courtesy of Long Island Boating World and West Marine
SETTING
An anchor must be “set” by placing tension on
the anchor line to ensure that it has penetrated the
bottom. This is done by making the anchor line fast
and applying lots of power in reverse. If your boat
moves when you try this, it’s time to reset the anchor
and try again. Only when an anchor is securely
set should you consider shortening scope while in a
crowded anchorage. Once an anchor has been set, it
will almost always hold the same amount of tension
that was used to set it, even if the scope is reduced.
This means that you can pay out long scope, pull
hard on the anchor rode using the engine, and then
shorten scope to reduce swinging room. However, if
your boat swings and the anchor has to reset itself,
it will have to do so at a reduced scope. This is also
known as Anchoring Russian Roulette.
RESETTING
It’s one thing to set an anchor when the wind and
current is consistently from one direction, but what
happens if they veer? Some anchors perform better
than others under varying angles of pull, but any anchor
can fail to reset if the boat swings far enough
to dislodge it from the seabed. Two techniques can
alert you when your boat swings:
1. If you have an anchor alarm on your GPS, set
it for a reasonable distance from the position your
boat assumes at the end of the rode so it will alert
you when the boat swings.
2. If you have a course alarm on your electronic
compass or autopilot, set it for the heading that your
boat assumes initially at anchor. It will “beep” you
if you assume a new heading.
ANCHORING BOW AND STERN
In tight anchorages, you may have to limit your
boat’s tendency to swing at anchor. By dropping an
anchor close to the beach, and a second anchor offshore,
you can locate the boat precisely in the anchorage.
You can also use the tension on one rode to
help set both anchors. If other boats are swinging
on a single anchor, they could swing into you if you
are the only one anchored bow and stern.
TWO ANCHORS OFF THE BOW
Bob Ogg, co-inventer of the Danforth anchor,
recommends setting one anchor into the wind or
current and a second anchor 180° away. Then take
both lines to the bow of the boat. This will allow the
boat to swing about a relatively small point, yet
allow the boat to pull against an anchor without
causing it to reset when the wind or current changes.
IF the wind is on the beam, the boat will settle back
on both anchors.
TYPES OF BOTTOMS
Sand: Some bottoms, like fine-grained sand, are
relatively easy for anchors to penetrate and offer
consistently high holding power and repeatable results.
Most anchors will hold the greatest amount in
hard sand. Best in sand are the Fortress and West
Marine anchors.
Mud: A broad shank-fluke angle and larger
fluke area allows an anchor to penetrate deeply to
where the mud has greater sheer strength and project
more surface area in the direction of pull. Peter
Bruce points out that mud commonly covers other
material, and pure mud anchorages are rare. Thus,
anchors that can penetrate through mud to the underlying
material will hold more. Fortress anchors
are easily converted to a broader fluke angle for superior
holding power in mud.
Rocks: Holding power is most dependent on
where you happen to drop the hook. Fixed-fluke
grapnel-type anchors, having high structural
strength to sustain the high point loads which occur,
generally work the best. These include Bruce, CQR,
Yachtsman and Delta.
Kelp: This is sort of a trick question, because
most kelp grows in the water and on the surface, not
on the bottom.Kelp does attach itself to rocky bottoms,
however, so it is likely that a rock anchor will
hold. You can also get a false set, due to the anchor
catching on kelp roots and not something solid.
Shale, clay and grassy bottoms: Tough bottoms
for all anchor designs and the weight of the
anchor, rather than its design, may be the most important
factor in penetration and holding power.
CQR and Delta anchors, as well as Yachtsman’s anchors,
are thought to be good in grass, due to their
“points” that penetrate the vegetation.
Continued on page 34
ANCHOR RODES
WHAT TO LOOK FOR
Not surprisingly, no one rode does the job for all
boaters. Each anchor rode is a compromise of qualities
that must be chosen for a given type of boating.
RODE TYPES
All Nylon Rodes: Small boats often use anchor
rodes made entirely of three-strand nylon because
they are lightweight, inexpensive and for boats
without a windlass or anchor well, easier to stow
than rodes with chain. Although all-nylon anchor
rodes can be quite strong, they lack the chafe resistance
of rodes with chain and are therefore not
appropriate for extended use or for use in rough
weather. as the primary rode for a lunch hook or
spare anchor, however, an all-nylon rode functions
quite well.
All-Chain Rodes: Larger boats with windlasses
generally use all-chain rode. This reduces the need
for long scope (except in shallow water) because
the chain is heavy and lies on the bottom until severe
conditions are encountered, when more scope
may have to be let out. Since chain has very little
elasticity, care should be taken to prevent the chain
from becoming “bar tight” in high winds by using a
snubber made of nylon line. The penalties for using
all-chain rode are weight, expense and the need for
a windlass. A windlass and all-chain rode may add
300-600 lbs. in the bow and can adversely affect the
performance of your boat. Modern lightweight
cruising boats probably will not be willing to suffer
the reduction in speed and increase in pitching that
this weight entails.
Mixed Rodes: A compromise to either allnylon
or all-chain rode is to use a short length of
chain (6-30’) connected to the anchor, with a long
length of three-strand nylon line connected to the
chain. This combination satisfies nearly all requirements
of a good anchor rode, except that it is
not abrasion resistant over its entire length, and
long scope must be used to keep the pull on the anchor
shank horizontal. Nylon is used because it is
naturally elastic. Its stretch reduces peak loads on
the anchor and your boat. One myth we’d like to
dispel is that a boat length of chain will keep the
pull on an anchor shank parallel to the bottom.
This is, unfortunately, not the case, since even a
15-knot wind will lift short lengths of chain clear
off the bottom. Yes, it is better to use chain but, no,
it isn’t effective as wind speeds increase. Its primary
mission is to handle the chafe from rough
bottoms that would otherwise abrade the soft nylon
line.
Rode Sizes and Lengths
Scope is defined as the ratio of water depth
(plus freeboard) to anchor line paid out. Most anchoring
texts and anchor manufacturers agree that
a scope of 7:1 achieves the anchor’s designed
holding power and more scope is better than less.
In theory, 7:1 scope is great, but at a crowded anchorage
most cruisers scoff at the idea of paying
out more than 3:1 or 4:1 – there just isn’t much
space for boats to swing. Any reduction in scope,
of course, must be made up for by using larger anchors
and/or larger chain.
As a general guide, for winds up to 30 knots,
we recommend the following anchor line and
chain diameters, using three-strand, high quality
line. This table assumes an 8:1 working load ratio.
Boat LOA: 3 Strand: Chain:
Up to 25’ 3/8” 3/16” PC
27 – 31’ 7/16” 1/4” PC
32 – 36’ 1/2” 1/4” PC
37 – 44’ 9/16” 5/16” PC/BBB
45 – 50’ 5/8” 5/16” PC/BBB
51 – 62’ 3/4” 3/8” PC/BBB
63 – 76’ 7/8” 3/8” HT
77 – 90’ 1” 1/2” HT
Conclusion
In inland, coastal, and performance cruising applications,
boaters should use a combination of
nylon line and galvanized chain. For serious cruisers,
all-chain rode is a better solution. The trade-off
is one of weight vs. abrasion resistance.
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