Mole Creek Caving Club
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~ Notes on 'Alpine-style' SRT* ~
by Sherry Mayo, NUCC
* this page is duplicated from a now defunct website, is not written nor necessarily
endorsed by MCCC or its members.
Why Bother?Unlike "Indestructible Rope Technique" (IRT), alpine-style SRT makes use of rebelays and deviations so that the rope hangs freely down the pitch avoiding rub points and other hazards such as waterfalls. This has the advantage that much thinner rope can be used which is much lighter and more compact to carry (or alternatively you can carry much more rope - useful if you are exploring a deep cave). Another plus is that abseiling or prussiking on a free hang is easier than abseiling or prussiking against an uneven wall. The (slight) downside is that you have to learn how to negotiate rebelays & deviations - the techniques and equipment used for these manoeuvres are summarised in these notes.
If you want more detailed information, read a good SRT
book such as "Vertical" by Al Warild, "Single Rope Technique" by Neil
Montgomery, or the recent e-book,
on a Line" (free download) by Dave Merchant.
SRT ascending/descending kit (descender omitted for clarity)
The Harness:this should be a purpose designed caving sit harness. A sit harness is fairly snug fitting and designed so that the central attachment point (i.e. the central maillon to which the chest ascender etc is attached) is fairly low on the body. This is important because the length of a prussik step is determined by the distance between the chest and foot ascender when the foot ascender is raised on the rope. If the chest ascender sits too high on the body this distance is reduced and the caver can only take short prussik steps which is inefficient. Several designs of harness suitable for caving are shown in the diagrams. A climbing harness is also shown for comparison. These can be used for SRT, but are far from ideal because the central loop is too high on the body. Also there is no central maillon and an intermediate krab or maillon has to be used to attach the chest ascender to the harness resulting in it sitting even higher on the body.
The chest ascender:As outlined above, for efficient prussiking the chest ascender must sit fairly low on the body (about on the stomach, just below the sternum). For this reason its is best to use an ascender without a handle, and better still, a purpose-built chest ascender such as the petzl croll which is designed to lie flat on the chest when clipped through the central maillon.
The chest harness:The purpose of the chest harness is to keep the chest ascender in position on the body so it moves cleanly up the rope when the caver stands in the footloops. It also holds the caver in more upright position on the rope which makes prussiking easier. If the harness is too loose, or the chest ascender too high, the caver will tend to lie back of the rope when sitting on the chest ascender, which is both uncomfortable and inefficient for prussiking. The chest harness should be done up sufficiently tightly that it is uncomfortable to stand in when you're not on the rope. Most people use a length of tape with a buckle as a chest harness (see picture). Purpose built chest harnesses are available but don't seem to work any better than the plain tape variety, and don't fit at all if you're female (i.e. if you have a bust). The chest harness isn't intended to be load-bearing and some people use a piece of bungee cord instead of a tape. This doesn't give the caver as much support on the rope but can be better for pulling the croll smoothly up the rope. Some cavers choose to use both a tape and a bungee cord (or similar) and have the best of both worlds.
Foot ascender, footloops and safety cord:The foot ascender can be a handled or standard (non-handled) ascender according to personal preference. It is attached to the caver via a safety cord of dynamic rope (8-9mm is suitable). The cord can either be clipped in directly to the central maillon by the knot in the end, or via an intermediate krab or maillon. There is no hard and fast rule about which is best, it comes down to personal preference. Clipping it in via a krab or maillon means that it can be unclipped from the central maillon while on the rope, however extra ironmongery on the central maillon can also cause problems if you get into a tangle. However, there are definite advantages to attaching the other end of the cord (and also the footloops) to the ascender via a maillon or krab, particularly if you're doing a rope rescue (see rope-rescue section on the pulley-style footloops rig).
The foot loops can be made of either tape or rope. Tape tends to be more hardwearing and if a rope is used, the bit that you stand on is best protected by a length of tubing. There is a risk with tape footloops that the tape can get jammed behind the chest ascender cam (this was the cause of an accident in the UK a few years ago), however, many cavers do use tape footloops and this type of incident seems to be rare.
Footloops can either be two separate loops, one for each foot, or a single loop for both feet (as in picture). It is important to get the lengths of the footloops and the safety cord just right. When standing in the footloops (off the rope) lift the foot ascender up till the footloops are taut. If the length is correct the camming part of the foot ascender should be just above the camming part of the chest ascender (see picture). Adjust the safety cord so you can reach the foot ascender when hanging from it on the rope by your safety cord.
