Since the major calm-water capsizes occurred in 1965/66,
much experimental work has been done to establish better
operational margins of safety. The general approach has
been to establish well defined limits of manoeuvrability
based upon available model and full-scale data. Mathematical
modelling of the ACV motion was used as a secondary approach
because the expressions involved are high in non-linearities
involving aerodynamic and hydrodynamic force terms of
similar orders of magnitude.
In this study, a numerical technique for the solution
of ACV non-linear equations is proposed and a two degree-of-
freedom model is built up using the digital simulation
language, SLAM. The simulation involved the use uf the
technique of storing values of the various non-linear functions
over a defined regime and then using these to provide updated
inputs as the craft changed its state. An ACV overturn sequence is studied by developing,
simulating and testing of equations describing the roll and
sideslip motion of the craft. In particular, the equations
take into account stiffness and damping forces associated
with both the hard structure and the craft cushion system;
inertial coupling effects due to craft deceleration are also
incorporated; induced trim effects due to the position of
the cushion wave system below the craft is modelled and
suitable phase lag is employed depending upon the deceleration
of the craft.
A basic configuration craft is chosen based upon critical
design parameters such as hull depth, skirt depth, VCG height
and hull angle of inclination. Extensive numerical testing of this
configuration is carried out involving a systematic method
of variation of the critical design parameters.
Results indicate that it is good philosophy to design ACV
hulls with planing capability applied to all faces of the hard
structure. The results also allow a set of ranges to be
established for the critical design parameters, which, if adhered
to will minimise the possibility of capsize for a craft
configuration of the type chosen for the study.
A Masters Dissertation, submitted in partial fulfilment of the requirements of the award of Master of Science of Loughborough University.