Setting up a “Frog” Ascending System

Setting up a “Frog” Ascending System
Warning! Do not attempt to use any ascending system for first-time climbing without
expert guidance. You may be hurt or killed. Don’t do it!
The rope ascending system that American cavers dub the “Frog” is unquestionably the
most universal rope ascending system in the world of caving. Although several other
ascending systems are considerably more efficient for climbing unobstructed ropes, the
Frog combines light weight and minimum bulk to create a system that is particularly
effective for expedition caving and for crossing mid-rope obstacles such as rebelays. It is
the first ascending system that cavers should master.
The Frog is a sit-stand system requiring two ascenders: A specifically designed “chest”
ascender attached directly to the seat harness and a handled ascender connected to both
feet via a long foot loop. A safety tether always connects the upper ascender to the sitharness. A sit/stand motion similar to doing deep knee bends is used to ascend.
A materials list for constructing a Frog System can be found at the end of this article.
Links in the chain
Considerable effort has gone into testing and refinement of the Frog. Although simple in
terms of equipment, the Frog is a very complex ascending system in terms of effective
implementation. A full understanding of the system is vital before variations are
attempted. Due to ignorance, there are probably more poorly implemented Frogs than any
other ascending system per capita. Any “weak link” in the chain of setup and adjustment
of a Frog System has a dramatic, negative consequence.
Link #1 – The climber
Fig. 1: Body type dramatically affects Frog
System efficiency. The climber on the left is taller
and his fingertip-to-Croll distance is also a greater
proportion to his total height. This means he
inevitably makes more vertical progress with each
sit/stand cycle than the climber on the right.
More than other common rope ascending
system, different body types affect the
effectiveness of the Frog. Tests have shown
that stature (height), torso-to fingertip distance,
chest breadth and body weight distribution can
radically alter climbing efficiency. Specific
results are dependent upon the individual, but in
general, short individuals, climbers with barrel
chests or short torso/arm combinations are at a
disadvantage compared to tall, slender climbers
with long torsos and arms. This aspect alone
however, is not sufficient reason to substitute
another ascending system without first learning
and mastering the Frog. For the majority of
climbers, the Frog offers a good overall
combination of efficiency and versatility.
Link #2 - The sit-harness
A sit harness designed specifically for “Frogging” is integral to the entire system and its
basic design must be considered as seriously as the hardware. Because the Frog is a sitstand system, the climber uses the harness at every cycle. It is essential that a Frog
harness have a low “tie-in” to place the lower ascender as low as is practical. The
potential distance between the two Frog ascenders is critical to efficient climbing. Rock
climbing harnesses are designed to prevent inversion during a fall and have a much
higher tie-in point than Frog harnesses. This makes them generally less effective for the
Frog System. The most common mistake for beginners is to purchase the wrong type of
sit harness for Frogging.
Fig. 2: Left: The Petzl “Fractio” caving harness designed for the Frog System. Right: A Petzl “Sama” rock-climbing
harness. The red arrows show the position of the tie-in points of each harness. Note the distinctly different designs.
Adjusting a sit-harness improperly can affect climbing efficiency. Most Frog harnesses
use specialized hardware at their tie-in point. The interplay of the hardware and harness
affects the ways the harness loads and consequently, the entire Frog system. Specifics
vary with each harness, but general recommendations can be made (see next section).
Link #3 – The harness connector
Most Frog sit-harnesses are designed to use 10mm screw links of specific design. They
are variously called “half-rounds, “half-moons” and “semi-circular screw links.” One
Petzl variation is constructed with a carabiner-style gate and given the proprietary name
“Omni” (See figures 3 A&B). The link may be made of aluminum, steel or stainless steel.
Using the proper screw-link is vital because the rest of the Frog system attaches to it.
Carabiners are designed to be loaded in one direction and are NOT acceptable for the
multi-directional loading that Frog harnesses experience.
Semi-circular screw links are
designed in combination with
Frog harnesses to load the
link from side to side and
downward (See figures 4A&
B). This prevents the link
Fig. 3A: 10 mm half-round, screw Fig. 3B: 10 mm Petzl “Omni”
from rotating or rising during
link harness connector.
carabiner-style half-round.
climbing. The rounded upper
portion of the link allows the various Frog components to articulate freely without
hanging up on a gate. A general recommendation for proper sit-harness adjustment is to
first adjust the waist strap tight enough to load the screw link from side to side without
unnecessary discomfort. Only afterwards should the leg loops be tightened to prevent
upward movement of the link.
