Ropes and Knots
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3-strand rope |
slip knot | ||
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bight |
tautline hitch |
sheet bend | |
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16-strand rope |
lead |
double fisherman's knot | |
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12-strand rope |
fall |
figure-8 knot |
Prusik hitch |
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hollow braid |
knot |
cow hitch | |
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24-strand rope |
hitch |
timber hitch | |
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double braid |
bend |
running bowline | |
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working end |
endline knot | ||
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running end |
carabiner |
clove + half hitches |
Ropes Used in Tree Care
Rope maybe considered the arborist's most important tool. The characteristics of a rope (strength, stretch, durability, etc.) are the result of the materials and techniques used to make it. To date, polyester is the material most widely used by arborists, and most commercially available climbing and rigging lines are made from this fiber. Nylon has high strength, stretch, and energy absorption but tends to lose strength when wet. Natural fibers are not generally as strong as the new, synthetic fibers and can rot over time. Newer fibers such as Kevlar show some promise but have not been widely developed for arborist rigging applications.
Many types of ropes are used in arborist climbing and rigging. 3-strand rope has relatively low strength and high elongation and is relatively inexpensive. It is appropriate to run through natural crotches for climbing or rigging, but it also runs well through a false crotch. A major drawback to 3-strand rope is
the twisting, or hock-ling, that occurs as the line is used.
Kernmantle ropes are those with a core and a cover. Most of the lines typically called kernmantle, however, are dynamic, rock-climbing lines. They are designed for the core to bear most of the load and the cover to serve primarily as a protective sheath. ........
16-strand braided figure 3.1 3-strand arborist lines have rela- rope, tively large cover strands for strength and abrasion resistance and a parallel core to keep the rope round and firm under load. In this construction, the core does not carry the load. 16-strand ropes are the most commonly used ropes for climbing.
figure 3.2 16-strand figure 3.3 12-strand rope. rope.
figure 3.2 16-strand figure 3.3 12-strand rope. rope.
12-strand rope is braided rope, usually without a core. Tightly woven, solid-braid, polyester-blend 12-strand lines are a popular choice for climbing and natural-crotch rigging. Loosely woven, hollow-braid, polyester, 12-strand rope is often used for rigging slings but would not be appropriate as a climbing or a rigging line. The number and diameter of the strands compared to the diameter of the rope determine whether the lines can be spliced. They also determine abrasion resistance and whether the rope remains round.
24-strand rope is a relative newcomer to the arboriculture industry. Like 16-strand lines, they have a core and cover, and they are primarily designated as climbing lines.
Double-braid lines are just that: a rope inside a rope. The core and cover are balanced and share the load almost equally. For this reason, they are not recommended for natural-crotch rigging, in which the friction of the cover with the tree figure 3.4 Double- . >
. . , causes an imbalance in the braid rope.
load taken by the core and cover braids. It is an exceptionally strong and low-stretch line but should be run only over the smooth sheaves of a block or pulley or the bollard of a friction device.
Knots
All tree workers should be familiar with the knots used in tree work. A climber should know how to tie and untie each of these knots.
A rope has a working end and a running end, or the ends in use and not in use, respectively. Anything not in use in between is the standing part. The illustration also shows examples of a bight, loop, turn, round turn, and the lead and fall of a line in use.
figure 3.5 Parts of a line.
Working end
Standing part
Working end
Standing part figure-8 knot
Part of knowing how to tie a knot is knowing how to "dress" and "set" the knot properly. To tie a knot, one must first correctly form the knot in the rope. The dressing of the knot is the aligning of the parts; setting it tightens the knot in place. A climber must know how each of the common knots is used and the advantages and disadvantages of each.
"Knot" is the general term given for all knots, hitches, and bends. A hitch is a type of knot used to secure a rope to an object, another rope, or the standing part of the same rope. A bend joins two rope ends together. There are several categories of knots, hitches, and bends. Tree climbers use endline knots, hitches, and bends to secure the climbing line
- clove hitch
figure 3.6 Knot, hitch, and bend.
to carabiners or rope snaps. Endline knots are also used to tie off branches being rigged.
A type of knot important in tree climbing is the climbing hitch. Climbing hitches are the "climbing knots" used by climbers to position themselves as they move and work in the tree.
Tautline Hitch
For years, the primary climbing hitch used by climbers in the United States has been the tautline hitch.
