/ Second/Toprope Anchor on Different-Height Bolts?

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dommc on 13 Apr 2017
On sport climbs with two bolts at the top, I use a quickdraw in each to secure the rope for anybody seconding/toproping the climb after me (quickdraw gates facing opposite directions, or even locking biners). This works well if the bolts are at the same height, but wondering whether it's still the preferred method when the bolts are at different heights, and if not, what is?

If a different technique should be used, I'm vaguely aware of one which involves putting a carabiner in each bolt, putting a sling into both carabiners, manually equalising and knotting the sling with an overhand/fig8(?), putting a locking biner into the bight created by the knot, and then clipping the rope into the locking biner. If this is the way to go, what length of sling tends to come in handy - 120cm?

Cheers, seems basic but haven't found much by searching!
John Stainforth - on 13 Apr 2017
In reply to dommc:
You don't need a knot, just a twist in one half of the sling. Best to use two krabs for the ropes to run through (redundancy, and less friction/wear on the ropes and krabs), so four krabs in all. Best still, use two slings of equal length for redundancy, each attached to both bolts, and each with a single twist in one of its halves. The slings should be fairly long, to get as far away from the dreaded American Triangle as possible.
Post edited at 14:04
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teh_mark on 13 Apr 2017
In reply to dommc:

If on a multipitch and there's no chain or anything connecting the bolts, I'll very often clip a quickdraw between them and hang/belay from the lower bolt. Obviously that's assuming there's nothing obviously wrong with the bolts - if there was I'd consider my options more carefully!

For a single pitch, at an anchor where it's not easy to clip a quickdraw to each bolt like you currently do, I'd probably equalise it with a sling and overhand like you suggest, using a single screwgate (usually a Boa or similarly large HMS) for the rope. Or two opposed snapgates.

Another option would be the sliding X.

https://www.petzl.com/BE/en/Sport/Installing-an-equalized-belay-station?ActivityName=Multi-pitch-cli... might give you a few ideas. The first options they look at are the sliding X, and below it equalising with a figure-of-eight (but with three bits of gear rather than two - the principle remains the same though).
dommc on 13 Apr 2017
In reply to John Stainforth:

Thanks John. I might be confused, because I'm not sure I understand the "single twist in one of its halves", but if you use two slings of equal length, am I right in thinking that means one of them is just hanging loose and only acting as a backup should the higher bolt fail?
buxtoncoffeelover - on 13 Apr 2017
In reply to dommc:

You can use 'draws of different lengths to achieve similar result ( I don't have specific sport 'draws & have an assortment of from 10 - 30cm, which usually covers any height offset between bolts). In a case of widely separated bolts linked by a chain, I clipped the lower one & a link on the chain near the upper bolt to have the 'draws level. No climbers were harmed by this act!!
Carless - on 13 Apr 2017
In reply to dommc:

If the bolts are at different heights, why not already thread the anchor and leave a quickdraw on the highest bolt to stop unnecessary wear on the lower-off ?
dommc on 13 Apr 2017
In reply to teh_mark:

Thanks for that - I'll have a look at the link in more detail later!
dommc on 13 Apr 2017
In reply to Carless:

Sorry, I don't understand the question. I'm asking about techniques to anchor my own carabiner(s) to bolts at the top of a climb, specifically so that anybody toproping the climb is using my gear instead of any fixed gear.
Carless - on 13 Apr 2017
In reply to dommc:

Sorry - should have made myself clearer

What I suggested is possible if the bolts are connected by a chain with a maillon/ring on the lower bolt
If the higher bolt is more than a quickdraw length above the lower bolt, thread the maillon but leave the rope also running through a draw on the higher bolt
Like that, the rope is already threaded and the insitu gear is not being used except for the last person lowering off
Mowglee on 13 Apr 2017
In reply to Carless:
I find the rope tends to get horribly twisted doing that. Better to have it running through a single point with the backup being loose.