Fig. 4A: The Petzl “Fractio” Frog harness loads the half
round steel screw link sideways to prevent it from
rotating. It uses the leg loop tension to prevent the link
from moving upward.
Fig 5: As the climber ascends, the motion of the climbing
rope can rotate the gate open if the Maillon is improperly
oriented. The Petzl “Omni” will not unscrew accidentally.
Fig. 4B: The On Rope “Goliath” Frog harness uses a
slightly different configuration to keep the half round
connector in place. A Petzl 10 mm Omni carabiner-style
connector is shown.
Safety note: Even the orientation of the
half-round screw link is vital to safety.
Screw links depend upon closed gates for
much of their strength. During the ascent,
the rope can rub against the screw link
gate in a downward direction. If the gate
is oriented to close to the climber’s left,
this motion will tend to screw the gate
closed. Oriented the other direction
(closing to the climber’s right), the rope
can unscrew the gate and open the
Maillon. Traditional threaded screw links
must be oriented so they screw closed to
the climber’s left. The Petzl “Omni” may
unlock, but does not lose strength and
cannot open due to a different design.
Link #4 – The lower ascender
Fig. 6: The Petzl Croll ascender attaches
directly to the half round. It uses half-twist
connector holes to keep it flat against the
climber’s stomach or chest.
A special mechanical ascender is attached directly
to the semi-circular screw link (Figure 6). It is
designed with a half-twist to allow it to sit flat
against the body. The most common ascender of
this type is the Petzl “Croll” and that name will be
used in this article to represent the basic design.
Other manufacturers also make similar “half twist”
ascenders designed for the Frog. Handled or nonhandled ascenders without the half twist will still
work, but since they will not lie flat, they throw the
climber’s weight away from the rope and greatly
reduce efficiency and comfort. A chest strap is
attached to the top of the ascender to allow “hand’s
free” operation (See next section).
Link #5 – The chest “harness” (strap)
A chest harness or strap is attached to the top of the “Croll” ascender and worn over the
shoulders. It serves two purposes: It raises the Croll automatically when the climber
stands up and it helps keep the caver upright when resting on rope. There are many
variations, but a common chest “harness” is actually a simple strap of 1-inch (25mm) flat
webbing with a quick-adjusting buckle. The strap is threaded in a specific manner to pull
only at the front of the harness. Many climbers use a small quick link to prevent the
buckle from moving. Although tempting, do NOT run the strap from the top of the Croll
and over the shoulders to the rear of the sit-harness. This will pull the sit-harness waist
loop up onto the climber’s kidneys with each sit/stand cycle. It is very uncomfortable and
not recommended (see figure 7).
Fig. 7: Three common Frog chest harnesses. A simple strap with steel buckle (left) is preferred for most expedition
caving. The “H” harness (center) is more comfortable, but bulkier and more complicated. Both the strap and the “H”
harness pull only on the front of the harness. The third type (right) passes over the shoulders and attaches to the rear of
the sit-harness. This is not recommended because it pulls the sit-harness up over the kidneys when climbing.
Proprietary Frog chest harnesses (The “H” harness in Figure 7) work reasonably well.
Unfortunately, they do not fit all climbers and are more complex and bulkier that the
simple chest strap. Many climbers claim they are more comfortable. Be sure to try one on
before purchase to be sure it will allow sufficient adjustment, particularly for larger
climbers. The plastic buckles also tend to break after only moderate use.
Important notes: The climber must be on rope with the Croll (lower ascender) loaded
with full body weight while adjusting the chest harness. Even if the harness is pulled tight
when standing, there may be as much as 1 foot (300mm) of slack in the harness after the
Croll is loaded. The climber should not hunch over when tightening the Frog chest
harness. Hunching will prevent the climber from sitting upright during the climb. Proper
procedure is to keep your back straight, pull yourself as close to the climbing rope as
possible and then tighten the chest strap/harness until it is snug. This approach applies to
all three types of harnesses shown above.
