8mm rope

[Mark O'Neal]

I've seen 8mm twin rope for sale marketed for glacier travel. Does anyone use an 8mm for rope glacier travel? What about as your main rope on a moderate snow slope (like Hood's south side)?

 

I'm thinking of ways to save weight if I have a long backpack in to a climb. I know the 8mm twin rope is suppose to be doubled for rock climbing, but are the forces less on a snow slope / glacier that you can get away with using a single 8mm rope?

[ericb]

I have a 60Mx8mm for glaciers and it works great...nice and light. You don't really need a single for the reasons you mention, and also, in the case of a fall into a crevasse, the friction of the rope running over the lip absorbs energy as well. One thing to keep in mind is that standard prussiks don't grab well on an 8mm due to the minimal diameter differential so you may need to get small diameter prussik cord.

 

I've also used the rope on a moderate rock climb where there was a long approach (weight a factor) a full 60M was needed for the

rappel, and the pitches were short/simulclimbable so we doubled it.

[kurthicks]

Eric is right on. I'd like to add that 8mm ropes also complicate crevasse rescue due to their stretchy nature and ability to dig into the lip more than fatter ropes.

[Mark O'Neal]

Interesting points. If I go the 8mm route, I was thinking of carrying 2X30m 8mm ropes. That way I have a 2nd rope if someone takes a crevasse fall, and if I need to rap off the route I'll tie the two ropes together. Plus I can split the rope weight between two people.

 

How's that sound for a plan?

[ericb]

Few thoughts....

 

If you only have two on a rope, you should each have coils to use in a rescue scenario. If you are planning on tieing on a second rope, how will you get the rope to run through the pulleys/biners of a rescue system?

 

If you are in a big team doing a running belay with pickets/screws, the knot in the rope will not run through biners.

 

Also, in a alpine w/rap descent, if you tie ropes together for 30M raps, having a knot increases the chance of the rope getting hung up when you pull it. It's a reasonable trade off to get 60M raps with two 60M lines, but I'm not sure about 2x30M

 

IMO, if the only advantage is sharing weight, divide the other group gear to balance out one person carrying the weight. I can't think of any real advantages to having two 30M ropes vs. 1x60M.

 

If you really want a 30M - which is very convenient for ski-mountaineering, etc, just buy it in addition to the 60M. They are very inexpensive.

[Mark O'Neal]

You make some good points. It depends on how many people I wind up with on the trip, but right now I was thinking 4. So I was figuring on having 2 people on each 30m rope. So if someone fell in, the other two would rig up the resuce on their rope. But perhaps it would be better to have all 4 folks on one rope so as to make arresting the fall easier. I own a 9.8mm 60m and my buddy owns an 8mm 30m. So I've been thinking about what I want to do. The only disadvantage of the 60m is the weight. Perhaps I should just force my buddies to carry all my food and the pro and we'll call it even...

[catbirdseat]

I'd put all four on one 60 meter rope. If there were five people I'd have three on one and two on the other. The team of three would lead.

[Dane]

I have and have used 8mms or the new 7.7s. Love them in the right place. I wouldn't use it as a single rope...past soloing and using it to bring up a second from solid anchors at both ends and a good belay plate. Play with one before you decide.

 

That said a 60m or 70m 8mm should work fine for what you are thinking. But just use it as a twin rope the entire time either as a 30m or 35m. Easy to get someone out of a crevass that way past the problems Kurt and Eric mentioned which are very real.

 

Still can't split up the rope weight on 60m but my Beal 7.7 twins are scary light and easy to carry. Few places where 4 on a rope wouldn't just jerk the odd man out before they ever really go in if anyone is awake

 

As an after thought...I wouldn't want to go into a big hole hanging on one strand of the 7.7 or 8mm myself. A good old single 9mm looks like a truck puller in comparison. YMMV

 

 

[Joe Ranger]

Do I need a 10.5mm to climb Rainier with 3 people or is it over kill? Can I get away with a 9mm + or - at 50m?

 

Joe

[Bug]

Do I need a 10.5mm to climb Rainier with 3 people or is it over kill? Can I get away with a 9mm + or - at 50m?

 

Joe

9mm plus or minus is fine. Divide the rope into four sections. Each climber clips into a loop. The end climbers carry a coil that is three meters longer than the distance to the middle person who is equi-distant from both.

[jhamaker]

I watched a team practice w/ skiis and sleds on an 8mm rope. The prusicks did not work. If I recall correctly, the 7mm prusicks worked better than the 5mm ones. Definately something you need to try out at home. Don't forget to size your prussicks to each person.

[spotly]

I use 6mm on an 8mm rope and it's worked fine on dry and wet ropes. Haven't had to ascend it when the rope is frozen though.

[tvashtarkatena]

Metolius makes a 7.8 mm rope (the Monster) rated for 6 falls as a double, which means you could use a single strand for your application. It's also rated as a twin. You'll need to figure out your prussik system on such a thin line, however.

[sobo]

This is a pretty good rule of thumb to remember for Prussik cords:

Prussik cord diameter should be between 2/3 and 3/4 of rope diameter.

 

8mm rope => 5-6mm prussik cord

9mm rope => 6-7mm prussik cord

10mm rope => 7mm prussik cord

11mm rope => 8mm prussik cord

 

The equation:

 

0.67*rope diam. < Prussik cord diam. < 0.75*rope diam.

[Layback]

I picked up a 30 M 9 mm Sterling rope last year at Feathered Friends for ~ $115 last year. Nice thing about a 9 mm, in addition to being a bit more fat, is that if need be, you could belay a technical pitch with it. While a 8 mm rope is safe for glacier travel, like others here, I don't like it's ability to cut into the lip or the fact that ascending it can be a bit trickier.

 

One could also buy a 60 M 9 mm rope for less than $200 and cut it in half with another "investor".