Table 4-3.--Dimensions for Tattletale Cords
Although line stretching can be beneficial to a job, it
can also be detrimental to the line, when overdone. The
Length of
Distance
amount a line stretches is directly related to the load
Type of
placed on the line. As long as the load is within the line's
Synthetic
Tattletale
Between Marks
safe working load (SWL), the line will be safe to use. To
Rope
(Inches)
(Inches)
ensure the longest life, use a line within its SWL. The
Nylon Three-
35 1/2
30
SWL of line ranges from one-sixth to one-tenth of the
Strand
minimum breaking strength (BS) of new line, allowing
for the type of application, the weather, and the blocks
Nylon Plaited
43 1/2
40
and other gear being used with the line.
Nylon Double-
43 1/2
40
If a line is loaded beyond its SWL, it may reach a
Braid
critical point, which is near the BS of the line. A line
Polyester
60
63 1/2
may repeatedly be brought to its SWL without
Three-Strand
impairing the line or reducing its useful life. From the
Polyester
62 1/2
60
standpoints of safety and economics, it makes sense to
Plaited
take precautions not to surpass the SWL of a line. A
simple device that will keep you from exceeding a line's
Polyester
62
60
SWL is a tattletale cord. A tattletale cord is a bight of
Double-Braid
six-thread manila hanging from two measured points on
the working line. The line, when tensioned to its stretch
Normally, synthetic-fiber line is furnished on reels
limit, will stretch to a certain percentage of its elastic
and is unreeled in the same fashion as wire rope. (We
length. When this point is reached, the tattletale cord
becomes taut, warning that there is danger of exceeding
discuss wire rope in detail later in this chapter.) If you
the stretch limit of the line. Figure 4-8 shows a tattletale
receive a synthetic line made up in a coil, do not open
cord on a three-strand nylon line. Table 4-3 shows
the coil and pull the end up through the tunnel as with
standard lengths of tattletale cords and the distances
natural-fiber lines. Set the coil on a turntable and pull on
between suspension points for various lines. Use
the outside end while somebody rotates the turntable.
tattletale cords and every other guide available to you to
Should a coil collapse and the line kink and tangle, do
ensure that you do not ignore the SWLs.
not try to untangle it by pulling on the line. Secure one
Concerning the BS of line, the current practice in
end and drop the remainder of the coil into the sea. In
the Navy is to use the minimum BS. Minimum BS is
the water, the line will relax and gradually uncoil
defined as the lowest BS encountered in all of the test
without forming permanent kinks or cockles. (DO
samples broken. Line manufacturers usually publish
NOT TRY THIS WHILE THE SHIP IS UNDER
average BSs, which may be 10 to 25 percent higher than
WAY.) This water treatment also removes bulges in
the minimum BSs. The actual BS of a line can be
anywhere from the minimum BS to 35 percent higher.
new, soft-laid line and hardens the line structure.
Figure 4-8.--Tattletale cord on a twisted nylon line.
4-7