ibinews.com International Boat Industry | JUNE–JULY 2019 91
diesel engine can be mounted either
ahead of the transmission, or behind it,
which increases the boatbuilders options.
The process becomes more challenging
for retrofits to yachts that have a
conventional shaft drive arrangement. It
is perfectly possible, of course, but may
require the engine itself being relocated
within the hull.”
The actual steering is carried out by
an ‘industrially-rated’ electric motor
within the saildrive unit. This rotates the
leg via the new ZF Joystick Maneuvering
System. This is designed to operate at
very low speed, and feeds engine power
to the leg via a hydraulic clutch. As with
all ZF joystick products, the speed is
proportional to the movements of the
knob, and the boat manufacturer can
set the maximum parameters for speed
according to the characteristics of that
particular model.
By harnessing the system to a bow-
thruster, the result is drama-free docking,
and well within the boat handling
abilities of a complete amateur. Because
no reverse is required (the forward thrust
is steered around a full circle) the unit can
be used with fixed or folding propellers.
The folding propeller option, never
quite as efficient in reverse anyway, also
optimises sailing performance.
NEW ELECTRIC VERSION
The new electric drive version will dispense
with the diesel engine and replace it with
a 60kW electric motor instead. “This
will be a high-end induction machine
developed by ZF group for Traction Drive
Application,” Perazollo said. “The electric
drive uses the same platform and shares
the same components, such as the power
inverter, that ZF is introducing widely for
construction and road applications. This
allows the growth of ZF’s know-how and
technology in E-Mobility to be applied to
the marine industry as well.”
The current test boat is equipped
with a 60kWh Lithium battery pack with
a dedicated fast battery charger, which
allows up to 22kW of input. This charger is
compatible with the most common types of
EV charging stations, which are increasingly
present as the charging infrastructure for
road vehicles expands. ZF says the battery
pack allows for displacement speeds
exceeding 7kts and a range of around 30
nautical miles.
“The battery pack is positioned at
the stern and is provided with a cooling
system for best performance,” Perazollo
explained. “The drivetrain is positioned
correspondingly and takes the place of
the diesel engine. The electric motor
connects to the ZF steerable saildrive where
maneuverability is further improved thanks
to smooth control of the electric motor
with no clutches involved.”COSTS OF OWNERSHIP
“Saildrives are very popular with OEMs,”
Alberto Perazollo said. “We currently
build around 5,000 units a year, so we
have economies of scale. However, with
this more complex system, the SPP will
probably cost around 3 to 4 times the priceof a conventional fixed saildrive. However,
this cost can be largely offset by not
requiring a bow or stern thruster, although
a bow thruster will certainly compliment
the system with increased ease of use.”
Maintenance issues are also on a par
with a conventional saildrive. “There isn’t
much difference,” Perazollo said. “The usual
service items remain the same – routine
checks of seal integrity and oil levels and
annual anode replacement, and that’s
about it.”
Currently, the SPP is available as the ZF
SD 12 SSP for engines of up to 92hp (68kW).
However, a new generation, the 15 SSP, will
be for engines up to 154hp (113kW).
ZF has long been a pioneer of hybrid
drives, but even with the all-electric version
hydro-regeneration isn’t yet an option, but
we have no doubt that ZF are looking into
it. Currently, a typical installation would
be to a conventional diesel engine with a
bow thruster, one ideally configured for
long run times.IN THE FIELD
One of the first engine companies to
take full advantage of the new system is
Yanmar. A promotional video shows a
40ft Beneteau powered by Yanmar’s latest
common rail 4JH80 engine and packing a
Vetus ‘extended run’ bow thruster.
Engaging the system requires a set
sequence that has to be followed precisely,
including putting the engine into neutral
and then switching on the autopilot to
centre the rudder. However, full engine
power is available during a manoeuvre,
adding extra security when docking against
a strong crosswind or fierce current. The
electric version has the added advantage
of fully controllable revs, ranging from a
few turns a minute to full power if needed.
There will be no noise or exhaust, either,
ideal for early starts from a sleepy harbour.
“Although the new system is a little
bulkier than a standard drive when
installed, we expect the new SPP to prove
very popular, especially with charter fleet
operators,” Perazollo said. “We are already
the sole supplier to volume producers such
as Bavaria, Beneteau and Hanse, and we
see this new system as bringing unmatched
manoeuvring capabilities to the market.
This will encourage more people to try
boating and to discover that berthing a
boat, even in a crowded marina, is a simple
and intuitive operation.” The system is designed for easy installation
The test boat has a 60kWh battery pack
and fast battery charger allowing 22kW input