EXPERIMENTAL AND NUMERICAL STUDY ON PROGRESSIVE FLOODING IN FULL-SCALE

A series of full-scale flooding tests was performed with a decommissioned fast attack craft. Various flooding scenarios were investigated and the floating position and progress of the floodwater were carefully measured. Also air compression inside a flooded tank was studied. The results were used to validate a state-of-the-art numerical flooding simulation tool. A comprehensive analysis of the experimental and numerical results is presented. A good correlation is found, especially when the applied permeabilities and discharge coefficients are properly selected. Finally, the stability of the flooded ship was studied by comparing the results of an inclining experiment and calculations with the lost buoyancy method.

Reliability analysis of GM and KG of ships from the inclining experiment

It is of paramount importance to determine the lightship characteristics of a newly built vessel correctly. Conventionally, an inclining experiment is performed after the ship is launched in order to determine the lightship GM and in turn KG values. However, there has been an ongoing debate about the validity of the results since it bears some assumptions during the test and calculation procedure. Although the inclining experiment is mandatory by the Intact Stability Code of International Maritime Organization, there emerged various alternative methods recently claiming to reveal better results. In this study, an uncertainty analysis has been carried out on GM and KG values of various sample vessels. Based on the results on the uncertainty analysis, a cumulative margin of error from various sources has been determined within a specified confidence level. Finally, the outcome for the sample vessels was detailed and evaluated in reference to that of the actual inclining experiment reports.

Kajian Kecepatan Dan Kestabilan Pada Beberapa Bentuk Kapal Pukat Cincin (Small Purse-Seiner) Di Sulawesi Utara (Study on the boat speed and stability of several Small Purse-seiner in North Sulawesi)

This study was aimed at analyzing theboat technical characteristics covering shape and size, analyzing the boat speed and stability-related capability, and evaluating the speed and stability values based on the present standard. Boat speed determination was done based on the speed length ratio (SLR), andits valuation was based upon the boat resistance value and the boat thrust estimation. The boat stability determination was based on inclining experiment system and the static and dynamic stability calculation. Results showed that three small pure-seiners from Bitung, Manado, and Molibagu had specific shapes, U-button (Bitung) and Round-Button (Manado and Molibagu). The best boat speed achievement, based on shape, resistance, and thrust, was recorded in Manado boat. All small purse seiners had stable balance condition, but only Manado and Bitung boats met the International Maritime Organisation (IMO) standard. Keywords: Speed, Stability, Purse Seiner, North Sulawesi Abstrak Penelitian ini bertujuan untuk: menganalisis kharakteristik teknis yang mencakup bentuk dan ukuran kapal,menganalisis kemampuan dalam hal kecepatan dan kestabilan kapal, dan mengevaluasi nilai kecepatan dan kestabilan kapal berdasarkan pada standart yang ada. Penentuan kecepatan kapal dilakukan berdasarkan SLR (speed length ratio), dan penilaiannya dilakukan berdasarkan nilai tahanan kapal dan estimasi daya dorong kapal.Penentuan kestabilan kapal dilakukan berdasarkan teknik momen system (inclining experiment) dan perhitungan stabilitas statis dan dinamis. Hasil penelitian menunjukkan bahwa: Tiga kapal pukat cincin (small pure-seiner) dari daerah Bitung, Manado, dan Molibagu memiliki bentuk yang spesifik yaitu U-button (kapal Bitung) dan Round-Button (kapal Manado dan Molibagu); Capaian kecepatan kapal terbaik berdasarkan bentuk, tahanan, dan daya dorong kapal dicapai oleh kapal dari daerah Manado.Ketiga kapal objeksmall purse seiner memiliki kondisi keseimbangan yang stabil, namun demikian hanya kapal Manado dan Bitung memenuhi standard IMO (International Maritime Organisation). Kata-kata kunci : Kecepatan, Stabilitas, Kapal Pukat Cincin, Sulawesi Utara.

BACK AGAINST THE WALL

An inclining experiment is the established method used to determine the vertical centre of gravity of a ship. At the same time, the other lightship properties can be found — displacement and the longitudinal and transverse centres of gravity. Only in exceptional circumstances will the traditional method of calculating KG deliver a completely accurate value due to the dependence on wall-sided theory. Although the result may be acceptable for large vessels which tend to be wall sided (or nearly so) at the inclining waterplane, there can be significant error on small vessels which typically have more shape in that region. The problem is discussed and the magnitude of potential error is investigated. An alternative calculation method is proposed, with validity demonstrated by calculation and example. The method overcomes the drawbacks of the classic calculations and allows the evaluation of KG and TCG of any hull form, inclined to any angle of heel or trim. This paper expands on a previous paper, Up Against the Wall, by the author [1].