Link #6 – The Cowstails
A safety tether is always attached from the upper ascender to the sit harness. Some
climbers prefer a dedicated tether (used only for the Frog system), while others use one of
two general purpose, load-bearing tethers called “Cowstails.” A set of two cowstails are
not specifically a part of the Frog ascending system, but when used as a Frog safety
tether, they must be considered within the context of the entire system. Cowstails are
used to secure the climber in a variety of situations. This author considers Cowstails
standard equipment for all vertical caving with ALL ascending systems.
Fig 8: A Cowstail set made of 11mm climbing rope. The
butterfly knot connects directly to the sit-harness maillon.
Cowstails are usually tied using a single
10 foot (3 meter) piece of 10-11mm
climbing rope. Dynamic rope is slightly
preferable. Several different knots can be
used and the knots described here are only
recommendations. The longer tail is fitted
with a locking carabiner and the shorter
tail with a non-locking carabiner.
Cowstails are designed to be a quick
attachment system and quick links should
NOT be used. A ½ Fisherman’s
(Grapevine) knot is excellent for tying the
carabiners to the tails because it cinches
around the carabiner to hold it in proper
orientation. Other knots may require the
use of a rubber band or tape to hold the
carabiner properly. A butterfly or figure-8
on a bight knot is usually used at the sitharness attachment (see figure 8).
*Be sure to secure the tails on all cowtail knots with duct tape. Unsecured tails can jam
into ascenders and cause severe problems. (See figures 8 & 9)*
The cowstails MUST be adjusted to
accommodate each individual. This is
the single-most critical adjustment of
the Frog system and pre-made
cowstails are seldom the correct
length. Improper lengths can cause
many problems, particularly during
complex rope work.
Generic methods for determining
cowtail length have been published
and most are notoriously unreliable.
Recommendations such as: “When the
cowstails are attached to the sit
harness, they should touch the chin or
reach the tip of your nose,” do not
address the real issues. Specific body
proportions of the individual must be
paramount. The “chin” or “tip of the
Fig 9A: The short tail
Fig. 9B: The long tail must
nose” lengths may work on average,
should measure
allow easy access to the upper
approximately from the
ascender when loaded. The
but will cause great difficulties for
elbow to the center of the
length is good when the finger
climbers whose body proportions are
palm. Fingers should curl
tips can just touch the top of
unique. Often these climbers simply
over top of carabiner.
the ascender when loaded.
accept the problems as “that’s the way
it is” when in fact, the cowstails are not adjusted to fit the climber’s real needs. Better to
base cowstails length on specific individual needs and the practical use of the cowstails:
1. The length of the climber’s arms compared to the rest of the body is the primary
determining factor for cowstail length. “Croll to Chin or nose” distance is irrelevant and
in my opinion, a foolish basis for determining tail length.
2. The actual use of the cowstails. The climber must be able to perform the necessary
functions on rope. Can the climber reach the equipment? Will it do the job?
The cowstails should be adjusted with the sit-harness on and the climber and the cowtails
attached directly to the harness Maillon via a butterfly knot. The short tail is less critical
than the long one, but still important. After loading the knots, the short tail should be
approximately the same as the distance from the elbow to the middle of the palm of the
hand. This takes the individual’s arm length into account and consequently their ability to
actually reach the gear! If the fingertips can close over the top of the carabiner when the
cowtail is pulled taut, it is usually sufficient (see figures 9 A&B).
The long tail is often used as the safety to the upper ascender and its length is more
critical than the short tail. Its length should be guided by a basic premise: When attached
to your upper ascender, it can not allow your ascender to be out of practical reach. It
makes no sense to have a safety tether that is longer than you can reach. Just being able to
reach the handle of the ascender is NOT sufficient. Here’s the test: When hanging from
your long cowtail attached to the upper ascender, you must be able to reach the cam of
the ascender to release it. If the tail is too short, it will restrict your maximum Frog
stroke. If too long, you can be stranded on rope if the ascender is out of reach. It usually
takes several attempts to adjust the cowstails. Be sure to load the tails with full body
weight and set the knots each time when adjusting them. Don’t shortcut this adjustment
or you will regret it. Remember that the tails will lengthen slightly with use.
