Concrete Ships
by Mike Creasy
Throw a piece of wood into the water. It floats, right? Now toss in a piece of metal. Nothing but ripples. If you intend to build a boat or a ship, which one seems like the obvious choice?
That was the way many sailors regarded the creeping introduction of iron into the shipbuilding process starting in the early 1700’s. Of course, the use of metal was pushed by a shortage of good clear wood – did they think about things like sustainable logging in this country which is only 1/3 the size of BC??? – and by the growing need for diagonal bracing as wooden ships grew larger. These added structures reduced internal spaces and added to the weight of the hull, causing problems for warships and cargo ships alike.
Anyhow, the critics claimed that iron ships would be too heavy to float, subject to massive damage when aground, hard to repair and cause compasses to spin wildly. By the mid 1800s, iron ships were becoming a common sight. Brunel’s 322’ steamer Great britain was launched in 1843 and soon became the first iron ship to cross the Atlantic. By the 1880’s, iron had almost completely replaced wood as the material of choice for larger ships.
With the success of iron, some designers began thinking of other unlikely materials for boat- and ship-building. In 1848, a Frenchman named Joseph Lambot managed to build a small dingy out of cement and iron wire. The boat floated and was displayed at the 1855 World’s Fair in Paris. (It’s still on display in a French museum.) Concrete showed some potential for marine construction – it was fairly inexpensive, didn’t require the new skill-sets associated with the new iron technology, it wasn’t affected by most bulk cargoes (such as salt) and it produced a smooth (low-drag) external surface. On the down-side it wasn’t as strong as iron and the thicker hull meant that internal volume would be reduced in a similar size ship.
So just how thick were these concrete hulls? Well, the SS Faith was launched in 1917 at Redwood City California. She was a 320 foot cargo ship of 8,150 tons displacement and about 5,000 ton deadweight capacity. Her concrete sides were 4 inches thick, while the bottom slabs were 4 ½ inches, poured on wire mesh reinforced with steel bars. Faith went into service without a hitch and no doubt influenced the American decision to try concrete as a replacement for steel, which was becoming scarce as the Great War ground on.
In 1918, the US Government ordered a number of 420 foot tankers, plus a number of smaller dry cargo ships to be built from concrete. These 7,500 DWT tankers would have 5 inch concrete shell slabs with steel reinforcing. Only 12 ships were completed by the end of the war and these ships went into commercial service while the rest were cancelled. One tanker, the SS Peralta, is still afloat today in the Powell River breakwater … not many steel ships could match that performance after nearly 90 years.
Concrete ships enjoyed a bit of a renaissance in the second Great War, when the Americans ordered a number of cargo ships, un-powered barges and smaller craft to be built from concrete. Once again, the ships provided good service and were sold into commercial trade after the end of the war. In the late 1940’s the Powell River Company bought several of the concrete ships to replace some steel breakwater ships which had sunk. Eventually the breakwater became entirely populated with concrete ships, sheltering
the mill from the vicious winter winds of Malaspina Strait.
Concrete never caught on as a shipbuilding choice, despite some obvious advantages in durability and reduced maintenance. These days, ferro-cement yachts are built with much the same technique as that used by Joseph Lambot, and they seem to face the same criticisms as in those early days. Despite all this, the 90 year old Peralta and her much younger sister ship – only 60 years old! – continue to prove that the wire mesh and reinforcing bars won’t rust away, that salt won’t penetrate the concrete and that a good idea will never sink!
Bibliography:
The Influence of Iron in Ship Construction: 1660 to 1830, Peter Goodwin, Keeper & Curator of HMS Victory.
Seagoing and other Concrete Ships, N.K. Fougner, Frowde Hodder & Stoughton, 1922