Goto Chockstone Home

  Guide
  Gallery
  Tech Tips
  Articles
  Reviews
  Dictionary
  Links
  Forum
  Search
  About

      Sponsored By
      ROCK
   HARDWARE

  Shop

DMM: Viper Size L (2013 model)- Dark Blue piping... Padded Adjustable Harness, 5 Gear Loops Fits: Waist 87-104cm Legs: 55-70cm   $89.00
41% Off

Chockstone Photography Australian Landscape Photography by Michael Boniwell
Australian Landscape Prints





Chockstone Forum - Gear Lust / Lost & Found

Rave About Your Rack Please do not post retail SPAM.

 Page 2 of 3. Messages 1 to 20 | 21 to 40 | 41 to 48
Author
Tag-line Rappel around a tree

sliamese
19/02/2013
11:37:05 AM
nah i think its heaps better only having one rope to deal with! for link-ups and speed stuff i've done, the value of only having one rope to deal with is heaps more. Less rope weight/drag, easy to tag up extra gear/drill/haul line. short-fixing, belay management is all easier! I guess if it will be beneficial to you, you will understand whats required however!

As for sharp edges, when ropes slice on an ironstone edge, i find it very hard to believe that two very skinny rope have any greater chance. I've had ropes coreshot from falling rocks, and think running twins would be good against that. Sharp edges should just be avoided at all costs. I guess I think a lot of people need more practice in using slings etc to run ropes away from sharp edges.

ajfclark
19/02/2013
11:58:59 AM
Mathematically, if the probability (p) of a rope being cut is x, with a pair of ropes in the exactly the same situation, the p of a single rope being cut is 2x but the p of both being cut x/2.

[Edit: Right idea, wrong maths. See below. ]

sliamese
19/02/2013
12:22:08 PM
haha what?! your taking the piss obviously. what happens to the second rope when it comes tight, across the same offending edge.

In theory there is no difference between theory and reality, in reality however...
uwhp510
19/02/2013
12:29:16 PM
On 19/02/2013 sliamese wrote:
>haha what?! your taking the piss obviously. what happens to the second
>rope when IF it comes tight, across the same offending edge.

The one occasion where one of my ropes was obviously and badly damaged in a big fall, the other one was totally fine. If you're using your ropes as doubles rather than twins I'd say this is the more likely scenario.

miguel75
19/02/2013
1:30:15 PM
Here's some more fun with numbers;


ajfclark
19/02/2013
2:59:58 PM
On 19/02/2013 sliamese wrote:
>haha what?! your taking the piss obviously. what happens to the second rope when it comes tight, across the same offending edge.

No I'm not. If you're talking about an event where the p = 1, it'll still cut both ropes, yes. If p is < 1, the chance of cutting both ropes is decreased while the chance of cutting one increases. This is only if both ropes have the same path, etc. If you're running halves along different paths, the likelihood of cutting both would be lower again.

Eduardo Slabofvic
19/02/2013
3:43:51 PM
On 19/02/2013 miguel75 wrote:
>>Here's some challenged:
>
Nice sideburns Miguel.

sliamese
19/02/2013
5:30:57 PM
wow, here i was thinking climbing required experience and time out climbing watching falls to understand them. Having so many variables it seemed like it would be tricky to forsee an outcome of an uncontrolled event, but I'm glad it can be reduced to such a simple equation.

Petzl do have an interesting video showing ropes cutting on edges at the bottom of this page. I'd love to see this done on a twin rope system and see how much extra protection twins do in fact offer.

argos44
19/02/2013
6:57:55 PM
I think people are getting confused with (half/double) ropes and twin ropes. I believe it would be extremely unlikely when using a half ropes (clipping each rope into different pieces of protection) that both ropes would be weighted over the same sharp edge. Remember ropes dont like sharp edges only when they are run over them and pulled tight.

ajfclark
19/02/2013
7:45:13 PM
So to you having two ropes offers no additional protection against cutting than one?

I did originally say mathematically, from a probability perspective. Of course that's going to be a simplification of the complete system, but my point was that you increase your chances of cutting A rope but lessen your chances of cutting ALL your ropes.

Zarb
19/02/2013
9:05:00 PM
Everyone talks about the system being a bit of a faff about. I think the main reason people would use the system would be to have the simplicity of a single rope climbing system, with the benefit of the same length rappels?

I know I for one would prefer to climb our example (BBB) on a single and have a little pile of 6mm cord in my light weight pack, rather than climb on doubles and have to deal with organising belays with that much bloody rope. But that 2nd(?) zig-zaggy pitch below the vegetation pitch would be nice on doubles... I'll give them that :D
uwhp510
19/02/2013
11:16:22 PM
uwhp510
19/02/2013
11:23:34 PM
On 19/02/2013 Zarb wrote:
>Everyone talks about the system being a bit of a faff about. I think the
>main reason people would use the system would be to have the simplicity
>of a single rope climbing system, with the benefit of the same length rappels?

