Originally Posted by Dave_S
Some ropes look ok, some look well worn. If they look ok are they ok? I don't know the age or milage.
is fairly easy to inspect and decide to retire or continue to use, based on (a) wear as shown by change in diameter of the rope; (b) cut fibres; (c) rust stains can also be good cause for retirement
, especially with laid nylon rope; and (d) nylon that has been soaked with diesel fuel
etc should probably also be retired.
Double braid requires more intensive examination. Double braid is supposedly 'balanced', meaning that the core
may be responsible for 60-70% of the tensile strength and the cover responsible for the remaining 30-40%. If the double braid was designed for your use, then its tensile strength should be such that your maximum load should have been about 20% of its breaking load, so that you are not pushing your lines past their elastic elongation limit.
That means that you really do not want to use double braid if the core
were compromised. And you should prefer not to use it if the cover were compromised.
If both cover and core were compromised, you're looking at something that has the form of rope but is without the essential substance of rope. Look for someone who wants PET for recycling (polyester is PET, same stuff as in the container of bottled water).
Cut fibres in the cover braid show as increased fuzziness with extreme cases to the point that the core is exposed.
Problems with the core require you to look and feel. If the strength of the core is compromised and has been put under load, you would expect your line to be stretched and so the first sign is the diameter shrinking. Problems with the core should also be revealed by feel: a hollow patch of the rope, lumpiness ... all reasons to retire it.
Several rope manufacturers, including Samson
Rope who claim to have been the first first to invent synthetic fibre double braid, have guides to retiring rope. Have a Captain
www.samsonrope.com/Documents/.../RM_Usage_Retirement_Guide_WEB.pdf (if that link does not work, please accept my apologies and put Samson Rope Usage Retirement Guide into a search engine).
Originally Posted by Dave_S
I've been told to buy bouble braided line. When I look it up there are 10 varieties, which one ?
Ha! What a question! If only some independent authority did a good job comparing the polyester double braid available in the market.
I can only suggest:
1. first, do the research
about how you will use your line. That means you must know:
(a) what diameter line suits you (your hands, your winches and rope clutches
, your blocks and sheaves);
(b) what tensile strength you need, meaning what safe working load (in pounds.force, kg.f, or Newtons - the units are up to you) you need. Take into account that usually that SWL is about 20% of the breaking load, about the same as the limit of elastic elongation for polyester double braid.
2. second, you need do the research
on what rope of your chosen diameter and SWL is available in the marketplace. I'd suggest you forget any rope that does not come with statements of:
(a) its linear density mass (in units of either pounds/100 ft or g/meter or kg/100 m) - that's a measure of how much polyester is in the rope. Polyester fibre gives tensile strength. The air trapped within the interstices of the braid contributes nothing except feel and perhaps ease of splicing (floppy rope is generally easier to splice than firm rope). The polyester costs money
. The air is free. The linear density mass of the different rope flavours from any one rope maker should correlate with the prices. In general, the higher the linear density mass, the stronger. The Chinese maxim of 一分钱，一分货 applies: no rope manufacturer sells polyester for nothing. You pay for what you get (within certain limits). Any rope that is low priced is more likely to be air than polyester. And not a bargain.
(b) its tensile strength, best stated as both safe working load and breaking load (although you'll be lucky to get both; if breaking load is on offer, then do the math yourself to work
out SWL). Some rope makers will give guidance about the use they have designed their rope: whether for halyards or sheets
, for what size of boat
, etc. That is their way of signalling the SWL, elastic elongation, breaking load, etc. I prefer to see the numbers (which suggest that the rope just might have been tested and perhaps certified against some national or industry standard).
(c) in some jurisdictions, it seems that rope manufacturers have agreed among themselves not to give out any more info than (a) and (b). A few rope makers will also tell you how many strands are in the cover and how many in the core. Some marine
supply stores have catalogues and staff that can tell you such things. You could spend time in a chandlery
supplies store counting cover strands (but please do not pull out the core to count the core strands - I prefer not to be the next customer in line buying
rope that has been unbalanced and disturbed).
(d) some rope manufacturers will have prestretched rope for certain applications (such as halyards). Or have added a coating to the cover to improve some characteristic. Such extras cost money
. Expect the rope manufacturer to tell about them. If nothing is mentioned, expect nothing.
3. third, look at and feel the line.
Brand new double braid of course will feel different from a line that has been used, but you should still feel it. At some point, you will likely be handling a line in bare or gloved hands.
So (a) the hand (hand feel) is important.
Look at the cover. Identify what braiding has been used (plain braid, in which a strand goes over 1 strand then under 1, hence also called 1/1; standard braid in which a strand goes over 2 strand then under 2 or 2/2; or hercules braid that is 3/3).
(b) the braiding of the cover (and the linear mass density of the cover - but good luck getting the separate linear density mass figures for both cover and core out of a manufacturer!) contributes to how much of the tensile strength comes from the cover and how abrasion resistant and snag-free is the cover. Some rope manufacturers only use 1/1 braiding for small diameter lines and use 2/2 for everything with a diameter of 9 mm and above. A few high quality manufacturers make specialist low stretch polyester double braid in 1/1 (and you will pay for it, of course). Hercules braid is okay for fishing
line in tiny diameters, but too snag prone for most working lines on a sailing boat
. While inspecting the braiding, measure the pitch
length (aka lay length) by following one strand and seeing how long (inches or mm, up to you) before that strand completes the spiral turn.
Consider the world from the rope maker's perspective:
1. polyester costs money.
2. high tensile strength means a polyester core braided with a long pitch
3. high abrasion resistance and snagging resistance means a 1/1 braid (or a tight 2/2 braid to keep prices down) and a short pitch length.
4. #2 and #3 make it harder to make a balanced rope at a low price
5. many customers prefer to buy the cheapest rope they can find, without looking at tensile strength number etc.
6. some rope makers are happy making retail sales and care less about brand reputation (or do not even have a brand - they're selling generic double braid).
7. times are tough. The boating
market seems to be contracting. So ... how lucky do you feel today, punk? (meaning that some rope manufacturers care about the reputation of their brand today, others never cared, and some are prepared to damage their brand just to balance the books
I've written the above assuming you are after polyester double braid and want an elastic elongation below 6% at SWL.
If you are after a more dynamic line, such as nylon double braid that is more stretchy so you can use it for dock
lines, then similar but different guidelines apply.
If you are after a high-tech high modulus core (such as of Dyneema
, PBO, Kevlar etc) with a braided jacket, then again similar but quite different guidelines apply.