About SADEP
Fishing vessels, given their small dimensions and hullforms, are particularly vulnerable to sea conditions such as large beam waves, following or stern quartering waves with approximately the same length of the ship or breaking waves, in which cases it is important to be able to calculate accurately their hydrodynamic behavior and its implications on the transverse stability of the vessel.
The hydrodynamic behavior of vessels in such conditions is still more important when towing the fishing gear or hauling it and if the fishing gear is full of fish or becomes fastened to the sea bottom. In that case, the forces applied on the vessel may cause significant heeling and even the capsizing, which indeed constitutes one of the main causes of fatalities in the fishing industry. This problem is especially relevant for stern or beam trawlers due to the large dimensions of the fishing gear which, if fastened or excessively loaded, may cause the ship to broach and capsize. Another dangerous situation occurs for purse seiners, which have to haul the fishing gear through the vessel's side from a point generally located well above the deck, putting in danger the transverse stability of the vessel and leading to an increased probability of falling overboard or embarking water on deck.
Having in mind these problems, this project aims at developing a decision support system for the fishing vessel master, which takes in consideration the prevailing conditions in each moment and provides advice on the following items:
• Verification of the compliance with the applicable criteria, such as the intact stability criterion, the weather criterion, and available guidelines concerning water-on-deck and maximum fishing gear moment.
• Guidance on operational measures to be taken in order to improve the floatability and stability of the vessel.
• Guidance regarding operational measures to be taken in order to avoid dangerous situations in following or stern quartering seas while subject to fishing gear forces or water on deck.
• Guidance on measures to be taken to prevent excessive heeling moments due to fishing gear hauling or water-on-deck.
The guidance provided to the master by the decision support system regarding the above items is to be based in detailed stability, dynamic and hydrodynamic analysis which require advanced stability and hydrodynamics-based software. This software will be further developed and customized for the present type of application, so that it is able to determine the stability and the ship dynamics in dangerous following or stern quartering seas, considering the effect of the towed fishing gear. In this way, more accurate guidance is provided to the vessel master since the proposed system does not merely indicate the compliance with the stability criteria and hydrodynamic guidelines, which represent minimum standards of safety, but aims at a more accurate analysis of the ship behavior in waves. The prediction of the ship responses to wave excitation is also based on estimates of wave conditions determined by a software which determines the directionnal wave spectra from the information of the ship motion sensors.
The onboard computer constitutes the core of the decision support system, since it integrates automatically the data provided by the various sensors using a dedicated computer program, which then calculates the stability and dynamics of the fishing vessel for the current conditions of the vessel.
The results of the stability and hydrodynamic analysis will be displayed in a user-friendly manner, indicating the current conditions of the vessel regarding stability and dynamic behavior, the safety margins and the maximum admissible fishing gear force. The screen shall also display the advised actions to the master, in order to maintain the safety of the vessel during the operations, taking in consideration the loading and sea conditions. The decision support system may also automatically alleviate the tension on the hauling cables when the safety limits are consistently exceeded. This feature prevents capsizing of the vessel, with all the inherent economical and human losses.
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