90 JUNE–JULY 2019 | International Boat Industry ibinews.com
TECHNICAL
PRODUCT SPOTLIGHT | ZF’S STEERABLE PROPULSION SYSTEM
GERMANY-BASED ZF RECENTLY LAUNCHED A NEW SAILDRIVE LEG THAT CAN
FULLY ROTATE FOR INTEGRATED JOYSTICK CONTROL. FROM NOVEMBER,
A FULLY-ELECTRIC VERSION WILL ALSO BECOME AVAILABLE
WORDS: JAKE KAVANAGH
QUITE LITERALLY STEERING its customers
towards ‘a clean and sustainable future’, ZF
has developed a fully electric version of its
new Steerable Pod Propulsion (SPP). The
original version could only be combined
with a diesel engine, but in response to a rise
in hybrid and all-electric leisure craft, ZF will
be launching an electric drive version at the
end of the year, most likely at METSTRADE.
Meanwhile, the R&D team are working on
a new generation of the SPP diesel model,
which will be boosted from its current 80hp
to a more meaty 150hp.
The arrival of the the diesel and all-
electric SPP units is very timely. With the
average production sailing yacht now
around 40ft (12m) and often quite skittish
due to its fin keel and shallow forefoot,
amateur sailors are often quite wary when
it comes to docking. For the motorboat
fraternity, however, systems like Volvo’s
IPS or Mercruiser’s Axius allow a complete
novice to drive intuitively using a highly-steerable and variable-speed thrusters. By
contrast, yachts have traditionally been
restricted to fixed propeller systems, with
only the smallest – and some multihulls- benefitting from steerable thrust via
outboards or sterndrives.
ZF has been making streamlined
saildrives for production boatbuilders for
years and hit on the idea of creating a unit
that could rotate all the way around to
give full directional control of the thrust.
There is actually no propulsion ‘pod’ on
the leg itself. The leg retains its sleek
hydrodynamic profile as apart from the gear
hub, all the workings are inboard. Perhaps
‘Steerable Drive Leg’ would be more
descriptive for this type of product? But
that’s a minor detail as the product itself is a
remarkable piece of engineering.
HYBRID ROOTS
The concept first arrived in a hybrid
experiment with Beneteau in 2009, where
the drive leg rotated and locked into the
forward-facing position when under sail.
This allowed the propeller to generate
electricity more efficiently. The designers
realised just how quickly the unit could
be flipped through 180o (less than a
second), so its potential was exploited.
The new Steerable Pod propulsion was an
evolution of that proven
design.
“We developed the
SPP as a retrofit item,”
explained ZF’s technical
director, Alberto
Perazollo. “For boats that
already have a standard
saildrive – and there
are thousands of them
out there – this unit
would simply slot into
the existing brackets
with minimal modification work required.
In most cases, it would be a straight swap
with plug-and-play connectors. The same
would apply to new builds, where OEMs
could offer this unit as an upgrade option
within an existing design. In addition, the ZF’s new Steerable Pod Propulsion Joystick handling for sailboatersZF’S STEERABLE PROPULSION
GOES FULLY ELECTRIC
The designers
realised just how
quickly the unit could
be flipped through 180o
(less than a second), so its
potential was
exploitedresponsive joystick, but sailboat owners
have been missing out. Now a leading
manufacturer of saildrives, ZF has released
its new Steerable Pod Propulsion (SPP)
system, and it is set
to revolutionise boat
handling – quite
literally.
Steerable propulsion
is nothing new; the
cruise ship industry
has been using it
for years to allow
incredibly unwieldly
ships to dispense with
the need for tugs. The
new generation of
autonomous ships, for example, will feature
steerable pods containing submerged
electric propulsion to allow computers
to manoeuvre with uncanny accuracy.
Incidentally, ZF is also highly active in this
sector, where it provides a wide range of