Nine bulk carrier models were tested in the Wartsila Icebreaking Model Basin (WIMB) in Helsinki, Finland. Eight of the models form a series with systematically varying parameters. This test series was the first one in which the influence of bow form, ship length and, ship beam on ice resistance was investigated systematically. The basic form was that of the existing Great Laker SS Ryerson, which was not originally designed for navigating in ice. The other models were modified in order to improve their icebreaking capability. The main objective was to study the icebreaking resistance in level ice, but in addition some tests were made for determining the ice resistance in a broken channel and for determining the steering ability of the models. All models were tested in level ice of 1, 2 and 3 ft thickness and at a speed range of 0–12 knots. Finally, a method for the calculation of the ice resistance and necessary power level of the Great Lakers is presented.