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Chapter 4 Fiber Line | Up
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Size Designation of Line |
TYPES OF SYNTHETIC FIBER LINES
Although natural fiber line is normally used, a
number of synthetic fibers are also used to make line.
The synthetic fibers used to fabricate line include the
following: nylon, Kevlar, Orion, and Dacron.
Of the types of line made from synthetic fibers,
nylon is the one used the most. The primary benefit
of using nylon line is that the breaking (tensile)
strength of nylon line is nearly three times that of
manila line. An additional benefit of using nylon line
is that it is waterproof and has the ability to resume
normal length after being stretched and absorbing
shock. It also resists abrasion, rot, decay, and fungus
growth.
FABRICATION OF LINE
The fabrication of line consists essentially of three
twisting operations. First, the FIBERS are twisted to
the right to form the YARNS. Second, the yarns are
twisted to the left to form the STRANDS. Third, the
strands are twisted to the right to form the LINE.
Figure 4-1 shows you how the fibers are grouped to
form a three-strand line.
Figure 4-1.—Fabrication of line.
The operations just described are standard
procedure. The product produced is known as a
RIGHT-LAID line.
The process is sometimes
reversed, then you have what is known as a
LEFT-LAID line. In either instance, the principle of
opposite twists must always be observed. One reason
for this is to keep the line tight or stable and prevent
the elements from unlaying when a load is suspended
on it. Another reason for twisting the elements of a
line in opposite directions is to prevent moisture
penetration.
TYPES OF LAYS OF LINE
There are three types of lays of fiber line with
which you should be familiar.
They are the
HAWSER-LAID, SHROUD-LAID, and CABLE-
LAID lines. Each type is shown in figure 4-2.
Hawser-Laid Line
Hawser-laid line generally consists of three
strands twisted together, usually in a right-hand
direction.
Shroud-Laid Line
Ordinarily, a shroud-hid line is composed of four
strands twisted together in a right-hand direction
around a center strand or core. This core is usually of
the same material but smaller in diameter than the four
strands. You will find that shroud-laid line is more
pliable and stronger than hawser-laid line. You will
also find that shroud-laid line has a strong tendency to
kink. In most instances, it is used on sheaves and
drums. This not only prevents kinking but also makes
use of its pliability and strength.
Figure 4-2.—Lays of line.
4-2
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