.Anchoring
techniques.
....Independent
gear test
(Yachting Life magazine UK)
Why
anchors drag- Royal Navy and other tests
The
Royal Navy's test on why anchors drag, show that
"When the shank is pulled above horizontal, the
efficiency of the anchor is greatly reduced. If the
angle of pull is 10 degrees off the seabed, the
anchor's maximum holding power is down to 60%. At 15
degrees, it is further reduced to only 40% of its
maximum holding power".
The additional pull when a ship yaws is
considerable..(tests)..have shown that only 100 of
yaw increases the pull by 60%".
(Information sourced from Admiralty Manual of
Seamanship. Vol. 2)
Tests
have shown that the correct size anchor of any
reputable design pulled horizontally, is more likely
to hold than an oversize anchor pulled upwards.
Recent
tests in the UK revealed that 5/16
chain unweighted, gave a maximum load of 0.44 tonnes
before the 35lb CQR anchor dragged. By adding a 12kg
or 26lb weight, the maximum load was increased to 0.58
tonnes, an increase of 0.14 tonnes. The ANCHOR
BUDDY AB30 and CAB30 anchor weights and the KIWI
ANCHOR RIDER AR30 and CAR30 models are 13.6kg or
30lb which would increase the maximum load levels even
further.
Keep
maximum chain on seabed
Earl
Hinz in his book "The Complete Book on Anchoring
and Mooring" says that the wind creates yawing
and swaying, the waves create pitching and heaving,
and the anchor restraint is involved with surging.
Surging of the boat sometimes as much as doubles the
loads felt from the wind drag alone. A vessel snubs
when her bow lifts to a sea and the chain is pulled
taut with a jerk.
These actions all raise the anchor shank and give
every reason for a skipper to question the integrity
of the anchoring system and worry about dragging.
The
secret when using an Anchor Buddy
Is to set it just off the seabed at low tide. Then it
acts like a spring or shock absorber to dampen the
sudden jerks caused by the wind and the waves, rather
than have them transmitted to the ground tackle and
raise the shank of the anchor.
"We
dive down the anchor chain to check the holding power.
Since deploying the Anchor Buddy our observation in a
variety of sea conditions, is we have observed no
weight at all pulling on our Delta anchor" Merv
Dobbs SY 'Meridian Passage'
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