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 Page 1 of 3. Messages 1 to 20 | 21 to 40 | 41 to 52
Author
Comments sought on natural anchor design
Tim_1964
24/07/2012
11:55:19 AM
Hi all, after extensive efforts I often find myself without a climbing partner using a self belay rig on smaller climbs (really just scaling up from bouldering). I am seeking comment on my anchor design - as follows:

1. Use 3 large rocks or trees
2. Place a sling around each
3. Clip a screwgate to each
4. With my dynamic rope tie a clove hitch to the first screwgate
5. After the clove hitch feed say 3m of rope out, then tie a figure 8 knot
6. Anchor X is now complete using a single strand of the rope

7. Feed 4m of rope after the F8 knot as this will be slack and non weight bearing
8. After 4m of feed, make a clove hitch on the second anchor
9. Repeat 5, 6, 7

Each anchor is therefore a single strand of dynamic rope with a F8 knot on the end
This will create 3 anchors with 3 F8 knots available to tie the main rope into (rope 2)
(I could use a single overhand rather than 3 F8 knots)

Clip 2 opposing screwgates into the 3 F8 knots
Equalise the length by adjusting the clove hitches
Tie the main rope into the 2 opposing screwgates with a figure 8 on a bight and toss it down the climb line.

From the bottom I clip in a petzel croll ascender backed up by 2 prussik loops and I am ready to climb. At this stage I am testing the rig and I check the croll and the prussiks before each move. I ensure that the croll is clean and clipped and that the prussiks will not feed into the croll. I have clocked up 10 hours on the rig with no significant issues. There is no fall factor and I use a static rope for the main rope (as the technique is more SRT than Lead)

I could run a second main rope with another croll and prussiks (to conform with industrial rope access standards) but this does not seem necessary at this stage.

Comments welcome.

Thanks

Tim
mikllaw
24/07/2012
12:25:51 PM
a messy sketch of the setup would be useful.

You enemies are rope stretch and wear; and how the thing clipping you to the rope behaves. the topic has been covered here:-
http://www.chockstone.org/Forum/Forum.asp?Action=Display&ForumID=6&MessageID=22064&Replies=1


Petzl has a good website on this;-
http://www.petzl.com/en/outdoor/self-belay-solo-climbing/solution1-rescue-rope

bring the anchor over the edge (with padding on the edge) and rebelay that to a piece if you can to elimate stretch and wear of the anchor system.

Petzl recommend using 2 devices for redundancy, prussics are hard work and sensitive to bioth roeps diameter and condition.

Eduardo Slabofvic
24/07/2012
1:28:14 PM
You lost me with all the figure 8s. I can't do messy sketches so Iíll use asci instead

(@)

I support you doing what ever it is you think is right for you.

I set up two seperate anchors on what ever is handy. I have a vivid imagination, so each anchor usually has at least 4 bits in it. Even if one anchor is absolutely stonkingly good, I'll still do 2.

I use a 70m rope, so there's plenty of rope to be had. I use a figure 9 (because I'm lazy and from Kweeeeenzlairnd) to tie the rope into each anchor leaving a loop of slack between each anchor so that the direction of pull on each anchor is over the climb. If there is a traverse anywhere on the route, or its particularly overhanging, I'll put in a bunch of directionals as required.

I throw both ends of the rope over the edge and rap down. Once past the edge I'll put a rope protector around the rope thats on the edge (a piece of carpet works well too).

I coil up the tails of each rope to create a bit of weight which makes my chosen device run a bit better, and attach my device to both ropes. I tie the coils off a few metres above the ground.

I use a shunt, because it's the only self belay device I own, and I'm too cheap to buy another one. I used to use a croll, but didn't like loading a toothed device with the resulting falls (which are really just slumps anyway).

I attach the shunt to my harness with a solid steal D shackle.

I also take a tibloc, a gri gri and a few slings with me on the climb, as I usually chuck a bunch of laps on what ever it is I'm on untill I get pumped, so I need to be able to escape the situation.

I think the text books say to tie knots below you device as you climb, which I some times do, but mostly not, again only because I'm lazy.

I've been climbing like this for 20 years or so. It's fine.



pmonks
24/07/2012
1:42:51 PM
On 24/07/2012 mikllaw wrote:
>You enemies are rope stretch and wear;

Upvote for what mikl said about wear - after a couple more rounds with my double-traxion rig (described on that other thread mikl linked) I'd definitely recommend investing in / making one or two rope protectors, particularly if the rock is hard and/or sharp (the chert here is both!). I now have two of them after leaving copious amounts of rope fuzz at Split Rock a few weeks back...
Olbert
24/07/2012
1:48:36 PM
Sounds like you've bought a semi trailer to transport your mower from your yard to your neighbours yard.

