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That was life on board the 14m Striker-class pilot boat Pania
operated by the Port of Napier soon after she was launched in 1992,
according to Tim Strange and Graham Joy of G&T Marine Installations
in Auckland. Cavitation was also a problem, especially in following
seas and tight turns.
The Pania was one of the three pilot boats
for Tauranga, Napier and Wellington designed by the Dutch naval
architect Guido de Groot and built by Q-West in Wanganui.
From launch day the Wellington and Napier pilot boats experienced
vibration and fatigue problems. "They were deemed "Ear Muff and soft
shoe boats", said Mark Power of Henleys Propellers and Marine.
The Tauranga boat did not appear to be as bad as it had different
diesels to the twin 8V932s fitted to the other vessels and they all
worked in significantly different conditions.
Another problem was that the Wellington and Napier boats were
fitted with second-hand propellers and engines, as the contract
didn't specify new engines, said Strange. "It was not right from day
dot".
Henleys was involved in the project and Power can recall
questioning the design of the underwater appendages" on what was a
very well designed deep-vee hull." Q-West went to de Groot regarding
comments that had been made, and were told that the vessels had been
constructed around the world without problems! According to Power,
Q-West built her exactly as designed, so they could not be held
responsible for any issues which arose later.
The biggest problem was that the underwater appendages consisted
of very big tubes, hanger bearings and poorly designed A-framed
struts. This caused approximately 25 percent shadowing of the
propellers, all of which delivered constant aeration to the
propellers and rudders.
"Even if the Pania was running in a straight line, air was coming
on to the prop, and that caused the cavitation, which created an
intense amount of noise. It was so bad you could be standing up the
front and you'd need earmuffs on. And you couldn't go down to the
steering room without wearing earmuffs", said Power.
The poor water flow and the cavitation actually stripped the
paint down to the aluminium. The struts were not also in line with
the propellers and went through the water sideways which was a huge
problem on its own.
"The poor integrity of the driveline caused a lot of stress for
the guys working on the boats" he said. "The worst part was that in
some conditions on Cook Strait and Napier there were times when the
safety of the boats probably would have been compromised. They were
limited as to how they could operate in certain conditions."
After many years of unsuccessful legal battles, the Port of
Wellington decided to tackle the problem. After spending something
like $250,000 on litigation they decided that it was better to spend
money on engineers and get the boat right.
As the first step, in 1998 Henleys was requested to supply new
four-blade Tiger Propellers to replace the original three blade
props. These significantly reduced vibration on the Wellington
vessel, and also on the Pania. The new propellers solved
99 percent of the cavitation, but the driveline problems still
persisted. The vessel was still only achieving an operating speed of
18 knots, although she was designed for a higher planing speed.
The second step involved G&T
Marine, who realigned the engines and drive train, and fitted new
Henley shafts and bearings.
"As a result, the Port of Wellington
vessel could now be driven without the use to TVA monitors on the
bridge or a welding machine on the wharf!" said Power. "The result
was very good, they were happy."
But it was the old story. "The result
was great, but unless you experience a significant number of
installations, you don't know how much further you can go," said
Power. "We knew that we could take it another step, and as a result,
Napier started to think that maybe it would be a wise investment to
go further with Pania." Power
says that between 1998 and 2002 the Port of Napier had to tolerate
the Pania's problem, as they had insufficient funding to make major
repairs, due to significant port upgrades, including new crane and a
new tug. In 2002,
arrangements were made for a major mechanical overhaul and refit of
the Pania. The first stage was to obtain the original building plans
of the vessel. Tim Strange, Graham Joy and Mark Power executed the
plan they believed would solve most of the vessel's problems.
The overhaul and refit included:
- a full engine rebuild
- a new underwater appendages with
Henley's easiflow tubes, seals, shafts, couplings and P Struts
- a full gearbox service by
Pacific Driveline
- re-engineering of the hydraulic
systems
- the installation of a new
steering system, and
- the construction and fitting of
a new exhaust system
G&T Engineering was contracted to
undertake and oversee the entire refit. The Pania was dry docked on
September 27, and work began. Giles of R&H Giles Tooling Ltd rebuilt
the main engines off site, while all other modifications were
conducted on site at the Port of Napier.
