doublehulled

Doublehulled refers to a vessel or structure built with two complete hulls, typically with a void between them. In maritime use, the inner hull carries the cargo and is surrounded by an outer hull that provides protection against breaches and contains any leakage within the space between hulls.

The space between hulls often includes ballast tanks and structural components; the outer hull acts as a safety barrier. The arrangement reduces the risk that a hull breach will result in a spill into the sea and can also improve resilience to grounding and collision.

Regulatory history: In the late 20th century, international rules for oil transportation shifted toward double-hull designs. The MARPOL convention amendments in the 1990s required new oil tankers to be double-hulled, and many jurisdictions implemented additional phasing-out measures for older single-hull ships, with programs under laws such as the U.S. Oil Pollution Act of 1990.

Advantages include spill risk reduction, secondary containment, and easier leak detection and response. Disadvantages include higher construction and maintenance costs, heavier weight that reduces cargo capacity, and greater fuel consumption and structural complexity.

In practice, the term is most closely associated with oil tankers and chemical carriers, where the two-hull design provides a critical barrier against environmental pollution. The concept is part of a broader approach to ship safety and pollution prevention.