Climbing Rainier next year via Emmons Glacier. I was planning on buying a 9.1mm rope, but saw something that said you should go with 10mm. And then after looking further, I got answers all over the place, people recommending everything from 8mm to 11mm. Any thoughts??
(2 teams of 4 people if this helps at all, so I'll be getting 2 ropes)

Lots of people use 8.5 to 9mm.

You want a dry treated half rope, between 8mm and 9mm in diameter. Many rope companies make shorter half ropes specifically for glacier travel http://www.backcountry.com/sterling-evo ... -S7MMXS30M.

Absolutely no need for a single rope, but beware the temptation to get the thinnest twin rope to save a few grams. Hauling or ascending is much easier on a nice, beefy half rope. Having been on both ends of a crevasse fall several times, my preference is for at least 8.5 mm. If you are climbing with two, four person rope teams, you will want at least 50 meter cords.

ExcitableBoy wrote:You want a dry treated half rope, between 8mm and 9mm in diameter. Many rope companies make shorter half ropes specifically for glacier travel http://www.backcountry.com/sterling-evo ... -S7MMXS30M.

Absolutely no need for a single rope, but beware the temptation to get the thinnest twin rope to save a few grams. Hauling or ascending is much easier on a nice, beefy half rope. Having been on both ends of a crevasse fall several times, my preference is for at least 8.5 mm. If you are climbing with two, four person rope teams, you will want at least 50 meter cords.

Agreed. Also, beware that if you travel with prusiks as your means of ascention after falling into a crevasse, you'll probably want thinner cord than you would have for a 9.8 or 10mm. I'd go with 5mm.

WyomingSummits wrote:
Agreed. Also, beware that if you travel with prusiks as your means of ascention after falling into a crevasse, you'll probably want thinner cord than you would have for a 9.8 or 10mm. I'd go with 5mm.

I use 5mm prusiks on 8 - 9 mm ropes.

ExcitableBoy wrote:

WyomingSummits wrote:
Agreed. Also, beware that if you travel with prusiks as your means of ascention after falling into a crevasse, you'll probably want thinner cord than you would have for a 9.8 or 10mm. I'd go with 5mm.

I use 5mm prusiks on 8 - 9 mm ropes.

Yep....same here.

the above posters are correct, and are the "textbook" method.
BUT... you could get a 40 to 50 meter static (yes, I said it) 8mm from the spool and save a ton of money and weight. use a wash in dry treatment.
downside is catching a fall is harder since there is no stretch. but the loading isn't like a lead fall.
upside is hauling, since there is no stretch or bouncing. other upsides are the aforementioned weight and cost.
I'm not saying that's the best solution for every glacier or team. but for Rainier, where you are more likely to slip/trip than punch through and end up free hanging, it's a viable option.

note: on my Rainier ascent this past July (third Rainier trip), I used a 50m x 7.8mm twin/half. I haven't used a static for this purpose since I have plenty of other types to choose from. but if I knew for sure I did not have any other need for a lead rope, and only needed a cord for Rainier, I'd feel safe with a static.

WyomingSummits wrote:Lots of people use 8.5 to 9mm.

"Lots of people" do not fall in crevasses, so they can take whatever they want, even a 4-6mm cord to save the weight

Just to make sure it’s a joke

Not sure I understand the above post.

The standard when I started doing stuff 30 yrs. ago was a 9 mm. Now with rope technology, you're probably OK going a little thinner. I'd be leary going with a static line. You might be OK, but if you ever have to stop and belay or lead a short section where you're belaying off of or using pickets for pro, I think the shockload on the rope in a fall could be bad news. The only thing I'd ever use a static line for is hauling or fixing, and you won't be doing either on a glacier.

if you are belaying or leading on the standard routes on Rainier, you are lost.

that said, to the OP with two teams of 4, I would geta pair of edelrid apus. 7.9x50m.
you willsave weight and money, and at the end you will have an awesome alpine setup.

50mi s fine for 4 people (the 30m glacier lines leave you no slack and you are close intervals) . those are my preferred alpine/glacier/ice lines, very happy with them.

pvnisher wrote:if you are belaying or leading on the standard routes on Rainier, you are lost.

that said, to the OP with two teams of 4, I would geta pair of edelrid apus. 7.9x50m.
you willsave weight and money, and at the end you will have an awesome alpine setup.

50mi s fine for 4 people (the 30m glacier lines leave you no slack and you are close intervals) . those are my preferred alpine/glacier/ice lines, very happy with them.

Not to be rude, but I completely disagree. Gaining the Disappointment cleaver is quite steep (the guide services fixe lines here) and I can see belaying a less experienced partner on this. Crossing the bergshrund on the Emmons can also be steep. I belayed my two less experienced partners across this. There are plenty of times when it is necessary to provide a belay across a big, sketchy snow bridge.

Try hauling and ascending a 7.9 rope before you make this recommendation.

if the OP is asking aboutrope diameter for a straightforward glacier (and yes, even though the dc was crazy this year the presence of the guide services make it straightforward), then I highly doubt they would be able to set up a hauling system or ascend anyway.
they could easily belay across the ladders if desired with a 7.8mm. I'm tailoring my responses to the actual questions, not theoretical other scenarios.

pvnisher wrote:if the OP is asking aboutrope diameter for a straightforward glacier, then I highly doubt they would be able to set up a hauling system or ascend anyway.

Straightforward glacier travels always involves the possibility of crevasse falls and therefore the necessity to build a haul system or the ability to ascend the rope. Nobody should set foot on a glacier without the knowledge, skills, and practiced ability to set up Z and/'or ZxC hauling systems and ascending a rope. In the event of a crevasse fall, a thicker rope is far easier to ascend and haul on, and adds little weight.

pvnisher wrote:... 7.9x50m. you will save weight and money

The difference between a 7.8 mm twin rope and a 8.4 mm half rope (Sterling Fusion Photo vs. Sterling Evolution Duetto) is 5.3 ounces for a 50 meter cord and 3.2 ounces for a 30 meter cord. The weight savings is negligible especially given the fact that the rope comes into play in emergency situations when everything becomes more difficult. If you are going to bring a rope at all, why not bring one that actually works well for its intended purpose?

pvnisher wrote:Rainier, where you are more likely to slip/trip than punch through and end up free hanging, it's a viable option.

There are plenty of folks who have fallen all the way into a crevasse and ended up free hanging, myself included. Safety systems should be designed to handle the worst likely situation, rather than the most common.

Uhg.. no way I'd use static for alpine. Not as a fall catcher. All your pro is crap, and you usually don't have enough of it... if you or your partner actually take any kind of fall at all, fixed belay, bootaxe or seated, running belay, whatever - you might as well not even have any pro in, 'cause it's gonna blow out like it wasn't even there.