/ What is the difference between static and semi-static ropes?

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dudders - on 24 Feb 2014
Which should I get for abseiling?
yesbutnobutyesbut - on 24 Feb 2014
In reply to dudders:

They're the same thing.

There's not really such a rope as true static as all nylon rope has some degree of stretch in it, even non - dynamic rope.
elliptic on 24 Feb 2014
In reply to yesbutnobutyesbut:

> They're the same thing.

No they're not.

Semi-static is the white-sheathed stuff used by cavers for SRT and is what you would normally use for an abseil rope. Far less stretch than dynamic rope but there's still a little bit of "bounce" when you're a long way down.

Fully static (eg black marlow) is polyester and used by men in balaclavas for making quick exits from helicopters. From personal experience it has about 20-30cm stretch under bodyweight at the bottom of a straight 100m abseil, is also heavy, stiff and a complete pig to handle.
GrahamD - on 24 Feb 2014
In reply to dudders:

As above. You want caving rope.
CurlyStevo - on 24 Feb 2014
In reply to elliptic:

Does some stretch not suggest that the rope is actually semi static as a true static rope should not stretch at all right?

Do you know why we don't tend to use the polyester or aramide ropes much for abseiling for climbing purposes? Are they less durable or something? I would have though less stretch would be a benefit for climbers (easier to prussic up, less sawing motion to abrade etc)
crayefish - on 24 Feb 2014
In reply to CurlyStevo:

> Does some stretch not suggest that the rope is actually semi static as a true static rope should not stretch at all right?

If the rope was made of high strength steel or carbon nanotubes, it would still stretch! The amount just depends on the elastic modulus and the load.
CurlyStevo - on 24 Feb 2014
In reply to crayefish:

I guess you are saying everything stretches to some extent? Hadn't thought of that.
elliptic on 24 Feb 2014
In reply to CurlyStevo:
Indeed, and so would a steel cable... it's just a matter of terminology *shrug*.

As I said above black marlow is relatively stiff & heavy and it does no harm for our purposes to have a little bit of give in the system. It's still much less than abbing on lead ropes.
Post edited at 14:29
CurlyStevo - on 24 Feb 2014
In reply to elliptic:

I guess the price could be one reason climbers don't buy the black marlow very often - that and the colour....
crayefish - on 24 Feb 2014
In reply to CurlyStevo:

Yep. The Young's modulus of plastic is generally very low so likely to stretch a lot.
elliptic on 24 Feb 2014
In reply to CurlyStevo:

> I guess the price could be one reason climbers don't buy the black marlow very often - that and the colour....

I had a mate who decided he wanted a full 100m reel of it for trips to Lundy. I was working in a gear shop at the time so we sorted out a deal for him!

To be fair it was quite a novel experience going straight down to the bottom of American Beauty and the Ocean on full-length abs, but carrying the ******** thing up and down the length of the island every day was backbreaking...
Snowdave on 24 Feb 2014
In reply to dudders:

Seriously bad advice given.....

You need Rope which conforms to EN 1891-A (semi-static rope for caving, abseiling, rescue). This will say on the end markings of the rope. If it has no end markings don't buy it as "illegal".

This rope will usually come in dia from 10mm up to 13.5mm. The usual dia to get for general abseiling is 10mm, 10.5mm or 11mm.

Forget colour as an "identifier" to the type of rope as various manufacturers make semi-static rope in white, red, yellow, black, olive, blue.

When you get the rope home from the shop put the whole rope (apart from the tagged ends) into a tub of tepid water and leave it there for 30mins (don't let it float). Then hang over clothes airier away from direct sun & heat. This will allow the outer sheath to do the final shrinking onto the inner core & make the rope wear better! This is recommended by the manufacturers. Allow up to 5% shrinkage in length, usually get 2%.

megamonkeyman on 24 Feb 2014
This guy knows his shit on rope man
deepsoup - on 25 Feb 2014
In reply to CurlyStevo:

"Static" is just what we used to call "semi-static", which is also a slightly old-fashioned term now, industrial suppliers generally call it LSK (Low Stretch Kernmantle) now. It's all the same stuff - rope that conforms to the EN1891 standard. EN1891A for normal ropes, EN1891B for less hard-wearing lighter weight ones (such as you might have sitting in a rescue kit in the expectation that if you ever had to use it you'd probably throw it away afterwards).

> I guess the price could be one reason climbers don't buy the black marlow very often - that and the colour....

And that it doesn't conform to EN1891 because it's not stretchy enough. (The EN standard specifies a maximum impact force the same way the standard for dynamic ropes does, so it actually requires a certain minimum amount of stretch.)

Marlow test 'Marlow Black' rope to an internal standard of their own instead of the EN one and sell it for abseil use *only* - ie: not for rigging etc., and definitely not for SRT. In a general purpose rope (for those of us who aren't doing stupidly long fast abseils out of helicopters with guns) a little bit of stretch is a good thing.

Not all black ropes are Marlow Black though, obviously. Lots of other manufacturers make fully EN-1891A compliant black static/semi-static/LSK/whatever ropes for police/military/hut-hut-hut-hut use. Eg: Beal Intervention.
deepsoup - on 25 Feb 2014
In reply to Snowdave:
> You need Rope which conforms to EN 1891-A (semi-static rope for caving, abseiling, rescue). This will say on the end markings of the rope. If it has no end markings don't buy it as "illegal".

^^ This.
Whether the person in the shop calls it "static" or "semi-static" (or LSK), the important thing is that it complies with that standard.

The bit about giving your new rope a soak in water and allowing it to dry again before it's first use is also good advice. The manufacturers recommend it, but climbers often don't bother.

CurlyStevo - on 25 Feb 2014
In reply to deepsoup:

I soak my rigging and ab lines before use for that reason.

Adam Long - on 25 Feb 2014
In reply to Snowdave:

> If it has no end markings don't buy it as "illegal".

Hmm. End marking tape is not very durable, and ropes get cut down. Thankfully a requirement of the EN1891 standard is that the rope must have an internal identifier ribbon running the whole length of the rope. If you want to check, cut the heat seal off the end and pull it out. Info includes brand, year of manufacture, EN conformance etc.

The soaking advice is good.

We have some polyester rope that conforms to EN1891A had handles fine. In my experience it is the black dye used for military ropes, not the fibre type, that causes stiffness.

I have used Kevlar rope in the past that had almost no stretch under bodyweight. There are various special use low-stretch ropes available now with various mixes of nylon, kevlar and polyester - for improved heat or chemical resistance typically.
dudders - on 25 Feb 2014
Thanks for all the helpful replies, another question, should you also soak new dynamic ropes like this?
Snowdave on 28 Feb 2014
In reply to dudders:

You can do but it won't make as much of a difference as with EN1891 rope, due to the way Dynamic EN 892 rope is made.

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