HULL RESISTANCE TEST IN FLOE OF SYNTHETIC ICE

With the increasing search for energy and mineral resources in cold regions, the performance of ships in ice has acquired growing importance. Laboratory investigations are mostly carried out in model-testing tanks in ice, under various conditions such as smooth and broken ice, and ice ridges. In view of the fact that the major part of the the voyage is made through broken ice, an attempt has been made to test a ship model in an ordinary towing tank using simulated ice, with the object of arriving at a preliminary estimate of ship performance in ice. The test was carried out in the Nagasaki Experimental Tank with a wooden model 5.35-m long, towed through a broken-ice field simulated by plate blocks of paraffin wax. The model was towed first at constant speed with a towing rod, then with a towing wire while allowing the model to surge, and lastly with a towing wire at constant tow force. The tests were made in different ice conditions and ship speeds. Tow force was measured and behaviour of floes adjacent to the ship observed. The measured tow-force values were in fairly good agreement with those calculated by Ryblin's formula. The differences in towing method had no significant influence on the results. Behviour of the floes near the ship was nearly the same as that reported with full-scale ships.