Roll motion stabilization for small fishing vessels

Weng, Chi (1995) Roll motion stabilization for small fishing vessels. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (9MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

A review of various roll stabilizing systems—bilge keels, active fins, passive bilge fins, rudder stabilization systems, passive anti-roll tanks, active anti-roll tanks, and paravanes—is given, along with a more detailed discussion on their suitability for small fishing vessels. Particular attention was paid to the passive flume tanks and paravanes, and an experimental study was carried out on these two kinds of stabilizers. -- A flume tank model and a pair of paravanes, as well as an oscillating bench simulating sinusoidal rolling, were designed and then constructed. The tank was tested on the bench for configuring the internal dimensions which give the desired natural frequencies, tuning, and damping. The analysis was carried out by inspecting the phase lags εt of the motion of tank water to the roll motion. -- Free roll decay tests for a fishing vessel model with the tank and paravanes were carried out for identification of the damping generated by the tank and paravanes. Non-dimensional equivalent linear damping ratios ζE were calculated and discussed. -- The stabilizers were tested in the wave tank at MUN, both in regular and irregular beam waves, to determine their effectiveness. The study of roll responses, roll energy spectra, response amplitude operators (RAO), and resonant and significant roll amplitude reductions at various wave and stability conditions shows that the tank can provide 50% to 70% roll reductions, which are approximately 30% more than the paravanes can do in the same circumstances. The effects of tuning, liquid level, and internal damping on the efficiency of the tank are discussed. Comparisons in the behaviors of the stabilizers for different wave conditions are also made. -- Some design considerations are presented, and further work is recommended to develop a systematic method to design passive stabilizing tanks for small fishing vessels.

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