Thyssen-Waas icebreaker concept model tests and full scale trials

Abstract

An icebreaker hull form based on a fundamentally new concept has been developed by Thyssen Nordseewerke in cooperation with the Hamburg Ship Model Basen (HSVA). The concept, originated by Dr. H. Waas, employs a novel icebreaking mode which leads to a considerable reduction in ice resistance and ice loads on hull and propeller. The ice is broken in a defined manner, initially by shearing followed by bending fracture. The broken floes are displaced in such a manner that the propeller area remains free of ice. The new icebreaker forebody has been developed within an extensive research program embracing systematic model tests in ice and open waters and full scale trials with an experimental icebreaker. The objective of the research work is the application of the concept to various marine operations. The research program was carried out in three stages: the definition phase, the optimization phase and the full scale trials. The first phase concerned the determination of the required form characteristics and parameters which were then optimized in the second phase. The experimental vessel used for the full scale trials is the converted icebreaker MAX WALDECK (55 m length, 3100 HP). A foreship section according to the Thyssen-Waas concept was fitted onto the existing hull. The trials were made in the Gulf of Bothnia during March/April 1981 and 1982. The program encompassed test runs in level ice, in brash and mush ice and through ridges. The trials confirmed the model basin tests in all respects. The modified MAX WALDECK demonstrated impressive performance under all ice conditions. The vessel broke ice upto a thickness of 90 cm in the continuous mode; the power take-off was about one third that required by conventional icebreakers of comparable size. Ridges with a total depth of about 8 m were negotiated in only two runs. The low power requirements, the effectiveness in irregular ice formations and the reduced loads on hull and propeller makes the Thyssen-Waas concept a technical and economical viable system for marine operations in arctic regions.