74 AUGUST–SEPTEMBER 2019 | International Boat Industry ibinews.com
TECHNICAL
SECTOR SPOTLIGHT |
Penta’s sterndrive specialist Jacob Claesson.
“These included total cost of ownership,
a high degree of comfort and what we
call ‘easy boating’. When you drive via a
DPI outdrive leg it should be smooth and
silent from forward to reverse. The old
characteristic ‘clunk’ is now history. This
was made possible by taking out the cone
clutch and replacing it with a well-proven
hydraulic disc clutch from the IPS systems.
The result is silent shifting and a low speed
mode for manoeuvring. By pushing a
button on the joystick, you now have
a low-speed mode offering 50% of idle
rpm speed.”
The lifecycle of the leg has been
improved by adding a gearbox oil filter,
but the most significant change is thesteer-by-wire facility, now standard on
each new unit. “This is a completely new
electro-hydraulic steering system,” Claesson
explained. “The pump unit, ancillary
hardware and software are now part of the
transom assembly – purged and ready to
install. There is no need to run hoses from
pumps at the helm. It is literally plug and
play. Because of the hydraulic clutch and
independent movement of each leg, dual
or triple installations can now be used with
the Dynamic Positioning System (DPS).
This allows the boat to be held over an
exact spot irrespective of wind and tide and
is a key component of auto-docking.”THE QUIET REVOLUTION
The comfort factor promoted by Volvo
Penta is increasingly important when
designing transmissions. Nobody wants a
noisy boat.
“The marine industry is under great
pressure to reduce pollution, which most
people would associate with exhaust
gasses,” said Jean-Baptiste Poussez,
a senior lecturer in yacht design at
Southampton’s Solent University. “In fact,
an underestimated and overlooked polluter
is the noise and vibration from a boat’s
power train. There is a greater need now to
reduce man-made underwater noise as the
impact it has on marine ecosystems is now
only just being realised. A noisy commercial
installation can drive a species out of an
area, affecting their ability to communicateand locate food, threatening entire eco-
systems. In Canada, they refer to ‘whale-
friendly’ equipment, as these creatures are
very sensitive to underwater noise.”
Noise can also be transmitted into
the boat via poor engine mounts or gear
couplings, setting up invasive resonance
that is wearing on the crew. In the
superyacht sector especially, the emphasis
on a quiet ship is now paramount. At last
year’s Cannes Yacht Festival, for example,
Turkey-based Numarine proudly described
their latest 40m yacht as being ‘quieter than
a public library when underway.’
Research continues into how to cut
vibration and noise to a minimum, and
there are already several cost-effective
ways to do this. The first is to put a flexible
coupling between the shaft and the
gearbox, such as those provided by R&D
Marine, Vetus, Aquadrive, Macour and SPW
(GmbH) to name but a few. These absorb
small misalignments between the engine
and shaft and also allow for temporary
distortion due to changes in loading.
“Flexible couplings not only reduce
vibration, but they also act as a kind of
safety system,” explained Alex Frith,
the MD of R&D Marine. His UK-based
company specialises almost exclusively in
this field.
“If you hit a submerged object, the
impact will be taken mostly by the coupling,
rather than the gearbox. Two steel straps
continue to hold the coupling together Volvo Penta’s new DPI drive can now
move independently of its partner in dual
installations, thanks to electro-hydraulic
steeringJEAN-BAPTISTE POUSSEZ, SNR LECTURER
SOLENT UNIVERSITYThere is a greater
need now to
reduce man-made
underwater noise as
the impact it has on
marine ecosystems
is just being realised Independently steered outdrive legs
allow for the use of dynamic positioning. If
a manoeuvre gets out of hand, let go of the
controls and the boat will stay right where it is