Switched on
Taking a Tesla for a test drive convinced an Aussie sailor to swap his classic yacht’s tired diesel for an electric propulsion system.
An inspired DIYER swaps his boat’s tired diesel for an electric propulsion system – and loves the result.
SWITCHED 0N
Built in 1967, the 28-foot Clipper is an Alan Buchanan design, stripplanked in American mahogany with oak beams. When I acquired her, she wasn’t in great shape. An argument with a floating rope had jammed the prop into the rudder. This twisted the engine mounts and the diesel sat at an unnatural angle. Still, her hull was sound.
As the refurbishment progressed, I realised that the 40hp Bukh diesel was far too big and powerful for such a small boat – it would have to go. But finding a replacement proved tricky. A new engine was too expensive for my limited budget, and I didn’t fancy taking a chance on a secondhand diesel.
Electric propulsion seemed an attractive alternative, but everyone I spoke to offered warnings and cited a lengthy legacy of failed electric installations. So I decided to research the concept – and quickly realised there were a lot of issues to consider: AC or DC? Lithium or wet cell batteries? Weight distribution? What about recharging?
Eventually, though, I decided to proceed. Converting Clipper to electric drive has been a slow and at times challenging process – largely because we live on a small income and had to balance the project’s cost with our lifestyle. But now that it’s complete, I’m delighted with the result.
In the end the total cost was less than A$8,000. The major components were: • A 10kw motor, electronics for the motor,
gear reducer, display unit, speed control • eight AGM batteries delivering 9.5KWH • six 160-watt solar panels.
Electric propulsion seemed an attractive alternative, but everyone I spoke to offered warnings...
FITTING THE MOTOR
Fitting the motor was probably the easiest part of the conversion. After removing the Bukh all I did was line up the shaft and make some mounts to fix the motor in place. The space gained in the process was remarkable – no more crawling around a cramped engine room.
The only engineering required was shortening the shaft, replacing the cutlass bearing and fitting a new stern gland. I left these jobs to the professionals.
Making the motor mounts was particularly easy – I found the perfect solution on Youtube. The old engine’s mounting holes were 19mm – I was using 12mm bolts to secure the motor. To eliminate the possibility of vibration, I used polyurethane resin.
As I held the bolts in position I poured the poly into the hole. It only takes about 90 seconds to set. I made some wooden moulds to hold the gear reducer at the correct horizontal height, then used two turnbuckles to align the gear reducer shaft with the prop shaft.
THE AGM BATTERIES
I was fortunate to source the system’s eight AGMS at the right price from a business that refurbishes old batteries. These were five years old and were previously used in an uninterrupted power supply unit (UPS). They have an estimated five to seven years of useful life left. The batteries weigh 400kg – comparable to the weight of an engine and its fuel.
I opted for the AGMS after speaking to the Teamarrow crew (Australia’s premier solar racing team). They advised that if weight wasn’t a problem, AGMS are preferable to lithium batteries – more reliable and easier to maintain when things go wrong.
Clipper’s electrical system pushes her along at four knots, drawing 15 to 30 amps an hour. The batteries easily allow the motor to draw its maximum of 120 amps an hour.
Easier maintenance was a significant factor in my decision to go electric. Costs are greatly reduced as the motor and reducer only have two moving parts – a diesel has hundreds of moving parts. Our fuel costs are now nonexistent and air locks in the fuel line or dirty fuel/filters are no longer a concern.
A 48V SYSTEM
I opted for a 48-volt system for Clipper.
The electric motor is a 48-volt model and I had to decide between two different electric systems – one 12-volt system for the house with a separate 48-volt system for the motor and its associated electronics, or – a single 48-volt system.
I’m not an electrical engineer and am not qualified to give advice, but the advantages of a 48-volt system are easily apparent. In layman’s terms the system uses four times less current while accessing the same amount of power.
This means you can use smaller diameter wire to run appliances with a high-power specification. The microwave is a classic example. We are only able to run high energy draw appliances because of the higher amperage we can draw from the batteries.
The 48-volt system allows me to run thinner wire from the battery bank in the stern to the bow. Thinner wire is cheaper. There is also less risk of fire and I can run more appliances. I step down the voltage to run the 12-volt wire a short distance to each appliance. Clipper’s electrical accessories include a fridge, microwave oven, slow cooker and even a milk frother for making the best cappuccino.
In addition, there is the great advantage of having a constant power supply with the 48-volt system. The most power fluctuation we’ve had has been 0.2-volt (between 11.9 and 12.1). This is insignificant compared to running a conventional 12-volt system where the fluctuation can be anywhere between 10.5 to 14.5 volts.
With the 48-volt system, the fridge runs more efficiently and the lights are brighter. After all, they are designed for 12-volts – and not 12.7-volts (a common problem with conventional 12-volt systems). And running LEDS at 14-volts requires a heat sink – they are not designed for higher voltages. The risk of fire is always present on a boat and any management of this risk is highly advantageous.
RECHARGING
I purchased a 400-watt wind generator to assess its performance – but it was noisy and dangerous and I quickly decided it wasn’t for me.
Solar turned out to be very affordable. I acquired six 160watt panels for less than $400 – and they’re getting cheaper all the time. This is more than enough to keep the batteries fully charged. Even on a cloudy day the panels do far better than the wind generator.
So far, moored on the Brisbane River, I am generating more power than I can use and the battery bank is fully charged every day. Visiting remote locations is a large part of the sailing experience, and without the fuel concern this is a much easier prospect. Electric propulsion also brings a sense of respecting the fragility of the eco- systems to these remote locations.
Today, going on adventures in Clipper is simply a matter of flicking the on switch. We are no longer constrained by fossil fuel needs, and with our budget, spending money on diesel was a very real limiting factor. BNZ