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The Otso and the Kontio, completed in 1986-87, are the most technically advanced icebreakers in the world. They resulted from committed technical cooperation between the Finnish Board of Navigation and the shipbuilder Wartsila. Economy of operation, high automation, and safety were major objectives in the O/so-class design. Apparently, all have been more than fulfilled.
The new class is diesel-electric powered. A central power station provides both the ship’s propulsive power and all internal energy needs (i.e., heat, light, and electronics power). Because no auxiliary generators are necessary, the entire plant can operate on less expensive heavy fuel oil. The propulsion motors are advanced, alternating current (AC) machinery developed by the Finnish firm Kymi-Stromberg. Motor rpm can be regulated directly by using cycloconverters to alter the AC frequency. Highly automated, computer-assisted control systems allow the main plant to be started and supervised from a control station in the pilothouse.
The Otso’s modem superstructure is a radical departure from recent Wartsila designs. The sweptback superstructure with its stylish color band has replaced the accommodation “blockhouse” typical of the Urho class and several Soviet polar icebreakers. The Otso looks sleek and effluent. Uniquely designed bridge wings extend from the superstructure and provide almost 360° visibility. The ship’s main control point is located in the starboard bridge wing. From here, a single individual can operate this 9.200-ton ship!
The Otso’s modem hull form—developed in Wartsila’s model ice tank—coupled with several innovative auxiliary Rebreaking systems allow the ship to continuously break more than three feet of ice at three knots of speed. Although the Otso carries a twin-screw design, in contrast to the twin forward and twin aft screw-arrangement aboard al1 other Finnish icebreakers, the ship also has the Wartsila air bubbler system. This creates a water-air flow around |he hull that enhances the ship’s icebreaking performance m snow-covered ice. By acting as a thruster, the air bub- mer also adds maneuvering ability. The system uses, at ^st, 13% of the central plant’s power. The air bubbler, me unusual stainless steel belt in the ship’s ice zone around the waterline, and the epoxy paint that covers all Underwater surfaces combine to minimize the Otso’s fric- honal resistance. For difficult ice conditions, such as ridg
ing, and for occasions when the Otso must be extracted from the ice, a traditional icebreaker ballast tank heeling system is available.
Wartsila has developed modular shipbuilding concepts in constructing recent cruise ships and polar icebreakers; these have been incorporated in the Otto-class design. An innovative change from earlier icebreaker arrangements is the location of the diesel-generator sets on the main deck, just beneath the helicopter deck. This allows for a far simpler cable and piping system to the electric motors placed directly below. Heavy fuel oil tanks are located amidships—below the accommodation superstructure, but above the hull plating to minimize the risk of pollution. Habitability is excellent. All crewmembers have single
The Otso________________________________ __ _______
cabins, each arranged well forward of the flight deck and machinery spaces, and above the noise generated by ice and hull interaction. The Otso’s gymnasium, two saunas, day rooms, and separate messes are all carefully designed to maximize comfort and provide recreation during the long winter season.
An articulated tow-lift has been incorporated aft for automatically transferring wire towing cables to the escorted ships. Bridge personnel can operate the lift while engaging the escorted vessel in the icebreaker’s towing notch. This is a prime example of a design innovation that reduces manning, improves safety, and increases efficiency. Such systems permit the Otso and Kontio to sail safely and effectively with a crew of 28, half the number required to operate a Baltic icebreaker a decade ago.
L. W. Brigham
thj1 eat|Jres proved in the Urho class in bre tar1^ 1970s ,ater appeared in the ice- art)a.er designs of other nations. For ex- •tiod C- ^r^o s hull form and accom. atlon block for a superstructure were sballI^,oratC<J in the Kapitan Sorokin, a for .u^'draft polar icebreaker completed iCaj e Soviet Union in 1977. Technolog- dasadvances developed for the Otso ~~m°dular ship construction, mod- ar, aj* othouse and bridge wing concepts, of aVanced hull form, and a high degree deSj„ ornat'on—will surely be used in the °n °f the nuclear-powered, shallow- draft polar icebreakers of the Soviet Taymyr class (under construction in Helsinki by Wartsila).
The importance of Finland’s Baltic icebreaker fleet should not be underestimated. For a small nation intimately linked to the sea during winter, these specialized icebreakers represent an enormous capital investment. They keep Finland’s foreign trade alive in the winter months. They give Finnish shipbuilding and heavy industries a testing ground for innovative technology. These technical advances, in turn, clearly influence the design of other polar icebreakers and icebreaking cargo vessels, particularly those Finnish shipbuilders provide to the Soviet Union. For the Finnish state, the icebreaker fleet is a significant maritime presence in the Baltic, and a key element in the maritime trade policies so vital to a country of limited resources.
A previous contributor to Proceedings and the Naval Review, Commander Brigham is commanding officer of USCGC Escanaba (WMEC-907).
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°Ceedings / March 1987
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