1,721,034 research outputs found
Multi-attribute concept design model of the Adriatic type of fishing vessel
No full textThe latest development of the multi-attribute concept design model of the fishing vessel is presented. A wide data base of fishing vessels made it possible to introduce reliable parameter relations in the design model. The model is aimed primarily at the Adriatic type of fishing vessels with the length of up to about 30 m. Steel, aluminium, timber or glass composites are possible choices for the hull structural material. Weight estimating is based on plating areas and selected building material. A ship cost estimating procedure is developed. A complete new regression analysis of the UBC model series was performed in order to enable resistance prediction of the low length-to-beam ratio hulls, since a large beam is a trend in modern fishing vessels. Freeboard at the bow is analysed and appropriate relations found. Statistical relations of design parameters were developed in order to constrain the model to realistic proportions. The model is included in the multi-attribute design procedure which explores design space and produces Pareto-optimal (non-dominated) designs in multi-attribute environment. Within these non-dominated designs the final design is selected by searching for minimal distance to the ideal design using fuzzy concept to describe the aspiration level, subjective decision making and Chebyshev metric in the decision space
Contributes to sailing yacht performance by foil hydrodynamic lift
No full textSince 2000 foils have been fitted to some racing sailing boats with significant results. Several multihulls as well as high performance dinghies use foils and take benefit from hydrodynamic lift. 2013 America’s Cup was sailed almost entirely over the water by foiled catamarans. Recently foil application has been successfully proposed on mono hull ocean racers with low ballast ratio as IMOCA60 s. The foils used on both racing mono and multi-hulls allow benefits on both motion resistance and transversal righting moment through the exploitation of hydrodynamic lift; the vertical component of hydrodynamic force produced by leeward foil(s) takes place of hydrostatic buoyancy, but differently from Archimede’s static force it increases with square speed. Larger righting moment and resistance reduction due to foils result in higher speed. The paper presents a general review of different foil applications on sailing craft and reports detailed characteristics of the most recent trends
Surf-Riding-Broaching and Pure Loss of Stability vulnerability on Systematic Series D1 Model
No full textThe development of the IMO second generation intact stability criteria is based on a multi-level approach. In each level the accuracy of the analysis is increased and if a possible vulnerability is detected the next level is applied. A ship, depending on its characteristics and external conditions, may be considered vulnerable to one or more stability failure modes. For each of the stability failure modes, the study will begin applying the first level of vulnerability, and in case the ship is considered vulnerable, to one or more failure modes, the second level of vulnerability will be applied to specific mode.
This paper is focused on the first and second level vulnerability assessment of the Surf riding/Broaching and Pure Loss of Stability. After testing the procedure on IMO benchmark ships, these two criteria are verified on the semidisplacement twin-screw round-bilge hull forms of the Systematic Series D, by Kracht and Jacobsen (1992), model D1. This model is representative hull form and service speed of Italian Navy ships and the considered loading condition is taken from the naval ship statistics. These two criteria are analysed for different operational characteristics to evaluate the speed limit
Analisi Teorico-Sperimentale delle onde prodotte da High Speed Craft nel Golfo di Napoli
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Analisi Teorico-Sperimentale delle onde prodotte da High Speed Craft nel Golfo di Napoli
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