ILS commissions:
Conceptual design
Basic design
Ice model tests
Open water model tests
Ship owner:
Finnish Transport Infrastructure Agency
Builder’s yard:
Turku repair yard Oy
Cost-effective icebreaking
DIBB is an invention designed to improve the cost-effectiveness of icebreaking operations. For icebreaking, the DIBB is connected to a pusher vessel. In times of no ice, the pusher vessel can be used for its own specific tasks. The savings achieved in this way are obvious.
DIBB’s propellers are placed on both sides of the stern part of the device, under the so-called reamer areas. The propellers, driven by straight propeller shafts and permanent magnet motors, point approximately four degrees outward from the centerline. The propulsion solution guarantees the combination good maneuverability in ice: the propellers located in the middle part of the combination provide the combination with a large turning moment when they are rotated in different directions. Good maneuverability is naturally a very important feature in escort icebreaking, which above all means assisting other ships. The solution is patented by us.
Two advanced versions of the concept have been made, which have also been analyzed in model tests: a 24 m wide one for Baltic Sea icebreaking, and a smaller, 12.4 m wide one for inland water icebreaking. The suitability of both versions for escort icebreaking has been confirmed not only in model tests, but also in scientific feasibility studies. Moreover, we have developed the third advanced concept for the conditions of the North American Great Lakes in cooperation with Vard Marine Inc.
The first steps in the design of Lake Saimaa’s DIBB were already taken in 2013, when the then Finnish Transport Infrastructure Agency commissioned us to review the future equipment of the Saimaa icebreaker. The review compared a large tugboat, a traditional bulkhead and – as a completely new idea – a detachable bow with its own propulsion mechanism.
Next, we further developed the DIBB concept in cooperation with the Finnish Transport Infrastructure Agency in a project co-financed by the European Union called WINMOS (Winter Navigation Motorways of the Sea). In the concept design, in addition to the two different size categories of DIBB, different propulsion options were considered. In the end it was decided to recommend an option where the pushing propellers rotated by electric motors are located in the rear part of the bow.
The combination of the pusher vessel and the bulkhead forms an icebreaker with a reamer hull shape similar to our designs Fennica, Nordica and Botnica. The advantages of the hull shape in question were verified once again also in ice model tests.
In the WINMOS II project, a smaller DIBB suitable for icebreaking in Saimaa was further developed. Ice model experiments were also connected to this development work. In 2018, the Finnish Transport Infrastructure Agency concluded an agreement for the construction of a prototype of a loose bow with Turku Korjaustelakka Oy, part of the BLRT Grupp. The shipyard ordered the basic design from us. The shipyard handed over the loose bow to the Finnish Transport Infrastructure Agency on 22 October 2020.