Link #7 – The proper gear positioning
This is the subject of considerable debate. Froggers agree that proper gear positioning
prevents many problems, but they don’t agree about which problems are important.
Rather than just saying “Do this because it’s done this way,” I present my preferences
with explanations based upon my own and other caver’s practical experience. For both
right and left-handed climbers, the cowstail set should be attached to the screw link on
the LEFT side of the Croll (the closed side of the Croll and to the climber’s extreme left).
When a left-handed Croll is manufactured, you can put the tails on the other side! Placing
the cowstails on the open (right) side of the Croll allows them to jam up against the Croll
cam and safety catch when the tails are loaded. This often makes it very difficult to open
the Croll. If the Croll is left open, it is also possible for the cowstails to enter the Croll
through the open gate and foul the system.
Figs 10 A & B: A common gear placement for a right handed climber is shown in Figure 10A (left).
Be sure that the Croll is closed before placing descender on the climber’s right. Figure 10B (right)
illustrates the danger of placing the descender on the climber’s right with the Croll gate open. The
descender carabiner has entered the Croll gate and closed the cam on itself. This can seriously damage
the Croll and/or the carabiner. Cowstails can also jam into the Croll if placed on the right side.
Any descender may be used with the Frog System, but some are better suited than others
for complex rope maneuvers with the system. In general, the type of caving that will be
done is the best determining factor in selecting a descending device. Descenders can
either be directly connected to the half round or connected via a locking carabiner. The
descender may be attached to either the right or left side of the Croll. Although righthanded climbers usually prefer to attach the descender to the right side of the Croll, the
practice warrants this warning: With the descender on the right side of the Croll (open
side of the Croll and the climber’s extreme right), there is the possibility that the
descender or the attachment carabiner may jam itself into the open Croll (see figures 10
A&B). This is very annoying and sometimes difficult to rectify. ALWAYS be sure that
the Croll cam is closed before placing a descender on the right.
The order: For right-handed climbers when looking down at their own gear, the preferred
positioning on the Maillon screw link is: Cowstails on your extreme left, Croll in the
center and descender on the extreme right. Left handed-climbers can place the descender
on either side although the same warning applies if placed on the right side of the Croll.
Link #8 - The top ascender/foot loop
Fig 11A The foot loops are often
connected to the upper ascender
with a quick link. This allows easy
attachment and detachment of the
safety tether (cowstail).
Fig. 11B A common foot loop
configuration: a single line to a
double loop. Some climbers prefer
a single large foot loop for both feet.
Others use separate lines to each
foot.
The upper ascender is usually
a handled ascender although
a non-handled ascender may
be used. Foot loops run from
the top ascender down to
both feet. Foot loops may be
made of either small diameter
rope (8 mm is common), 5.5
mm spectra cord or webbing.
Many climbers attach the
foot loop cord to the ascender
with a 6-8 mm oval Maillon
Rapide link (see figure 11A).
Maillon makes attaching and
removing the safety tether
carabiner easier than clipping
it into the holes of the
ascender or a knot loop. It
also increases ascender
versatility since the foot
loops may be easily removed
if necessary.
Foot loop configuration is a matter of personal preference. Some climbers use a single
line with one large loop for both feet and some prefer a separate line for each foot. The
most common setup is a single foot line ending in a double loop knot such as a double
figure 8 (see figure 11B). Many climbers place plastic tubing inside the foot loops to
make the loops easier to get the feet in and out of and to reduce wear. Both foot loops are
the same size, usually just big enough to get on your feet without using your hands.
The length of the foot loops should
generally be as short as possible without
allowing the two ascenders to hit each
other when the legs are fully extended. A
starting length recommendation is: When
the legs are fully extended during
climbing, the two ascenders should be
close to each other, but should not touch.
With experience, this length can be
modified to suit the individual climber’s
needs.
Fig. 12 With legs fully extended on rope, the upper and
lower ascenders should be very close to each other.
Proper foot line adjustment is critical and
VERY personal. If too short, the lower
ascender will hit the upper ascender
before the legs are fully extended during
the standing part of the cycle. Short foot
lines also throw the climber away from
the rope if too large a step is attempted.