I just clip a draw to each bolt and go for it. It's only loading one, the other is there as backup. If anything fails, there's enough rope out (i.e. at least a pitch worth) such that the shock onto the remaining bolt isn't going to be much higher than if perfectly equalised. If it looks at all dodgy I'll put a long draw on the last bolt too, as a 2nd backup.
Post edited at 15:25
John Stainforth - on 13 Apr 2017
In reply to dommc:

I'm sorry that I was not very clear in my post. I was talking about the self-equalising "sliding X" that teh_mark refers to. If using two slings (simply for redundancy), they should be set up identically using the same carabiners etc. John Long has good diagrams of the self-equalising slider knots in his books ("Rock Climb!", p. 97; and "Advanced Rock Climbing",co-author Craig Luebben, p. 85), which I highly recommend. In addition, for top-roping, I am suggesting two karabiners for the running rope to reduced friction and wear on both karabiners and the rope.
jimtitt - on 13 Apr 2017
In reply to dommc:

All the top anchors I install are like this and plenty of other people do it the same, roughly one bolt 200mm away and at 45° up from the other. For top-roping just clip two draws like usual and accept one is slack or use two draws chained together on the upper bolt and one on the lower bolt.
jimtitt - on 13 Apr 2017
In reply to John Stainforth:

> In addition, for top-roping, I am suggesting two karabiners for the running rope to reduced friction and wear on both karabiners and the rope.

Using two karabiners increases the friction (and thus the wear).
3
wbo - on 13 Apr 2017
In reply to jimtitt: I was also taught to place them like this, but for a QuickDraw on the upper, screwgate on the lower. Am I a bad man?

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Misha - on 13 Apr 2017
In reply to John Stainforth:
Sling with a twist - ok as long as both bolts hold. If one fails, the attachment point will slide to the end of the sling, shock loading it and potentially breaking it. Now you might say that a bolt is unlikely to fail. Yet the very reason anchors have two or even three bolts is in case on fails... So if you're going to use the equalised sling method, put a knot in it.

Useful to have different length QDs as well.

Linking the two bolts with a QD of the right length and anchoring off the lower bolt only can also work.
1
Misha - on 13 Apr 2017
In reply to buxtoncoffeelover:
If the bolts are linked by a chain, just stick a screwgate in the lower bolt.
jkarran - on 13 Apr 2017
In reply to Misha:

The rope is the load limiter if a sliding x fails in a bottom rope set up.
jimtitt - on 13 Apr 2017
In reply to wbo:

Just a krab in the lower bolt can cause the rope to twist but it´ s not the end of the world I just whack a couple of draws in.
John Stainforth - on 14 Apr 2017
In reply to jimtitt:

I don't think the friction is increased, because the load on each carabiner is halved; I suspect the friction on each is about halved. Anyway, having done it both ways for prolonged periods over many decades, the visual *impression* is that the wear per carabiner is less when using two. There is also the separate issue of redundancy.
John Stainforth - on 14 Apr 2017
In reply to Misha:
I totally agree that if it looks as though there is a significant chance that an anchor could fail, then one should also add knots to reduce the potential shock-loading. I was presuming here that the OP was referring to standard "good" bolts, in which situation I don't bother with additional knots. I usually add knots when the anchors are nuts etc.

The purpose of multiple anchors is *not* just to have back-ups if one should fail (although that is very important , of course), but to reduce the load on each. If the anchors are properly equalised, each anchor experiences a fraction of the total load, i.e, with two anchors the load on each is about halved, with four it is about quartered - which greatly reduces the chance of failure.
Post edited at 00:40
1
jimtitt - on 14 Apr 2017
In reply to John Stainforth:

> I don't think the friction is increased, because the load on each carabiner is halved; I suspect the friction on each is about halved. Anyway, having done it both ways for prolonged periods over many decades, the visual *impression* is that the wear per carabiner is less when using two. There is also the separate issue of redundancy.

The friction over two karabiners is increased by ca 8-10% compared with a single one, the friction continues to increase as you add karabiners at a steadily decreasing rate until about 5 to 7 karabiners (depends on the rope and the karabiner diameter). This is easy to measure.
The load is shared by the two karabiners but the contact area is also halved, however this is neither the cause nor the effect, the increase is due to the force required to bend the rope around the first 90°, straighten it and bend it 90° again. This is somewhat harder to measure.
Misha - on 14 Apr 2017
In reply to jkarran:
May be to some extent but why chance it? Just put a knot in the sling instead...
1
jkarran - on 14 Apr 2017
In reply to Misha:

There's nothing to chance, the only rigid mass impacting on the sling if a sliding x bottom rope anchor fails is the krabs which is insignificant.
Jk
Andy Peak 1 - on 14 Apr 2017
In reply to jkarran:

Put a knot in it;-)
Andy Peak 1 - on 14 Apr 2017
In reply to jkarran:

When I set up top ropes on bolted anchors I put a long quick draw with two screw gates on the top one and a screw gate on the bottom, now there about the same height and if one fails it will fail to safe.
Putting a sliding x on will probably be ok but if it fails it will generate heat as it slides so potential to fail.

