If you are looking in the 9-10mm diameter range, there is quite some variation in quoted strengths for a given weight per metre given it is all nylon. I accept there are different constructions, but still.

In the never-ending struggle between how much you can get in one bag on one hand and abject terror on the other, I have sort of decided I would like Type A rope, but not too heavy.

9.5mm Edelrid Super Safety is quoted at 59g/m for 2200kg. So about 37kg/g/m.
Gleistein 9mm is 54g/m for 2700kg. So 50kg/g/m.
Spelenium Gold 9.5mm is 33kg/g/m. I own quite a bit of this. The whole spec is exactly equal to the Type B spec, which seems a bit of a threshold thing to a suspicious engineer.

So some ?interesting? things going on.

I am going to get some of the Edelrid. I trust them and it?s tested to Type A. That?s my selection criteria.

I go for the cheapest a caving shop sells.  trust in the shop, more rope for the cash.

I think I would actually trust something like Beal Spelenium 8.5mm more than a basic 9mm or maybe even 9.5mm. The core-sheath bonding is relevant if the rope gets loaded over a bad rub point -- I have seen this happen on a real caving trip, and I believe the "fancy" rope made the difference between life and death.

Of course, that should never happen, but I think ropes are far more likely to fail from caver cock-up than because they have a slightly lower-rated breaking strength.

Since most gear is rated to 22kn and I doubt you weigh over 420 stone or will be vertically lifting two cars, isn't the point a tad academic?

I would think my 3-4 year old Spelenium is no more than 10kn when knotted now if you believe their quoted strength when new. Possibly less.
If you drop-tested a locked descender or Stop you would probably be getting there at FF1. Which does encourage you to space out single bolt rebelays.
I flatly refuse to go down any pitch where the rope is rubbing these days. Happy to go home. Being able to see the belay from below with your new very bright light helps too.

FF1 on semi-static rope (very little is truely static now) will do you more damage than the rope. The danger is more where the rope ends up rubbing due to the drop...

For information the EN 1891:1998 standard (yes still not updated) lays down slightly different criteria for Type A & B ropes, notably:

    % minimum mass in core for A - 4800/D^2% v B - 4000/D^2% (where D is rope diameter).  So less mass in core.

    Static strength without knots greater than A - 22kN v B - 18kN and with knots greater than  A - 15kN v B - 12kN.  So weaker.

    Fall arrest peak force of under 6kN for a Fall Factor 0.3 drop using a mass of A - 100kg v B - 80kg.  So less energy put into rope.

    Dynamic performance withstand 5 falls without releasing a mass of A - 100kg v B - 80kg.  So less energy put into rope.

Not sure that helps. 

 

Fjell said:

Spelenium Gold 9.5mm is 33kg/g/m. I own quite a bit of this. The whole spec is exactly equal to the Type B spec, which seems a bit of a threshold thing to a suspicious engineer.

Click to expand...

Spelenium Gold is not a purely nylon rope; there is (I think) a kevlar core strand that makes it less elastic (but at the expense of being less strong in breaking tests, presumably as the kevlar breaks first before the nylon really gets loaded). It is great rope though.

& Beal say it is a class B rope: https://sport.beal-planet.com/index.php?id_product=1626&controller=product&id_lang=1

Fjell:

9.5mm Edelrid Super Safety is quoted at 59g/m for 2200kg. So about 37kg/g/m.
Gleistein 9mm is 54g/m for 2700kg. So 50kg/g/m.

Click to expand...

What is the significance of this (X kg/g/m)?

incidentally, I believe that Gleistein 9 mm is an A-rated rope, though it certainly looks thicker that our 9-mm Mammut Performance Static. It's excellent rope and handles very well, though it is quite expensive.

Is Gleistein 9-mm the only A-rated 9-mm rope?

It's an attempt to compare the strength to weight ratio.

Most other 9mm used by cavers are not type A: https://www.gleistein.com/en/geo-professional-rope/geostatic-ne-din

Another option: https://www.skylotec.com/uk_en/industry/products/ropes/super-static-9-0-r-055.html#!product-details

Seems Mammut no longer do the 9mm: https://www.mammut.com/uk/en/cat/3023/static-ropes/?page=1

I suspect the ropes are subjected to the test that they are most likely to pass, so some B ropes may be as strong as As.

This is a useful document: https://www.honor-safety.nl/wp-content/uploads/2017/09/Static-Ropes-Handbook_Kernmantellijn-HONOR-exclusief-distributiepartner.pdf