Fenders are devices or entities used as guards for a vessel against impact with a jetty, dock, quay, berth, or any other ship close to a shore, preventing resultant structural damage.
Fenders act as cushions or absorbers that reduce the impact of mutual contact by absorbing kinetic energy through elastic action.
All vessels need to berth at their designated points. During this process, the ship must position itself at a definite location to serve its purpose based on the availability of space and other factors in the jetty, port, dock, pier, quay, etc.
Hence, there is a high chance of direct collision or impact of the vessel with the structure, even though the ship’s speed may be very low.
Later after the vessel is stationed suitably, the risk of contact is still highly prevalent. Though the vessel’s speed is zero after docking or berthing, the nature of the water is highly dynamic.
Thus, even a floating stationary vessel comes in contact with the shore structure now and then by the continuous inherent motions due to water currents, tides, and waves.
Moreover, at a jetty, pier, dock, berth, or quay, there are multiple vessels catering to their operations. Thus, there is also a fair chance of direct contact between the individual ships.
Furthermore, when a vessel is near a port or harbour with great traffic, the risks associated with a collision with another vessel are also high.
Also, two vessels can be berthed to each other for various utilities like bunkering or cargo transfer in what is known as Ship-to-Ship berthing (STB).
This also creates a similar situation, where two vessels are likely to collide continuously. Therefore, the question arises: Can there be any means of protection similar to bumper and mudguards in vehicles or buffers in rail cars? The simple answer is fenders.
Remember those tyre-like things on the sides of the hull and the jetty platform when you first went for your pleasure boat ride?
Those are nothing but simple forms of fendering again. From small speedboats to large cargo carriers, all vessels must have a fendering system to protect their hull structure and any shore structure or other ships from localised collisions or impacts.
However, due to the momentum of the vessel (that further depends on its size) and often continuity, the effect of these kinds of impacts may be significant enough to damage the land structure or cause high localised stress concentrations that can be enough to be called structural damage and even a localised failure for the vessel itself or any other vessel.
Fenders are usually disposed in a single line at more or less regular intervals at regions with the most likely influence of interactions.
On a quay wall, pier, or jetty, they are distributed at the outermost edge where there is the likelihood of contact with the vessel hull. On ships or boats, the fenders are disposed on the side shell in areas close to the waterline and the deck edge.
Types Of Fenders
Based on shapes, some common types of fenders are:
· Cylindrical fenders
· Square fenders
· Corner fenders
· Circular fenders
· Cone fenders
· Doughnut fenders
· Arch fenders
Depending on their mobility, there can be:
· Fixed fenders
· Floating fenders
Based on the construction and design, fenders can again be broadly categorised as:
· Flat fenders
· Pneumatic fenders
· Foam fenders
*By Subhodeep Ghosh