The fender is mainly to withstand the impact force of the ship when the ship is docking, leaving the dock and other forms (such as when the ship is tied to tow), and transmits it to the hull structure of a larger area. Wooden fenders have buffering effect. Although steel fenders have poor buffering effect, they have better strength and can be included in the section of the hull girder (the welding strength must be guaranteed). Especially for large-open deck barges, they can make up for the deck The lack of effective cross-sectional area is conducive to longitudinal strength. Steel materials cannot be used for the fenders of oil barges and small oil tankers.
Large seagoing vessels usually do not have fenders. River boats, work boats, permanent double-track fenders, one of which is located on the upper deck, and the other is located slightly higher than the designed waterline