Home' Ausmarine : November 2009 Contents Polyline, specialists in High Density
Polyethylene (HDPE) construction, have
delivered two 10.2-metre line boats to Go
Marine of Port Hedland.
Polyline vessels have typically resembled
RBBs, but these are along the lines of
conventional plate aluminium craft and
were fabricated in much the same way. The
builder is confident that they are the
world's largest conventional design HDPE
boats. A significant difference between
HDPE and aluminium is its ability to take
up compound curves without the need for
pressing, and the line boats have taken
advantage of this property in their bows.
The sister hulls were given different
layouts. One, intended purely for harbour
work, has a centre console and can operate
under the wharf. The other will have a
secondary workboat role, transporting
personnel and light cargo as far as the outer
anchorage. To suit this, it was equipped with
an open-backed wheelhouse, the glass of
which is glued in place. This is the usual
system on aluminium vessels, but it is the
first time it has been used on a plastic vessel.
Aft of the wheelhouse the aim was to
provide maximum clear deck space; this is
capable of accepting up to six pallets with a
total load of over three tonnes.
The design philosophy was to produce
the simplest possible vessels that would do
the job, making the maximum use of plastic.
Handrails use the material, and so do the
bitts that are also lifting points. Even the
central tow post is plastic. The maintenance
cradles are plastic as well, and these double
as transport cradles. They can be used to
launch the vessels off a flatbed trailer and,
since they float, are easily retrieved. The
vessels' beam was held to 3.5 metres to
minimise legal restrictions on towing.
The greatest attraction of HDPE to an
owner is the minimal maintenance it
requires, resulting in low whole-of-life costs.
The material is coloured rather than being
colour coated so paint has no part to play.
Corrosion and fatigue cracking are not going
to happen, and normal wear and tear is
generally less than with aluminium. In
moderate impacts the HDPE flexes rather
than bending, and wear from abrasion is low
due to the material's slipperiness (HDPE is
used for fendering strips on aluminium
vessels because of that property).
Power is supplied by 278kW Yanmar
engines driving Hamilton Waterjets.
Polyline built them special exhaust systems
to suit operations in the high temperatures
Port Hedland specialises in. The bilge
pumps were given extra capacity to convert
the deck wash into a fire pump when
needed. To suit that role, the deck wash
hose has extra length and is carried on a
reel. The bilge manifold is conveniently
under the adjacent coaming.
On trials the Yanmars produced a
bollard pull of 1,870kg, and a top speed of
29.2 knots for a likely cruising speed of 20
knots. They proved extremely fuel efficient,
each burning only 100 litres over the first
seven hours at an average speed of 22
knots, giving a range of over 900nm.
Manoeuvrability was excellent, aided by a
large diameter, specially-fabricated wheel.
Trials were run on a moderate to rough
day, giving the craft the opportunity to
demonstrate typical HDPE behaviour. The
material's properties meant the ride was
considerably softer than hull form alone
could account for, and the noise generated
by the hull was negligible. Engine noise too
was low, reducing one of the factors in
operator fatigue. Hull form presumably was
responsible for the almost total lack of spray.
For further information contact:
Polyline Industries, Western Australia.
PH: (08) 9414 1535, FX: (08) 9414 1452,
'Piparn' and 'Yikara'
Type of vessel:
In survey to:
Other deck equipment:
Work boat / line boat
4 tonnes light ship
1 x ZF280
1 x 322 Hamilton Jet
North Star VHF
Deck wash, towing bollard
Marine carpet, non-slip Poly
1 x RFD 10-person Coastal
3 + 6 special personnel
Focus on WESTERN AUSTRALIA
November 2009 AUSMARINE
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