Dyneema Lifelines

Public Service Announcement - They call this a Lifeline for a reason - don't skimp here and do it properly.

I love Dyneema but it blows for lifelines unless done correctly.

Firstly, it usually isn't legal for Coastal and Offshore racing. Mainly for the reason stated above.

Next, everyone and their cousin thinks they can splice up a Safe/Strong/Accurate lifeline which usually is not the case. Many owners fit diameters too small or too stretchy to do any good or the splices are loose and sloppy, frayed, and rarely pre-stretched. The splice needs to be stretched as well.

Lashing is even more of an issue. Learn to do this properly or do not do it at all. I've seen too many people go in the water due to bad lashings coming apart.

Do it right or even better, stick with cable.

 
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someoldsalt

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Thanks for the salient thoughts - estarzinger-I hear you on the long bury splice versus brummel, but then the use of WR2 maybe makes less sense as I don't think it would be possible to milk the cover over that long splice?  The cover would then terminate about 20" or so from the eye, maybe that is fine although less attractive?  NER recommends a brummel splice with a bury for the cover that ends up with about 11'' of exposed core before the cover.  The tightly woven dyneema cover makes for a pretty nice hand and of course helps at stanchion chafe points as well-seems like pretty good stuff.  I'd guess that the long bury spice would also shorten the rope more than a brummel?

 

someoldsalt

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While I am at it, another question for you, e, would you recommend the long bury for running rigging/standing rigging as well? I am adding a dyneema innerforestay and runners to my rig (Hood 38) and wonder if you reckon the long bury is superior there.  If that is so, why is everyone (Colligo) etc recommending the brummel splice...? Thanks in advance-hopefully this is helpful to all

 

SloopJonB

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Public Service Announcement - They call this a Lifeline for a reason - don't skimp here and do it properly.

I love Dyneema but it blows for lifelines unless done correctly.

Firstly, it usually isn't legal for Coastal and Offshore racing. Mainly for the reason stated above.

Next, everyone and their cousin thinks they can splice up a Safe/Strong/Accurate lifeline which usually is not the case. Many owners fit diameters too small or too stretchy to do any good or the splices are loose and sloppy, frayed, and rarely pre-stretched. The splice needs to be stretched as well.

Lashing is even more of an issue. Learn to do this properly or do not do it at all. I've seen too many people go in the water due to bad lashings coming apart.

Do it right or even better, stick with cable.
I really liked the idea of Dyneema lifelines for their "hand" but talking to my rigger, this thread and a serendipitous find of 1X19 has convinced me to go with uncoated wire.

 

estarzinger

Super Anarchist
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 would you recommend the long bury for running rigging/standing rigging as well? I am adding a dyneema innerforestay and runners to my rig (Hood 38) and wonder if you reckon the long bury is superior there.  If that is so, why is everyone (Colligo) etc recommending the brummel splice...? Thanks in advance-hopefully this is helpful to all
yes, long bury here. The Brummel is a 10% strength loss when done correctly (more if diyed a bit wrong with say more distortion to braid).  That's not a huge issue with stays sized big for creep reduction, so really 'whatever' is the technical answer, but the long bury is just 'proper' because it is technically superior.  The brummel was very trendy when sailors started using dyneema - it was a bit unknown, so gave you some 'secret handshake cred' and it solved the 'low load slipping' problem.  But after people examined and tested the options, anyone serious has moved any from it except for a few particular situations.

 then the use of WR2 maybe makes less sense as I don't think it would be possible to milk the cover over that long splice?  The cover would then terminate about 20" or so from the eye, maybe that is fine although less attractive?  NER recommends a brummel splice with a bury for the cover that ends up with about 11'' of exposed core before the cover.  The tightly woven dyneema cover makes for a pretty nice hand and of course helps at stanchion chafe points as well-seems like pretty good stuff.  I'd guess that the long bury spice would also shorten the rope more than a brummel?
I'm personally not a huge fan of WR2.  I would rather the dyneema I pay for is all actually load bearing, and half that line (the cover) is not load bearing. And that half does not provide very good UV protection either.  It does provide decent chafe protection . . but if it was all load bearing in the first place you would have more meat to absorb little nicks and dings - and if you wanted you would then just provide little covers for the stanchion passages - but if you polish those they dont need sleeves.

IDK much about splicing options for it.  I've done it only a few times. You can in fact milk the cover back over a well tapered long bury, but it can be a bit of work. I have not tested the splice alternatives.  So I can't really add anything factual information around splicing it. 

 

slug zitski

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You're better off with stainless tops , Unless you sleave the top line to prevent Genoa chafe and sheet burns 

fabric is wothwhile for the protected lower lifelines 

black singlebraid   technora  works well ,,its stable   long lasting and easy to splice 

 

TJSoCal

Super Anarchist
Regarding strength, there was a study done by the Naval Academy that found that when a lifeline system failed it was pretty much always the pulpits that gave up first. I suspect this would be true even with less-than-perfect dyneema splices or lashings (assuming no chafe, which I know is a big assumption but is at least readily inspectable). 

