Be vigilant when you are handling lines by capstan.
Warning of a dangerous strain is given by the creaking,
stretch and reduction in circumference of the line when
you are using nylon lines.
BLOCK AND TACKLE
A block consists of a wooden or metal frame (or
shell) containing one or more rotating pulleys called
sheaves. When a line or wire is reeved through a block
or a pair of blocks, the whole arrangement becomes a
tackle. Usually, the purpose of a tackle is to multiply the
force applied on the hauling part of the fall. The number
of times it is multiplied, disregarding friction, is the
mechanical advantage of the tackle.
Every tackle contains a fixed block, attached to
some solid support, and a movable block, attached to
the load. The force applied at the hauling part is
multiplied, excluding friction, as many times as there
are parts of the fall at the movable block.
A block ordinarily is referred to by the number of
sheaves it contains: for example, single sheave, double
sheave, triple sheave. Its size is determined by the
length of its frame (in inches). The frame is the main
body of the block, and contains the metal strap support-
ing the pin on which rotates the sheave(s). Multiple-
sheave blocks usually have both inner and outer straps.
The closed upper end of the strap on a wooden block
holds the hook or shackle; the other end accommodates
the becket, for securing the end of the fall.
Wooden blocks are used exclusively with line; they
are never used with wire. Blocks for wire normally are
all-steel, heavy-duty, roller-bearing blocks, either self-
lubricating or equipped with fittings for grease guns.
A snatch block is a single-sheave block, a part of
which (strap) opens on a hinge so a line may be layed in
the block. Fairleading, causing a line or wire to lead
angularly around an obstruction and then straight to
some desired point, is the usual purpose of a snatch
block. See Boatswain's Mate, Volume 1, NAVEDTRA
10101, for further discussion on the blocks and tackle.
Standing rigging, usually of 6 by 19 galvanized
high-grade plow-steel wire rope, is used to support the
masts. The fore-and-aft supports are called stays, and
the supports running athwartships are called shrouds.
Stays and shrouds are set up at the lower end with
turnbuckles, and those in the line of fire of the guns are
also fitted with pelican hooks so they may be moved
quickly. Vibration often causes turnbuckles to back off,
To prevent this, keepers are installed on turnbuckles in
All standing rigging is grounded to the ship's struc-
ture with a bonding strap to eliminate the effects of
charges in rigging induced by electromagnetic radia-
tion. When you make any adjustments to the shrouds
and stays, the bonding straps must be disconnected to
prevent damage and/or breaking. Upon completion of
adjustments they must be reconnected.
If shrouds and stays are allowed to become slack,
their effectiveness is reduced. Standing rigging should,
therefore, be inspected periodically and tightened if
necessary. The following procedure should be observed
when considerable adjustments are required:
1. Disconnect bonding straps. Loosen turnbuckles
to slack all shrouds and stays so no unbalanced forces
are applied to the mast.
2. Take up the slack as uniformly as possible until
sag is eliminated from all stays and shrouds, and turn-
buckles are hand-tight. Measure the distance between
the ends of the turnbuckle bolts.
3. Tighten each turnbuckle so it is shortened by a
distance equal to 1 inch for each 60 feet of stay length.
Reconnect the bonding straps.
Insulators should present clean surfaces. They
should not be painted, tarred, varnished, or coated in
All electrical bond straps on standing rigging
should be inspected for damage, broken or missing
fittings, and excessive deterioration at points of contact
between dissimilar metals as specified by the PMS
periodicity and procedures. Deficiencies should be
reported to the work center supervisor and/or division
LEARNING OBJECTIVE: Explain the impor-
tance of deck safety.
Lines must never be made fast to capstans or gypsy
heads, but only to fittings such as cleats or bitts pro-
vided for that purpose. When hawsepipe covers are
removed for any purpose, a safety guard must be
installed forward of each hawsepipe to prevent
personnel handling lines from stepping or falling into
the opening. When heaving around or veering the anchor
cable, only authorized personnel may remain on the