Reviews
Although the book is entitled Another chapter deals with the to reduce the wash of conventional
‘supercritical’, in fact half the book is environmental impact of ship waves. subcritical ships (some patented) are
about subcritical situations in shallow This is a modern topic that attracts a lot described, but to my knowledge none are
water. However, the book is not about of research work both in terms of how in practical use.
supercritical operation in sea-keeping to design a vessel for minimum wash Reference is made to the phenomenon
terms. but also the effect the wash has on the that wash height differs widely whether
There are seven chapters, and environment (river banks, other users of the craft is proceeding upstream or
pages of theory are interlaced with the waterway etc). downstream, but no explanation is given.
descriptions of ships and boats that This section fails to talk about the truly The failure of the Pacificat ferries in
work in shallow waters; shallow in this low wash catamaran vessels operating Vancouver is also referred to, a problem
context includes the Irish Sea and the in Holland, Australia, and on the River that could ‘easily be solved’ – but how?
HSS ferries that used to ply their trade Thames in the UK, and how they have Trimaran configurations feature
there. Some of the descriptions of ships achieved their purpose. The only clue strongly in the book and there are lots
and their performance are gleaned from lies in the statement: ‘Relative hull length of comparisons with catamarans and
journals and magazine articles therefore should be as high as possible.’ It takes monohulls. Also included are numerous
sometimes the statements have to be some time to figure out what it means model test results. A large section is
taken with a pinch of salt – the reference - relative to what? It’s to displacement, devoted to the effect of shallow water
to SLICE and the Quadrimaran for usually called length-displacement ratio. on the propulsors, using experimental
example. In other words, the longer you make the studies. This relates to coasters and river
Russia, of course, has extensive shallow hull for a given displacement, the lower barges.
waterways which are heavily used by the residuary resistance and the lower the While the term ‘ship motion’ is
both sub- and supercritical vessels, and level of wash. regularly used it means horizontal
some of these are highlighted. The sharp This is actually quite simple; it is a motion through calm water, but there
rise in resistance near the critical speed is shame this is not emphasised as the only is an interesting bit on the motion of a
demonstrated by numerous extracts from practical way of reducing wash that a cargo vessel in waves in shallow water
model and full scale tests. The change in naval architect has in his toolbox, apart compared to deepwater. In fact the book
trim and sinkage is also dealt with in one from adopting a hydrofoil or hovercraft is full of interesting bits. Just forgive the,
chapter. arrangement. Many devices claiming at times, odd translation! NA
The Naval Architect February 2008 107
NA Feb 08 - p105+106+
107.indd 107 05/02/2008 12:32:55
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