Experimental Investigation on Two Displacement Catamarans: Systematic Variation of Displacement, Clearance & Stagger

The aim of this study has been the evaluation of the effects due to the variation of longitudinal stagger, transverse separation and displacement on the resistance of two symmetric hull forms suitable for catamaran configuration over a speed range corresponding to Fn < 0.5. To achieve this aim at the Dipartimento di Ingegneria Navale di Napoli (DIN) an intensive experimental investigation has been carried out on two models in three configurations: monohull, symmetric and staggered catamaran. In particular, for one model, 6 clearances in the symmetrical configuration and 4 longitudinal staggers have been tested; for the other one 3 clearances and 3 staggers have been tested. The influence of displacement on resistance has been evaluated by testing the models for three different displacements

The Naples warped hard chine hulls systematic series

An experimental study was carried out to evaluate still water performance of a Systematic Series of hard chine hulls in planing and semiplaning speed range. Models of the Naples Systematic Series (NSS) were of varying length-to-beam ratios of the parent hull. The parent hull, shaped with warped bottoms, was derived from a pre-existing hull extensively tested in a towing tank. This hull was validated by many work boats built in the last fifteen years. To simplify the construction of vessels with rigid panels (aluminium alloy, plywood or steel) the original hull form was transformed to obtain developable hull surfaces. The models were tested at Re>3.5×106, in speed ranges Fr=0.5−1.6 and Fr∇=1.1−4.3. The series studies the influence of LP/BC and Ⓜ ratios that vary respectively in the ranges of 3.45–6.25 and 4.83–7.49, for two positions of CG. All the models were tested both with and without interceptors. To enable model-ship correlation following the ITTC recommendations, in addition to the resistance coefficients of the models, dynamic wetted lengths and surfaces were provided as tables. To facilitate the implementation of Velocity Predict Programs, all the data (resistances, lengths and surfaces) were also furnished in polynomial form. In addition to the use of series in the design field, this study was done to provide data to improve the numerical simulations of a planing craft. With this aim, in addition to the resistance data, the wave profiles, obtained by wave cuts, were provided to carry out validation procedures

STAGGERED CATAMARANS: EXPERIMENTAL DATA AND FEASIBILITY STUDY FOR ENVIRONMENT FRIENDLY SERVICE

In the last years, displacement hulls for intermediate Froude numbers (Fn<0.6) have been studied at the Dipartimento di Ingegneria Navale of the Università degli Studi di Napoli FEDERICO II (DIN). Amongst the solutions tested, asymmetric multihulls seem to be quite interesting. Particularly, the scarce amount of experimental data available for staggered catamarans led to a research program in the towing tank, to evaluate the relation between total resistance of ship, stagger of demihulls and displacement. In this paper we will present the experimental data obtained in the first step of the carried out research. Particularly, hull performances evaluated for three Length to Displacement Ratios (L/1/3 = 4.62, 5.08, 5.76) and four staggers (6, 10, 20, 30 % of LWL) are shown for Fn < 0.5. The obtained results highlighted the suitability of the studied solutions for inland waterways and especially for urban services, where low environmental impact (wave wash and atmospheric pollution) is growing in social interest. The feasibility of the tested solutions was evaluated through a case study about passenger ferries in urban service. In the paper, general arrangements and cost considerations are presented

A new logic for Controllable pitch propeller management

In this study we want to propose an active logic that, continuously, optimizes the configuration of the propeller and motor speed taking into account changes in resistance and wake. The working principle of the control system is based on the measurement of the torque absorbed by the pro-peller and the engine speed, to obtain the actual thrust and advance speed coefficients. Based on these data, the controller identifies the configuration of the propeller for the best performance of the entire propulsion chain, from engine to propeller. Moreover, in addition to torque and speed limits of the en-gine, the control system chooses pitch angle taking into consideration the propeller’s cavitation