Wet nylon

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!!!
 
nylon rope strength when wet

mick said:
.... 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? ......
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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.
 
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.
 
boatropes said:
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.
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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.
 
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Nylon rope for anchoring?

craigsmith said:
......blindly recommending nylon for anchoring ..... presented as unquestioned lore ....
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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.
 
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