Short and Longer term plans for Instruments, Navigation, Communications, Safety

True to form we are going to be ripping out all the original instruments, after 44 years they are all well past their useful life. Both the speed and depth sensors used holes in the hull (and we are determined to minimise holes!). Nothing is connected to anything else and their were no updates to technologies such as DSC on the VHF radio (allows private direct calls between radios), AIS (potential to receive and transmit details of your boat, location, speed and direction for warnings of potential collisions), or GPS (position). Even the compass has problems as it’s light doesn’t work and there is air inside it instead of oil.

Later we need to get onto other essentials such as navigation lights, as the current ones are all either broken or very UV damaged and none of then are LED.

When thinking about instruments and navigation there are almost an infinite number of options available and the choice can be bewildering. Hence, a very common choice is to fully equip with a range of sensors and multi-function displays from a single manufacturer connected using (for new systems) NMEA 2000 (a wiring and data standard). However, this is way beyond our budget (probably by at least an order of magnitude). The biggest names supplying everything are B&G, Raymarine and Garmin.

Obviously, there are significant advantages in buying a complete set of instruments, and electronics from one company. Principally it should all connect and integrate seamlessly. Installation should be simpler and the learning curve should be reduced.

However, there are disadvantages besides the cost.

  • With a fully integrated system you can only see the output from a sensor (for example the depth) if the sensor, the network, the system cpu and a multifunction display are all powered and working. That is a lot of potential points of failure and potentially a lot of power consumption.
  • Another disadvantage is the extent to which you get locked (literally or emotionally) into a single ecosystem. That means when you decide to add something new (for example connecting to the boat systems using your phone over the Internet) you might find yourself waiting for the one supplier to add this feature or unlock it for others to connect to.
  • Until you start connecting items from other manufacturers you can never be quite sure how standards compliant the system is. So if a sensor breaks do you buy what is available locally or wait until you can get something from the same manufacturer?

At the other end of scale are the cheap but not connected products. For example you can have  standalone depth sounder (sensor and display), a GPS, a VHF radio with AIS that doesn’t share the data with anything else.

In the middle are options to buy individual items that can be connected using a standard interface (most commonly now NMEA 2000). This way you can start with specific paired sensors and displays (such as wind speed and direction) that can later be connected to other things. With some skill and luck you can mix and match from different manufacturers.

Once you have fully integrated instruments and navigation you can have a big chart plotter screen that doesn’t just show the chart and your position but adds radar overlays and AIS targets and predictions based on wind speed/direction (current as well as forecast), even camera views can be added. But at this point you have gone beyond the data speed/capacity of NMEA and are needing to look at using WiFi.

That brings us to some leading edge developments that are starting to bring in new competition and disrupt the marketplace. Principally Bluetooth LE, WiFi, 4G and solar.

An obvious example is to have a solar powered, wireless wind sensor for the top of the mast. This is potentially much simpler and more reliable than running data and power cables in the mast. The traditional companies now have these. However, they typically wirelessly connect with a proprietary protocol to a little black box that is physically connected to the NMEA 2000 network. As far as the rest of the system is concerned it appears exactly the same as a wired sensor. An alternative is skip a few technological steps and use other standards, such as Bluetooth. This means you can have a solar powered, wireless wind sensor that connects directly to your phone which displays the data using your choice of app. No NMEA network, no other devices needed.

Also there are more options than just the proprietary NMEA standard. For example there are black boxes available that connect to NMEA 2000 and make the data available over open Internet standards (both WiFi and wired). The Bluetooth sensor companies are also adding black boxes that connect their devices to NMEA.

Another development is to bring the Internet culture of Open Standards and Free Software, that can run on a variety of different hardware, to the marine instrument and navigation arena. Two notable examples are SignalK (an open standard that replaces NMEA and runs on Internet standards) and OpenCPN which is a free/open navigation tool (runs on many operating systems and also phones).

At this point these are not really mature consumer options, they require a fair bit of DIY (potentially to the level of soldering circuit boards), some familiarity with system setup & administration and even programming.