Cowstails:These are a pair of safety cords used for protection during manoeuvres. The long cowstail is used for general security when passing rebelays, deviations and knots. The short cowstail is used specifically for passing rebelays while descending, during which your weight is hanging from the short cowstail alone. Cowstails should be made of 10-11mm dynamic rope with snap krabs clipped through the knot loop at the end of each cowstail (some cavers use 9mm rope in which case fig 9 knots should be used for tying the cowstails). A screwgate krab can be used as an alternative to a snap krab on the long cowstail for extra security while rigging. The krabs can be secured to the knot loops with snoopy loops (loops of tyre inner tube rubber) which hold them in place.
The picture shows how the cowstails are tied (there are alternative methods of tying cowstails but this method is the most common one). To tie the cowstails take a piece of dynamic rope about 2.5-3m long, and tie a double figure 8 (or figure 9) knot in one end, tie another double figure 8 (or figure 9) knot as close to the original knot as you can. Then tie a third double figure 8 (or figure 9) knot leaving about about 40 cm of rope between it and the second knot. Swami knots can also be used for the ends of the cowstails - these help hold the krabs in place. Some cavers use overhand knots for the ends of the cowstails as they are less bulky than fig 8's etc, but these do reduce the strength of the rope more than other knots (bear in mind the thickness of the rope you are using).
Make sure all the knots are correctly stacked and then tension the cowstails by hanging your weight from them. The lengths should now be about right. Remove any excess tail rope using a hot knife to seal the ends (the tails needn't be more than 10cm long) and tape the tails of rope to the cowstails. The short cowstail should be about 25-45cm from knot loop to knot loop, and the long one about 50-70cm (it should be at least short enough that you can reach the krab when it's taut). If you clip the cowstails to your central maillon via a krab or maillon you'll want them a bit shorter than if you clip the knot loop into the central maillon directly (see comments about attaching the safety cord above).
Descenders:There are many kinds of descenders that can be used for caving but most alpine cavers use bobbins, autolock descenders ("stops"), solid descenders or racks. The pictures show the way a rack and bobbin are rigged, for abseiling and for locking off (i.e. to lock the descender so it can't move on the rope). The stop works in basically the same way as the bobbin, except it also has a brake lever.
Racks:These provide friction by weaving the rope around a series of aluminium (or sometimes steel) bars. Commonly the first (uppermost) and third bars on a rack are fixed, and the second, fourth and fifth bars unclip on one side allowing the rope to be looped behind them. It is possible to "suicide rig" a rack by looping the rope around the wrong side of the bars - this will undo itself as soon as any weight is put on it so always check you've rigged it right!
Bobbins:The rope is wrapped around two fixed wheels to provide friction and then clipped through a braking krab (see picture). One side of the bobbin can be unclipped at the bottom allowing it to be swung open for attaching or detaching the rope. If the rope is very "slow" (i.e. fat and stiff therefore slowing the descent) a bobbin can be "C" rigged with the rope passing around both wheels in a "C" rather than "S" configuration. If the rope is very fast, abseiling with the bobbin on half lock can be used to slow down (see picture).
Autolock descender ("stop"):These are a more sophisticated version of a bobbin with a brake lever. When the lever is squeezed you will "go" and when the lever is released you will stop. If you're going too fast remember to let go, it sounds obvious but "it isn't always the most natural reaction" as it says in the Petzl catalogue (people sometimes squeeze the handle thinking it will brake their descent). Some versions of this type of descender are designed to stop when the handle is either squeezed or released and only "go" in the middle position, but these tend to be much bulkier.
Whaletails and Goldtails:
These solid block style of descenders (Spelean WhaleTails and SRTE GoldTails) deserve special attention, because of their popularity with Australian cavers, and have particular advantages for Tasmanian caving. These are suitable for most general caving and feature simple fail-safe rope-threading. The newest ones come with 2 safety gates for maximum security. The method of locking off is similar to that used for racks, shown above. Their disadvantage is they are more heavy and bulky (machined out of a solid block of aluminium) and also they are quite long which can make otherwise straightforward SRT manoeuvres a little more difficult since they take up more room on the rope. Their advantages include the in-line design that avoids any rope twist; superb heat capacity for longer pitches; spreading the friction over more rope and avoid tight strain points for greater rope longevity; excellent friction control (by varying the number of slots in use, as well as lower hand control) to cater for various descent speeds, rope thickness and bottom rope weight; can be used for doubled rope descents; and are also ideal for rescue applications.