That said, that's not necessarily a bad thing. Much better you over engineer than under engineer.

Eduardo Slabofvic
24/07/2012
2:04:17 PM
On 24/07/2012 pmonks wrote:
>>my double-traxion rig

Just for the sake of pedantry, is that two traxions, or is there a "double" one available?
Tim_1964
24/07/2012
3:08:21 PM
Thanks all for discussion and urls. Its quite surprising how many folks have used self belay in their time.

IdratherbeclimbingM9
24/07/2012
7:34:46 PM
On 24/07/2012 Tim_1964 wrote:
>Hi all, after extensive efforts I often find myself without a climbing
>partner using a self belay rig on smaller climbs (really just scaling up
>from bouldering). I am seeking comment on my anchor design - as follows:
>
>1. Use 3 large rocks or trees
>2. Place a sling around each
>3. Clip a screwgate to each
>4. With my dynamic rope tie a clove hitch to the first screwgate
>5. After the clove hitch feed say 3m of rope out, then tie a figure 8
>knot
>6. Anchor X is now complete using a single strand of the rope
>
>7. Feed 4m of rope after the F8 knot as this will be slack and non weight
>bearing
>8. After 4m of feed, make a clove hitch on the second anchor
>9. Repeat 5, 6, 7
>
>Each anchor is therefore a single strand of dynamic rope with a F8 knot
>on the end
>This will create 3 anchors with 3 F8 knots available to tie the main rope
>into (rope 2)
>(I could use a single overhand rather than 3 F8 knots)

Sounds a bit like overkill to me. Why not just use a cordalette?

If you are going to continue with your system, why not use the first anchor knot as a fig 8, then use the clove hitch at the self-belay-rope-anchor end to easily adjust tension from that point, given that the anchor is safe-as due being a good knot?


>Clip 2 opposing screwgates into the 3 F8 knots
>Equalise the length by adjusting the clove hitches

...easier done if the clove hitches are at that point as explained above.

>Tie the main rope into the 2 opposing screwgates with a figure 8 on a
>bight and toss it down the climb line.

Leave plenty of slack in the tail of that knot (to allow for slippage), or back it up with half a fishermans knot.
I say this because you have incorporated redundancy x 3 into your anchor system, but have nil redundancy on the critical master knot in the anchor!
>
>From the bottom I clip in a petzel croll ascender backed up by 2 prussik
>loops and I am ready to climb. At this stage I am testing the rig and
>I check the croll and the prussiks before each move. I ensure that the
>croll is clean and clipped and that the prussiks will not feed into the
>croll. I have clocked up 10 hours on the rig with no significant issues.
>There is no fall factor and I use a static rope for the main rope (as the
>technique is more SRT than Lead)

Two prussiks ?
Seems like overkill again to me...
I tend to go with the 'keep it simple' system and have found by experience that the more things you incorporate into a system, then the more things that 'Murphy' can tamper with to cause you grief within it!

If you had a second prussik on a second rope I could understand your logic, but as it is, you have doubled up on redundancy in various parts but are still relying on only one rope...
>
>I could run a second main rope with another croll and prussiks (to conform
>with industrial rope access standards) but this does not seem necessary
>at this stage.
>
>Comments welcome.
>
>Thanks
>
>Tim
>
egosan
24/07/2012
9:26:43 PM
On 24/07/2012 IdratherbeclimbingM9 wrote:

>If you had a second prussik on a second rope I could understand your logic,
>but as it is, you have doubled up on redundancy in various parts but are
>still relying on only one rope...

Given that one of the modes of failure of toothed devices like the croll is the stripping of the sheath, prussics might not even be providing any redundancy at all. If you are going to use a toothed device on your rope tying knots under you periodically is probably a better back up.

IdratherbeclimbingM9
24/07/2012
9:37:09 PM
Good point egosan.