I wouldn't normally comment on threads like this but it's better than Columbo
dommc on 15 Apr 2017
In reply to Carless:

No worries, got you now, cheers
dommc on 15 Apr 2017
In reply to John Stainforth:

No worries, thanks for the info - makes sense now
springfall2008 - on 16 Apr 2017
In reply to dommc:

Personally for top roping I put a screw gate into each bolt and run the rope through both. If one bolt were to fail it's a dynamic rope anyhow and the distance between them is so small the loading would be minimal compared to a normal lead fall.
purplemonkeyelephant - on 16 Apr 2017
In reply to springfall2008:

Do you mean the American Death Triangle?
David Coley - on 17 Apr 2017
In reply to John Stainforth:

> I totally agree that if it looks as though there is a significant chance that an anchor could fail, then one should also add knots to reduce the potential shock-loading.

I would say that "if it looks as though there is a significant chance that an anchor could fail", don't use the anchor. Down climb, or climb over to another anchor, or head off the top, or lower off the last bolt; just about anything but use it to lower off or bring another climber up.
springfall2008 - on 17 Apr 2017
In reply to purplemonkeyelephant:

No, I just meant through both screwgates as a top rope, if the higher bolt failed then the rope would have a little slack in it before weighting the lower bolt, but it's pretty small compared to a lead fall. Agreed you are only loading one bolt but it's a top rope so the loading is low anyhow.
John Stainforth - on 18 Apr 2017
In reply to David Coley:

That's my attitude with bolt anchors. Adding knots to equalising slings to reduce potential shock loading is something that I only do with trad anchors where one may be slightly substandard. (I usually use four trad anchors.)
dommc on 19 Apr 2017
Wasn't planning on bumping this thread again, but came across this video which shows how to use a sling and clove hitch as an anchor: http://mountainmoxie.com/climbing/using-clove-hitch-climbing-anchors. Seems faster and easier to tie and untie than the sling and overhand/fig8 method, and would work in the situation which I started the thread about, so thought I'd share for anybody who finds the thread in future looking for anchor info..
David Coley - on 19 Apr 2017
In reply to dommc:

I used to use a clove for a long time, and it was recommended in Petzl's pdf on multi pitch climbing. However it has one serious issue. If the shelf is used and the locker through the clove removed, whoever is hanging on the shelf may well die. Whether the shelf collapses depends on just how the clove was tied, but is in essence random. Now, you might be thinking, just don't remove the locker, but as many accidents come about from the unexpected, "oh, I'll just take that", or systems others might not know the rules of, I'd stay clear of it.
dommc on 19 Apr 2017
In reply to David Coley:

Thanks for pointing that out. I was really just thinking about use as a single-pitch sport anchor here (so technically a bottom-rope); don't think the shelf danger is one you'd really run into in that situation. But good to bear in mind for multi-pitch!
Toerag - on 19 Apr 2017
In reply to jimtitt:

> All the top anchors I install are like this and plenty of other people do it the same, roughly one bolt 200mm away and at 45° up from the other.

Hi Jim,
what's the logic behind this configuration? Why not just have the two bolts level with each other, or directly above each other?
jimtitt - on 19 Apr 2017
In reply to Toerag:

> Hi Jim,what's the logic behind this configuration? Why not just have the two bolts level with each other, or directly above each other?

There are a number of reasons.

Two bolts level with each other and directly threaded tend to twist the rope.
At a multi-pitch belay it is nicer to arrange the bolts so the lower one can be clipped with a standard girth-hitched sling as a cows tail and the other a bit higher for those who prefer to bring up the second with either a guide plate or a re-direct.
If the bolts will be (in the future) joined by a chain then with two horizontal bolts you ideally need 2 chains, with them staggered you only need one which is cheaper.
If you are installing chainsets then the range of possible placements when they are horizontal is very limited, with the inline system it is vastly greater.
When the bolts are horizontally installed and used threaded direct the wear on each bolt is equal, therefore when one becomes dangerous the other is also dangerous, with an offset installation one bolt becomes dangerous when the other is still safe.
Finding a suitable location to install two bolts horizontally is often not so easy!
Toerag - on 20 Apr 2017
In reply to jimtitt:

cool ta
DubyaJamesDubya - on 20 Apr 2017
In reply to Misha:

> May be to some extent but why chance it? Just put a knot in the sling instead...

Thus significantly weakening the sling.
Misha - on 20 Apr 2017
In reply to DubyaJamesDubya:
Rather that and a static load than a shock load (ok in a TR scenario the rope will absorb some of the force but we're talking about anchor failure here, so there would have to be significant force regardless of the rope and hence a shock load).

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