Thoughts on Dyneema for guard rails?

over-specified for the job ? over-expensive for the job ? Guard wires sometimes come in for a bit of heavy abrasion from wrongly threaded anchord chains or cross spinnaker guys, and I suspect that steel has a better score on the Moh scale than dyneema.
 
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sarabande said:
over-specified for the job ? over-expensive for the job ? Guard wires sometimes come in for a bit of heavy abrasion from wrongly threaded anchord chains or cross spinnaker guys, and I suspect that steel has a better score on the Moh scale than dyneema.
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A quick look and I see pvc coated ss for about 2.50 mtr, then the connectors at 4 for swaged or 12 for screw connect so all 4 will cost a couple of hundred squids.
i find dyneema for about £1 mtr and i can knot it on
Stu
 
skipper_stu said:
A quick look and I see pvc coated ss for about 2.50 mtr, then the connectors at 4 for swaged or 12 for screw connect so all 4 will cost a couple of hundred squids.
i find dyneema for about £1 mtr and i can knot it on
Stu
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PVC coated SS tends to harbour corrosion, I would rather have plain SS with loose plastic tubing over it.
Dyneema sounds a good idea, is it acceptable to any racing authorities you come under? Will it chafe?
I suspect the devil is in the detail, if the dyneema is done right it should last a long time. If it holds moisture against the wrong sort of stainless you may get pitting which causes chafe. I've seen that in lashings on the pushpit.
 
I think Yachting authorities still require uncovered SS for lines. Perhaps for the reasons Sarabande mentions. Certainly on the big ocean racers 100fters Sydney to Hobart SS safety lines are about the only SS on the boat. olewill
 
From the recently revised and re published Yachting NZ safety regs which can be downloaded here
http://www.yachtingnz.org.nz/sites/yachtingnz/files/YNZ Safety Regulations 1316 FINAL.pdf

sample
LIFELINES
17.17 The minimum diameter lifeline wire shall be:
Yachts under 8.5m (LOA) 3mm
Yachts 8.5m to 13m 4mm
Yachts over 13m 5mm
Wire manufactured with a plastic coating
shall not be used.
Grade 316 Stainless Wire is recommended –
1x19. Tape unacceptable.
If fibre used instead of wire e.g. single
braided dyneema, spectra, vectran, dynex
or similar, there can be no tolerance for
wear. Material must be protected from U.V.
and chafe by a sheath.
Sheath can be taken as an overbraided core
over the main load member of the same
material or another type of material.
The strength of the fibre must be equal to or
greater than that of the appropriate stainless
steel wire.
The wire shall show no significant signs
of corrosion or weathering. When plastic
tubing has been used it should be cut at its
lowest point to allow any water to drain.
17.18 Lifelines shall be taut. When a deflecting
force of 50N (5kg) is applied to a lifeline
midway between supports, the lifeline must
not deflect more than 50mm.
etc etc

These are the applicable rules for NZ - i am sure there are equivalent publications in the UK. This is noteworthy as it is very recent and presumably (hopefully ) the recommendations are based on science rather than opinion....
worth reading the whole doc in my opinion.
Good luck
 
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Seems to me that different contributors to this thread are talking about 2 different things - guard rails, as per the OP, and lifelines, which go along the deck and are for clipping safety lines onto.
Using Dyneema for guard rails may have some disadvantages as it chafes easily, particularly where it passes through stanchion eyes, and shouldn't be knotted - as per the last post.
 
greenalien said:
Seems to me that different contributors to this thread are talking about 2 different things - guard rails, as per the OP, and lifelines, which go along the deck and are for clipping safety lines onto.
Using Dyneema for guard rails may have some disadvantages as it chafes easily, particularly where it passes through stanchion eyes, and shouldn't be knotted - as per the last post.
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I can see why you say that but the NZ article doioes make it clear that the lifelines as they call them are guard rail wires as opposed to jackstays which is what I think you are thinking of.

I can see only three reasons why not to use dynema for guardrails:
1/ once you have spiced a loop they will no longer run through the guardrail eyes is you ever want to.
2/ how do they cope with sun long term? stainless wire is a once only fit. how would you know that dynema had become weaked by the sun?
3/ how do they cope with abrasion - I would have thought well enough but I am not sure
 
It's a good idea. The RORC and the IRC as far as I know haven't given it the green light yet, no doubt for the same reasons as posted here but it's only a matter of time in my opinion. I'd certainly consider using it if I was changing my guard rails. Chafe and UV resistance are about as good as you get for rope and 5mm will be more than strong enough. It's already used on some classes.
 
RORC still demand uncovered SS wire for lifelines, as do JOG. Don't think I really want to sail on boats where the breaking strain of the lifelines is something to worry about.
 
