An Air Cavity Hull was a hull with a broad cavity full of compressed air which reduced drag and increased efficiency. It was a revolution in surface ship technology.
The hull of a ship was very important. It kept water out, not counting the water needed for drinking. For most of history, the hull of a ship was made of wood. In the 1800s, wood was replaced with iron and, later, steel. The hull was not always full-proof. In 1912, the Titanic sunk in the Atlantic Ocean after striking an iceberg which broke the rivets. The hull of the Titanic was made of steel plates connected together with rivets. Ironically, the Titanic was labeled unsinkable. In truth, there was no such thing as an unsinkable ship. Ships made of steel in the late 20th century were differnt. Temperature control was now very important. This increased the strength of the steel which was now welded. Efficiency was increased. Of course, carbon fiber composites would replace steel in the hulls of ships in the 21st century. This increased efficiency. However, there was one problem with efficiency that materials could not solve. The hull cut through the water which increased drag. The solution was an air cavity hull.
Tech Level: 10
An air cavity hull used a cavity at the bottom of the ship to reduce drag and increase efficiency. The air cavity hull was pioneered by the DK Group, headquartered in Rotterdam, the Netherlands. Air built up in the cavity under pressure. The air was sent into the cavity by a compressor. This also solved the problem of air seeping out. Early versions had efficiency of 7-10%. Later versions had reached maximum possible efficiency of 20%. This, of course, was dependent on weather conditions just like all ships. DK Group also designed a retrofit process that could modify existing vessels with an air cavity hull. All Gerald R. Ford-class aircraft carriers were retrofitted with air cavity hulls. All megaships had air cavity hulls, too. This saved 2 years of fuel at early 21st century fuel prices.