Page 176 - The Complete Rigger’s Apprentice

Stretch (in inches) at 5,000 lbs in 692 inches length, 13 mm/16 mm dux and various sizes
of Kevlar and ECsix carbon. 13 mm/16 mm dux is from actual lab test data.
2.5

2.144121813
2 1.96 1.92
1.79

1.49
1.5 1.45

1

0.5

0
Dux 13 mm Dux 16 mm Kevlar #6 Kevlar #7 ECsix-15 ECsix-19
(Colligo Marine)
Figure 5-32 Stretch (in inches) at 5,000 pounds in
692 inches length, 13 mm/16 mm Colligo Dux and
various sizes of Kevlar and ECsix carbon. Note that Construction F
13 mm/16 mm Dux data is from actual lab test data.
Results are comparable to those for New England rod rigging stainless 4.45 5 10-6
Rope’s HSR. 1 x 19 carbon 6.98 5 10-6
stainless 7.79 5 10-6
P = load on rope in pounds 7 x 7 carbon 1.07 5 10-5
D = nominal rope diameter stainless 1.20 5 10-5
F = the reciprocal of (A 5 E 5 100) 7 x 19 carbon 1.20 5 10-5
stainless 1.62 5 10-5
The factor “F” is the tricky part of the equation
because it is the result of a fairly complex equation Don’t let those numbers intimidate you; Figure
itself. “A” is the cross-sectional area of metal in a 5-33 renders them into some real-life examples.
wire rope of given diameter, and “E” stands for the Theoretical 50-foot lengths subjected to a load of
modulus of elasticity, which is to say how much a 25 percent of their rated strength would stretch by
substance stretches per pound of tension applied. the amounts shown. A load of 25 percent reflects
Carbon steel, for example, has a higher modulus of high rig strain for most vessels. From the 1.05-inch
elasticity than stainless steel. Stays with the greatest stretch of the rod rigging sample to the 2.07-inch
cross-sectional area, made of materials with the low- stretch of the stainless 7 x 19 sample, one sees an
est modulus of elasticity will stretch the least. Values increase of elasticity with increase of numbers of
of the factor “F” for the materials and constructions strands. But once more, the returns diminish as we
commonly used in rigging are as follows: approach minimum elasticity, with only a 0.44-

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