does not lie as well however she does not try to sail to her anchor as some modern lightweight flyers do. I do not know if the bilge keels contributed to stability but guess they may have.

 

[dunedin]

We tried out a new anchor snubber this summer - with an anchor hook at the bottom, then a rubber snubber spring designed to be outboard of the roller to absorb initial shock loads, then a spliced Y onboard to lead to both deck cleats (otherwise if use just one it leads badly off the bow roller).
Not had to test in a full gale, but seemed to work pretty well in near gale conditions when was stretching fully but avoided any big snatches in the gusts.
Certainly will be using again next year

 

[Neeves]

To our resident anchor gurus
Of these affects of a snubber, which is the best reason to use one or in which order should they be ?

1. To reduce the likelyhood of a snatch load causing the anchor to let go
2. To save wear and tear and stress to the bow roller/cleats
3. To provide a more comfortable experience at anchor
4. To reduce the chance of the chain breaking
5. Any other reason .....

There should be no opportunity that the chain will break, unless it is grossly undersized or very badly corroded. 8mm x G3 chain has a Working Load Limit of 0.8t and a min breaking strength of 3.2t (the WLL and Break Load can vary - depends where its made) and might be found on a yacht upto 40' (I have not checked the size of yacht).. But a 800kg snatch load is huge (for a 40' yacht) - its huge for a 50' yacht and as there is the 4:1 safety factor - its the reason chains generally do not break.

The bow rollers should be strong enough that they really do not need protection (though they do bend, I suspect on trying retrieve jammed anchors).

To minimise snatch loading and having a more comfortable time at anchor are cause and effect, if there is no snatch loading you should be much more comfortable. A decent anchor should actually not pull out even with snatch loads. But high snatch loads can be frightening, it feels as if you have just been rammed - and its a yacht, so do not rely on the anchor holding with high snatch loads!

So in order, 1, 3, 2 (and 4 should not be part of the equation).

Another reason is to move the point, or points, of load to a strong point. Samson posts have disappeared from most small to medium (and even large) modern yachts and many yachts do not even have a bow cleat (because they get in the way of sheets - or the sun lounger - do you still have sun in the UK?.) The windlass is commonly not well attached or better stated as not be designed to take exceptional load. So having a snubber allows you to use whichever strong point you deem strongest (cleats being obvious but also winches)

Snubbers, as Delfin mentioned, stop the chain rattling or grinding on the bow roller - which engenders a bit more silence in the forepeak (or owners suite - dependent on the size of yacht).

Jonathan

 

[Storyline]

There should be no opportunity that the chain will break, unless it is grossly undersized or very badly corroded. ld
.....
Jonathan

That is good news. All this talk of G30/G40 chain has had me wondering, as when we got our chain I was not aware of this so do not know which one we have got. All I know is that it is 3/8".

Edit: I agree about the demise of the samson post. Personally I think this is a sad thing and as you said we do not even have a centre cleat. This is why we need our knitting to keep the snubber and the chain central on their rollers. The lines pull them away from the direct route from the rollers to their cleats. These lines are made of nylon and also add a bit more give into the system. When I installed our windlass i massively over engineered the mounting pad and backing plate but am still reliant on the M8 studs that hold it in place. As the loadings are lateral I should imagine it would be able to take quite a lot of punishment. It is a vertical windlass with a drum which is normally only used to haul swmbo up the mast.

I also agree with the comfort at anchor. In the rare occasions we are stuck in full blown gales I sleep in the forepeak, the theory being i can hear things going wrong. The snubber does help stop the banging of the chain on its roller as we veer.

 

[vyv_cox]

That is good news. All this talk of G30/G40 chain has had me wondering, as when we got our chain I was not aware of this so do not know which one we have got. All I know is that it is 3/8".

If it is definitely 3/8", not 10 mm, then it is either USA or UK manufactured. All the dimensions are on my website at http://coxengineering.sharepoint.com/Pages/Chaindefinitions.aspx but the easiest to measure in your case is the internal link length, 31 mm for USA and 30 mm for UK. The internal width of a link differentiates between USA G30 and G43. If it is UK made I would assume it to be G30. Your gypsy, if you have a windlass, is probably marked as to the chain it takes.

