V-Thread vs A-Thread

[jmace]

Saw this on Gravsports

 

www.beverlymountainguides.com/file_download/5/Ice-Climbing-Anchor-Strength.pdf

 

Conclusions:

 

Essentially that Vertical V-threads are stronger than horizontal Vthreads and that 1" tubular webbing also contributes to a stronger thread.

 

I switched to tubular webbing late last year for all my threads, less bulky, easier to tie a knot. However pushing it through the hole is harder.

 

The article also talks about re-boring,and more or less is totally opposite to what I would have suspected with regards to the orientation of the thread.

 

Anyways good stuff

[G-spotter]

Not so sure that I agree that lake ice and waterfall ice behave the same - a hanging icicle is under different load stress from gravity than a flat lake ice, and the direction of pull in the test in the PDF is 90 degrees different between the two cases. IE on lake ice, the pull is at 90 degrees to gravity stress whereas on vertical ice, the pull is in the same direction as gravity... on vertical ice, fractures prefer to spread horizontally while there should be no preferred direction on a flat lake.

[Don_Serl]

interesting reading. always good to see 'testing' instead of speculation.

so let me add some 'speculation'...

to me, the differences between orientations are noticeable, but not very dramatic, esp when one thinks that we often rap off 6mm or even 5mm cord, or 3/4 to 1/2" webbing. (actually, i'll only rap off 1/2" as a last resort - its tensile strength is only about 1000 lbs (500kg, 5 kN) - too close to 'the line' for comfort). the failure point with these lighter materials is likely to be the cord/web, not the ice. and i suspect that horizontal loading lighter cord/web shares the load into the two strands better, so material failure (rather than ice failure) is less likely.

plus it's just plain easier to use (and place) a horizontal V-thread.

nice to see the reinforcement of the notion that one anchor is just NOT good enuf on ice - i guess the implication is that some people climb off single anchor belays - fools!

btw, did u notice that the death-falling climber in figure 17 came off because he burned out using leashless tools - but that was only because he was not wearing crampons!

cheers,

[marc_leclerc]

I agree with what Don said and I would like to add something. I see a lot of climbers build V-Threads, thread their cord and rappel without sawing the cord against the back of the V-Thread to dull the corner of the tunnel the cord runs over. This is really sharp when the V-Thread is built, I think if someone built an 'A' Thread and didn't take any time to dull the corner of the tunnel and rapped with all the pressure pulling a 5/6mm cord againt that edge bad things could happen.

[tomtom]

btw, did u notice that the death-falling climber in figure 17 came off because he burned out using leashless tools - but that was only because he was not wearing crampons!

 

And the belayer was using a Grigri. What's up with that?

[hafilax]

I agree with what Don said and I would like to add something. I see a lot of climbers build V-Threads, thread their cord and rappel without sawing the cord against the back of the V-Thread to dull the corner of the tunnel the cord runs over. This is really sharp when the V-Thread is built, I think if someone built an 'A' Thread and didn't take any time to dull the corner of the tunnel and rapped with all the pressure pulling a 5/6mm cord againt that edge bad things could happen.

What does dulling the corner do? It will fracture or pressure melt the moment it's loaded.

[G-spotter]

Exactly.

[jmace]

btw, did u notice that the death-falling climber in figure 17 came off because he burned out using leashless tools

 

Speaking of Fig 17

 

That is the second time I have heard/read that it is a bad idea to clip the belay as your first piece yet everyone I climb with insists its a good idea..

 

anyone care to comment on that..??

[shannonpahl]

My guess is that its due to many effects, one being the pulley effect - the clipped biner on the anchor effectively becomes a pulley with the belayer's rope on one side, the falling climbers rope on the other side. Of course without this, there is still the sum of the falling climbers force and your weight on the anchor, but without the pulley, you have more real rope to absorb the force (the rope is not short circuited by the biner) and you also have the belayers body and some rope slippage in the belay device all helping to absorb some force, making for much less direct impact force on the anchor

[alps]

Well, the total force on the anchor is probably smaller when not clipping the belay. But when belaying off your harness, I think there are other reasons why it is a very good idea to clip the belay as your 'first piece'.

[hafilax]

btw, did u notice that the death-falling climber in figure 17 came off because he burned out using leashless tools

 

Speaking of Fig 17

 

That is the second time I have heard/read that it is a bad idea to clip the belay as your first piece yet everyone I climb with insists its a good idea..

 

anyone care to comment on that..??

It's a compromise. Clipping the anchor as a first piece maximizes the force on the anchor but minimizes the forces handled by the belayer and vice-versa. If you have a solid anchor clip away, if it's suspect hand the belayer a pair of gloves and don't fall.

 

Another interesting suggestion has been to lower to a stance well below the anchor and belay from there. The forces involved will be less with more rope in play.

