This paper deals with high speed tests carried out on three
geosim models of a catamaran hull and of its hard chine
demihull, of a trimaran hull and of its round bilge main hull. The
current scaling procedures ITTC 57 and ITTC 78 were applied
with the aim to provide a better understanding of appropriate
resistance breakdown and scaling for high speed single hulls and
multi-hulled vessels.
The approach used for the ITTC 78 procedure consists in
obtaining a form factor for each Fn by iso-Froude method, then,
for each scale, by direct measurement of the wave pattern
resistance by a longitudinal cut method, by examining the Ct-
Cwp curves at high Froude numbers. This approach was carried
out with the goal to obtain validation of form factor determined
by running the model bow down (transom emerged) with
Prohaska and/or Hughes methods, by enveloping versus Rn the
curve of Ct obtained by low speed model tests. In the case of
multi-hulls the form factors should include also the interaction
among the hulls.
A numerical method based on Rankine sources for the evaluation
of the wave resistance and of the wave pattern analysis was also
applied and a comparison with the experimental results was
carried out in terms of wave resistance.