 

[Storyline]

If it is definitely 3/8", not 10 mm, then it is either USA or UK manufactured. All the dimensions are on my website at http://coxengineering.sharepoint.com/Pages/Chaindefinitions.aspx but the easiest to measure in your case is the internal link length, 31 mm for USA and 30 mm for UK. The internal width of a link differentiates between USA G30 and G43. If it is UK made I would assume it to be G30. Your gypsy, if you have a windlass, is probably marked as to the chain it takes.

It is from a foundry in France. I used to be a weight is everything type of person and when we got Storyline I got a bee in my bonnet about maximising the length of chain we could carry vs weight. Of course it all a compromise and if we had gone for 10mm it would have added a bit too much weight to the bow. In the end I settled on 70m of 3/8" (20m of which is led aft). Jimmy Green were very helpful sourcing the chain and Lewmar were o/s and flew the gypsy from the US at no extra charge.

In the back of my mind I had regretted not getting 10mm but I did not realise at the time how easy it was to lead some chain aft. I have been very pleased to read you and Jonathan's (and others) discussions recently about chain weight not being of crucial importance. I was sceptical at first but I do now accept that once the chain has lifted, weight does pay a part but not as much as I thought it did so I am happy with the 3/8".

 

[lw395]

The Dyneema Dux is annealed, so there is no stretch at all. I read that riggers use ceramic knives to cut the stuff and they wear out after a dozen or so cuts, so I think it is pretty resistant to chafe. Yes, in my setup the rubber is inboard of the roller and there is enough room for it to stretch as much as it is going to between a 14" yachtsman cleat and a high density roller it goes over before joining up with the nylon snub line.

Maybe you should talk with the manufacturer of the rope about this?
Dyneema of any flavour does not have 'no stretch at all', its modulus is high not infinite.
I don't know what the peak load will be on your rode, obvious depends on the wind and waves, but you must be in the 'several percent of breaking' area?
Dyneema is great, I use it a lot on dinghies, but it is not as magic as some people like to think.
I don't know about ceramic knives, I cut the smaller sizes easily enough using a Stanley knife, or a decent pair of SWMBO's scissors.
It is certainly easier to cut than Kevlar or carbon fibre.
HTH.

 

[Neeves]

I am surprised and bemused that a French chain manufacturer made/makes an imperial chain - perfidious Albion strikes again. But its not unique, to make metric and imperial. If you bought from jimmy green you should have documentation somewhere defining link size and/or if its G3 (or G30), G4 (or G40) (which seems to be a more 'metric' designation) or G43 (which seems to be American). The fact you have a Lewmar gypsy from America certainly suggests its imperial - but as BBB, G30 and G43 links are different I would have thought Lewmar would need to know what you had to supply a matching gypsy - but maybe the gypsy comfortably takes imperial BBB, G30 and G43 (this is new ground for me)

If you have G3 or BBB - it will be more than strong enough, I'm interested academically not fearing for safety G40 or G43 are obviously stronger and maybe worth a bottle of malt when its blowing 50 knots but otherwise I'm not sure necessary (unless you went down in size).

I would be interested in which French supplier makes both Metric and Imperial, its a service worth noting. I'm also interested in what or how the gypsy is defined (might be on the invoice). Is it simply 3/8 inch, or 3/8th inch x G30 (or BBB or G43). Finally I'm interested in how much the gypsy cost - as my limited foray into gypsy costs suggest they are sufficiently expensive (certainly in Oz) to deter anyone changing chain size (though we are changing).

Another civil, educational and fascinating ground tackle thread

Jonathan

 

[Neeves]

I don't know about ceramic knives, I cut the smaller sizes easily enough using a Stanley knife, or a decent pair of SWMBO's scissors.
It is certainly easier to cut than Kevlar or carbon fibre.
HTH.

I don't know where your SWIMBO gets her scissors but I'd like a pair (of the scissors). We installed 6mm Lyros unsheathed Dyneema for our lifelines, to replace the supplied sheathed stainless ones, and cutting the stuff was not as easy as you imply (but then I've never tried to cut carbon fibre nor Kevlar) and certainly, cutting the Dyneema was, much more difficult than cutting similar sized stainless.

