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mick
20-01-11, 19:13
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?

Quandary
20-01-11, 19:45
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.

Salty John
20-01-11, 19:50
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.

Cymrogwyllt
20-01-11, 19:52
Am I the only one who thinks of wet Nylon and does not have 'kinky' in the thought?;)

mick
20-01-11, 19:56
Am I the only one who thinks of wet Nylon and does not have 'kinky' in the thought?;)

Yes, that did occur to me as I typed.

Quandary
20-01-11, 20:01
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.

charles_reed
20-01-11, 20:04
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?
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.

Cymrogwyllt
20-01-11, 20:10
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,

car or tree?;)

craigsmith
21-01-11, 00:56
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.

SHUG
21-01-11, 10:24
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...............)

SHUG
21-01-11, 10:24
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...............)

Twister_Ken
21-01-11, 10:53
www.rocna.com/kb/Rope

its ability to withstand the same forces can be decimated by up to half.

A pendant speaks...

Decimated means to reduce by one tenth.

Halved means to reduce by one half.

Decimated by a half presumably means to reduce by 5%.

craigsmith
21-01-11, 11:19
Decimated means to reduce by one tenth.
Except when it doesn't. We're not in ancient Rome. Go away.

Norman_E
21-01-11, 11:20
....... 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.

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.

Leighb
21-01-11, 13:02
Yes, that did occur to me as I typed.

Me too, I was thinking this thread should be in the Lounge. :D

alan_d
21-01-11, 14:19
Except when it doesn't. We're not in ancient Rome. Go away.

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.

MonniotC
21-01-11, 15:01
A pendant speaks...


I don't mean to be pedantic, but don't you mean: "A Pedant speaks"

Unless you're a light-fitting, perhaps.

Quandary
21-01-11, 15:18
I don't mean to be pedantic, but don't you mean: "A Pedant speaks"

Unless you're a light-fitting, perhaps.

No, just a little ray of sunshine, perhaps?

NormanS
21-01-11, 17:08
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.

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

Quandary
21-01-11, 17:31
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.

It felt like that for the driver, though we did not even leave the property.

SHUG
21-01-11, 17:38
Ahem.....remind me what we were discussing... ah yes...., the title of this post should have been "The reduced strength of nylon rope when saturated with water".
"Wet nylon " is far too brief for this erudite panel!!!

boatropes
22-01-11, 11:32
.... nyon rope loses up to 70% of its strength when wet. Is this true and if so should we really be using nylon for anchor line? ......

I don't understand that claim at all, it sounds like a misquote.
Nylon rope when dry is ~15% stronger than polyester or PP, and when wet is commonly claimed to lose ~15% of its strength. As water sports are invariably wet (!) the difference hardly concerns us at all and the big majority of sources still recommend nylon for all anchoring, largely on account of its stretch characteristics. Manufacturers BL figures are for new dry rope.

Bobobolinsky
22-01-11, 12:08
Agree a climbing rope looses 30% of it's strength when wet and distorts when rappelling under load (I was often used as the test load, if its good for Bobo it's fine for us) It also refers to sheathed lines, rather than anchor plait etc. Don't forget that there is a further reduction of a minimum of 30% dependent on knots.

craigsmith
22-01-11, 13:46
I don't understand that claim at all, it sounds like a misquote.
Nylon rope when dry is ~15% stronger than polyester or PP, and when wet is commonly claimed to lose ~15% of its strength. As water sports are invariably wet (!) the difference hardly concerns us at all and the big majority of sources still recommend nylon for all anchoring, largely on account of its stretch characteristics. Manufacturers BL figures are for new dry rope.
As indicated above, if not a mistake/misquote then it presumably refers to worse case scenario, summing the potential issues with nylon to a single figure: -20% when wet, then halve again for severe cyclical loading. From that we could say "nylon can lose up to 60% of its strength when wet", with an unknown error margin on the actual data - 70% doesn't seem outside the realm of possibility. Whether that's applicable to climbing or not is besides the point of this thread.

Figures I have here for 8-braid are closer to a 10% difference between nylon and polyester strengths, and 15-20% drop in nylon when wet. That tips the balance in favor of polyester even using the liberal numbers. 3-strand is different.

If "the big majority of sources" are blindly recommending nylon for anchoring, then this says more about how it's easier to give simple answers, presented as unquestioned lore, to customers rather than carefully working out what the best solution for them might be... or a widespread lack of knowledge of the risks associated with nylon. Particularly for larger boats, it is not the ideal rope for anchoring/mooring and suffers from serious flaws that should be acknowledged.

pvb
22-01-11, 14:29
"Wet nylon " is far too brief for this erudite panel!!!

DO NOT do a Google Images search for wet nylon! :eek:

fergie_mac66
22-01-11, 14:32
Am I the only one who thinks of wet Nylon and does not have 'kinky' in the thought?;)

no I did wonder what was going to be on this thread :eek:

boatropes
29-01-11, 14:46
......blindly recommending nylon for anchoring ..... presented as unquestioned lore ....

I am concerned that new boaters could be following this thread and becoming alarmed at so much differing opinion and advice. On the one hand the possibility of 70% strength loss when nylon rope is wet and cyclically loaded, on the other hand a fairly common acceptance that nylon rope is a good choice for anchoring. The latter view is rather more than 'lore' and even finds its way into MCGA advice:

The Maritime Coastguard Agency publishes a code of practice for small (up to 78 feet, max 12 passengers) commercial vessels in sport and leisure use. On the subject of anchor rode it recognizes that nylon rope (with some chain) is normally used and it recommends minimum diameters for different boat sizes. See section 20.1 of this:- http://www.mcga.gov.uk/c4mca/red.pdf
It is hardly a technical dissertation but it should give confidence to any newcomer who follows the crowd and chooses nylon. Other sections of this fairly comprehensive document would also be a useful browse for newcomers.