/ Combining half and twin ropes on easy climbs

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BnB - on 08 Apr 2013
Expert opinions welcomed:

I have a 30m dynamic twin scrambling rope (for safeguarding my kids on scrambles) and a 30m half (carried as a safety backup when soloing snow/ice).

As a means of saving and distributing weight between climbers, not to mention avoiding the cost of a new rope, I'd like to know if combining the two can work effectively.

When looking to protect short, hard scrambles (say Mod - Diff) which is the best option (as an alternative to taking a 50m half rope doubled over into two 25m halves)?

For longer pitches (15 -30m)

a) climb on both as half ropes clipped alternately/separately
b) climb on both as twin ropes clipped together in each runner

I'm interested to know if there is any (safety) downside to combining the two types other than the differential stretch.

For short pitches (5-15m)

c) climb on the half rope doubled over
d) climb on the twin rope doubled over

Any dangers inherent in doubling a rope to halve its length?
GrahamD - on 08 Apr 2013
In reply to BnB:

I don't think there is any hard and fast rule you can follow. The easiest one to answer is that halfropes doubled is a pretty nornmal technique however due to the tie in, the belay etc your useable length will be substantially less than half the total.

Whether you treat ropes as twins or as half ropes depends on the terrain - where are the haxards ? what are you likely to hit ? what are the ropes running over ?
JIMBO on 08 Apr 2013
In reply to BnB: I think the weakest link is the "twin" rope so should be used as twins...
BnB - on 08 Apr 2013
In reply to GrahamD: All your riders are understood. I think my question boils down to the choice between a) and b), where b) would better comply with safety guidelines but would place more strain on runners and a) would be more practical (less drag, lower impact force) but with more risk of the twin failing.

Half ropes are not automatically rated for twin use I note on Beal's website?
Neil Williams - on 08 Apr 2013
In reply to BnB:

Because there might be not enough stretch if you do that, so your gear pulls out / you get too hard a catch?

john arran - on 08 Apr 2013
In reply to BnB:

Half-ropes are invariably fine used as twins.

One factor you may not have considered is that very thin ropes may be difficult to control with your belay device; usually ok if using ropes in twin mode as the force will come onto both ropes at the same time but if you're using them as doubles the whole fall may have to be held on one twin-rope strand by a belay device not designed for it. Again it may be ok but best to be aware of the possible limitations whwenever you're considering using gear in a non-textbook way.
GrahamD - on 08 Apr 2013
In reply to BnB:

On easier terain, I'm more worried that I'll end up hitting ledges on rope stretch than I am strain on gear. With 10m or more of rope out there is loads of elastic in the system. Assuming you are only placeing the odd runner as you would on a scramble, personally I'd just clip both ropes together if I bothered with two ropes at all. Exceptions might be traverses or lines with very accute changes in direction.
The Ex-Engineer - on 08 Apr 2013
In reply to BnB: My expert opinion is that you are over-analysing this.

If you actually fall off most scrambles, Mods or Diffs, whether you are using a single rope, twin ropes or no rope, the consequences won't be much different, you are likely to end up seriously injured regardless.

As such, all the methods you suggest will offer little real advantage on easier routes over using either rope singly. Even a twin rope used singly (with an appropriate belay plate) will hold the sort of fall you can potentially encounter on that type of route.

On a route like Tower Ridge I'd prefer to use a 30m half-rope singly as opposed any of the options you suggest. That is because the advantages of using one rope in terms of taking/dropping coils to switch between short roping, short pitching and long pitching easily outweigh any theoretical advantages of double or twin rope technique.

FWIW on harder mountain rock routes with pitches less than 30m I'd be happy to go with twin rope technique.
Ramblin dave - on 08 Apr 2013
In reply to BnB:
It's a slight derail, and I feel a bit "special" for asking, but what specifically is the problem with leading on a single half rope? I've never quite grokked this, given that often when you lead on two halves there will be times when you're effectively only using one of them (up until the second piece of gear, for starters)...
The Ex-Engineer - on 08 Apr 2013
In reply to Ramblin dave:
> what specifically is the problem with leading on a single half rope?

The issue is all about what is an appropriate safety margin combined in part with decisions on when to replace ropes.

A 'single' rope will hold 5+ test major falls. That is what was considered by the experienced climbers at the UIAA many years ago as sufficient to ensure a sufficient safety margin even when a rope is well worn.

In contrast 'half' ropes are tested with test falls specifically designed such that 5 'half rope' falls roughly equaled 1 'single rope' test fall. This was based on the premise that half ropes should at least hold one major fall when new, but that a more discerning test was required.

So, looking at current ropes:
A Mammut Serentiy 8.7mm (51g/m) holds 5 major test falls.
A Mammut Genesis 8.5mm (48g/m) would perhaps hold 4 major test falls.
A Mammut Pheonix 7.9mm (42g/m) would perhaps hold 2 major test falls.

