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yannbuse
Feb 16, 2005, 5:00 PM
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I noticed back when i was chamonix that on high traffic routes on steep snow/ice that guides or the previous climbing party would set an ablakov anchor for a fixed line. Ususally these anchors were made with webbing or thick cord rapped around it a couple times. Now after considerable use of these fixed lines i noticed that the webbing would slowly 'eat' away at the anchor. As in the webbing would create a bigger and bigger groove in the anchor. I suppose my first question is, how much does it weaken the ablakov anchor?
This leads into the meat of what im wondering... When on multi-pitch and creating anchors, obviously there are many different ways but for the sake of an example lets say you have at least one ablakov in your anchor. I like the idea of using a dynema sling or cordalette because it gives a little more room and handling with the hook when proding for the sling in the depths of the ablakov anchor (plus its light). OK, so how would the groove eating into the anchor change between a thick sling, such as webbing (more surface area) and a skinny sling such as dynema (less surface area)? Although ablakov anchors are strong does it have any real impact and if it does what kind? (i know the groove wouldnt really develop since the anchor on multi-pitch will be set up for a relatively short period of time, this leads into my next thought...)
I was thinking, what if on these high trafficed routes at altitude had a dynema sling instead of webbing on the ablakov anchors for fixed lines. Would the webbing take a longer time to weaken the anchor after much use? In conclusion the question becomes, over a period of time is a dynema sling or webbing preferrable for an ablakov anchor.
Thank you for your time.
Yann
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brianinslc
Feb 16, 2005, 5:12 PM
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In reply to: In conclusion the question becomes, over a period of time is a dynema sling or webbing preferrable for an ablakov anchor.
I'd think wider would be better as the force would be more spread out and any groove would also be wider (and possibly less deep over time/use).
Since its a rappel station, strength of the cord wouldn't be as much of an issue.
I kinda like 7mm perlon for v-thread ice anchors, myself. Also use 9/16" webbing too. Or whatever's handy.
-Brian in SLC
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montafoner
Feb 16, 2005, 5:19 PM
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I don't think material, per se, matters. I would suggest that you use the fattest possible webbing, sorry. You're goal is to reduce the pressure on the ice, thereby reducing the melt-through effect that leads to gouged anchors. If I remember correctly, the formula is Pressure = Force/Area
There are two ways to reduce the pressure.
1) Reduce the force aka don't fall or weigh the system
2) Increase the area of contact aka fatter webbing or larger ablakov anchors
A simple comparison: When you are ice skating, the pressure produced is enough to melt the ice (temporarily) and produce those ruts that need to be Zambonied after every period. In this case the pressure is very high; force (your weight) / area (bottom edge of blade).
I hope this helps.
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lambone
Feb 16, 2005, 5:24 PM
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I use 7mil cord fro rap V-threads. one is enough in good ice, but if questionable I will place two.
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slobmonster
Feb 16, 2005, 5:44 PM
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What concerns me (most basically) is that these V-threads are being left in place and essentially treated as *fixed.* And as time goes by, the sun rises and sets, and our climate slowly and imperceptibly changes, the holes in the ice get a bit worked. It's up to you whether or not to use these... there are several ways to 'test' questionable gear in a fully-loaded but safe manner.
In any place sunny, I always stuffed my V-thread holes with snow. This seemed to help.
Regarding choice of material, I think your question has been answered. Dyneema or not really doesn't matter; you're really concerned with the materials width/diameter.
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paulraphael
Feb 16, 2005, 9:55 PM
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In reply to: What concerns me (most basically) is that these V-threads are being left in place and essentially treated as *fixed.* And as time goes by, the sun rises and sets, and our climate slowly and imperceptibly changes, the holes in the ice get a bit worked. It's up to you whether or not to use these... there are several ways to 'test' questionable gear in a fully-loaded but safe manner.
fixed v-threads definitely scare me ... i can't think of a found anchor that would be harder to evaluate. are you talking about bounce testing them, with something like ice screws for backup?
as far as the cord melting through under load, the other obvious variable is the temperature of the ice. on warm days with 32 degree ice it's possible to melt screws out under body weight. a skinny cord through a v-thread would be no different. if the ice is 20 degrees colder than that, you're probably not going to melt through it with any kind of pressure you can generate on a screw, cord, or webbing.
oh, there's one more "melt through" variable: time. the longer the anchor is going to sustain pressure, the bigger a concern it will be. for an anchor that has to hold a fall, peak strength is more important than resistance to melting through. the opposite is true for a rap anchor. an anchor for a hanging belay needs a lot of both.
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lambone
Feb 16, 2005, 11:51 PM
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fixed V threads are bomber, th elonger they have been there the better....until spring comes.
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slobmonster
Feb 17, 2005, 1:38 AM
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In reply to: fixed V threads are bomber, th elonger they have been there the better....until spring comes. |
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paulraphael
Feb 17, 2005, 3:13 AM
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and by the way, it doesn't even have to be above freezing for ice to deteriorate. direct sunlight can erode ice even when it's very cold. so can dry wind. ice can sublimate--which means to evaporate directly without melting to water as an intermediate step. ever notice how frozen waterfalls deteriorate if the water supply dries up, even if it stays below freezing? it becomes porous and brittle and eventually just crumbles.
there are also situations where ice gets stronger--where moisture is taken on and incorporated, where it gets denser, or where more layers get added onto the top.
thing is, when you find a fixed ice anchor of any kind, it's not so easy to tell if the ice has gotten better or worse since it was built. or how good it was in the first place. and how often with these fixed v-threads is the cord or webbing so frozen that it won't slide? in these cases, how do you even know the state of the cord that's in the ice? sounds like you're trusting a lot of unknowns when you assume one of these things is good.
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lambone
Feb 17, 2005, 5:16 AM
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In reply to: Jesus Lambone, not to bust your balls over this, but I watched a good friend fall 150 feet to the ground when a "fixed" V-thread pulled out. NB it was sunny, and above freezing.
hmmmm...well, 95% of the fixed V-thread I have seen while ice climbing have been filled in with new ice, the holes are full, and you can barely clip into the chord because it is buried. way more bomber then when the thread was first placed...
of course they could be bad also, I am sorry to hear about your friend. use good judgement, when in doubt...back it up. But often I think people over back up v-threads.
the Bard Harrington Wall in Lee Vining Canyon is covered with a redicoulous amount of v-threas...in fat blue ice. which is silly because you can walk off the thing.
as long as someone picks them up in the summer, but you have to keep in mind...v-threads are litter. leave them behind and you are littering in the mountains.
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kman
Feb 17, 2005, 6:19 AM
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In reply to: hmmmm...well, 95% of the fixed V-thread I have seen while ice climbing have been filled in with new ice, the holes are full, and you can barely clip into the chord because it is buried. way more bomber then when the thread was first placed...
So are people leaving rings on the cord to rap through? We all know what happens to cord as mutiple people pull their rope through it right?
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lambone
Feb 17, 2005, 6:24 AM
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In reply to: In reply to: hmmmm...well, 95% of the fixed V-thread I have seen while ice climbing have been filled in with new ice, the holes are full, and you can barely clip into the chord because it is buried. way more bomber then when the thread was first placed... So are people leaving rings on the cord to rap through? We all know what happens to cord as mutiple people pull their rope through it right?
sometimes people leave rings, i rapped off one with a quicklink at LVC last week.
and if not, when it's frozen, no not much. sure if people are top-roping and lowering off the shit...yeah. but if you think you need a brand new chord for every rappel you are mistaken.
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