Just because you can take a bigger step
does not mean that you should.
Conversely, if the foot loops are too long, vertical progress is limited on every stroke.
Overly long foot loops also make rope maneuvers such as changeovers and rebelays very
difficult. Do not dogmatically attempt to get the two ascenders close to each other by
over-lengthening the foot lines. This hinders the ability to unload cowstails during
changeovers and when unclipping from rebelays, particularly if the climber’s arms are
short. Arm length (specifically: the Croll-to-fingertip distance) affects the potential length
of the long cowstail/safety tether, which is the limiting factor of the Frog system. The
practical length of the foot loops will vary depending upon the proportion of the
climber’s leg length to their Croll-to-fingertip distance. With experience, foot line lengths
will be modified depending upon personal preferences and body type.
Materials list
1. A sit-harness with a low tie-in point designed for the Frog system. Do not use a rock
climbing harness.
2. A 10mm half round (semi-circular) screw link or the equivalent designed for human
loads for the sit-harness. Do not use screw links purchased at a hardware store! Buy
the screw link from a reliable caving/climbing dealer. Do not use carabiners on harnesses
designed for a semi-circular screw link.
3. A “Croll” type chest ascender.
4. A 10 foot long (3 meter) chest strap of 1 inch (25mm) flat webbing with buckle OR a
pre-made Frog chest harness. Avoid designs that connect to the rear of the sit-harness.
5. A handled mechanical rope ascender. It is not essential to use a handled ascender as
the top ascender in the system, but most climbers prefer it.
6. At least 15 feet (4.5 meters) of 8mm climbing rope for the foot loops. Spectra cord or
the equivalent is also acceptable. 2 feet (.75 meters) plastic tubing for inside of foot loops
is optional
7. At least 10 feet (3 meters) of 10-11mm climbing rope for cowstails. Dynamic rope is
preferred, but not mandatory. Factory made cowstails are not recommended. They are
usually the wrong length and NOT adjustable.
8. Two (2) “D” shaped carabiners:
One (1) wide-mouth, non-locking, “D” shaped, carabiner for the short cowtail.
One (1) wide-mouth, locking, “D” shaped, carabiner for the long cowtail.
9. One (1) 6-7mm oval screw link to attach foot loops to upper ascender. Do not use
screw links purchased at a hardware store! Buy the screw link from a reliable
caving/climbing dealer.
The Good, the Bad and the Ugly
The Good:
1. The Frog System is virtually universal. It is unquestionably the world-wide standard.
This means that training and methods are relatively consistent around the world. Most
expedition rigging is designed with the Frog system in mind. It is the first ascending
system a caver should master.
2. The Frog System is simple, light and very compact. It is slightly faster than the
Mitchell System (my opinion AFTER testing) for crossing mid-rope obstacles such as
rebelays. It is well-suited for multiple pitch caves where the pitches are relatively close
together or relatively short (less than 40 meters).
3. “Gearing up” and “gearing down” (travel readiness) times are minimal with the Frog.
No other system approaches the Frog in this regard.
4. Initial tests indicate that the Frog system may be one of the best overall ascending
systems for carrying heavy (expedition size) cave packs.
The Bad:
1. The Frog requires more energy and/or more time to climb an unobstructed rope when
compared to many other systems. The longer the pitch, the less effective the Frog
becomes.
2. The Frog is extremely equipment specific and is somewhat difficult to adjust properly.
Once it is done however, it need not be redone until it is time to replace equipment such
as cowtails.
The Ugly:
1. Extensive testing indicates that certain body types are significantly less effective with
the Frog system than others. If you fall into that category, you will be able to use the
Frog, but it will require more energy than more efficient body types.
2. Good Frogging technique requires lots of practice and constant attention to maintain a
vertical position. Fatigue can hamper proper technique, forcing the arms to take more of
the load.
References
“The Frog Ascending System – A Detailed Description” by Matt Oliphant. NSS News, May 1996. On
line publication: October 14, 2000, with revised discussion of pick-offs at:
http://technology.darkfrontier.us/Vertical/Frog/ Author’s note: Oliphant’s article is authoritative and
based on extensive practical experience. It does however, omit some of the small details that are addressed
in this article. It contains more than Oliphant’s personal recommendations for constructing a Frog system.
