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Dispatch 23: Icebreakers around the World

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Peter Lourie

October 14, 2016

Chief Mate Trevor has mentioned before that the date for the Louis decommission has now been extended to at least 2021 and possibly 2023. Maybe living legends can’t live forever. I love the photo I found on the ship’s server of the Louis from a whole new perspective.  The ship’s computers are filled with thousands of photos the crew and visiting scientists have taken over the years, many by one of the crew’s carpenter’s Gary Morgan, who can often be seen around the ship with his professional cameras and lenses.

(Below is a list of some of the Canadian ice-breaking boats operating today, some about to be built.

Strength of icebreakers

Icebreakers and other ships operating in ice-filled waters require additional structural strengthening against various global and local loads resulting from the contact between the hull of the vessel and the surrounding ice. As ice pressures vary between different regions of the hull, the most reinforced areas in the hull of an ice-going vessel are the bow, which experiences the highest ice loads, and around the waterline, with additional strengthening both above and below the waterline to form a continuous ice belt around the ship.

Short and stubby icebreakers are generally built using transverse framing in which the shell plating is stiffened with frames placed about 400 to 1,000 millimeters (1 to 3 feet) apart as opposed to longitudinal framing used in longer ships. Near the waterline, the frames running in vertical direction distribute the local ice loads on the shell plating to longitudinal girders called stringers, which in turn are supported by web frames and bulkheads that carry the global hull loads. While the shell plating, which is in direct contact with the ice, can be up to 50 millimeters (2.0 in) thick in older polar icebreakers, the use of high strength steel with yield strength up to 500 MPa (73,000 psi) in modern icebreakers results in the same structural strength with smaller material thicknesses and lower steel weight. Regardless of the strength, the steel used in the hull structures of an icebreaker must be capable of resisting brittle fracture in low ambient temperatures and high loading conditions, both of which are typical for operations in ice-filled waters.

Where the Louis fits into Icebreaker Evolution

The world's first diesel-electric icebreaker was the 4,330-ton Swedish icebreaker Ymer in 1933. At 9,000 horsepower divided between two propellers in the stern and one propeller in the bow, she remained the most powerful Swedish icebreaker until the commissioning of Oden in 1957. Ymer was followed by the Finnish Sisu, the first diesel-electric icebreaker in Finland, in 1939. Both vessels were decommissioned in the 1970s and replaced by much larger icebreakers in both countries, the 1976-built Sisu in Finland and the 1977-built Ymer in Sweden.

In 1941, the United States started building the Wind-class. Research in Scandinavia and the Soviet Union led to a design that had a very strongly built short and wide hull, with a cut away forefoot and a rounded bottom. Powerful diesel-electric machinery drove two stern and one auxiliary bow propeller.

These features would become the standard for postwar icebreakers until the 1980s.

In Canada, diesel-electric icebreakers started to be built in 1952, first with RCN Labrador (was transferred later to the Canadian Coast Guard), using the USCG Wind design but without the bow propeller.

Then in 1960, the next step in the Canadian development of large icebreakers came when the CCGS John A. Macdonald was completed at Lauzon, Que. A considerably bigger and more powerful ship than Labrador, John A. Macdonald was an ocean-going icebreaker able to meet the most rigorous polar conditions. Her diesel-electric machinery of 15,000 horsepower was arranged in three units transmitting power equally to each of three shafts.

Canada's largest and most powerful icebreaker, the 120-meter (390 feet) CCGS Louis S. St. Laurent, was delivered in 1969. Its original 3 steam turbine/9 generator/ 3 electric motor system developed 27,000*shaft horsepower. A multi-year mid-life refit project (1987-1993) saw the ship get a new bow, and a new propulsion system. The new power plant consisted of 5 diesels/ 3 generators/ 3 electric motors giving about the same SHP.

22 August 1994 Louis S. St-Laurent and USCGC Polar Sea became the first North American surface vessels to reach the North Pole. The vessel was originally scheduled to be decommissioned in 2000 however a refit extended the decommissioning date to 2017. (Wiki)


Canadian Coast Guard

CCGS Louis S. St-Laurent (1969–)

CCGS Amundsen (1979–)

CCGS Des Groseilliers (1982–)

CCGS Terry Fox (1983–)

CCGS Henry Larsen (1987–)

CCGS Pierre Radisson (1987–)

CCGS Samuel Risley (1985–)

CCGS John G. Diefenbaker (2020s–; proposed)

The information about other icebreakers made in China, Finland, France, Germany, Japan, Norway, Russia, Sweden, UK and US is available at

To learn more about Peter Lourie click here.

Last updated: October 7, 2019

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