How can I decide whether I need a Short Tower DuoGen or a Long Tower version?
Will DuoGen put enough power into my batteries to allow me to run everything on passage?
Is there a 24 volt version available?
Is DuoGen fitted with a regulator?
Can I run my engine while the DuoGen is running?
How does DuoGen in water mode compare with other towed impeller systems on the market?
How much speed would I lose by towing DuoGen?
What are the mounting options for DuoGen?
Where is the best place to mount DuoGen on a catamaran?
Can I run DuoGen's wind turbine in very strong winds?
Is DuoGen compatible with a self-steering system?
How can I decide whether I need a Short Tower DuoGen or a Long Tower version?
The critical consideration when deciding tower height for DuoGen is the yacht's
freeboard at the stern. For the Short Tower machine (actually only suitable
for modern yachts under 30 ft and larger older yachts with very low freeboard),
the pivot point of DuoGen's alternator needs to be between 800mm to 1000mm from
the static water line.
The alternator yoke is reversible and depending upon which way it is fitted,
the alternator pivot point can be raised by 100mm or lowered by 40mm from the
mount point on the yacht. This gives a total range of possible attachment heights
on the yacht of between 700mm and 1040mm for the Short Tower machine.
In the air mode, the bottom of the air blades will be between 2325mm and 2525mm
above the water. The height from the water to the top of the blades will be
between 3425mm and 3625mm. Where possible, we aim for a vertical distance of
2400mm between the cockpit floor and the bottom of the air blades.
The Long Tower machine is 300mm longer in the main tower tube and the specification
we most commonly sell. The alternator pivot point height should be between 1000mm
and 1200mm. This allows a range of possible attachment heights on the yacht
between 900mm and 1240mm.
In air mode, the bottom of the blades is between 2825mm and 3025mm from the
water. The vertical distance from the cockpit floor to the bottom of the blades
generally comfortably exceeds 2400mm. Back to questions
I have the following electrical equipment on my yacht.
Will DuoGen put enough power into my batteries to allow me to run everything
on passage?
Navigation lights
Cabin lights
VHF
Log
Echo sounder
Short wave radio receiver & laptop for weatherfax
Fridge
CD player
Pressurised water
Autohelm (usually only with the engine running - otherwise windvane
steering)
Electric anchor windlass (only used with the engine running)
Assuming an average speed of 5kn, for roughly how many hours per day
would I need to use a DuoGen in water mode? I have 3x 110ah batteries, currently
charged by the inboard engine alternator, via a splitting diode.
With the sort of electrical equipment you list, excluding refrigeration, a
yacht on passage may well see a steady drain of 3 amps during daylight and 6
amps at night.
During a 24-hour period, this equates to about 110 amp hours.
Refrigeration could add a further 50 amp hours per day giving a total of some
160 amp hours, or roughly half of your battery capacity.
At 5 knots boat speed DuoGen would produce a continuous output of 6 amps with
a drag penalty of about 20 lbs which could cost you less than one tenth of a
knot. This equates to 144 amp hours per day and would replace most of the power
being consumed.
At 6 knots boat speed DuoGen would produce 192 amp hours per day, so arguably
the system would only need to be deployed 20 hours per day.
Output in water mode rises very rapidly with increasing boat speed.
At 7 knots 11.5 - 12 amps is produced and at 8 knots 16 amps.
Thanks to the three phase alternator design, the power is also of a high quality
ie. 'ripple free' DC. Back to questions
Is there a 24 volt version available?
DuoGen is available in both 12 volt and 24 volt versions.
Is DuoGen fitted with a regulator? Surely a regulator is required to protect my batteries, especially if the machine is left running when I am away from my yacht.
We can supply a regulator which is of the 'dump' variety which diverts power
from the DuoGen to a pair of resisters when a preset battery terminal voltage
is reached.
The regulator is adjustable between 11.5 and 17V. You set the voltage in accordance
with the battery manufacturer's recommendations and as this voltage is reached,
the regulator progressively diverts DuoGen's output to a pair of large wire
wound resistors where the excess power is lost as heat.
One of the problems with all regulators is that they rely on sensing battery
terminal voltage in order to decide when to start dumping power. Secondary charging
sources such as solar panels can elevate battery voltage and cause power to
be dumped prematurely. For this reason some of our customers prefer to do without
a regulator and actively manage their batteries by referring to their battery
monitor and simply stopping or starting the machine as required. It all depends
on how you use your boat.
A good compromise, which we recommend, is to fit a regulator, but install a
bypass switch. On passage when you monitor the system, bypass the regulator.
When you leave the boat, switch it back on. Back to questions
Can I run my engine while the DuoGen is running?