Other descenders:Lightweight descenders that are often popular with climbers such as Figure 8s, or stitch plates are not suited to caving as you have to unclip them completely to get them off the rope (making dropping them and falling more likely on a rebelay crossing). They also have poor friction control, cannot be easily locked off, and tend to put a twist in the rope (which is really annoying when you're spinning round on the prussik back out) and wreak internal damage to the rope. Such devices are strongly discouraged for any caving, and are absolutely banned from use on MCCC ropes or club caving trips.
Notes on abseiling
Controlling speed while abseiling:
Once you have attached your descender to the rope you are ready to abseil. The principle is the same for all descenders - it is the tension of the rope below the descender that determines your speed. When abseiling hold the lower rope firmly with one hand down away from the descender. If you hold the rope taut you shouldn't move at all, and to move just let the rope slip slowly through your hand. With a bit of practice you should have no trouble controlling your speed. As well as being able to control speed you also need to know how to lock off a descender so that you can "park" on the rope without needing to hold the rope below you. Methods of locking off a bobbin and a rack are shown in the diagrams
This can be used to provide extra security for novice abseilers. The belayer stands holding the bottom of the rope. If the abseiler gets out of control and starts going too fast the belayer can slow them down (and stop them if need be) by pulling on the rope. This tensions the rope passing through the descender which increases the friction and slows the descent.
PrussikingPrussiking is the method of ascending the rope in SRT. Traditionally this was done using prussik knots which was slow and awkward, but mechanical ascenders have made prussiking much easier. The ascenders have a sprung loaded cam which slides up the rope but not down it. The caver wears a chest ascender attached to the sit-harness and held in place with a chest harness (see picture). A second ascender is attached to the caver via a safety cord. A pair of footloops are attached to this ascender (the foot ascender). The ascenders are put onto the rope by opening the cam, slipping the rope in and letting the cam close on the rope. The cam is usually prevented from opening fully by a safety catch which has to be disengaged for getting the ascender on and off the rope - for any other manoeuvres the safety catch should be left in place.
The chest ascender is put on the rope below the foot ascender. The caver sits down on the chest ascender which will be supporting their weight on the rope. The feet are put in the footloops. While sitting on the chest ascender the foot ascender in raised up the rope (you will need to lift your feet at the same time to take the weight off the foot ascender). Then the caver stands up as far as possible in the footloops and the chest ascender slides up the rope. The caver sits back down onto the chest ascender. This sequence is repeated over and over to progress up the rope. The footloops need to be adjusted so that when standing up in them the chest ascender almost meets the foot ascender.
Sometimes the rope won't slide freely through the chest ascender, particularly when you are at the bottom of the rope. With practice you can grip the rope between your feet while standing up in the footloops which will pull it through the chest ascender. When standing up in the footloops, push your feet downwards under your bum rather than out forwards as it makes prussiking easier and more efficient.
This can be used to assist ascending cavers. The belayer
stands holding the bottom of the rope with a firm, but gentle weight to aid the
rope passing through the chest ascender. Of course, the last party member to
ascend will have to self-feed the rope through.
NOTE: You will find this manoeuvre more difficult if you use a
long descender such as a whaletail which takes up a lot of space on the rope.
It is difficult to rig it far enough up the rope so that your foot ascender
safety-cord is slack when you sit back on the descender, particularly if your
safety-cord is on the short side. One way around this is to stand in your
footloops and clip your short cowstail into your foot ascender. Remove the
chest ascender from the rope and sit onto the cowstail. Removing the chest
ascender makes more room on the rope for rigging the descender. When the
descender is rigged (as high up the rope as possible, just below the foot
ascender) stand in the footloops to unclip the short cowstail and sit back down
onto the descender. The safety cord should now be slack allowing the foot
ascender to be taken off the rope. This "sneaky" method of doing a changeover
can't be wholly recommended as you are hanging from a single ascender at one
point, which strictly speaking isn't safe. A variant of this technique
can also be used for speeding up knot passes (provided you have a short
When prussiking the procedure is almost the same:
If prussiking, start as if passing a normal
rebelay (use the pendulum loop to pull in the slack on the upper rope). When
your ascenders are on the upper rope you will find your cowstail is taut. Pull
yourself towards the rebelay to slacken and unclip your cowstail and then use
the pendulum loop to let yourself out across the pitch (otherwise you will go
flying across the pitch which is rather unpleasant).
