Concrete ships sound like an April fools joke, but in fact there were many examples built in the last hundred and fifty years. Most were built during times of war when steel and timber supplies were scarce. The disadvantages of concrete boats are many; they are heavier, more costly to construct and as the walls are thicker their carrying capacity is much less. The advantages are that much less steel is required. The fact that they are heavy, robust and difficult to dispose of means that although they are no longer sailing the seas, a lot of the ships built still survive as breakwaters.
The most famous example of concrete ships were the British built mulberry harbours. These were built during the Second World War and towed to Normandy for use as temporary breakwaters and pontoons as part of the invasion of occupied France. They are still visible today off the Normandy coast. Other less well known concrete ships were built and used by the British and the US Navy to transport troops and supplies during the Atlantic and Pacific campaigns in the same war. I would be interested to know, if attacked, how well they resisted damage from bombs or torpedoes compared with steel ships. I suspect they would be more resistant to damage, but have been unable to find any evidence for this.
The first known concrete ship was featured in the 1855 World’s Fair in France and constructed by Joseph Lambot in Southern France in 1848.
In Ireland the SS Creteboom lies unused in the river Moy near Ballina, County Mayo. It was one of twelve ships constructed during the First World War for use as tug boats, to tow barges filled with supplies of Iron Ore from Northern Spain to Britain. It was built by the Wear Concrete Building Company in England in 1919. However the war ended before the boat was finally launched. The ship was never used commercially and was abandoned in the River Moy in 1930’s. Plans to use her as a sand stop never materialised.
There are many concrete ships still in use as breakwaters in Britain. But one of the sister ships of the SS Creteboom, above, is still visible and lies in the River Wear in Sunderland, England. During the Second World War it was damaged in an air raid and later sank as it was being towed up river.
The largest concrete ship that is still afloat is the 120m long and 6,000 tonne S.S. Peralta. This ship was built as an oil tanker by the San Francisco Shipbuilding Company in the United States and launched in 1921. The ship is one of ten concrete ships used as a floating breakwater to protect a log storage pond on the Powell River in British Columbia, Canada.
There is no longer any large scale concrete ship building taking place. Although concrete barges are still being built in Europe for house boats and there are some specialist one off concrete yachts. However this may change in the future. Concrete technology has greatly improved and is becoming more suitable for concrete ship manufacture. For instance specialist high strength concrete is now available, and when used with corrosion resistant fibres this would allow a thiner walls, thus reducing the disadvantages of concrete ships (i.e. heavy and less capacity). Alternatively light weight concrete could be used to reduce the ship weight. Therefore there is a possibility that concrete ships will again be built in the future, especially if steel prices continue to rise.