Given the constraints of our budget and time, the lack of anything to build upon, we have decided to get afloat with the things we see as essential, have them mostly standalone with goals of low cost, reliability, simplicity, low power consumption and the ability to add more DIY functionality later.


Compass: New bulkhead compass to replace the original “Big Ben”. Not connected to anything but a light (at the end of the day a compass, a watch, a sextant and paper charts make a safe fallback situation that should be available even after a lightning strike)

Depth: Our first choice would be an in hull depth sensor (no hole in the boat needed) with a dedicated screen (with features such as a shallow water alarm) plus interconnection potential so that in the future  we could check the depth on our phones while ashore (in case we have miscalculated the tides and we are about to go aground, could also be that the wind changed and blew you into shallower water). Unfortunately, I haven’t found this combination so we will probably go for the Nasa Clipper Depth (approx £130) which doesn’t have any connectivity options at the moment.

Wind Speed and Direction: We want a wind instrument that uses a solar powered, wireless sensor at the top of the mast – that means one less wire in the mast, and one less hole in the deck to leak (hence a much simpler installation). This eliminates one of the most common causes of problems (the wire or the connections) and must surely reduce the chance of lightning taking out all your instruments. We want it’s own dedicated display for installation simplicity and to increase reliability by keeping the number of points of failure down. However, we also want the option to be able to connect it to other devices in the future. That allows better information on the chart plotter. Much more than that, by connecting NMEA to our Raspberry Pi systems (probably via SignalK) we can connect phones locally using wifi and remotely via 4g over the Internet. Not only does that let you to display things on your phone such as a graph of wind direction and speed over say 24 hours, but it also lets you pick that up while the boat is anchored and you are shopping. Then you can see if there might be a problem coming (is there a wind increase that will make it harder to get back in the dinghy? Or might your drying laundry be about to blow away?). The Clipper Wireless Wind (True) looks a good initial option (but only Nasa themselves seem to be selling the True wind version at the moment at £373) . While we would not have the true wind display initially, it would be available once we connect it to NMEA with a GPS device also connected. An alternative would be the innovative solar, Bluetooth LE but it is over £100 more and we would have to use a phone as the display until we have a connected computer display.

No speed: We are not going to have any measure of speed through the water. It always requires a hole in the boat so we are ruling it out. We will rely on GPS (and there are going to be multiple GPS systems). These can now use multiple satellite systems which improves reliability. They don’t allow us to directly see the effect of tide or current but we feel this is something we can live with for reliability (the paddle wheels used in the ones we could afford are vulnerable to damage and growth) and safety (look at the Sailing Zingaro where he nearly sank his Oyster because the speed sensor leaked and note that he should have also had a working bilge water alarm and automatic bilge pump as we already have ready to install).


Initially we are going to use our phones and Android tablet. There are plenty of apps that we can use. I’d like to start with OpenCPN which is what we eventually plan to run on Raspberry Pi computers.

While I have most of the stuff to setup the Raspberry Pi navigation system (and there will be lots to write about that in the future) I doubt I will have time before our first launch. Maybe it will be a project whilst we are out sailing on my sabbatical – but I don’t want it to be something we rely on without a lot more time to develop and test it. Even then I’m not planning to have it as the only way to view instruments or navigate – just too risky.

In the long term though the plan is for a “chartplotter” in the cockpit that can be seen and controlled when steering. It will be powered by a Raspberry Pi 4 below decks controlling a 15.6″ touch screen (with the option of bringing out a wireless keyboard and mouse in suitable conditions). This will display a chart with the boat position and AIS overlay. So it will be used primarily for live navigation.

We will have another Raspberry Pi 4 below, using a 21″ TV as it’s display (again a wireless keyboard and mouse). This will be able to function as a chartplotter (principally for planning, backup and keeping an eye on things when nipping below when on watch). It will also run our entertainment, office and editing software. We will have a 3rd system (with a more basic screen) pre-configured and up-to-date that will be wrapped with a battery in multiple layers of foil and plastic that will act as a Faraday cage so that it should survive a lightning strike.


