Atle-class icebreaker
Class of Swedish/Finnish icebreakers
From Wikipedia, the free encyclopedia
The Atle class comprises five icebreakers built for the Swedish and Finnish Transport Agency. The two Finnish ships, Urho and Sisu, are sometimes considered a separate class, but all are operationally identical.[1]
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| Class overview | |
|---|---|
| Builders | Wärtsilä Helsinki Shipyard, Finland |
| Operators | |
| Built | 1974–1977 |
| In service | 1974–present |
| Completed | 5 |
| Active | 5 |
| General characteristics | |
| Type | Icebreaker |
| Displacement | 9,500 t (9,350 long tons) |
| Length | 104.6 m (343 ft) o/a |
| Beam | 23.8 m (78 ft) |
| Draft | 7.3–8.3 m (24–27 ft) |
| Propulsion |
|
| Speed |
|
The ships were built by Wärtsilä Helsinki Shipyard in Finland, and have entered service in the mid to late 1970s.[1] The maneuvering system, incorporating dual rudders and dual bow propellers, represented significant technical innovation. They are also notable for their high level of crew comfort (for their time), to a point where Urho has served the Finnish government as a VIP transport.
Design
General characteristics
Power, propulsion and performance
History
Background and development
By the mid-1960s, it had become apparent that the existing Finnish icebreaker fleet could not ensure year-round access to the Gulf of Bothnia during average winters. Despite the commissioning of the 12,000-horsepower (8.9 MW) Tarmo in 1963, the number of icebreakers was still insufficient and all Finnish ports north of Naantali had to be closed due to ice in the following winter. As a temporary solution, the Finnish Board of Navigation recommissioned the 1907-built steam-powered Tarmo that had been renamed Apu and handed over to the Finnish Navy after its diesel-electric successor of the same name had entered service.[2][3] The following winter of 1966 turned out so severe that, in addition to all ports in the Gulf of Bothnia, even the easternmost Finnish port in the Gulf of Finland, Hamina, had to be closed for some time.[4] On 27 October 1966, the Finnish Board of Navigation was authorized to order to additional Tarmo-class icebreakers.[3] When the diesel-electric Apu was commissioned after a severe winter of 1970, Director Helge Jääsalo stated for the first time in public that from that point onward the goal of the Finnish Board of Navigation would be to keep all Finnish ports open during average winters.[4] This was achieved for the first time during the following winter.[3]
In April 1970, the Bank of Finland Institute for Economic Research published a paper on icebreakers and winter navigation which, while not directly supporting year-round navigation in the Bothnian Bay, recommended expanding the Finnish icebreaker fleet with two additional icebreakers by 1975 and 1–2 more by the end of the decade.[5] Immediately afterwards, teh Finnish Board of Navigation filed a supplementary budget proposal for the acquisition of two 18,000-horsepower icebreakers by 1975. Even though it was clear from the beginning that the Finnish Parliament would never accept the funding for two new icebreakers as a supplementary budget, the Board of Navigation was in fact aiming for the next year's budget which was already being prepared at the Ministry of Finance. The plan worked and funding for the construction of one icebreaker was included in the budget of 1971.[6]
Construction
Until the construction of the 18-megawatt (24,000 hp) Oden in 1988 and the 19-megawatt (25,000 hp) Polaris in 2016, the 16.2-megawatt (21,700 hp) Atle- and Urho-class icebreakers were the most powerful vessels in the Swedish and Finnish icebreaker fleets, respectively.
Replacement
Ships in class
| Name | Flag | IMO number | Contract date | Laid down | Launched | Delivered | Status | Picture |
|---|---|---|---|---|---|---|---|---|
| Atle |  Sweden |
7347627 | 10 May 1971[7] | 10 May 1973[8] | 2 October 1974[8] | 21 October 1974[7] | In service |  |
| Urho |  Finland |
7347615 | 11 December 1970[7] | 19 December 1973[9] | 30 May 1974[9] | 5 March 1975[7] | In service |  |
| Frej | Sweden |
7359668 | 28 February 1973[7] | 3 June 1974[10] | 18 December 1974[10] | 30 September 1975[10] | In service |  |
| Sisu | Finland |
7359656 | 27 April 1971[7] | 31 December 1974[11] | 29 May 1975[11] | 28 January 1976[11] | In service |  |
| Ymer | Sweden |
7505346 | 24 March 1975[7] | 17 February 1976[12] | 3 September 1976[12] | 25 October 1977[12] | In service |  |