But the peak loads on Delfin's rodes are reduced because he is using a snubber so he should be many several percent away from breaking loads. Moreover the Dyneema runs over the bow roller itself which might be a polymer and should rotate (and have low abrasion). I suspect his snubber will break before the Dyneema. A 3/8th inch Dyneema has a breaking strength of 5t, and would stretch 1.5% - 3% at break? (and hopefully he is never imposing even 20% of this on the Dyneema strop). But I do not know about strength degradation of Dyneema in salt water nor subject to repeated cyclic loading??

Jonathan

 

[GHA]

For anyone making shackles, I struggled a bit but found this to be the easiest instructions to follow for the diamond knot..

http://zipkinci.com/galeri/data/media/4/cak305cev305z305.jpg

 

[Delfin]

Maybe you should talk with the manufacturer of the rope about this?
Dyneema of any flavour does not have 'no stretch at all', its modulus is high not infinite.
I don't know what the peak load will be on your rode, obvious depends on the wind and waves, but you must be in the 'several percent of breaking' area?
Dyneema is great, I use it a lot on dinghies, but it is not as magic as some people like to think.
I don't know about ceramic knives, I cut the smaller sizes easily enough using a Stanley knife, or a decent pair of SWMBO's scissors.
It is certainly easier to cut than Kevlar or carbon fibre.
HTH.

Dyneema is not Dyneema Dux. I thought that would be clear if I spelled it out, but I guess not. In the lengths I am dealing with, there is effectively no stretch, Dux is the most highly abrasion resistant synthetic line material made, and going over the roller will not induce fatigue with any effect that would reduce its strength below that of the nylon snubber. No material on earth has infinite modulus, so you got me there.

The base fiber for Dux before annealing is something called SK-75, which I read is used to make butcher's gloves out of because of its resistance to cutting.

http://www.rigworks.com/running-rigging/dynex-dux-line.htm

 

[Storyline]

..... If you bought from jimmy green you should have documentation somewhere defining link size and/or if its G3 (or G30), G4 (or G40) (which seems to be a more 'metric' designation) or G43 (which seems to be American). The fact you have a Lewmar gypsy from America certainly suggests its imperial - but as BBB, G30 and G43 links are different I would have thought Lewmar would need to know what you had to supply a matching gypsy - but maybe the gypsy comfortably takes imperial BBB, G30 and G43 (this is new ground for me)

If you have G3 or BBB - it will be more than strong enough, I'm interested academically not fearing for safety G40 or G43 are obviously stronger and maybe worth a bottle of malt when its blowing 50 knots but otherwise I'm not sure necessary (unless you went down in size).

I would be interested in which French supplier makes both Metric and Imperial, its a service worth noting. I'm also interested in what or how the gypsy is defined (might be on the invoice). Is it simply 3/8 inch, or 3/8th inch x G30 (or BBB or G43). Finally I'm interested in how much the gypsy cost - as my limited foray into gypsy costs suggest they are sufficiently expensive (certainly in Oz) to deter anyone changing chain size (though we are changing).

Another civil, educational and fascinating ground tackle thread

Jonathan

I will try to find out the name of the foundry and the original JG invoice which will show the gypsy cost. I am now intrigued to know what i have got. I think Vyv might know the foundry.

Agree about the civil tone of the thread. It makes complete sense as all we are trying to do is help each other. I have not used the forums for several years and have been surprised how rude (and defensive) some people can get. Sometimes it is although a few individuals feel their logic in a discussion is improved by the use of abusive language. I am sure they would not behave like that in a yacht club bar.
A couple of times I have had to stop myself rising to the bait

 

[lw395]

Dyneema is not Dyneema Dux. I thought that would be clear if I spelled it out, but I guess not. In the lengths I am dealing with, there is effectively no stretch, Dux is the most highly abrasion resistant synthetic line material made, and going over the roller will not induce fatigue with any effect that would reduce its strength below that of the nylon snubber. No material on earth has infinite modulus, so you got me there.

The base fiber for Dux before annealing is something called SK-75, which I read is used to make butcher's gloves out of because of its resistance to cutting.

http://www.rigworks.com/running-rigging/dynex-dux-line.htm

Dyneema Dux is dyneema sk75 heat treated and impregnated with a type of duracote, AFAIK.
SK75 is one of the common flavours of dyneema used by Marlow for dinghy ropes.
The heat treatment removes the creep from the SK75, which is essentially what makes garden variety sk75 no good for standing rigging.

