Chapter 23: Anchor Rode
acceptable for marine use. 304 suffers from
potentially severe pitting corrosion. 316
stainless chain is available from various man-
ufacturers to match standard proof-coil,
BBB, and high-test chain dimensions to suit
standard windlass chain wildcats.
Stainless chain is only about 30 percent
stronger at WLL than proof coil and has a
lower WLL than high-test chain of the same
size. The advantage of stainless chain is
mostly cosmetic—fewer rust stains, shinier
chain—though stainless chain should last
longer (when considering many years) than
hot-dip galvanized steel anchor chain.
Chain Fittings
The old saying about something being no
stronger than its weakest link comes literally
from chain. The various connecting fittings at
the ends of a chain (or between two lengths)
are the potential weak spots.
Shackles
The common anchor shackle is the standard
connector. What we usually refer to as an
anchor shackle is a bow shackleof hot-dip
galvanized steel (Figure 23-2 and Table 23-5).
For anchor use, it must be stamped with the
working load limit (WLL) as in the photo, and
the WLL must be equal to or greater than that
of the chain that the shackle is attached to. To
save space, WLL is usually stamped in tons,
and these are landlubber short tons of exactly
2,000 pounds (which is 907 kg), notmarine
long tons of 2,240 pounds (1,016 kg). Clearly
you should select an anchor shackle with the
same WLL or somewhat higher than the chain.
The rule of thumb for proof-coil and BBB
chain is that that the anchor shackle should be
one standard size larger than the chain. So for(^5) / 16 - inch (8.4 mm) chain, you would use (^3) / 8 - inch
(9.52 mm) shackles. For high-test chain to gen-
erate its full strength, however, a shackle two
sizes larger is generally needed.
Note that there are bronze and stainless
steel bow shackles for rigging use. These are
not stamped with a WLL and shouldn’t be
used for anchor gear. Stainless bow shackles
with certified breaking and WLL loads should
be used on stainless chain. Suncor is one
manufacturer of stainless anchor shackles
stamped with WLL.
Anchor or bow shackles provide more
freedom of movement at the attachment and
a larger surface through which to a tie rope
rode to an anchor ring shackle (using an an-
chor bowline or anchor bend). Standard
chain shackles, however, can be used when
connecting chain to chain, or chain parts to
swivels or other connectors. (See Table23-6.)
Chain and swivels are best attached directly
to the anchor with an anchor shackle rather
than a chain shackle, however, so as to improve
the range of motion without binding.
Chain shackles are also known as “D-type”
or “D-shackles,” as they roughly look like the
letter D (Figure 23-4).
Stainless anchor shackles are available
from several manufacturers including Suncor,
and Table 23-7 gives typical dimensions and
WLLs.
The pin on an anchor or chain shackle is
specially manufactured to generate maximum
strength. It can never be replaced with an
ordinary bolt. If you see a shackle fitted with
an ordinary bolt instead of the proper shackle
pin, the shackle must be replaced. Shackle
pins come in three standard forms: round pin,
screw pin, and safety(Figure 23-5). The
screw pin is most common and easiest to
use.To ensure that the pin can’t work loose,
it must be seized with light Monel wire
through the screw pin’s hole and around the
nearest leg of the shackle. This safety wire
Figure 23-3. Anchor or bow shackle
(Courtesy Chicago Hardware and Fixture Co.)