Tensile Strength of Gear & kN to lbf Conversion
1 kN = 225 lbf
9.5 mm static rope
9/16" (14mm) Spectra webbing
loop or Standard biner (open)
6200
5800
5600
Wire gate biner (open)
5400
1" webbing loop
w/ water knot (climb spec)
10 mm (3/8") Dynex
webbing loop
4600
4200
Runners or Loops:
1 loop make with a knot is
~150% stronger than a single
strand. A two loop anchor is
twice as strong as a 1 loop
anchor. A 3 loop anchor is 3
times as strong as a 1 loop
anchor. [1]
4000
1" (25mm) webbing (tubular climbing spec, BW)
3800
3400
Typical harness tie-in loop
or 9/16" webbing loop
3000
7 mm cord (Perlon)
2600
Anchors From Loops
Made with a Knot
1 loop 7mm cord = 19kN
2 loop 7mm cord = 38kN
1 loop 9/16" web = 15kN
2 loop 9/16" web = 30kN
1 loop 1" web = 27kN
2 loop 1" web = 54kN
9.5 mm dynamic rope
2200
1800
9/16" (14mm) webbing
1700
1400
(tubular climb spec, BW)
6 mm cord
1240
(Perlon)
1000
5
6
7
8
9
10
11
12
13
5 mm cord
14
15
16
17
18
19
20
21
22
KiloNewton (kN)
[1] http://www.xmission.com/~tmoyer/testing.
23
24
25
26
5963
Runners or Loops:
1 loop made with a knot is
~150% stronger than a single
strand. A two loop anchor is twice
as strong as a 1 loop anchor. A 3
loop anchor is 3 times as strong
as a 1 loop anchor. [1]
2250
1238
5.5
1440
6.4
1710
7.6
10.0
6075
6075
50
45
lbf
kN
4950
35
4005
26.5
3375
2318
10.3
2610
11.6
40
2880
12.8
27.0
27.0
22.0
15
30
25
17.8
20
15
10
5
KiloNewtons to Failure (kN)
Pounds Force to Failure (lbf)
6500
6000
5500
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
m
m
9/
16
8.
5
m
m
st
at
ic
co
rd
dy
na
m
"(
ic
14
6
ro
m
m
pe
m
m
)w
st
at
eb
9.
ic
5
bi
co
ng
m
rd
m
(c
dy
lim
na
b
m
sp
ic
ec
ro
)
pe
(M
ax
7
im
m
H
m
)
ar
st
ne
a
ss
tic
8
tie
co
m
-in
rd
m
l
s
oo
1"
ta
p
tic
(2
or
5
co
m
9/
rd
m
16
)w
"w
10
eb
m
eb
m
bi
lo
ng
(3
op
/8
(
c
")
lim
D
1"
b
yn
sp
w
ex
e
ec
9/
b
w
16
bi
)
eb
ng
"(
b
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i
lo
ng
9.
op
5
m
lo
m
m
w
op
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)S
/w
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pe
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or
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d
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r
0
[1] Comparative Testing of High Strength Cord, Tom Moyer. 2000.
http://www.xmission.com/~tmoyer/testing.
27
MountaineeringLife.org 2009
Rope, Webbing & Cord Tensile Strengths
5
Pounds Force (lbf)
5000
Anchors From Loops
Made with a Knot
1 loop 7mm cord = 19kN
2 loop 7mm cord = 38kN
1 loop 9/16" web = 15kN
2 loop 9/16" web = 30kN
1 loop 1" web = 27kN
2 loop 1" web = 54kN
MountaineeringLife.org 2009
Strength of Webbing & Cord in Anchors
Single
Strand
Single
Loop
Double
Loop
Triple
Loop
(1 strand mfr rating)
(2 strands)
(4 strands)
(6 strands)
No
Knots
Water
or Dbl
Fisher
Knot
Water
or Dbl
Fisher
Knot
% of Single Strand Strength
100%
150%
350%
450%
*Includes 75% knot efficiency. 1 - 2 loops
based on tests. 3 loop is theoretical.
MountaineeringLife.org 2009
Strength of Anchor Configurations
Webbing
Cord
Configuration
Knot Efficiency
(dbl fisher for cord & water for web)
Number of
Strands
(1 loop = 2
strands)
9/16"
climb
spec
7mm
Perlon
80%
1
75%
1" climb
spec
6
75%
10mm
Dynex
6
100%
9
2
2
2
1
Single Strand Strength
12
10
18
NA
(no knot)
2,698
2,448
4,046
NA
3
7
3
2
Single Loop Anchor Strength (kN)
19
15
27
22
(lbf)
4,316
3,372
6,070
4,946
% Stronger than 1 strand
160%
150%
150%
NA
4
7
7
4
Double Loop Anchor Strength (kN)
38
30
54
36
(lbf)
8,632
6,744
12,139
8,093
% Stronger than 1 strand
320%
300%
300%
164%
5
5
5
6
Triple Loop Anchor Strength (kN)
58
45
81
(lbf)
12,948
10,116
18,209
% Stronger than 1 strand
480%
450%
450%
Bottom Line:
1 loop with a knot is ~150% stronger than a single strand. A two loop anchor is twice as
strong as a 1 loop anchor. A 3 loop anchor is 3 times as strong as a 1 loop anchor.
Theory: Since the knot is the weakest point, we just need to figure at what point
there is enough force on one strand to fail the knot. This assumes perfect equalization.
2
8
Data Sources
1. From tests. http://www.caves.org/section/vertical/nh/50/knotrope.html
2. Mfr ratings and tests.
3. From tests. Comparative Testing of High Strength Cord, Tom Moyer. Nov. 2000.
http://www.xmission.com/~tmoyer/testing.
4. Calculated which correlates well with the Dynex tests. See Equation 1.
5. Calculated (theoretical). These results do not correlate well with tests done in Source 3.
Those tests showed triple anchors testing at about the same as a single loop?
6. Backed out of tests done in Source 3.
7. Calculated. See Eq. 1. These correlate well with tests from Source 8.
8. From tests. Black Diamond testing 7/16/08.
http://www.bdel.com/scene/beta/qc_kp_archive.php#071608 The sliding X configuration w/o a
knot did not fail to the maximum of the test equipment (36 kN), so the strength is more than that.
9. Dynex runner has no knot, but is sewn.
Eq 1. % improvement in strength over 1 strand = 1 strand strength x knot efficiency x number of strands (1 loop = 2)
MountaineeringLife.org
2009