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The principal points of excellence in an anchor
are: holding power under various conditions, strength, quick holding,
quick tripping, freedom from fouling, facility of stowing, and of fishing,
facility of sweeping, and facility of transport in or by boats. Slight
differences in design make a considerable difference in the holding power
of anchors.
The center of gravity of any type of anchor should be located as near
as possible to a line perpendicular to the shank passing through the bills
when the anchor is placed on the ground in order to have the maximum pressure
or weight on this part. But at the same time , to prevent any toppling
over when the anchor is lying on inclined or uneven ground, it is necessary
that the center of gravity should be kept near the head. It is customary
for this reason, when designing anchors of the admiralty pattern, to place
the center of gravity at about 0.42 of the total length of the anchor.
With stockless anchors, because of the great weight of the head and the
absence of stock, the center of gravity is located very near the axis
around which the flukes swing and, therefore, beyond the vertical line
passing through the bills. The weight and pull on the chain prevent any
tipping over. The dimensions of anchors are in proportion to the total
volume of the ship and the scantlings of the different parts are arrived
at by empirical deductions after testing.
The weight of anchors is determined by the section of the cable, the diameter
of which is determined by the ship's displacement. Anchors used by sailing
vessels are heavier than those by mechanically propelled vessels of the
same displacement on account of windage.(International Maritime Dictionary) |
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