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From: (no name) (no email)
Date: Mon Apr 14 2008 - 16:21:24 EDT
Anchoring 101 - About kellets.
Anchor kellets are weights suspended from an anchor rode to assist in the
anchoring process. In theory both chain and nylon rodes, or any combination of
the two, are special cases of a hypothetical general anchoring system which
consists of a weightless, unstretchable line connecting the anchor and the boat
with a single concentrated weight, representing the underwater weight of the
rode, hung somewhere along its length. The weight serves two purposes. It keeps
the anchor shank angle more nearly horizontal, reducing the chance of the
anchor pulling out or dragging; and, it gives a degree of elasticity to the rode,
requiring the weight to be lifted before becoming taut and jerking on the
anchor. The kellet merely adds to the weight of the rode. It has the advantage that
it can be placed anywhere along the length of the rode to modify anchoring
characteristics.
The best position for the weight depends on what you want to do. To keep the
anchor shank as flat as possible, the weight should be attached to the lower
end of the rode near the anchor. Danforth and Fortress type anchors, and their
near relatives, require that the shank be kept nearly parallel to the bottom
for best results. A boat length of chain connected between the anchor shank and
a nylon rode is the usual prescription. The chain resists abrasion and
assists anchor setting. A kellet near the anchor can help if the chain is short or
light in weight.
For best rode elasticity, the weight should be positioned at one water depth
from the upper end of the rode. Maximum elasticity is achieved when the rode
hangs straight down from the bow to a weight resting on the bottom, then goes
horizontally to the anchor. This is normally the case when an all chain rode is
used. It is an oversimplification to assume that a chain forms a catenary
between the anchor and the bow. In most cases the chain drops almost straight
down from the bow, then lies flat along the bottom to the anchor. As more strain
is placed on the rode by wind and current, additional chain is lifted off the
bottom. A catenary curve is achieved only under considerable strain, just
before the chain becomes bar tight and all elasticity vanishes. A kellet, attached
to the anchor rode at one water depth, can materially delay this point.
But this kellet position hurts the bow's ability to lift over the waves. For
permanent or long term moorings an anchor buoy can be used to support the end
of the anchor rode with a pennant extending to the boat's bow. The often
repeated suggestion that the kellet be hung halfway along the rode is a compromise
between the conflicting requirements for a flat anchor shank and maximum rode
elasticity.
Larry Z
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