Dux is a great product, but I would be wary of using it in the way you are proposing.
Firstly you are not respecting the 5:1 bend radius : rope diameter.
Secondly your pendant is small. People who recommend this stuff seem to be touting 7mm pendants for a boat less than a tenth of your displacement.
General advice seems to be go for a nominal breaking strain at least 5x the weakest metal link in your rode.
Of course the actual peak load is unknown, what are you wanting to anchor through?
To my mind, all this talk of snubbers makes me think we are talking about anchoring through 'a bit of weather' rather than a lunch hook.
I've happily kedged a 40ft boat in no wind on 6mm polyprop.

Another point, I see references to Dux 'softening up in use' when used for spinnaker guys. Does this mean it loses some of its difference from common sk75 when bend cycled?
Dux is optimised for standing rigging.
Use as you do and I don't think the suppliers will want to know if your boat takes a one way trip to the beach, to steal a line from one of the comments I found.
You might seriously want to consult the manufacturer.
I believe the best line to go over a bow roller is the biggest polyester that will fit.

 

[Delfin]

Dyneema Dux is dyneema sk75 heat treated and impregnated with a type of duracote, AFAIK.
SK75 is one of the common flavours of dyneema used by Marlow for dinghy ropes.
The heat treatment removes the creep from the SK75, which is essentially what makes garden variety sk75 no good for standing rigging.

Dux is a great product, but I would be wary of using it in the way you are proposing.
Firstly you are not respecting the 5:1 bend radius : rope diameter.
Secondly your pendant is small. People who recommend this stuff seem to be touting 7mm pendants for a boat less than a tenth of your displacement.
General advice seems to be go for a nominal breaking strain at least 5x the weakest metal link in your rode.
Of course the actual peak load is unknown, what are you wanting to anchor through?
To my mind, all this talk of snubbers makes me think we are talking about anchoring through 'a bit of weather' rather than a lunch hook.
I've happily kedged a 40ft boat in no wind on 6mm polyprop.

Another point, I see references to Dux 'softening up in use' when used for spinnaker guys. Does this mean it loses some of its difference from common sk75 when bend cycled?
Dux is optimised for standing rigging.
Use as you do and I don't think the suppliers will want to know if your boat takes a one way trip to the beach, to steal a line from one of the comments I found.
You might seriously want to consult the manufacturer.
I believe the best line to go over a bow roller is the biggest polyester that will fit.

Dux is recommended for standing rigging by some and not by others. The bend on my roller is greater than 5:1. The pendant does not need to be any longer than necessary to get over the roller. My pendant, as noted, is 10 mm. The softening of Dux simply refers to its hand, that is, it is stiff to begin with but softens with use. It's strength is not affected. Straight Dyneema pendants are in use by a lot of people and the breaking strength exceeds that of the nylon snubber, the abrasion resistance is greater than 3 strand nylon, there is no heat loading from stretch, so I doubt I will be salvaging the vessel off the beach anytime soon. Dux is used by loggers dragging timber through the woods, so do you really think it unsuitable for the purpose? According to the rigger I purchased the Dux from, this is the ideal product for the application, which is confirmed by virtually every rigger posting information on the Internet, if you care to look. Dux, being stronger than steel wire of the same size is simply an easy way to provide an abrasion resistant line from a cleat to a snub line. Not too complicated a concept, I should think.

"Dynex Dux starts as the more commonly known Dyneema, a super-strong, low-stretch braided synthetic rope, used mostly as high-tech running rigging on racing boats and performance cruisers. The Icelandic company Hampidjan then treats the Dyneema in a special steam oven, simultaneously heating and stretching the rope. What results is Dux — the treatment work hardens the fibers, increasing its abrasion resistance, reducing stretch to virtually zero (less than wire, incredibly), and making for a smooth yet extremely strong braided rope."

"Strength for Diameter
Strength to Weight
Stretch/Elasticity
Creep (elongation over time)
Abrasion resistance
UV resistance


Dynex DUX has the best scores on ALL of the above qualities when compared to other high tech fibers."