Page 175 - The Complete Rigger’s Apprentice

Stretch Comparison, Colligo Dux vs 1 x 19 wire, millimeters stretch for a 10 meter length
versus load in kilograms. Lab test data on Dux, published data on 1 x 19 stainless wire.

100

90
5 mm 1 x 19
80 Dux 7 mm
6 mm 1 x 19
70
Dux 9 mm
7 mm 1 x 19
60
Stretch (millimeters) 50 Dux 11 mm
8 mm 1 x 19
Dux 13 mm
40
10 mm 1 x 19
30

20

10

0
100 500 1000 1500 2000 2500
Load in kilograms

(Colligo Marine)
Figure 5-31 Stretch comparison: Colligo Dux versus
1 x 19 wire, millimeters stretch for a 10-meter length
inelastic once constructional stretch is removed versus load in kilograms. Lab test data on Dux, pub-
(see sidebar), they tend to have a huge amount of lished data on 1 x 19 stainless wire. Results are com-
constructional stretch. Even if the manufacturer parable to those for New England Rope’s HSR.
does everything possible to minimize this at the
factory, much of it will return simply from being reference mark at your desired finished length. As
wound onto a spool, let alone from being handled soon as you release the tension the rope shrinks in
in the loft when splicing. Addressing this level of length, with the fibers reassuming their original
constructional stretch is the biggest practical con- position.
sideration for a rigger working with the stuff. For And then there’s elastic stretch, a function of
instance, after you splice one end, it is important load and diameter relative to the inherent elastic
to put a temporary eye in the other end and stretch properties of the metal used in making the rig. A
the piece out, with a load of about 10 percent of formula for the approximate percentage of stretch
the line’s break strength. This removes the con- for a given length of rigging is as follows:
structional stretch from the standing part, as well
as any excess shrinkage you created when splic- e = [P/D ] 5 F, where
2
ing. Once the rope is stretched out, you make a e = elastic stretch as percentage of length

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