Thursday, July 23, 2009

Watertight bulkheads in cruise ships and theory insubmersibility

by Charles Roring

Cruise ships have many accommodation rooms for passengers. Yet, they don't function as watertight bulkheads which are important in protecting the ships from sinking. How Titanic sank, during her maiden voyage, raised questions to many people whether modern passenger ships may face such tragic accident at sea. All ships may face accidents at sea and it is the responsibility of naval architects to design ships that are stable and cannot easily sink if their hulls are broken due to collision with iceberg, other ships or explosions.

Naval architects when designing ships know that they have to divide the ship into a number of smaller compartments as a preventive action to protect the ships from easily drowning in case if they experience fatal flooding during their voyages. As a standard, there will always be forepeak (collision bulkhead) and after peak tanks, and double bottom tanks in large ships. To give more protection to the ships, naval architects will add some watertight bulkheads, according to the rules stipulated by classification societies and the calculation of flooding table which was introduced for the first time by Admiral Makarov and A.N. Krylov, two scientists from Russia.

The shameful defeat of the Russian Navy from the Imperial Japanese Navy during the naval battle of Tsushima on 27-28 May 1905 encouraged Russian Naval Scientists to thoroughly review the designs of their warships especially the battle ships. During the naval battle, the Russians lost two thirds of their entire fleet. The defeat inspired A.N. Krylov and other Russian scientists to introduce the concept of insubmersibility which in most western naval architecture textbooks are known as watertight subdivision.

When I was still studying Naval Architecture in Pattimura University in Ambon of Maluku islands, I was introduced with this concept. Insubmersibility, according to the book entitled Statics and Dynamics of the Ships written by Semyonov and translated into the English language by Maria Konyaeva, is the ability of a ship to remain afloat when one or more of her compartments brake and are flooded with sea water. A.N Krylov formulated that when a compartment is flooded with water, one or some compartments have to be filled with water to restore her stability. In addition, he introduced the concept of dividing ships, especially naval vessels, with smaller compartments to protect them from sinking. The development of the insubmersibility study of naval vessels led to the introduction of 100 percent insubmersibility concept. This is a very innovative idea which was formulated by A.N. Krylov and other Russian scientists. In this concept, a war ship will remain a float, and still have her fighting capability although her whole compartments are broken during a naval battle. The theory of reserve buoyancy is thoroughly discussed in the book to support the concept of 100 percent insubmersibility of a naval vessel. I find that insubmersibility is a brilliant idea from Russian naval scientists which naval architects from around the world should study. The subject is well presented in the Statics and Dynamics of the Ships. If you are interested in studying this subject, I suggest that you read the book. It is now offered on the internet. Also read: The interior of passenger ship and cruise ship and Cruise ship and passenger ship