He has also included procedures for negotiating many of the rope maneuvers common to expedition-style
caving. This is good, solid information from an authoritative source.
On Rope: North American Vertical Rope Techniques for Caving by Bruce Smith and Allen Padgett.
National Speleological Society Vertical Section. Second edition, Jan. 1997. Author’s note: The section of
On Rope discussing the Frog system has a definite American bias toward the setup and use of the Frog
system. This differs in some ways from the International style, but is worth reading for another point of
view. The approach is somewhat superficial and lacks practical insight on the details of the Frog system. It
occasionally takes unnecessary “pot shots” at European techniques.
Notes on Alpine-style SRT. This is an on line publication at: http://wasg.iinet.net.au/srt/srt.html
Author’s note: This is an Australian-based web site. It approaches the Frog System as the ONLY way to
ascend a rope and dismisses other systems without intelligent cause. It is somewhat superficial in its
descriptions and illustrations, but does carry the disclaimer that these are “notes” on the topic. Some of
the recommendations are directly at odds with notions that both European and American authorities agree
upon. It briefly outlines procedures for negotiating a number of common rope obstacles and situations.
Vertical - A Technical Manual for Cavers by Alan Warild. Fourth Edition, 2008. A pdf version can be
downloaded at: http://www.cavediggers.com/vertical/ Author’s note: Another Aussie approach to
general vertical caving. Comprehensive regarding the Frog. However, the descriptions and conclusions
about the effectiveness of other ascending systems are inaccurate to varying degrees, obviously due to lack
of actual experience with them. Detailed information about harnesses and the Frog system. This is a good,
in-depth resource.
Life on a Line – The Underground Rope Rescue Manual by Dr. David Merchant. Second Edition, June
2007. Downloadable for a price at: http://www.lifeonaline.com/ Author’s note: “Life on a Line” is more
about cave rescue than the Frog system. However, valuable information about the Frog’s good and bad
points can be inferred by examining the rescue tactics targeted at both the Frog method and the gear. It is
interesting that Merchant’s rescue methods as described in print seem somewhat at odds with practical
rescue experience. This is particularly true of some of Merchant’s equipment recommendations. Merchant
informed me that he was limited by British publishing restrictions related to an “official” rescue
publication. A comprehensive work, but unfortunately somewhat suppressed.
Alpine Caving Techniques by Georges Marbach and Bernard Tourte. English Edition, Translated and
adapted by Melanie Alspaugh. 2002. Author’s note: Truly authoritative, but extremely biased toward
French methods. There are arrogant and unnecessary swipes at anyone other than the “true believers.”
One gets the idea that all other ascending systems are worthless under all conditions. A diligent reader can
separate mindless dogma from fact and it is well worth reading this book carefully. In many ways, this is
the best overall text on the topic of Alpine SRT.
"Typecasting the Vertical Caver" by John Woods. Nylon Highway #53, Dec. 2008. National
Speleological Society Press. On line at: http://www.caves.org/section/vertical/nh/53/Typecasting.pdf
Author’s note: This is an ergonomic study of the Frog ascending system. Specifically addresses the topic
of different body types and their potential effectiveness with the Frog System. It reveals surprising test
results for many Frog system devotees.
"Comparisons of the Frog and Mitchell ascending systems for crossing common mid-rope obstacles"
by John Woods. Nylon Highway #53, Dec. 2008. National Speleological Society Press. On line at:
http://www.caves.org/section/vertical/nh/53/MitchvsFrogPart2.pdf Author’s note: Real-world
comparisons of the Frog and Mitchell ascending systems. It discusses the both system’s effectiveness in
negotiating rebelays, crossing knots, deviations, for changeovers and for overall vertical effectiveness.
Contains comparative information on relative system sizes, weights, and bulks. Dispels many common
myths.
“Converting the Mitchell System to a Frog System" by John Woods. Nylon Highway #53, Dec. 2008.
National Speleological Society Press. On line at:
http://www.caves.org/section/vertical/nh/53/ConvertMtoF.pdf Author’s note: A practical method of
converting a Mitchell System to Frog system on-site or on rope.