When David Bishop bought a 30-year-old boat, the batteries were dying and the wiring was a mess. He decided to rebuild the nav system using several Raspberry Pis
Back in May 2021, my wife Lydia and I purchased our first boat, a 1994 Dehler 34 called Troppo Bella, and spent the summer exploring the beautiful waters around Conwy. Planning to venture further afield the following year, I decided it was time to rebuild the somewhat vintage navigation station.
With much of the wiring 30 years old and a scant complement of switches, the navigation station hadn’t kept pace with the numerous navigational devices, lights and living comforts that had been added over the years. Unfortunately, half of these additions had since been decommissioned due to faults, including the Navtex receiver, SSB weather fax receiver and autopilot. Sat at anchor using camping lights in the saloon to preserve our fading batteries, it was also clear we had to be able to control power consumption if we wanted to spend more than a night away.
We set a couple of aims for the revamp. Firstly, we wanted to make full use of the existing equipment that was still functional. This included the Furuno GP32 Navigator GPS at the navigation station and the Raymarine C80 multi-function display that was mounted on the binnacle. These devices are robust, waterproof and adventure-ready. Budget was also limited so upcycling what we had, rather than installing the latest navigational tech, was essential.
Secondly, we wanted to use the navigation station to plan and plot a route on screen, push it to the GPS, chartplotter and Navionics on our tablet, and be able to view our progress while sailing. While a laptop could do this job, space at the chart table was tight, plus recharging a laptop would be a hefty draw on house batteries during extended trips. We’d need something small and low power for the job.
But before any of this could be achieved I had to take out the moulded switch panel and instrument board and remove all of the old switch wiring. I was then left with a simple set of power and data wires coming in from instruments around the boat, which I carefully labelled. Realising I had now effectively made the boat unusable, the project suddenly felt epic: there would be no sailing until this project was complete!
The original layout had 10 switches and I calculated that I would ideally like around 30 to give complete control of our power usage. There was no room for ready-made switch panels, so I opted for a collection of individual Blue Sea Systems Contura switches that I could group and mount easily as space allowed.
Having decided we wanted an integrated computer for route plotting, the next step was to decide which one to use, how to fit it into the small space available and where to mount the display.
My daughters and I had already been tinkering with Raspberry Pis, a cheap computer no bigger than a pack of cards, designed to encourage children to learn about technology. These computers are easy to set up and well documented with many free books available from the Raspberry Pi Foundation.
Since their invention, Raspberry Pis have been used by sailors in boat computers for a range of purposes including navigation and autopilot systems, to monitor engines, bilges and tank levels, as well as manage solar power generation. This miniature computer was ideally suited to power our new navigation solution.
To plot a course, display our position on a digital chart and see AIS Targets, I wanted to use OpenCPN chartplotting software with licensed charts from o-charts.org and was delighted to discover OpenPlotter to get me started. This software bundle provided everything I needed, including the Raspberry Pi operating system, OpenCPN and Signal K. This last bit of software can be used to connect up the boat’s instruments (wind, speed, depth, GPS, routing, AIS) and make the data available over WiFi and
so was going to be vital in pushing information to our Raspberry Pi-powered chartplotter and Navionics.
I realised that the decommissioned Navtex box would make the perfect, protected place to hide two little Raspberry Pis; I would use one of the mini computers for getting the instruments to talk to each other via Signal K and another to power my OpenCPN chartplotter.
Like a couple of hermit crabs they were soon installed in their new home. Moving things around on the instrument board I was also able to find a space for a 7-inch LCD touchscreen which could be used for our route plotting as well as reviewing weather information or as an instrument panel.
I hadn’t fully realised how much extra wiring three times the number of switches would create but, armed with many cable ties, I managed to fit it all in and the system was ready for its first sea trial in May 2022 when we set off for the Isle of Man.
The OpenCPN chartplotter and screen proved an immediate hit and we settled into a routine of creating the route on OpenCPN and then loading it via a GPX file into Navionics. In this way all our devices followed the same route and displayed the same data.
Updating the logbook became a quick and easy task, plus both helm and navigator had a real-time view of our progress. We were also really pleased to have the Raymarine C80 we’d inherited fully integrated into our navigation. While we like the portability of the iPad and the clarity of Navionics charts when on deck, in bad weather or when the helm wants to view a simple feed of boat data, the C80 comes into its own. So far so good!
Our onboard power consumption was also back under control thanks to the additional switches I had fitted and we could now keep the depth and wind instruments on while at anchor without the drain of other electronic devices hanging off the same wires.
This switch-per-device approach which was one of the main objectives of the upgrade has had some other unexpected benefits too – if AIS targets stop being received, for example, being able to reboot the AIS receiver without turning everything off and on is a real plus.
I’ve a few more plans for the navigation system, mainly to improve our access to weather forecasts when at sea or in anchorages off the Welsh coast that 4G can’t penetrate. Top of this list is to use it to receive and display in-depth weather information via WeatherFax and Navtex. I think I could squeeze another Raspberry Pi in there somewhere if I needed to!
Reduce the drain
Managing power consumption is key. Modern tablets and phones use a lot more power than you think, especially compared to older purpose-built marine technology. Removing your dependency on them for long trips will give you greater sailing range.
Make intelligent use of your navigation aids. In a storm, tablets and smart phones are not reliable and you may be unable to escape the helm to consult paper charts. Legacy marine navigational equipment was designed for the sea so make sure you have loaded your route in case the weather takes a turn for the worse.
Know your electrics
Most sailors know how to bleed their engine, but few have a working knowledge of the boat electrics. However, depth and wind speed/direction are vital for sailing. Gaining a basic understanding of your boat’s electrics and boat data is a sensible skill for modern seamanship.
Prepare for frustration
Rebuilding my navigation station was a hugely rewarding and exciting project. However, I had never tinkered with boat electrics or boat data before and the process required a lot of learning, dead-ends and frustration along the way as I tried to get devices to talk to each other.
Add extra time
Don’t underestimate the effort and time required to rebuild or rewire your switch panels. This project was only just completed in an off-season and it took many hours of effort.
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