Propulsion and Maneuvering Model Tests of the USCGC Healy in Ice and Correlation with Full-Scale

Propulsion model test results of the USCGC Healy are reported here and correlated with full-scale data. The design requirement for the Healy was for “continuous icebreaking at 3 knots through 4.5 ft (1.37 m) of ice of 100 psi (690 kPa) strength”. The full-scale trials were designed to test this capability. Unfortunately, the ice strength found on the trials was approximately half of that specified. One of the objects of the model tests was to determine the effect of ice strength on the delivered power necessary for the Healy to meet her icebreaking specification. Propulsion overload tests in open water combined with limited ice tests, and the IOT standard method for analyzing propulsion tests in ice, gave consistent results for delivered power, which agreed well with the available full-scale data from the Healy. A correlation friction coefficient of 0.05 was again shown to be appropriate. From the analysis of the resistance and propulsion tests, the Healy, with its total shaft horsepower of 30,000, was shown to be capable of its design requirement. Using a similar analysis, an imaginary “Polar 8” icebreaker of the Healy design was shown to require 85,000 HP to continuously break ice of 2.44 m (8 ft.) thickness, of 500 kPa strength, at 3 knots. Free running maneuvering tests performed in the ice tank gave arcs of circles whose diameters agreed well with the full-scale data of turning circles obtained on the ship trials.