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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 KIWI
ANCHOR RIDER and ANCHOR BUDDY anchor
weights AB30 and CAB30 models are 13.6kg or 30lb which
would increase the maximum load levels even further.
Swinging
(yawing), pitching, heaving, surging - all
raise the anchor shank and give every reason for a
skipper to question the integrity of the anchoring
system and worry about dragging.
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.
The
secret
when
using a Kiwi Anchor Rider or 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
- changes
the angle of pull to keep maximum chain and the shank of the
anchor on the seabed which helps it dig in
- reduces
the swing of the vessel considerably which reduces
the chance of the anchor 'rolling out'
Keith
Eade, designer and owner/builder for 25 years of
Keith Eade Boats, Steadecraft Ltd and Chico Yachts,
plus sailor of over 130,000 sea miles says
"I
have swum in clear water of 15 to 40ft to watch
it working. On one occasion in 60-80ft of clear
water, I watched the anchor and the Kiwi Anchor
Rider working together when other yachts were
sailing around out of control. In wind conditions
you would think it not possible to anchor, "Soulmate"
stayed safely anchored while all other boats finally
had to leave.
The advantages it gave to our comfort on board
and the reduction in our swing circle were so good
that we would use it all the time whether we needed
it or not and we would never leave the boat without
setting the Kiwi
Anchor Rider"
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I have all
chain anchoring
- do I need a Kiwi Anchor Rider?
Read
gear test results and what cruising boat owners say
about the Anchor Buddy/Kiwi Anchor Rider anchor weights
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