If you can't lift the casualty:Lifting someone by standing in your footloops isn't easy. If you cant lift them you can re-rig your footloops to give a 2:1 pulley advantage which should enable you to lift almost anyone. To re-rig your footloops, unclip the safety cord and footloops from the foot ascender and tie the footloops to the safety cord. Run the safety cord through a krab (or if you have one, a pulley) which is clipped to the foot ascender (see picture). Now when you stand in the footloops you'll find you are expending less effort in standing up (although you'll only move half as far). You may find the footloops are too long in this arrangement and you'll need to tie out a small section to shorten them. With this re-rig, you effectively have no safety cord between you and your footloops. You could clip in your long cowstail to your foot ascender as a safety cord (otherwise you'll spend a short period during the manoeuvre attached to the rope only by one ascender which is unsafe).
If your footloops safety cord is taut when you sit onto your descender:Conventionally you would stand in your footloops, re-attach your chest ascender, move the foot ascender down a bit and try again (i.e. stand in footloops, remove chest ascender and sit back onto descender). At a pinch (and time is of the essence here) you could just stand in your footloops to slacken the safety cord, unclip the safety cord from the foot ascender and sit down onto the descender, It is possible that you would be unable to recover the foot ascender if you did this, but don't forget you have a spare attached to the casualty.
Rebelays:If possible derig any rebelays/deviations between you and the casualty on your way up. This wont be possible if the pitch has been well travelled, or if you approach the casualty from the top of the pitch. If you do have to pass rebelays on the way back down, treat the casualty as a heavy tackle-bag and proceed as usual. You may need to use your footloops to unweight your short cowstail prior to unclipping it, and re-rigging your footloops as described above would help.
Use your brain (& practice lots):You may not be able to do this manoeuvre exactly as described here, but if you are familiar with the basic techniques and equipment you should be able to work around any difficulties in safety with a bit of cunning.
Hybrid Frog-ropewalkerAll this requires in addition to the frog-rig in an extra ascender which is attached to the foot firmly with a webbing strap. The other foot still uses the footloops as is the conventional frog-rig. If you use a single footloop rather than a pair, you will probably need to shorten it a little to make it the correct length for use with one foot only.
Clip in the chest ascender and footloop foot ascender as usual. Also clip in the ascender attached to the other foot. Instead of ascending by standing up with both feet at the same time progress is made by a walking motion, first lifting the footloops then standing up in the footloops and raising the other foot sliding its ascender up the rope ready for the next step.
This is a very simple modification to the frog-rig which can give some of the speed advantages of rope-walking, however it is not really a true rope-walking rig.
The 'Caving Supplies' Combination rigThanks to Nigel Whittington for this description which I've quoted straight from his email.
This is a simple modification of the 'Frog' rig that enables energy-efficient ropewalking technique to be used on long pitches and Frog technique to be used on alpine style deviations and rebelays using the same personal rig.
It uses the standard 'Frog' rig with the addition of an extra jammer, buckled footloop, elastic cord and two carbine hooks. A slight modification to the footloop is also made.
Make or buy a webbing strap (load bearing!) that will wrap around your ankle and foot in a fig 8 pattern. Use this to fix a non-handled Petzl (™) jammer to your LEFT foot.
Modify the footloop on your top jammer so it can be shortened to about 15-20 cm. This can be done several ways, e.g. an extra knot or just clipping the lower loop into the crab or maillon on the jammer. The jammer is attached BELOW the chest jammer and the footloop should be adjusted so that with the right foot raised the jammer is just below the chest jammer, with the right foot raised the foot mounted jammer should not foul the floating jammer.
Attach an elastic cord to the top of the jammer with a carbine hook, run the cord over your shoulder and attach to the back of your harness via a second carbine hook.
A crab on the chest harness can be used to clip onto the rope to prevent the possibility of inversion and hanging from ones ankles in the event of the chest jammer accidentally opening.
Clip in all three jammers as described, and take short, alternating steps. At the foot of a pitch you may need to weight the rope to ensure the rope runs through the foot jammer.
To transfer to Frog:
Disconnect the floating jammer.
Et Voila, Le Frog!
To transfer to ropewalking:
Connect foot jammer.
Et Voila, Ropewalking.
If you want more detailed information, read a good SRT book such as "Vertical" by Al Warild, "Single Rope Technique" by Neil Montgomery, or the recent e-book "Life on a Line" (free download) by Dave Merchant.
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