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  • Writer's pictureSarah Whiteford

Knock Nevis: the largest ship ever built

Known by a few names over its 30 year lifespan, the Knock Nevis was the world’s largest self-propelled ship in history. Longer than many skyscrapers are tall, the Ultra Large Crude Carrier (ULCC) supertanker had the greatest deadweight tonnage ever recorded at 564,763 tonnes. It had a displacement of 647,955 tonnes when fully loaded with up to 4.1 million barrels of petroleum, according to gCaptain. Let’s take a closer look at this massive ship and its storied history of name changes, being sunk in a war, refloated, and eventually decommissioned.

Knock Nevis being pushed by tugs. Image from Largest Ship in the World.

The ship was built from 1974 to 1979 at the Oppama shipyard in Yokosuka, Kanagawa, Japan by Sumitomo Heavy Industries (S.H.I.). It was unnamed for quite some time, instead known by its hull number 1016. During sea trials, it had severe vibrations going astern, and the Greek owner refused delivery. After a long arbitration and settlement, it was sold and received the name Oppama by S.H.I. The shipyard made a deal to sell the vessel after lengthening it by a few meters to add 146,152 tonnes of cargo capacity. Two years later, in 1981 the ship was relaunched as Seawise Giant, a pun on “C.Y.’s”, since the vessel was owned by C.Y. Tung, a naming convention used on other vessels like the Seawise University, another ship owned by the Hong Kong Orient Overseas Container Line founder.

Upon relaunch, the Seawise Giant was at its full deadweight tonnage of 564,763 tonnes. It was 458 meters long with a draft of 24.6 meters, or almost 81 feet! The draft is so deep that the ship could not navigate many common natural and manmade waterways like the Panama Canal, Suez Canal, or English Channel. With the massive cargo area, the vessel was “so huge that she would comfortably swallow up India’s largest ship, the 25,000-tonne aircraft carrier INS Vikrant, in her holds”, according to Largest Ship in the World. The length of the vessel ranks it as the longest vessel ever built, putting it in tall company even when compared to land-based buildings. It was longer than the Empire State Building is tall, and approximately the length of Apple Park. It had a top speed of 16.5 knots, taking 5.5 miles to stop from that speed and 2 miles to make a u-turn. A single propeller 30 feet in diameter moves the ship - it weighs 50 tons and is accompanied by a 230 ton rudder for steering. Combustion Engineering designed the 2 Mitsubishi V2M8 boilers that power the vessel.

“Knock Nevis, ex-Seawise Giant (in red) compared to large ships and buildings:

The Pentagon, 1,414 feet, 431 m

RMS Queen Mary 2, 1,132 feet, 345 m

USS Enterprise, 1,123 feet, 342 m

Hindenburg, 804 feet, 245 m

Yamato, 863 feet, 263 m

Empire State Building, 1,454 feet, 443 m

Knock Nevis, ex-Seawise Giant, 1,503 feet, 458 m

Apple Park, 1,522 feet, 464 m”

By Fosnez - Own work using:, Public Domain, Image from Wikipedia.

After being launched twice in two years, the new ship was sunk in 1988. During the Iran-Iraq War, an Iraqi Air Force attack dropped parachute bombs that struck the Seawise Giant while it was carrying Iranian crude oil. It ignited and sank in shallow water, being declared a total write-off. Norman International bought the shipwreck not long after the war, salvaging and repairing her. The vessel was towed from the Persian Gulf to Keppel Shipyard in Singapore, renamed Happy Giant and re-entering service in October 1991. The new name wouldn’t last long as that same year, Jørgen Jahre bought the vessel and renamed it Jahre Viking. It was owned by Loki Stream and flew the Norwegian flag from 1991 to 2004. First Olsen purchased the vessel in 2004, when it was named Knock Nevis and “converted into a permanently moored storage tanker in the Qatar Al Shaheen Oil Field in the Persian Gulf”, according to Wikipedia. It functioned as a floating storage and offloading unit, or FSO, until 2009.

Video from Top Gear about the ship while it was the Jahre Viking.

Amber Development was the last owner of the vessel, renaming it Mont and reflagging it to Sierra Leone where it took its final voyage to India. It was scrapped by Priyablue Industries after being beached on December 22, 2009, finally finishing the scrapping at the end of 2010. The ship’s 36 tonne anchor was donated to the Hong Kong Maritime Museum in 2010 and later moved to a Hong Kong Government Dockyard building on Stonecutter’s Island.

Knock Nevis compared to other large vessels, from top to bottom: Knock Nevis; Emma Maersk, largest container ship; Queen Mary, largest ocean liner; Berge Stahl; and USS Enterprise, longest naval vessel ever built. Image from Container Transportation.

The vessel started out unnamed, later it became the Oppama and then the Seawise Giant. It sank and was renamed several more times to the Happy Giant, Jahre Viking, Knock Nevis, and finally the Mont before being decommissioned. The largest ship in the world survived war after being sunk and rebuilt and never went through the Panama or Suez Canal due to its massive size. A ship like the Knock Nevis may never be built again - with such a deep draught and large size, it was a risky ship to operate. Look for future articles where we'll cover other large ships seen above like the Emma Maersk and the largest cruise ship.

Until then, happy Fun Fact Friday!


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