August 2005 43
Finland
By David Tinsley
Finnish-built Color Fantasy has raised
the benchmark in cruise ferry design,
and a competitively important as well as
technically challenging component of
the quality standard achieved has been
the integrated approach to noise and
vibration issues.
Representing one of the largest-ever
single-ship investments made by a
Norwegian company, the 74,600-gt
Color Fantasy was contracted at Euro
302.5m from the former Kvaerner
Masa-Yards, since reconstituted under
the guise of Aker Finnyards, and is
deployed on the service linking Oslo
with Kiel, Germany. The extremely high
expectations of owner Color Line, for
whom the ship is pivotal to a develop-
mental strategy covering not only the
ferry operation, but also the company's
expanding business in tourism, hotels
and leisure facilities, set particular
design criteria with regard to habitabili-
ty in all conditions.
Custom-built for the short cruise phi-
losophy in application to a scheduled
transportation link, the result achieved is
such that Color Line refers to its new
asset as "the world's largest cruiseship
with car decks" rather than as a ferry. A
second such vessel was ordered this year
not long after Color Fantasy had made
her debut on the 360-nautical mile
crossing.
The new ship was designed to meet
Det Norske Veritas' Comfort Class 1
notation, governing noise and vibration,
using a conventional, twin-screw
propulsion system and controllable
pitch propellers. In a presentation* by
technical specialists from the yard and
propeller manufacturer to the 'Ship
Noise and Vibration Conference' in
London recently, it was claimed that
"The vibration levels on Color Fantasy
are astonishingly low in all the passen-
ger and crew areas, even at the service
speed of 22-knots."
In achieving the highest comfort stan-
dard, the most challenging area proved
to be the a la carte restaurant in the stern
of the vessel, just above the garage sec-
tion. The stern-first navigation that has
to be made at the German end of the
route, in Kiel harbor, also shaped the
owner's requirements as regards
onboard comfort. Furthermore, habit-
ability expectations have to be seen in
the context of a vessel in which the inte-
rior quality, passenger capacity(2,750)
and the number of passenger cabins are
comparable to a typical Panamax cruise
ship.
One of the outstanding technical fea-
tures of the new ship is a three-deck,
nine-m high promenade running for
163-m of her 224-m overall length.
Innovative Kvaerner Masa-Yards, as it
was then, had introduced the revolution-
ary concept of such a huge internal
space in the 58,400-gt Baltic ferries
Silja Serenade and Silja Symphony,
delivered in 1990 and 1991, respective-
ly.
So as to achieve the requisite noise-
and vibration-free environment for pas-
sengers, hull lines and appendages had
to produce the optimal inflow to the pro-
peller, and the propellers had to be able
to absorb the power and deliver the
required thrust at high efficiency, with-
out generating excessive pressure fluc-
tuations against the hull. Minds had to
be concentrated and close cooperation
had to be the order of the day between
the shipyard, the propeller maker and
the model test basin involved so as to
reach these goals.
The Comfort Class notation set a noise
level criteria of under 55-dB in public
spaces and 44-49-dB in cabins, and a
vibration level below 1.5-mm/s for pas-
sengers. The yard and the owner sought
to achieve this standard in normal oper-
ating conditions, over both deep and
shallow water areas, and in all engine
modes. This included asymmetric pro-
files with the four-engine, twin-shaft
installation, where one main engine acts
on one shaft and two engines act on the
other.
Optimization of the hull form for dif-
ferent operating conditions and the
Finnish shipbuilder's development of a
revolutionary wave damping after-
body(WDA) were carried out using
CFD(computational fluid dynamics)
tools. The WDA improves flow, obvi-
ates the typical low pressure area in the
afterbody, and results in the generation
of much smaller waves compared to typ-
ical, earlier vessels. For the Color
Fantasy, several appendage designs
were investigated to determine the low-
est resistance and best wake field to the
propellers.
Pressure pulse levels and propeller-
excited broadband noise are, of course,
vital considerations for a passenger ship,
as they influence habitability. To fulfill
DNV Comfort Class 1, propeller cavita-
tion had to be kept to a minimum, in
particular as regards tip vortices. The
southern part of the Oslo-Kiel route was
an important consideration in arriving at
an overall technical solution, since ship
resistance and propeller loading is
increased in shallow water.
It was reported that, with the good
wake field achieved and with the large
propeller-to-hull clearance incorporated,
equivalent to 40-percent of the screw
diameter, the requirements were ful-
Comfort as a Technological Driver
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