Thought on this myself (but I'm not familiar with dyneema, this was the reason), one obvious thing - dyneema is prone to chafe, low melting point. So for safety margin quite big diameter would be advisable. Another - forget about breaking strength; consider safe working load. Then having lifeline nice to touch and bigger diameter than steel would be nice.
Personally I'm putting steel onto; have been a alpinist, ye know...
 
Lifelines (Guardrails) of Dyneema

On terminology, English is not easy.. meaning of words depend on where you live.
Lifelines & Guardrails are both used to describe the same thing.

Jackstays goes along the deck for clipping safety lines.

greenalien said:
Seems to me that different contributors to this thread are talking about 2 different things - guard rails, as per the OP, and lifelines, which go along the deck and are for clipping safety lines onto.
Using Dyneema for guard rails may have some disadvantages as it chafes easily, particularly where it passes through stanchion eyes, and shouldn't be knotted - as per the last post.
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in ISAF Offshore Special Regulations - Complete Version 2012-2013, you can read this.
Source http://www.sailing.org/tools/documents/OSR2012Complete24012012Colour-[11765].pdf
3.14.6 Lifeline Minimun Diameters, Required Materials,Specifications

a) Lifelines shall be of :
- stranded stainless steel wire or
- Single-braided High Modulus Polyethylene (HMPE) (Dyneema®/Spectra® or equivalent) rope

<---- snip ---->

e) When HMPE (Dyneema®/Spectra®) is used, it
shall be spliced in accordance with the
manufacturer’s recommended procedures.
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4.04 Jackstays, Clipping Points and Static Safety Lines
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Dyneema is a UV stable fibre that withstands chaff better than other fibres, but it does not like to go over sharp edges.
Extra chafe protection can be added if you feel that you need it.

EdBeynon said:
How do you know it doesn't look mint but UV has killed it?
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UV will work from the outside in, it will be visible long before it is dangerous.

On SS wires it is the swage terminal/wire area that is the week point, difficult to inspect.

Dyneema is easier to inspect replace and repair.
 
Rossynant said:
Thought on this myself (but I'm not familiar with dyneema, this was the reason), one obvious thing - dyneema is prone to chafe, low melting point. So for safety margin quite big diameter would be advisable. Another - forget about breaking strength; consider safe working load. Then having lifeline nice to touch and bigger diameter than steel would be nice.
Personally I'm putting steel onto; have been a alpinist, ye know...
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"Dyneema is prone to chafe" - what is your source for this information?

If the melting point is a problem - you have other problems to look after first..

"according to DSM, it is not advisable to use UHMWPE fibers at temperatures exceeding 80 to 100 °C (176 to 212 °F) for long periods of time"
Source: http://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene
 
knuterikt said:
"Dyneema is prone to chafe" - what is your source for this information?
If the melting point is a problem - you have other problems to look after first..
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Synthetic rope fails because of melting. When it's loaded friction appears, this means heat. Cant say for dyneema at the moment, forgot - but this is polypropylene, bout twice lower temp (in celsius) than nylon, for instance. Imagine a knot - it tightens rapidly when a sudden load (body falling against) is applied - this raise temperature in there and fiber loses strength or gets damaged. Dyneema is stiff rope - not much elasticity - so loads will be high, not 'shock-absorbed'. A body flying fast against will exert a force about 1-2 tonnes. This will be against stiff rope perpendicular to load, so multiply this by 10-20. Now you have a loading which a knot or splice at the end has to withstand.

So to give general idea, oversimplyfing. More would be physics lecture, which I'm not able to give in English, sorry :o

PS Otherwise this is good stuff, resistant to water, lightweight, quite usefull. But give it a good safety margin in case you want it for safety. "Lifelines" it is.
 
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Rossynant said:
Synthetic rope fails because of melting. When it's loaded friction appears, this means heat. Cant say for dyneema at the moment, forgot - but this is polypropylene, bout twice lower temp (in celsius) than nylon, for instance. Imagine a knot - it tightens rapidly when a sudden load (body falling against) is applied - this raise temperature in there and fiber loses strength or gets damaged. Dyneema is stiff rope - not much elasticity - so loads will be high, not 'shock-absorbed'. A body flying fast against will exert a force about 1-2 tonnes. This will be against stiff rope perpendicular to load, so multiply this by 10-20. Now you have a loading which a knot or splice at the end has to withstand.

So to give general idea, oversimplyfing. More would be physics lecture, which I'm not able to give in English, sorry :o

PS Otherwise this is good stuff, resistant to water, lightweight, quite usefull. But give it a good safety margin in case you want it for safety. "Lifelines" it is.
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From what I have found out so far,

the breaking strain of 6mm dyneema is about 3 times that of 4mm SS (which basically is what we have at the moment)
I dont see the guard rail as worth anything, if I fall it will probably tip me overboard anyway! The height is such!
I see them as a phsychological thing and fender line anchors only!
Stu
 
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