Interaction between Brash Ice and Boat Propulsion Systems

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Interaction between Brash Ice and Boat Propulsion Systems

K. L. Haskins / Z. R. Courville / D. S. Sodhi / J. M. Stanley / L. J. Zabilansky

Increased interest and ship traffic in ice-covered Arctic waters necessitates the determination of the range of conditions in which current, small non-ice-hardened vessels can operate and the best operating procedures in ice-covered conditions. A series of tests in varying brash ice thickness conditions were conducted at a range of speeds in the CRREL test basin using a model craft with shrouded and open propellers as well as an intake pumping propulsion system. Results from the testing indicate that boats operating in brash ice fields should operate at slow speeds (5 knots) to prevent increased strain on the outboard motors and possible damage to the propulsion system. Waterjet impellers appear to have greater protection from brash ice than an outboard propulsion system. It was thought that the shrouds would protect the propellers from ice impacts, which they may have done, but a secondary effect was that the brash ice caught inside the shroud area could not be forced away by the propellers as could be done in the open-propeller tests. This could mean that shrouds may still offer protection to the propellers but in a different configuration than the one tested.