TM 5-850-1
considered to be expensive in combined first cost and
and the fixed tire-wheel type is feasible for pier-corner
maintenance costs.
protection.
(a) Advantages.
(b) Disadvantages. The disadvantages
The advantages
include favorable energy-absorption characteristics for
include its use in fixed dock-fendering being limited to
both berthing and mooring ships.
bulkhead-type structures and high maintenance cost.
(b) Disadvantages. The disadvantages
d. Gravity-type fender systems. Gravity fenders
are high initial and maintenance costs.
f. Floating fender systems. As a supplement to a
suspended from heavily constructed wharf decks.
Impact energy is absorbed by moving and lifting the
number of the fender systems mentioned above, the
heavy concrete blocks.
High-energy absorption is
floating fender, camel, or separator is often used. In its
achieved through long travel of the weights.
simplest form, the camel may consist of floating logs,
Movements may be accomplished by a system of
which ride up and down against the timber bresting face
cables and sheaves, a pendulum, trunnions, or by an
and are attached to the face by chains or other means.
inclined plane. The type of gravity fender suited to a
given situation depends on tidal conditions, energy-
timber, with one protected by heavy rubber. Another
absorption requirements, and other load environmental
type of camel, occasionally used commercially and
factors, such as exposures to wind, waves, and currents.
often used around naval establishments, is a heavy
Heavy, vertically suspended gravity fenders are
timber box section made up of timbers dapped and
commonly used in exposed locations that have large
bolted together. This box-type of camel or separator is
tidal ranges.
generally rectangular in shape, sometimes measuring to
(1) Advantages.
Smooth resistance to
30 feet in length, but may have different shapes in the
plan designed to fit the contours of the ships being
impacts can be induced by moored ships under severe
docked. This type of device may be used to absorb
wave and swell action. Also, high energy-absorption
some of the bresting loads during docking but more
and low terminal load can be achieved through long
generally is used to keep ships away from a dock or to
travel for locations where the excessive distance
separate ships tied up adjacent to one another.
between ship and dock is not a problem.
(2) Disadvantages. Heavy berthing structure
9-3.
Selection of fender system type.
is required; heavy equipment is necessary for
installation and replacement; initial and maintenance
A variety of factors affect the proper selection of a
costs are high; and the excessive distance between
fender system.
These include local marine
dock and ship caused by the gravity fender is
environment, exposure of harbor basins, class and
undesirable for general military piers and wharves.
configuration of ships, speed and direction of approach
e. Hydraulic and hydraulic-pneumatic fender
of ships when berthing, available docking assistance,
systems.
type of berthing structure, and even the skills of pilots or
(1) Dashpot hydraulic. This system (fig 9-20)
ship captains. It is considered impractical to standardize
fender designs since port conditions are rarely identical.
consists of a cylinder full of oil or other fluid so arranged
Previous local experience in the application of
that when a plunger is depressed by impact, the fluid is
satisfactory fender systems should be considered,
displaced through a nonvariable or variable orifice into a
particularly as it applies to cost-effectiveness
reservoir at higher elevation. When ship impact is
characteristics.
released, the high pressure inside the cylinder forces the
a. Exposure conditions. In exposed locations or in
plunger back to its original position and the fluid flows
areas subject to seiche, a resilient system, such as a
back into the cylinder by gravity. This system is most
rubber fender system, should be used. In sheltered
commonly used where severe wind, wave, swell, and
basins, a standard timber-pile system, a hung system, or
current conditions exist.
(a) Advantages.
a retractable system is generally used.
The advantages
b. Berthing ship versus moored ship. The choice
include favorable energy-absorption characteristics for
of a fender is dependent on whether its chief function is
both berthing and mooring ships.
(b) Disadvantages. The disadvantages
to absorb kinetic energy of berthing ships or to keep a
ship safely moored during loading and unloading
are high initial and maintenance costs.
(2) Hydraulic-pneumatic floating fender. In
operations.
(1) For locations where berthing operations
this system, a floating rubber envelope is filled with
are hazardous, stiff fender systems with high energy-
water or water and air, which absorbs energy by viscous
absorption characteristics, such as Raykin fenders or
resistance or by air compression. This fender seems to
rubber-in-axial-compression pile fender systems, are
meet certain requirements of the ideal fender but is
advisable.
This is the case when berthings are
conducted
9-4
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