Wet nylon

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mick

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Sterling Rope make climbing ropes and on their website they claim that nylon rope when wet loses up to 70% of its strength. Is this true and if so should we really be using nylon for anchor line? I note that 14mm nylon is rated at 3.2 tonnes breaking strength. What is the SWL and does this take into account the loss of strength when wet?
 
I think it more of a case of 'can or could lose' rather than will. The fibres do not change significantly but depending on how it is laid water will lubricate it encouraging permanent stretch and distortion. The marine rope makers know their stuff will get wet but address the issue in the make up, most other artificial fibres, except poypropylene etc. are stronger than nylon but may not perform as well on applications where elasticity is an advantage. Thats why I and many others prefer nylon for anchor and mooring lines and they certainly get wet.
I would be very surprised if the makers figures for marine rope were only safe for the dry product.
 
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My information is that wet nylon can lose 10% to 15% of its strength. Its other properties of stretch and abrasion resistance make it excellent for anchor rodes and mooring lines.
 
I you have ever forgotten your sleeping bag and had to sleep wrapped up in a spinnaker, 'kinky' is the last thing nylon makes you think of.
We used to bring our 26' Trapper 300 up the slipway on a 12mm. nylon rope because the stretch was easier on the clutch of the Sierra, never broke! I once tried to pull down an awkwardly placed tree at the bottom of the garden with the same car and rope, almost managed to launch it into space, chafe is a much bigger risk for anchor ropes.
 
mick said:
Sterling Rope make climbing ropes and on their website they claim that nylon rope when wet loses up to 70% of its strength. Is this true and if so should we really be using nylon for anchor line? I note that 14mm nylon is rated at 3.2 tonnes breaking strength. What is the SWL and does this take into account the loss of strength when wet?
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Only happens when wet and under repeated hysterisis - the figure I've seen is 30-40% reduction (suspect a misread). It's due to the rope heating up due to internal friction when it's stretched to near its elastic limit.

Unlikely problem with nylon as an anchor rode, but does rear its head in storm conditions with a parasail.
 
www.rocna.com/kb/Rope

Nylon is not the preferred choice for anchor rode with larger vessels, not only because it tends to provide more stretch than desirable at larger scales, but because of its serious drawbacks with wetness and internal friction.

As Charles suggests the figure quoted probably includes all ramifications, not just the nature of being wet (to reproduce you would have to violently cycle-load the rope before testing the breaking strength). This internal friction issue is serious; when the rope is repeatedly loaded at high forces, its ability to withstand the same forces can be decimated by up to half. It also becomes much more vulnerable to external chafe when wet.

To the query re WLLs being adjusted - sort of, but not entirely; WLLs for rope for anchor rodes tend to be set at a ratio of 5:1 to break, vs 4:1 for chain. Nylon loses about 20% of its strength due just to being wet. You should size rope to have its WLL higher than the chain's if possible.

None of these issues are beyond the realm of reality for anchoring, or mooring. Kiwi Roa has smoked (literally) through rope snubbers in bad gusty conditions. The other scenario where high loads are always generated, and usually in a cycling manner courtesy of surge, are upon anchor recovery (if it's stuck) - if in deep water and you're still on rope, that can be a serious problem.
 
Under shock loads ,synthetic ropes can fail by melting at the point of highest stress.. Isn't some water going to give some useful cooling?
(Thinks.... maybe the failure is so fast that there is no time for heat dissipation...............)
 
Under shock loads ,synthetic ropes can fail by melting at the point of highest stress.. Isn't some water going to give some useful cooling?
(Thinks.... maybe the failure is so fast that there is no time for heat dissipation...............)
 
Quandary said:
....... I once tried to pull down an awkwardly placed tree at the bottom of the garden with the same car and rope, almost managed to launch it into space, chafe is a much bigger risk for anchor ropes.
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That conjured up a vision of a cartoon sequence of the Sierra bending the tree like a bow, until it snapped back and launched the car into the next county.
 
craigsmith said:
Except when it doesn't. We're not in ancient Rome. Go away.
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We are not in Ancient Rome, but we are speaking English and if we are to understand each other it is important that words have an agreed meaning.
Decimate (from the Latin decem, meaning ten) originally meant to reduce by a tenth. Some people have misundertood this to mean a reduction to a tenth, and in modern colloquial English it has come to mean "reduce by a lot." To talk about "decimate by up to half" loses all connection with the notion of ten, and will seem to many as perverse as saying "halved to a quarter of its initial size". If you want to communicate effectively it makes sense to try and use language in a way that will not annoy or confuse your readers or listeners.
 
alan_d said:
We are not in Ancient Rome, but we are speaking English and if we are to understand each other it is important that words have an agreed meaning.
Decimate (from the Latin decem, meaning ten) originally meant to reduce by a tenth. Some people have misundertood this to mean a reduction to a tenth, and in modern colloquial English it has come to mean "reduce by a lot." To talk about "decimate by up to half" loses all connection with the notion of ten, and will seem to many as perverse as saying "halved to a quarter of its initial size". If you want to communicate effectively it makes sense to try and use language in a way that will not annoy or confuse your readers or listeners.
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He's a Colonial. You have to make allowances. He doesn't half get annoyed if you cast aspersions at his Dad's anchor though.:D
 
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