There is no problem and no risk of damage when running your main engine at the same time as DuoGen. However, if you were running your engine specifically to charge the batteries, isolating secondary charging sources such as solar panels or DuoGen would ensure your engine's alternator regulator or smart charger unit accurately assessed battery state and applied the optimum charge. Back to questions
How does DuoGen in water mode compare with other towed impeller systems on the market?
The major load on all water generating systems is the drag from the impeller.
At six knots boatspeed, a competitor towed impeller system produces just under
5 amps. The
published figure for drag in these conditions is around 35 lbs.
At six knots and a full 8 amps output, the drag on DuoGen is around 25 lbs,
ie. 30% lower drag and 60% more power!
The main reason for the superior performance is that DuoGen does not suffer
from the parasitic drag and losses associated with the 100 ft of rope which
is integral to competitor systems.
Competitor systems are usually mounted by ropes between the upper and middle
pushpit rails. The drag force mentioned above therefore has a lever arm through
which to act.
DuoGen's alternator is usually mounted to a vertical pushpit rail at deck level
where the drag forces are readily absorbed by the yacht.
Some competitor systems are designed around a 100 watt two phase alternator
whereas DuoGen features a three phase 400 watt alternator.
Finally, unlike other towed systems, where the impeller surfaces at speeds much
in excess of 6.5 knots, DuoGen's impeller stays down at higher speeds, controlled
by the integral diving plane.
Operating in water mode, DuoGen is hinged and free to move both vertically and
laterally at the alternator yoke.
It tracks behind the yacht like an obedient dog.
Due to the hinging, there are no shearing forces on the mounting bracket.
Back to questions
I usually sail at an average of 6.5 knots when cruising. How much speed would I lose by towing DuoGen?
In answer to your question about speed loss, not a lot!
Unlike conventional water generators which use a heavy impeller on a long line,
DuoGen's water mode operates in the stern wave of the yacht. Amp for amp, we
have measured over a third less drag from DuoGen than from 'towline' machines.
In terms of speed loss, and by way of example, the smallest of our test boats,
a 27 footer weighing two tons, lost 0.15 - 0.2 of a knot at 6 knots with DuoGen
producing a steady 8 amps.
Clearly with a heavier, more powerful yacht the losses would be even smaller.
Drag does rise sharply with increasing boat speed, but at 6½ knots, your
average passage times won't be greatly effected, and you will be putting a steady
10 amps into your batteries. Back to questions
What are the mounting options for DuoGen?
We produce a universal mounting kit. This contains all that is needed to mount
to most yachts.
The 'universality' of the universal bracket comes from the fact that it is very
adaptable and can be altered in length if required.
Once it is fitted it provides the ideal mount for DuoGen.
Occasionally it is necessary to customise this kit to accomodate, for example,
unusual rail sizes etc. If you have any concerns about the suitability for your
yacht first have a look at the photos on this web site, and contact our sales
staff who can advise.
There is no problem with mounting DuoGen off-centre, but we normally recommend
that where possible the mount should be within 0.8 - 0.9m of the yacht's centreline.
We do supply the system complete and you should not need to purchase anything
else other than a cable gland to bring the cable onto the yacht. Back
to questions
Where is the best place to mount DuoGen on a catamaran?
As with yachts, catamarans vary in terms of size and architecture so as with
most new additions to your boat, it is worth taking some time and thinking all
the options through in order to achieve the best installation.
DuoGen is a new product and as yet we have relatively little experience of mounting
to cats. Most cat owners who have ordered from us are proposing to mount from
the bridge deck, sufficiently out from the centreline to enable the boom to
clear. Others are proposing to mount off the transom of one of the hulls. This
will probably be fine as long the hull doesn't lift!
Example of mounting options for a 41 foot Apache catamaran
Back to questions
Can I run DuoGen's wind turbine in very strong winds?
A strong, steady wind regime produces lots of power, of course.
DuoGen in wind mode is protected by self-furling which reduces wind loadings
whilst maintaining high electrical output. In line with other microturbine manufacturers,
however, we recommend that DuoGen is stopped and made secure if storm force
winds are expected. Back to questions
I am interested in DuoGen, but I have a self-steering
system on my yacht.
Are the two compatible?
There is usually no difficulty in fitting Duogen alongside self-steering systems.
In water mode, the arc of movement of the water impeller falls outside of the
range of movement of the servo paddle.
In situations where contact could occur, we can supply a 'limit pin' which precludes
contact when fitted.
Air mode is generally no problem as:
a) the water mode is usually deployed when the wind steering is operating
b) there is generally clearance between the air turbine and the steering system's
wind vane anyway.
This does mean fitting DuoGen off-centre but as long as the machine is within
800mm or so of the yacht's centre line it will perform well.
For example, we have a customer who has installed DuoGen on an Island Packet
420 which is fitted with a Monitor wind steering system. There are photographs
of this installation here. Back to questions