When we discuss Titanic’s watertight subdivision, one of the often-overlooked aspects of her construction is the double bottom. Titanic had what could be called a second or inner skin within the visible exterior hull plates that made up her bottom. 

As we discussed last week, Titanic had a vertical keel that extended upward from the keel plates themselves. This formed the center point for the double bottom, which took the form of a series of small compartments that formed something of a “honeycomb” at the bottom of the ship under her tank top. Each of these tiny compartments were formed by “floors” at each frame and three longitudinal structures (the keel itself and two margin plates, each located 30’ outboard on either side of the vertical keel). The spaces ranged from 63” to 75” inches in height, being thickest under the heavy reciprocating engines. 

Each of these “cells” or “tanks” could be utilized for various purposes, from ballast to storage of water. They also were important for Titanic’s stability, preventing water from sloshing around large spaces along the bottom of the ship. Most importantly when it comes to safety features, this cellular bottom and the inner skin it created would help the ship survive grounding collisions where the bottom of the ship was opened to the sea by some obstruction. Rather than a large compartment being opened to the sea and perhaps completely disabling the liner, a small void space would be opened up, giving water much less space to roam free and preventing the ship’s vital components from being damaged or put out of service.

As with the keel, Titanic’s double bottom structure can still be viewed today on the two pieces of double bottom that may have formed the final connection between the ship’s bow and stern sections as the liner plunged to the ocean floor. 

Next Week: Titanic’s Hull

Written By: Nick DeWitt

Photo Credits: Titanic Connections Archive