Single vs. Double Hull Ships

Ships are commonly used for cargo transportation. They play a vital role in world trade. The shipping companies across the world spend millions of dollars in research so that they can come up with a better ship. Everyone wants to have the fastest and the strongest ship. This craze of creating the best ships has evolved the ships a lot. In the last one century itself we have seen innumerable changes in the ships and the ship building process. Ships are no longer simple boats made of wood. They are highly complex and sophisticated. They are designed and maintained by highly skilled professionals. We will now discuss about Single vs. double hull ships in this article.

Single Vs Double Hull Ships

There are two types of hulls that you can find in a ship. They are single and double hull ships and the names itself give a little idea. The double hull ships are the ones that have double layers of watertight hull surface. Single hull has only one layer of watertight hull surface. The double hull ships are better protected. When the ship enters rough waters it is the hull of the ship that takes the maximum bashing. If the hull is weak then there can be cracks in it. This may result is grave consequences. Especially if the ship contains hazardous substances then the marine life will be in danger.

Single vs Double Hull Ships

Single vs Double Hull Ships

In case of a single hull ship the threat to marine life is higher as the ship can develop crack easily. Tankers carrying hazardous chemicals are always made double hulled. The IMO the international maritime organisation states clearly that any tanker that has a capacity of five thousand tonnage dead weight and above must have a double hull. This has helped the marine life a lot. Today most tankers strictly follow this rule.

The double hull of a submarine is different from that of a ship. The double hull ships ensure that the space between the two hulls can be used to store fuel and ballast water. The corrosion of a double hull ship is slower than a single hull ship. This is mainly because the ship has two layers in the hull. The sea water cannot affect both the layers at the same time. This is one primary reason why double hull ships are preferred.

Cost Difference

The cost of building a double hull ship is much higher as compared to a single hull ship. This is mainly because a single hull ship building process is much simpler. This reason often discourages the ship builders to build double hull. However, if you look at it closely the making of a double hull is going to be profitable in the long run. This is mainly because a double hull ship will take a longer time corroding. A double hull ship cannot crack easily either.

The interesting part is that double hull ships have been used in passenger ships for a long time. Even before they were made compulsory for tankers they were used in passenger ships. This was done as double hull ships provide more protection to the ship. One main disadvantage of a double hull ship is that it raises the center of gravity. This is exactly why the ships become less stable. This also reduces the metacentric height. This was one of the reasons of lesser use of double hull ships.

When there is a collision the chances are that a double hull ship will be able to take it better as there is a hull beneath the other hull. However, it has been noticed that in case of high energy collisions many times even the inner hull is damaged. So we cannot say that a double hull ship may be more collision proof. As construction of a double hull ship is expensive so is the repair of it.

We hope that you have understood what a double hull and a single hull ship is. You must have also realized the concept of single vs. double hull ships. They both have their own set of pros and cons. As per the purpose of the ship and the utility of the ship the shipbuilders decide if they should use a single or a double hull. Most of the big ships today use double hulls. The tankers have been told by IMO to use double hulls. Single hulls are preferably not much in use. However, some small ships still prefer to use the technique of single hull.

Image Courtesy: Tokyo Marine

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