... or another option is to run it out even further depending on the climb! ~> My inclination if using your system, would be simply to tie into a second (dynamic) rope sufficiently high enough not to deck out in the event of catastrophic failure of the primary system, and run laps as inclined, but being prepared to take the fall if the primary system fails!
By the way I invested in a Silent Partner device for my roped soloing, as it is excellent for a variety of solo type applications. ;-)

On the subject of prussiks.
I agree with mikl's comments above particularly;
>prussics are hard work and sensitive to bioth roeps diameter and condition.
as they need to be tailored to your need regarding ease of sliding up but not slipping down when needed in all situations.
Back in daze of yore, the Barnett system (that incorporated a huge prussik), had documented instances of it slipping badly under large falls (effectively failed resulting in one climber death, and would have resulted in another death of a climber if he had not tied in to the end of the rope), even though it 'grabbed' for lesser falls.

pmonks
25/07/2012
6:00:08 AM
On 24/07/2012 Eduardo Slabofvic. wrote:
>On 24/07/2012 pmonks wrote:
>>>my double-traxion rig
>
>Just for the sake of pedantry, is that two traxions, or is there a "double"
>one available?

Yeah sorry, wasn't clear - that's two traxions, one on each strand of the rope.

muki
25/07/2012
12:14:27 PM
I would stick with a totally static system ,no dynamic elements such as your dynamic rope anchor, as this can lead to the stretch that allows the part of the system that runs over the edge to rub, and that friction causing wear and tear damage, edge protectors or rope protectors are critical, you don't mention using any ?
And I also like the non toothed rope grabs for this activity, e.g. petzle micro or rescue senders, these are great, and have been copied by Ferno, check out their site, good stuff.

gnaguts
25/07/2012
12:52:12 PM
On 25/07/2012 muki wrote:
>I would stick with a totally static system ,no dynamic elements such as
>your dynamic rope anchor, as this can lead to the stretch that allows the
>part of the system that runs over the edge to rub, and that friction causing
>wear and tear damage, edge protectors or rope protectors are critical,
>you don't mention using any ?
Would you use a rope log for your ropes in that situation?
Any falls involved would really be more like slumps on a stolen shackle as Eddy points out above?
Tim_1964
25/07/2012
10:13:00 PM
Thanks again all.

Good point about dynamic rope muki

Would love a silent partner...will save my pennies : )

Fair point about inefficient use of second prussik - this was added recently just because the system was working smoothly enough to allow more redundancy but yes, a second rope would certainly be a good approach.

I do need to add rope protectors also.

Good feedback on overkill - the upside is its robust! (theoretically)

M9 - I dont suppose you could sketch it out? - and thanks for the tip on the tail - I need to add that for sure.

egosan - thanks I need to look into the stripping issue.

In some ways its nice to climb self belay but I am working hard on finding partners. I am fortunate enough to have lots of time to climb at the mo and its great to have so much rock near Launceston...now, if all the local climbers would just stop working....
egosan
26/07/2012
12:33:15 AM
http://www.youtube.com/watch?v=I0J_pg9Q1fs

showing a device mechanically identical to the croll shredding the sheath

pmonks
26/07/2012
4:21:22 AM
On 25/07/2012 muki wrote:
>I would stick with a totally static system

I wouldn't - even short slumps on a static rope can generate dangerous loads on your body and the anchors.

> no dynamic elements such as your dynamic rope anchor,

I do agree with not using a dynamic rope in the anchor system though. I use a 15m static rope for the anchor, with the tie-in points for the dynamic rope hanging over the top of the climb. For overhanging climbs this means the dynamic rope (which is what I'm clipped into and my ascenders are running up) isn't touching the rock at all. Best of both worlds.

>as this can lead to the stretch that allows the
>part of the system that runs over the edge to rub, and that friction causing
>wear and tear damage, edge protectors or rope protectors are critical,
>you don't mention using any ?

I use rope protectors, typically wrapped around the static anchor rope since it's the rope that's running over edges, not the dynamic that I'm clipped to.

Here's a high quality engineering diagram of my setup:



The only potential problem with this setup is that I'm using the same device on each strand of the rope. I'd originally tried using a grigri on one of the strands, but having to stop every other move to feed rope through the device sucked.


tnd
26/07/2012
11:37:21 AM
Do you always climb facing out Pete? ;-)
Tim_1964
26/07/2012
12:37:04 PM
nice video ergosan - expected max force is 1.5kn so should be in the envelope there.

thanks pmonks will look into that design.
egosan
26/07/2012
1:18:00 PM
Climbing on a static rope, it would only take a 40 or 50cm slump to generate 6kn. One of the engineer types can give us the distance. One little c--k up of the device not running freely and bang. The shunt is good in this situation in that it is designed to slip at 2-3kn.

Can someone gives us a little curve of peak force against the length of the slump on a "theoretically static"top rope?
Tim_1964
26/07/2012
1:25:59 PM
I use this one http://hyperphysics.phy-astr.gsu.edu/hbase/flobi.html

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