 

estarzinger

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Regarding strength, there was a study done by the Naval Academy that found that when a lifeline system failed it was pretty much always the pulpits that gave up first. I suspect this would be true even with less-than-perfect dyneema splices or lashings (assuming no chafe, which I know is a big assumption but is at least readily inspectable). 
You have a link/copy to the study? I can imagine that would be true with new dyneema in a test lab environment.  But we know it is NOT true out actually on boats racing in the real world.

 

TJSoCal

Super Anarchist
You have a link/copy to the study? I can imagine that would be true with new dyneema in a test lab environment.  But we know it is NOT true out actually on boats racing in the real world.
Don't have a link to the actual study but below links to a Practical Sailor article. 

Granted a bit dated (2012) and may be unique to stern pulpit designs similar to the Navy 44. But their finding was that the solid structures failed significantly below the breaking strength of 1x19 wire. 

I don't know but would suspect that real world failures are mostly as found in the study or a result of compromised swage fittings. Are there any cases of wire lifelines parting in the middle of a span? 

https://www.practical-sailor.com/safety-seamanship/usna-lifeline-test-reveals-weak-spots

 

estarzinger

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I don't know but would suspect that real world failures are mostly as found in the study or a result of compromised swage fittings. Are there any cases of wire lifelines parting in the middle of a span? 
There certainly were many when we used coated wire. There are way fewer with bare wire, but there are a some - bend fatigue failure leading to stranding at stanchions (quite a few caught before the wire actually gives way because stranding is not hard to spot if you are doing actual inspections).  But yea, the end failures have been a continuing majority - mostly operator/installer error, but also some 'aging/corrosion'.

I'm aware of way more wire (and HDPE) failures than I am of pulpit failures.  The pulpit failures I am aware of are I think all due to using small tabs or wire loops welded to the pulpit, without much weld meat.  I dont believe I have ever seen a pulpit failure where the life lines that have been attached to the full pulpit tubes  (eg as in lashed with dyneema right around the full tubes).

Both new wire and new dyneema of lifeline spec are pretty strong.  The specs are designed so that the lifelines can take a 50% strength reduction and still do their job. Failures tend to be due to aging or operator error rather than raw load failure.

I have seen this sort of pulpit/stanchion crimping failure when the boat brushes something - a concrete fuel dock or a trawler you are rafted to for instance. But I dont remember having seen it with simply human loaded (hiking) lifelines.

 
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TJSoCal

Super Anarchist
Sounds like the USNA experiment was done with shock loading - "several crew being hurled against the lifelines." 

They also noted that the leg of the stern pulpit was vertical, at a right angle to the deck where the bow pulpit was angled and survived better. 

 

slug zitski

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Sounds like the USNA experiment was done with shock loading - "several crew being hurled against the lifelines." 

They also noted that the leg of the stern pulpit was vertical, at a right angle to the deck where the bow pulpit was angled and survived better. 
That is the expected scenario ....full crew  against the lifelines 

 

estarzinger

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Sounds like the USNA experiment was done with shock loading - "several crew being hurled against the lifelines." 
I guess my interpretation is that what that study shows is:

#1 that, when new and properly installed/constructed, the current strength specs for the system are satisfactory (including under dynamic loading) . . . because the failure mode is those crimped tubes, which we dont really see in real life.

#2 what we need to be careful of is aging and improper methods. 

 

slug zitski

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I guess my interpretation is that what that study shows is:

#1 that, when new and properly installed/constructed, the current strength specs for the system are satisfactory (including under dynamic loading) . . . because the failure mode is those crimped tubes, which we dont really see in real life.

#2 what we need to be careful of is aging and improper methods. 
Lifelines fail at the terminals 

almost always bad engineering 

lifeline. terminals must articulate ...toggle and tee .. or the stud will  bend , fatigue and fail 

the  pictured fabric lifeline termination is poor 

the stud will bend and fail 

AFF614B3-24A9-4415-B55B-B3DFD37E16EE.jpeg

 

Rain Man

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Lifelines fail at the terminals 

almost always bad engineering 

lifeline. terminals must articulate ...toggle and tee .. or the stud will  bend , fatigue and fail 

the  pictured fabric lifeline termination is poor 

the stud will bend and fail 

View attachment 440614
Agreed, this is a really bad design.  If the crew leans on the lifelines hard  a few times that toggle will be toast.  

It isn't hard to do this correctly though.  One of the key things to keep in mind with dyneema is that the bend radius of the spliced loop has a minimum.  There are special thimbles made for dyneema for this purpose.  A lot of people don't use them, and that is a problem.   In addition to the problem SZ points out, in the picture above it looks like the radius is below the minimum.  

 

slug zitski

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Agreed, this is a really bad design.  If the crew leans on the lifelines hard  a few times that toggle will be toast.  

It isn't hard to do this correctly though.  One of the key things to keep in mind with dyneema is that the bend radius of the spliced loop has a minimum.  There are special thimbles made for dyneema for this purpose.  A lot of people don't use them, and that is a problem.   In addition to the problem SZ points out, in the picture above it looks like the radius is below the minimum.  
The correct engineering is a welded tang and toggle 

the bottom lifeline  could be inferior spec because it is subject to  lower loading 

EAFDBDAF-B7F8-46D4-A323-06E94FF36635.png

 




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