Used as a climbing (friction) hitch Requires a stopper knot (figure 8) Has a tendency to roll out Must be adjusted (tended) frequently
Blake's Hitch
Blake's hitch is growing in popularity because it maintains more uniform friction and does not roll
Climbing (friction) hitch, often preferred over the tautline
Stays dressed and set, less need to tend Doesn't roll out (although a stopper knot is still recommended)
Higher tendency to glaze on a long or rapid descent
Ropes and Knots
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Figure-8 Kn • Fast and ea |
¡topper knot isy-to-tie endline knot | |||||||
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1 |
11 |
jä) ^ |
• The basis fi (running be double bov |
t for forming a loop :ie, even after loading ar other knots in the "bo* >wline, bowline on a bigt /line) |
vline family" it, sheet bend, | |||
Running Bowline
• Often used in tying off limbs
• Functions as a slip knot; can be tied around something that is far away and "run up" the line
• Easy to untie after loading
Midline Clove Hitch
Endline Clove Hitch with Two Half Hitches
• Used (when backed up with at least two half hitches) to tie off limbs or sections of wood
Slip Knot
Almost any knot can be "slipped." Typically this means the final tuck of the working end is replaced by tucking a bight instead so that the knot can be rapidly untied by pulling on the working end. The knot known as the slip knot is a slipped overhand knot. The bow with which we tie our shoes is a doubly slipped square knot.
Easy to tie, even with one hand
Experienced climbers find many uses for this knot
A directional knot—it tightens when loaded one way but spills when pulled from the other side
Sheet Bend
• Used to join two ropes of different diameters; often used to send a line up to the climber
• The smaller line should be the one tucked under its own standing part
Double Fisherman's Knot
• Primary arborist use is to form a Prusik loop
• May be difficult to untie after it has been loaded
Prusik Hitch
• Friction hitch used in both climbing and rigging applications
• Bi-directional in some applications
• When used as a Prusik loop (as in the secured footlocking technique), a smaller-diameter rope is used to attach the Prusik to a working line. The type of rope affects how the knot will work
Cow Hitch with Half Hitch
• Tied with a sling and used for securing hardware to a tree
• Variation on a simple girth hitch but formed with a line instead of a loop
Timber Hitch
• Tied with a sling and used for securing hardware to a tree (especially on large trees when the rope sling is not long enough to tie a cow hitch)
• Always make at least five wraps, spread around the stem
• This hitch is most secure when tied on larger pieces and when the pull is always against the bight so that it tightens the hitch on the stem. The sling should never be loaded away from the bight because doing so could loosen it
Half Hitch and Running Bowline
Tied for Butt-Hitching
• Used to tie off a section when butt-hitching or when there is no secure point for a running bowline alone
• The half hitch shares the load with the running bowline and reduces the chances of the knot slipping off the piece, once cut
CHAPTER
3 . WORKBOOK
Matching
_16-strand rope
_working end
_double fisherman's knot
_cow hitch
A. curve or arc in a rope
B. common climber's friction hitch
C. used to secure hardware to a tree
D. core and cover share the load
E. most commonly used for tree climbing E the end of a rope in use
G. used as a stopper knot
H. often used to form a Prusik loop figure-8 knot double braid Blake's hitch
_bight
True/False
Polyester and polyester blends are the materials most commonly used for arborists' ropes.
3-strand rope is known for its high strength, high price, and resistance to twisting and hockling.
Double-braid lines are recommended for natural-crotch rigging.
The standing part of a rope is between the working end and the running end.
"Knot" is the general term given for all knots, hitches, and bends.
A hitch is a type of knot used to secure a rope to an object, another rope, or the standing part of the same rope.
"Dressing" a knot aligns the parts; setting it tightens the knot in place.
For years, the primary climbing hitch used by climbers in the United States has been the running bowline.
One limitation of the Blake's hitch is a tendency to glaze on a long or rapid descent. An advantage to using the running bowline to tie off limbs is that it is easy to untie after loading.
The figure-8 knot is a good example of a "slipped" knot. A midline clove hitch is commonly used to send equipment up to a climber. When using an endline clove hitch to tie off limbs, it should be backed up by at least two half hitches.
There are very few knots that can be "slipped."
The knot known as the slip knot is a slipped overhand knot.
The primary arborist purpose of a sheet bend is to form a Prusik loop.
When using a Prusik loop (as in the secured footlocking technique), a smaller-diameter rope is used to attach the Prusik to a working line.
18. T F When tying a timber hitch in a sling to attach hardware to a tree, you should always make at least five wraps and spread them around the stem.
19. T F A sheet bend is used to join two ropes of different diameters and is often used to send a line up to a climber.
20. T F Natural fibers are not generally as strong as the new, synthetic fibers and can rot over time.
Sample Test Questions
1. A type of knot used to secure a rope to an object, another rope, or the standing part of the same rope is a. bend b. bight c. hitch d. slip
2. A common, easy-to-untie knot for forming a loop is a. bowline b. clove hitch c. tautline hitch d. sheet bend
3. Which of the following is an advantage of the Blake's hitch over the tautline hitch?
a. it stays dressed and set b. less need to tend c. it doesn't roll out (although a stopper knot is still recommended)
d. all of the above
CHAPTER 4
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