Knots & Hitches - National Speleological Societycaves.org/commission/ncrc/national/NCRC_Instructor_Area/Instructor...Knots & Hitches The loop formed by a knot should be about ... Huge

© 2007 National Cave Rescue Commission, page 1

Knots & Hitches

The loop formed by a knot should be about the size of the item that is going to clip into it. Huge knots waste rope, get in the way, are cumbersome and inefficient. Cave rescue demands compact, efficient rigging.

Figure Eight on a Bight

Figure Eight Bend

Figure Eight Follow-through

Double Figure Eight


Bowline (with half-hitch backup) Bowline (with Yosemite backup)

Double Frost Knot

Two ends of webbing terminate in

center of loop

Double Overhand Bend (aka Dbl Fisherman’s,

Barrel, Grapevine)

Ring Bend (Water Knot)

Butterfly


Trucker’s Hitch

A slip knot is commonly used to create the in-line loop, but for rescue work, a fixed loop is often preferable.

Trucker’s Hitch on slip knot

Trucker’s Hitch on fixed loop

(preferred for rescue)

Tied-Off Trucker’s Hitch

(backup not shown)

Tying a Trucker’s Hitch:

Step 1: Attached end of rope to an anchor or object (not shown) Step 2: Tie a loop (slip knot, butterfly, 8 or overhand bight, etc.) Step 3: Pass rope around or through an anchor/attachment point. Step 4: Thread end of rope through in-line bight. Pull to tighten. Configuration provides modest mechanical advantage and allows tension to be retained and secured. Step 5: Secure with a half-hitch on a bight, then back up with an overhand on the bight (backup not shown)

Münter Hitch (For one-person load belays)

Prusik Hitch Double-wrap (1-person loads)

Triple-wrap (rescue loads)

Clove Hitch (overhand backup)


Anchoring

Tensionless Hitch (round turn)

Wrap 3, Pull 2 (webbing or rope)

Basket Rigging (knot at back)

Load Sharing Anchor System (fixed length legs). Appropriate for

Levels 1 and 2.

Girth Hitch (reduces rigging strength ~ 25%)

Load Distributing Anchor Systems (aka self-equalizing, self-adjusting) Failure of any one leg could lead to shock load and catastrophic failure of entire anchor system. Application of these techniques is a Level 3 skill.


Pre-tensioned backtie is an adjustable stabilizer that utilizes mechanical advantage( typically 3:1)

The effective length of a pre-tensioned backtie may be extended by using a trucker’s hitch, but this

configuration will have more stretch under load than the full-length 3:1 version.

If the anchor for a backtie is not reasonably in line with the direction of

load, multiple backties will be necessary to stabilize focal point.

Backup Anchors

Pre-tensioned Backties

Backtie Anchors

Focal Point

Load

Load

Interlace Webbing

Focal Point

Tie off or secure with prusik hitch

Front rigging point is focal point, back-up is primary

anchor.

Backup using long-tail bowline

Backup using in-line figure

eight

Backup using double figure

eight


Force Multiplication

Load

Resulting Force, Each Leg

Angle between

Legs

19

Deviation Forces


Belays Münter Hitch - Allowed for single person load only, moderate to low angle. Tandem Triple-wrapped Prusiks • NCRC’s primary rescue belay system • Prusik cord must be flexible and of appropriate diameter for rope • Short prusik must be sized to work efficiently with PMP • Long prusik must be 3 to 4 inches longer than short prusik • Use PMP when belaying during raising operation • Have students remove PMP for lowering operation, and belay

using proper handling technique • Minimize slack in the belay system Mechanical Rescue Belays • Available for demonstration • 540 belay: highly sensitive to rope diameter • Nano Rack belay: essentially a 3-bar rack loaded upside down

Simple Pulley System rules 1. The number of support lines determines the IMA. 2. If the haul rope starts at the load the IMA will be Odd. 3. If the haul rope starts at the anchor the IMA is Even. 4. If the last pulley in the system is secured to an anchor it is a directional. Compound Pulley System rules 1. Compound systems are 2 or more simple systems acting on each other.

Mechanical Advantage

A tandem prusik belay with PMP

PCD with PMP

Simple 2:1 Simple 3:1 Compound 4:1 Compound 4:1

PCD

Pull Pull

Pull

Pull Offset

anchors

PCD


34

“Even” Hauling Systems

Anchor

To Load

PCD Option 1: between load and haul system

PCDAnchor

Haul rope fastened to

anchor

To Load

PCD Option 2: at anchor

“Odd” Hauling Systems

Anchor

To Load

Progress capture at anchor

PCD

Haul rope fastened to load


Anchor

Tether

Second person for

counterweight

Fixed Line

Rappeller(using rack

on fixed line)

Rappelling Counterbalance

• Avoid Friction!• Consider rockfall

potential• Main anchor takes

double load• Prepare for transition

when load reaches top

Rescue Load

Belay Line

Counter-balance line

with PCD

Anchor

Anchor

One or more persons serve as a counterweight

Basics of Counterbalance Systems

Rescue Load

The counterbalance line runs from the load, through

a pulley, and back to the counterweight.

If the counterweight is heavier than the load, the load goes up and

the counterweight goes down!

The pulley provides a change of direction, but no

mechanical advantage


Anchor

Rescuer climbs on counter-balance

line

Diminishing Loop Counterbalance

Patient

Belay Line

Counter-balance line, generally no

PCD

Tether from rescuer to

patient must be utilized



double load• Prepare for transition

at top• Rescuer AND patient

must be secure before either disconnects from the counterbalance line!

18

Anchor

Anchor

Fixed Line

Two climbers, each with ascending system on counter-balance

line

Climbing Counterbalance

Rescue Load

Belay Line

Counter-balance line

with PCD

Each climber attaches to

fixed line and climbs in

place



double load• Getting climbers in

position requires forethought

• Prepare for transition at top


Illustrations courtesy Rick Lipke, Contera Technical Systems, Inc.

To Anchor

To Load

Start with small Fig-8

on bight

Münter hitch with in-feed on gate side of carabiner

Reduce distance between

carabiners to about 4 inches

Form a bight and fabricate a half hitch

(steps 3 & 4)

Tie an overhand around the bundle (using the bight

created above) as shown in steps 5 &

6

• Use 10 meters of 8mm accessory cord to fabricate the Radium Release Hitch • Control release by slipping the Münter hitch

Radium Release Hitch


Allowable focal point connections: long-tail butterflies or bowlines, not interlaced, long-tail bowlines, interlaced. Attaching

the lines without long tails (and using tethers for the attendant and patient con-nections) are allowed but discouraged.

Litter attendant clips to tail of mainline, moves up and down on ascending sys-tem, and clips to one spider leg using tether as second point of attachment.

Carabiner gates oriented in and down

End of belay line attaches to patient. Line passes through neck opening in packaging.

Litter Rigging

Litter Bridle

Fig 8 on bight, tied compact

Double overhand bend (better if tied on outside

of litter) Clove hitches

Rig short, bridle will stretch when loaded.


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Assessing System Safety Ratio

• Identify minimum breaking strength of each component, as configured in system

• Identify load experienced by each component in system, as configured

• Calculate component load ratio on each component (MBS/expected load)

• Lowest component load ratio (weakest link) is system load ratio

• Determine if this ratio is high enough to satisfy your safety criteria

NCRC System Safety Ratio

NCRC targets a minimum system safety ratio of 7:1

for its instructional events.

Documents

Knots & Hitches - National Speleological Societycaves.org/commission/ncrc/national/NCRC_Instructor_Area/Instructor...Knots & Hitches The loop formed by a knot should be about ... Huge