[marc_leclerc]

btw, did u notice that the death-falling climber in figure 17 came off because he burned out using leashless tools - but that was only because he was not wearing crampons!

cheers,

 

I didnt notice at first... wow!

[Choada_Boy]

Not so sure that I agree that lake ice and waterfall ice behave the same - a hanging icicle is under different load stress from gravity than a flat lake ice

 

I agree with your disagreement.

 

Water Ice Polymorphism

[G-spotter]

I want to see the Utube when you swing your tools at some of that 500K, 20 GPa, Ice-7.

[Choada_Boy]

Leashless?

 

We are obviously dealing with ice I in both instances (lake v. WI), but there is clearly a macroscopic difference between the two as evidenced by the way they refract light (clear v. opaque respectively)

 

Regardless, v-threads are strong, so who really cares. I can't remember ever hearing of a v-thread failing. We set one up once, and connected it to a 3:1 with 4 people pulling on it. We then chipped out the ice between the cords under load, and it failed with about 2 inches between the cord.

[Paul_detrick]

Whenever I get to the top of pitch 1 ( or 2 or whatever) I set a screw that I run the rope tru that goes to my 2nd. If he comes off all the pull goes to it and not my anchor. When he starts up the next pitch this becomes his frist piece. So I allways try to have 3 screws for the anchor. Just the way I do it, you may try or not, or flame on.

[jmace]

Do you find that puts twists in the rope at all?

 

 

[Paul_detrick]

I drape the rope over whatever im using to tie in with (slings or clove hitch) and it plays out just find. Sometimes the last few feet might be, but it goes out find.

[genepires]

Hey Justin, Scott Decapio broke a v thread once while rappeling down in new england somewhere. He was rapping off and came to a existing v thread that was in the sun. He clipped into it without a backup. I think when his partner put his weight also on it, the anchor blew. Their rope got tangled up in another teams rope, which kept them from going all the way to the ground. I think that is how he related it to me.

 

So there, you know one person now.

 

 

[Don_Serl]

Hey Justin, Scott Decapio broke a v thread once while rappeling down in new england somewhere.

 

and patrick delany blew a V-thread on (IIRC) moonlight falls in the kananaskis. the whole block the thread was in sheared - luckily, he was first on rappel, and had a back-up screw in. it was cold, but not extreme, and the ice was not sun-rotted, just fine winter ice...

 

i always have screw as a back-up for the 1st rapper, and if i'm 1st, i tend to tie the bottom ends of the rope together thru the bottom rappel on a multipitch climb to protect the 2nd. i remember chris bonnigton (again IIRC) saying he'd personally seen two lives saved when upper rap anchors failed but the victum didn't go all the way cuz of the ropes being tied to the bottom anchor. yup, you'd fall a hell of a long way, but you might well survive...

 

cheers,

[Paul_detrick]

I like that, have to remember that trick.

[BlitZ933]

++ Props for the 'actual testing' as opposed to speculation.

 

Of course, this is all dependent on temperature, if the ice is in sunlight or shadow (I've seen a 16cm ice screw melt out on a 20 degree day in less time than it took the leader to complete the pitch, when I seconded it I pulled the screw out without unscrewing it), lots of little factors.

 

Ice Climbing is risky business, and we're each putting it on the line every time we go out and swing our tools. Personally, weather I clip into the anchor or not as the leader has more to do with the next pitch and how sturdy the anchor is than any 'habit'. If it doesn't look like I'll get a solid placement for 15 feet (chandelier or aerated ice), probably better off not clipping the anchor (or placing a screw just off the anchor, as high up as I can reach from the belay stance). If everything looks kosher and the belayer perfers to, I'll clip through the anchor. Evaluate risks for yourself, and use what you believe is the best technique for YOUR situation.

 

Be safe out there. Oh, and clip a screamer on those crummy 'psychological' placements, they might be better than you think!

 

[Joe_Poulton]

Hey Justin, Scott Decapio broke a v thread once while rappeling down in new england somewhere.

 

and patrick delany blew a V-thread on (IIRC) moonlight falls in the kananaskis. the whole block the thread was in sheared - luckily, he was first on rappel, and had a back-up screw in. it was cold, but not extreme, and the ice was not sun-rotted, just fine winter ice...

 

i always have screw as a back-up for the 1st rapper, and if i'm 1st, i tend to tie the bottom ends of the rope together thru the bottom rappel on a multipitch climb to protect the 2nd. i remember chris bonnigton (again IIRC) saying he'd personally seen two lives saved when upper rap anchors failed but the victum didn't go all the way cuz of the ropes being tied to the bottom anchor. yup, you'd fall a hell of a long way, but you might well survive...

 

cheers,

 

That's some really good info....thanks for writing this down on here.