Giant cargo ships are named after the canals and straits they can squeeze through
A freighter's size class is really a map of the bottlenecks it can pass. Panamax, Suezmax, Malaccamax and Seawaymax each describe the biggest ship a particular canal, strait or lock will accept, while Capesize vessels are too large for either major canal and must sail around the tip of a continent.
Each limit comes from a different obstacle. Length and beam decide which lock chambers a hull will fit, draught rules out shallow straits and harbours, and height matters wherever a bridge spans the route. The Suez Canal has no locks at all, yet its Suezmax standard still caps length, and a road bridge over the waterway sets a ceiling on height. The Panama Canal Authority publishes its own rulebook, covering both the older Panamax and the newer Neopanamax dimensions.
Capesize bulk carriers are the heavyweights of dry cargo, typically around 170,000 tonnes deadweight, 290 metres long and 18 metres deep in the water. Barred from both big canals, they pass Cape Agulhas or Cape Horn to switch oceans. The Strait of Malacca, about 25 metres deep, defines Malaccamax, the size chosen for very large crude carriers hauling oil from Arabia to China. Chinamax stretches further still, to 360 metres long, the scale of the Valemax ore carriers.
Some names honour a single port or a pricing system. Q-Max stands for the largest liquefied natural gas carrier able to dock at Qatar's terminals, and these are the largest of their kind anywhere. Aframax, covering tankers of 80,000 to 120,000 tonnes, comes from a freight rate scale that Shell created in 1954 to standardise contracts.
At the top sit supertankers, the largest movable structures people have ever built. An ultra-large crude carrier can hold 2 million barrels, more than the United Kingdom burned in a day in 2009, when it used about 1.6 million. Their distant ancestor, the Uluburun ship of the 14th or 15th century BC, measured just 15 metres yet carried 20 tons of cargo, including 11 tons of raw copper.
Source: Cargo ship