We do have a basic handheld VHF radio which we will keep for emergencies and dinghy to boat communications (bit with mobile phones likely to be the preferred option if there is a signal).

We will add a fixed VHF radio with DSC and a new aerial. Possibly something like a basic ICOM IC-M330GE for around £200

We will setup a WiFi network for the boat and eventually we would like to add a full 4G mobile connection to that using big aerials to pick up a mobile phone signal several miles offshore.


AIS: We will install a minimum of a full Class B AIS system that both transmits and receives. We are looking for models from Digital Yacht that provide a WiFi interface (simplest for both our Android devices and Raspberry Pi’s). So at the budget end an iAISTX for £522.00

I think that if we upgraded to the iAISTX plus version (£642) which has an NMEA interface then it should be possible to connect the AIS to the VHF DSC system allowing you to pick a target and directly connect to them on the VHF using DSC. So if the AIS tells you that a ship will collide with you 5 miles ahead then you can call them to ask what they plan to do about it. Without this you can find the call details on the AIS and manually put them into the VHF (tricky if it is rough and you are stressed/tired and the wind is changing etc).

If we could afford it I would like the Digital Yacht Class B+ device as it transmits at twice the power. Hence, we would be detected by ships at a much greater range than 8 to 10 miles as well as more reliably in very busy areas with lots of signals. However, the AIT5000 with WiFi is £1,074.

Whichever AIS we get, we will add a Man Overboard alarm and Man Overboard devices to our life jackets. That means if we fall into the water an alarm automatically goes off on our boat (and any others within range) and the chartplotter will show the position of the person in the water so that you can find them again.

The AIS will probably use an aerial splitter so that it can share the aerial with the VHF radio.

Radar: For the foreseeable future radar will remain on our “would be nice to have” list. Cost is approaching £2,000 for the radar dome, mounting bracket etc. OpenCPN already includes support for a growing number of Radars so you can see the radar scan on top of the chart (makes it easier to work out if the radar image is showing land, rain, a ship or a buoy). For collision avoidance we think AIS is much cheaper, it gives much more accurate and detailed information, however not all vessels have it. Radar is great for fog, rain squalls and navigation in busy waters at night. Radar is much better for detecting fishing boats (who frequently don’t want to advertise their position on AIS).

At first launch

So we will have the following before we launch:

  • Compass
  • Depth with dedicated display
  • Apparent Wind speed and direction with dedicated display
  • 2 phones and a tablet all with chartplotter software and charts (with waterproof cockpit mounts and USB charging)
  • AIS class B (displaying on the phones and tablet) with MOB alarm
  • AIR MOB transmitters for our life jackets
  • VHF radio

Medium term

  • connect the devices that support it, with NMEA 2000 (gives true wind on the Clipper Wind, AIS integration with the Radio (including MOB support)
  • Raspberry Pi 4 powered chartplotter in the cockpit
  • Raspberry Pi 4 powered chartplotter, office and entertainment in the saloon
  • Spare Raspberry Pi system in Faraday cage

Long Term

  • Long range 4g connection for the whole boats WiFi
  • Additional sensors and monitoring through a web interface on all our devices anywhere as long as boat and we have an internet connection (battery state, solar, motor temperature, tanks levels, bilge pump alarms, lots of environment data such as temperature and humidity etc)
  • Mast mounted forward looking camera with night vision for watch keeping
  • Security cameras
  • Radar
  • Long range WiFi connection for the whole boat (as free WiFi comes to more places)
  • Extra Raspberry Pi powered screen in the cockpit for a customised dashboard next to the chart (wind, depth, battery, solar, cameras, AIS text).
  • Automation (alerts to phones, full management of solar power including control of dump power – eg heat water, run dehumidifier, electric blankets, boat heating)
  • Add PyPilot software to control original electric autopilot motor

That should be enough to keep us going for a while and also plenty to spend our entire living budget for several years  – which gives an idea of how much of it will happen 🙂

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.