28 July 2005
CHAPTER 5. FENDER SYSTEMS
The fender system is the interface between the ship and the shore facility.
During the berthing of a ship, the fender system is meant to act as a buffer in
absorbing or dissipating the impact energy of the ship without causing permanent
damage to the ship or the shore facility. Where ships are to be berthed against
relatively inflexible solid piers and wharves, protection of the ship is a critical
function. When ships are to be berthed against pile-supported piers, wharves,
and dolphins (which are relatively flexible), protection of the structure may be the
more serious concern. Once the ship is successfully berthed and moored to the
shore facility, the fender system continues to provide the interface between ship
and shore and transmits the environmental loads (wind, waves, and current) on
the ship to the structure. For submarine and other low-profile ship berthing, the
fender system also provides a physical barrier to prevent the vessel from going
underneath the pier.
The selection and design of a fender system is highly dependent on the berthing
practice employed at the particular facility. Typically, two or more tugboats assist
large ships into the berth. In some locations, smaller ships may be allowed to
come in on their own power. When assisted by tugs, the ship would arrive off the
berth and parallel to it. The ship then stops dead in the water and the tugs push
and pull the ship transversely toward the berth in an attempt to make contact with
as much of the fender system as possible. When unassisted by tugs, the smaller
ship will be eased into its berth at some slight angle, referred to as the angle of
approach. In both cases, the initial contact is limited to a relatively small portion
of the fender system. Assumptions will have to be made regarding the approach
angle and contact length.
Camels & Separators.
Camels are located between ships and piers or wharves. Separators are located
between nested ships. This practice is the most significant difference between
commercial ship berthing and naval ship berthing. Berthing against camels
concentrates the impact energy to a small length of the fender system as well as
applies the energy at some distance below the deck. This aspect must be
recognized in all fender system design for Navy ships. A fender system
designed for commercial ships will, in general, not be satisfactory for Naval
applications. The practice of using camels has resulted in a general trend for a
minimum of hull protrusions near the waterline. Fender systems with higher
fender contact area are more susceptible to damage from longitudinal movement
of the vessel due to snags.