UKC

I saw that BMC have a video showing how to set up a top rope anchor for Southern Sandstone. It shows the instructor using a single sling attached to a screwgate carabiner, noting that redundancy is provided by the anchor bolt connected to a second bolt by a wire.

Is it common to use a single sling as an anchor or do people tend to use two slings or equivalent for redundancy? Doesn't make sense to me to say redundancy is provided by the bolt, as if the sling fails the system fails, which seems more likely than an anchor bolt failing.

Thanks in advance.

In reply to mouseliveson:

It's common, climbing slings are designed to take a fall from a leader (via the rope)  
When top roping, the falls are so small that the sling is never pushed anywhere near to it's limit.

 Obviously inspect the sling beforehand, and don't use one that's quite a few years old. 

In reply to mouseliveson:

Slings don't fail, unless cut over an edge. I often toprope on a single sling.

A second sling would provide greater redundancy against screwing up however.

In reply to Dan Arkle:

Not really.  Add-ons more steps and complication is more likely to result in mistakes.  KISS and all that

In reply to Dan Arkle:

How does one screw up placing a sling?

In reply to Michael Gordon:

You can be sure somebody will have found a way to do that and all sorts of other implausible mistakes.

In reply to mouseliveson:

 

It is very common. The sling is not the anchor. The sling is used to equalise a number of anchor points.
e.g. you place three nuts appropriately, put a karabiner on each of them, put a sling through the three and bring it to a "pinch point" perhaps via an overhand knot. The sling is now acting like three sling (call them "loop A", "loop B" and "loop C"). If somehow some part of the sling fabric in loop A fails and snaps, loop B and loop C provide redundancy. 
This is a common diagram in instruction books. 
e.g.
http://rockandice.com/wp-content/uploads/Article-Images/News-Photos/Feb-201... 

 

In reply to Michael Gordon:

You might run it over a sharp edge

In reply to harold walmsley:

Yes, I have usually doubled up everything, i.e., two equalised slings and two karabiners for the running rope, partly for the redundancy (which is extremely unlikely to ever be needed) but also to reduce the stress and wear on the slings, carabiners and rope (which always happens)

In reply to mouseliveson:

The sling as well as the karabiner, rope, harness etc is PPE thus the history and use is known and it is regularly inspected and replaced as nescessary. Redundancy is unescessary and unusual.

The bolts are of unknown age (to the user), condition since you can´t see down the hole and rock is a constantly changing medium of unknown quality. Redundancy may be desirable and in a commercial environment more so.

In reply to mouseliveson:

You climb on one rope without considering redundancy, seems much the same concept as using a single sling

In reply to harold walmsley:

On Southern Sandstone?  That would be um..  unlucky.

In reply to harold walmsley:

Or place it on a spike without enough room behind it, so rope movements while toproping cause it to come off

In reply to mouseliveson:

It's normal on Southern Sandstone because it would be unimaginable for a normal sling to fail. Up to you though

A bolt pulling out of soft sandstone - unlikely but plausible and might be BMC or Bowles having to defend the decision

In reply to John Stainforth:

You wear two harnesses then?

In reply to mouseliveson:

I always enjoyed watching people who had spent too much time following instructions and not thinking arranging multiple point belays at High Rocks on multiple large pine trees.

I don't know what they thought the braking point of a 3ft wide pine tree was.

 

In reply to mouseliveson:

Thanks all for the opinions.

On the topic of slings, in the context I have described are there any issues connecting two or more slings via girth hitch to extend the length? If not what is the best practice to connect two or more slings?

In reply to mouseliveson:

Not really your question, but if you are going to be climbing on sandstone regularly a 5-10m length of 10mm static rope will come in handy for setting up top rope anchors.

 

In reply to mouseliveson:

In debates I've seen before the conclusion was that, while girth hitch/larks foot greatly reduces the strength of the sling (50% I believe), a sling is so strong it doesn't matter in most cases.

However if it worries you joining with a Krab or looping the sling to half length are options.

In reply to DubyaJamesDubya:

Yes I saw similar figures on the DMM website testing exactly that, but was wondering in practice if it makes any difference in the real world. It'd be interesting to know if any sling connected with a girth hitch has ever failed under sensible practice during top roping...

Static rope is great, so may get some for future sessions but always helps to make do with what I have already...

In reply to mouseliveson:

why not arrange for a bouncy castle if toproping is so alarming

In reply to Brown:

Depends how fast the pine was going before it stepped on the brakes 

In reply to mouseliveson:

Well it's not likely to as the strength is reduced from 2000kg down to 1000kg.

In reply to Slarti B:

Does anyone have data on perception/reaction time for a pine tree? I think we should consider overall stopping distance.

 

In reply to profitofdoom:

Not so many spikes to be found on Southern Sandstone. Anchors are bolts or trees.

In reply to Brown:

I'd guess the breaking point of a tree might be at the knots

I also find it bizarre that people think a big pine on flat ground  isn't enough to be a safe belay on its own..

In reply to Offwidth:

Or indeed that if 20 tonnes of tree does fall off the edge, their back up is going to be any use to stop it !