All heavy underwater structure was
replaced and supplied so the waterflow was much cleaner, the
engine beds were reconfigured, and the engine mounts changed from
4 to six points to provide more engine stability.
An excessive number of power take
offs ran off the engines, including a steering pump, and
hydraulic pumps for accessories, and a bilge pump.
These were reconfigured, eliminating
four sets of auxiliaries and belts, which created more space in
the engine room and significantly reduced maintenance levels.
The bilge manifold had completely
rotted and was replaced and several filters were relocated to
improve accessibility and servicing.
The full hydraulic power steering
replaced the power assisted Kenworth truck steering box,
eliminating considerable slop, and making the steering more
positive. The
airconditioning had never operated properly, apart from 10 minutes
each time it was looked at. The condenser was found upside down,
forcing water to go through the wrong way.
"We found some crazy things," said
Strange. "For example, a stainless steel band held the original
exhaust onto the engine. If you took the bands off, the exhaust
would actually blow off the engine, so we eliminated all that." he
said. The new exhaust system prevents any backwash, providing the
Pania with an extra safety margin.
The instrumentation in the deckhouse
was also completely replaced as many controls were obsolete or not
working. The Pania was
relaunched on November 1 under Tim and Graham's guidance. The
improvements resulted in an immediate increase of three knots, and
the pilot boat easily achieved 21 knots.
The marine services manager for Port
of Napier, Keith McIntosh, and the launch master, Chase Rodda,
said they were very impressed with the overall performance and
professionalism of T&G Marine, which had achieved a timely and
cost efficient rebuild of the Pania.
"Our initial concerns of a possible
continuation of vibration and cavitation problems were not
realised", said McIntosh. "The money invested in the rebuild has
given us a new vessel at a fraction of its replacement value."
Power said the Port's $300,000
investment meant they could now operate the pilot boat for another
10 years, rather than spend $1 million on a new boat.
But in Power's eyes the Pania is
still not quite as good as she could be. "If they ever smack their
rudders up we would replace those, because we think they are small
for the boat and the design of the hull."
Power says the team could not have
done the job as well in 1992-93 as was achieved now. "We've got a
bit older and have a lot more experience of how to do these things
better. We didn't eve have through hull struts or the concept of
using resins to install tube and struts.
The work took about 8 weeks and 1500
man-hours to complete, including electrical work. Sea trials
took place in November.
According to Power, Port of Napier barrowed a Tauranga pilot boat,
a 12 m RIB, and had been asked why they were spending money on the
Pania when they could have a new RIB, "They said there was
no way they would ever go back to a RIB. Pania was the best boat
for the conditions with her heavy displacement and deep-vee hull
boat you want to be in. And this is has also been borne out by
Ports of Wellington." He
says the pilot boat project is a prime example of how naval
designers need to better ensure that the quality of the
engineering especially the driveline, is to the same
standard as the rest of the vessel.
"When you're building a boat the
designer is God. If we see something we don't like we'll tell the
designer we don't agree with it, but very rarely will a
boatbuilder go against the designer's specifications."
A designer might try to do the whole
thing himself, or have different companies, from different
backgrounds fo in and do their bit. "They don't care about the
others involved but in fact is it the designer's problem because
if the design isn't integrated, when the owner turns the key it
doesn't work, and the end result is not up to their expectations.
What we've tried to achieve all the
way through is that we get involved in each other's line of work
to ensure that the marriage is perfect and that the owner gets a
long-term result." Sydney
has eight or nine Striker class pilot boats, and Power says his
agents have talked to port officials. "They also have problems,
but we've not taken it further because up until this job we'd only
partly fixed the problem anyway. But we're going to take it
further now, for sure." |