Doubles are the way forward. Less rope drag, EASIER to set up belays, less chance of ironstone rope cutting induced death etc...

ajfclark
20/02/2013
7:57:46 AM
On 19/02/2013 uwhp510 wrote:
>

Fark, you're right. Epic fail on my part.

It's obviously been too long since I did probability work. It's probably x * x for the first one and but I should do some reading and drink some coffee before our I try and work this out.

[Edit: So, if P=x=.6, the P of cutting both ropes is x * x, of cutting rope A but not B would be x * (1-x), Not A but B would be (1-x) * x, and not cutting either would be (1-x)*(1-x). The middle two can be added together into one category because we don't care which rope is cut:

So for P=.6

Cut Both = 0.36
Cut One = 0.48
Cut Neither = 0.16

So your P of having at least one rope still good is .64 while with a single it'd be .4. You're P of not cutting a rope at all drops to .16.

Does that sound better?

(And yes, I know Simon, this completely ignore the fact that halves are thinner, etc)]
uwhp510
20/02/2013
8:35:28 AM
Yep, spot on. Its easy to screw up since for x<<1, 2x is pretty close to 2x(x-1).

ajfclark
20/02/2013
8:37:50 AM
Yeah, total brain fart on my part. I've gone back and <del>eted the incorrect stuff above.
singersmith
21/02/2013
1:19:05 PM
On 18/02/2013 Zarb wrote:
>

I'm all for the Euro Death Knot (and even tie in with it) but you shouldn't use it with two different sized ropes because it can roll and fail. An 11 and a 9 might not be far enough off for a failure but there are other factors such as all ropes being slightly different sizes or how worn and supple your ropes are. If this is set up for a single rope rap on grey with red as a retrieval line you'd be fine (although its hard to tell how big the rap link is), but if one were to rap double rope off of this setup (as suggested up thread, without the biner back-up) it is something to be aware of. There was a pretty awful accident recently off Serenity Crack when, due to different sized ropes, the knot cinched down tight and slipped through the anchor.

sliamese
21/02/2013
1:29:59 PM
Yeh more than one death has resulted from not tying an alpine butterfly! two ropes can often offer more protection, dont think twins would have saved nik, and two 11mm ropes didnt help the IRATA technician that died last year. I think, based on real world incidents that two ropes running together will most likely suffer similar fates from an catastrophic failure. Please don't put any faith into an equation when making a real life decision out climbing, I know im incapable of that mental arithmetic even if i wanted to! ;)

regarding EDK, i can't for the life of me work out why people dont just put another overhand in and cinch it up against the first to stop it rolling! works well with two different diameters(6 with 9.4 is what i've used most)

If you want to use doubles that's cool!! :)
gfdonc
21/02/2013
3:54:07 PM
On 21/02/2013 sliamese wrote:

>regarding EDK, i can't for the life of me work out why people dont just
>put another overhand in and cinch it up against the first to stop it rolling!

Can't be arsed trying to find it but that's just what was recommended by an article somewhere that tested this (on wet and dry ropes too I think I recall).

The tag-line stuff is cute, but really why take the risk? I own an 8.0 as a second rope for long raps, doesn't weigh much more than a tag line but so much safer and more versatile. Oh, and I tie it with a double fishermans.
.
singersmith
21/02/2013
5:39:03 PM
The advantages of the EDK are fourfold: uses the least amount of rope; ties quickly; the flat side naturally rotates to the rock minimizing chances of getting stuck; breaks [unties] easily. If it came to backing it up with a second knot (due to, say, different ropes) I'd see the chances of getting stuck going up so I'd switch to another knot, probably a figure 8. Untying fisherman's knots is irritating.

 Page 2 of 3. Messages 1 to 20 | 21 to 40 | 41 to 48
There are 48 messages in this topic.

 

Home | Guide | Gallery | Tech Tips | Articles | Reviews | Dictionary | Forum | Links | About | Search
Chockstone Photography | Landscape Photography Australia | Australian Landscape Photography

Please read the full disclaimer before using any information contained on these pages.



Australian Panoramic | Australian Coast | Australian Mountains | Australian Countryside | Australian Waterfalls | Australian Lakes | Australian Cities | Australian Macro | Australian Wildlife
Landscape Photo | Landscape Photography | Landscape Photography Australia | Fine Art Photography | Wilderness Photography | Nature Photo | Australian Landscape Photo | Stock Photography Australia | Landscape Photos | Panoramic Photos | Panoramic Photography Australia | Australian Landscape Photography | Mothers Day Gifts | Gifts for Mothers Day | Mothers Day Gift Ideas | Ideas for Mothers Day | Wedding Gift Ideas | Christmas Gift Ideas | Fathers Day Gifts | Gifts for Fathers Day | Fathers Day Gift Ideas | Ideas for Fathers Day | Landscape Prints | Landscape Poster | Limited Edition Prints | Panoramic Photo | Buy Posters | Poster Prints