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Powercats – the way of the future?
Is it easier to stand on one leg or two?
Boaties
the world over have always been very traditional in their attitudes to new
design concepts, and nowhere more so than here in New Zealand. We are wary,
suspicious and at times downright cynical when faced with a new boat concept
that is somewhat different to what we have always accepted. There have often
been good grounds for these attitudes for many a new concept has flopped,
sometimes through unflattering performances, but often through poor
engineering and construction.
The
development of power catamarans (now commonly called powercats) has been a
typical example. Tales of split hull joints, smashed wingdeck sections and
hard pounding into head seas did little to encourage boaties to join the
multihull brigade in the latter quarter of last century. The evolution of
powercats, particularly in New Zealand, was slow and painful, though many hung
to the belief that these craft were the way of the future.
Many
amateur efforts, at both design and construction, produced some aesthetically
‘unappealing’ craft, but in some you could not fault the performance
outcomes.
Several
of our professional designers recognised the potential of powercats and thus
began an evolution that has seen large numbers of these boats not only
cruising our coastlines but venturing across oceans as well. Today, a
well-designed and built powercat holds it value exceptionally well, a
testament to the many factors that give it significant advantages over the
traditional monohull vessel.
It
is timely to examine the differences between the two hull forms and endeavour
to find some justification for the often repeated sayings, “once you’ve
had a cat, you’ll never go back to a monohull!” or “if its not a cat
it’s a dog!”
Firstly,
let it be said that all boats are compromises. What suits one person does not
necessarily suit another – for a multitude of obvious reasons. However we
can explore a number of the characteristics of each boat type that can be
measured or quantified.
STABILITY
A
powercat’s twin hulls focus the buoyancy around the outside of
the boat, rather than in the middle, creating much greater stability.
Very beamy monohulls do exist and they can be a pleasure to sail in. They do,
however, produce a much greater wetted surface, which produces more drag and
consequently affects fuel economy. The flatter deadrise of a beamy monohull
also compromises its rough water attributes and dryness from bow spray.
Underway,
a well-designed powercat, whether of a planing, semi-displacement or
displacement hull type, will produce a much smoother and stable ride than the
average monohull. (Note: Some very heavy, and some narrow hulled displacement
monohulls can give exceptionally smooth rides but other factors, like
excessive rolling, nullify the benefit.)
A
powercat at speed gains lift and cushioning from spray and air being pressured
through between the hulls. As well, there is the obvious advantage of two
narrow hulls slicing smoothly through the waves. Think of the benefits when
cooking, when travelling long distances, and when striving for a good
night’s sleep!
SPACE
More
beam means more useable space inside a powercat, and around the decks. Without
the ‘pointed’ shape of the bow of a monohull, a powercat gains
considerable deck space forward.
The
wingdeck area does encroach into a powercats internal accommodation but
designers have found very clever ways of getting around this, more often to
the boat’s advantage.
Two
hulls also offer greater use of underfloor areas – all space can be used for
berths, tankage, refrigeration and accessible stowage
ECONOMY
Few
boaties would argue against the desire to own a fuel efficient boat. Published
trials have shown that between a planing powercat and a planing monohull there
is very little difference. The cat takes a little more power to get up on the
plane but then tends to run more efficiently. However the powercat with
displacement hulls is a different beast altogether. Depending on the hull
sizes it is not unusual for ultra efficient speeds well in excess of 20 knots
to be achieved in the economical displacement mode. Hence the proliferation of
large catamaran ferries in service all over the world. Fuel economy is a major
consideration when running any business!
LOAD CARRYING
These
same ferry owners recognise that powercats are able to carry much greater
loads without significant loss of stability or performance. Overload a
monohull and you may unleash an unstable monster, a fact demonstrated in some
third world countries where overloaded monohulled ferries tragically overturn
on a regular basis.
PRIVACY
FACTORS
Few
boaties must enjoy sleeping in forward cabins of boats with others (apart from
partners) a mere metre or so away. The noises and odours of nocturnal
activities can often be unsavoury to say the least. With a powercat there is
at least the separation of the hulls to insulate against these unpleasantries!
MANOEUVRABILITY
In
terms of costs, it can be deemed a disadvantage of powercats that they require
two engines – one in each hull. However apart from the safety factor of
having a ‘spare’ power source should one engine fail, there is the huge
advantage of having exceptional manoeuvrability. Few other characteristics of
a monohull turn people off boating more than the struggle to berth a
single-engined monohull launch on a windy day. A powercat will out-perform
even a twin engined monohull simply because the props are so far apart.
If
you cannot spin a powercat 360 degrees within her own length, you should
seriously consider giving up alcohol.
DRYNESS
Under
way you cannot beat a powercat for dryness. The days of gallons of water
sluicing across your windscreen when in a beam sea will be gone forever. The
narrow hulls slice through the water throwing minimal amounts of water up for
the wind to toss back at you, whereas many monos, at even moderate speeds,
tends to throw large amounts of water much further out to the side, and up,
for the wind to catch.
HAULOUTS, MARINAS AND
BEACHING
Powercats
over about 12 metres do have problems with the odd travel lift operator either
because they are two wide for the hoist, or the operator’s slings are too
short. That aside, the yards like them because they can be sat on blocks and
require no lateral support. Smaller powercats with legs or outboards can even
be beached.
Finding
marina berths is generally not a problem. Unless excessively beamy, powercats
merely fit more snugly into a berth and utilise the whole area.
COST
Because
of the need to build two hulls to create a powercat, the building costs will
be greater than the monohull of similar length. However, the lengths of the
two boat types do not equate in terms of space. It is said that a 10 metre
powercat equates in size more to a 12 metre monohull, a 12 metre to a 15 metre
and so on. Hence, if your purchase is based on available deck and internal
space, the powercat will actually be cheaper when lengths are compared.
Granted,
a second engine does effect the costings, though these days twin installations
in all power boats over 12 metres is almost commonplace.
SEA TRIALS
The
ultimate test as to the merits of a powercat is a sea trial. When you are
belting through a short 2 metre sea at 20 knots, there is no spray lashing
against the windscreen, Mum’s leaning back reading a book, and the beer
glass in your hand does not threaten to smash your front teeth each time you
sip, then you will understand why powercats will soon rule the waves!
Here at Alloy Cats, we are prepared to show you these
features - in real seas!
Copyright Alloy Cats (NZ)
Ltd
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