Single ropes therefore have a LOT more durability in terms of major falls (+150%) compared to half ropes, with only a SMALL increase (+21%) in weight. Whilst this extra 'durability' is in once sense fairly theoretical and it is debatable how much use it is in the real world, there is a very compelling argument that the extra durability and all-round robustness is well worth the fairly small increase in weight in most climbing situations.

Equally, if there are no particular risk factors (likely repeated falls, sharp edges or rough rock) you are never going to be in any danger of snapping a fairly new half rope.

I'd be happy leading on one (brand new) half rope in a whole variety of situations, including on hard trad and alpine routes. However, if I did that regularly, I'd end up replacing ropes at least thrice as often as if I was using a thicker single and it'd cost me a small fortune.

needvert on 09 Apr 2013

Interesting post there.

Makes me wander which I'd prefer, high % core low % sheath, or high % sheath low % core. The sheath is much much easier to inspect, and I'd much rather a sheath than core failure. Ergo perhaps I should go for high % core low % sheath.
BnB - on 09 Apr 2013
In reply to BnB: Glad to be provoking some debate. For hard scrambles with ledges and only short pitches between them, is the consensus to carry just the half rope (even less weight to worry about) and climb it either as a single or doubled up, depending on pitch length, abrasiveness of rock etc?
GrahamD - on 09 Apr 2013
In reply to BnB:
> (In reply to BnB) Glad to be provoking some debate. For hard scrambles with ledges and only short pitches between them, is the consensus to carry just the half rope

Thats what I do.
The Ex-Engineer - on 09 Apr 2013
In reply to BnB:
> For hard scrambles with ledges and only short pitches between them, is the consensus to carry just the half rope (even less weight to worry about) and climb it either as a single or doubled up, depending on pitch length, abrasiveness of rock etc?

Scrambles are a really tricky one. That is partly because a high level of skill is needed to attempt them in the most efficient manner. Many climbers are unaware of the various techniques that can be used as they differ from standard climbing are these days seems to be mainly the preserve of mountaineering instructors and guides. This is perhaps because when people attempt scrambles as an equally competent pair, they will generally be able muddle through so feel they have no real incentive to learn new skills.

The scenario of a competent leader (instructor) and a novice second is actually easier to deal with as there is a very well developed method by which scrambles are undertaken by professional instructors and guides. As mentioned above, that revolves around using a SINGLE strand of rope and quickly taking or dropping coils in order to transition quickly between different options (walking roped up, short roping, short pitching and long pitching).

In an ideal world, most instructors I know would prefer something like 35m of Beal Joker 9.1mm (especially if it isn't their rope!). However, in practice most instructors/guides will use perhaps 40m of 10mm single rope that has been retired from lead climbing. The hassle of the extra weight (and bulky coils) is offset by saving money and the fact a thicker rope is arguably better for short roping, providing a tight rope from a braced stance and body belaying. The reasons for using a older, thicker single rope are because scrambling is hard on ropes and the cost of replacing dedicated thinner ropes would mount up, rather than any great concern that a half rope is intrinsically unsafe on that sort of terrain. For example, in February the group I was in trashed one of PyB's expensive and nearly newy Jokers on Sron na Larig (Winter grade II) :-(

Going back to the scenario of attempting scrambles as a pair of equals. As mentioned this is generally a more confused situation. A lot of the time (possibly the majority of time), it will transpire that the rope is carried, ready to be instantly deployed but is un-used.

But when the rope is to be used, the best option would be to approach the route in a similar manner as a guide/instructor would. Unfortunately many climbers/scramblers do not have the level of understanding needed to do this as the methods used are rather different from normal climbing and most crucially REQUIRE PRACTICE. This means that there is a fair degree of confusion and many people try to adopt a singular approach in an attempt to keep things simple. Some will try to pitch everything, others will try to move together throughout, neither of which is ideal.

This would be my standard set of options if on a harder scramble:
- initial easy ground - one member has all the rope taken in chest coils, tied off in two sets of coils and the pair solo together unroped.
- short pitches - leader drop first set of coils giving c.15m of rope, (second ties in if not already) and leads the short step with a belay if needed.
- long pitches - leader drops all coils giving 30m of rope and leads the pitch as per standard rock climbing.
- intermediate ground - pair moves together with anything from 10m-30m of rope out (rest in chest coils) and leader places regular runners. [Terrain such pinnacled ridges where this is appropriate is rare in the UK. Other options are often better.]
- easy sections - leader has chest coils but pair close up and carry rest of rope as hand coils.

As you can see, the various options all revolve around using a single strand of rope but varying the amount of rope out to suit the terrain. Also once tied in to the ends of the rope, it is normal to stay tied. As such, I just can't see any scenario where I would use twin/half rope technique on a scramble either with a novice nor an other experienced partner. Even in the Alps when carrying two ropes, as soon as I'm on easier ground, the second rope would be packed away and I'd revert to a single strand and taking coils as needed.

Anyway, hope that makes sense.

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