Electronics

Speedwell has collected various electronics and navigation equipment over her life. We upgraded most of these systems during the winter of 2009/10.

Sailing Instruments

When we bought Speedwell she was fitted with B&G speed, depth and wind instruments. Despite probably being 20 years old these are good quality easy to read displays but there were a couple of shortcomings:

I contacted B&G who suggested upgrading the digital display unit to a newer model with NMEA output and changing to a new log impeller with a flap valve in the skin fitting. That seemed like a nice solution so I started to look for quotes.

It proved to be difficult to find prices for B&G instruments on line. B&G suggested contacting Diverse Yachts but they didn’t reply to my emails. I did manage to get a quotation from Fox’s chandlery, but the price for the two upgraded items was practically the same as the price for a complete set of brand new instruments from Raymarine. I got the impression that B&G are not widely stocked so there’s not much price competition.

Although an upgrade of the B&G instruments was possible I was concerned that the bulk of the system would still be 20 years old and so may well be reaching the end of its useful life. That would lead to a round of upgrades, with what were turning out to be expensive instruments. So I decided to remove all of the B&G equipment and fit new Raymarine ST60+ instruments. Fox’s electronics gave us a good deal to supply the instruments and fit the transducers.

Our sailing instruments are fitted over the main hatch and we’ve got space for a row of 4 displays. We decided to fit separate displays for speed and depth (rather than a combined display) to give nice clear displays and also to allow the depth sounder to be turned off if it interferes with the forward looking sonar . We have a single wind display (previously we had separate wind speed, direction and close-hauled direction) and the fourth slot contains an ST60+ Graphic that we can configure to display any data that’s on the instrument bus (we usually have this displaying speed over ground).

Radar and Plotter

The original chart plotter and separate radar were both functional but rather old. I’m sure that we wouldn’t be able to get up to date chart cartridges for the plotter so clearly an upgrade was a good idea. On our previous boat we had a single unit handling the plotter and radar. We found this to be a nice solution, overlaying the radar on a chart display is a great way of double checking position in poor visibility and of putting radar contacts in context with the topography (especially amongst the sandbanks of the Thames estuary), so a combined display was the way to go.

There’s no way that a modern plotter display will integrate with a 20 year old radar scanner so we bit the bullet and ordered a new scanner.

As we’ll mostly be sailing short handed we wanted a display in the cockpit as well as at the chart table. Sailing in poor visibility it’s really nice for the watch keeper to be able to see the radar without having to go below decks. The cockpit plotter can also act as a display for the forward looking sonar, so we needed a system with video input that could support dual station operation.

We settled on a pair of Raymarine C90 Wide displays. One is fitted at the chart table and the other is under the windscreen in the cockpit. The C-Wide series displays work with Raymarine’s digital scanners so we now have a 18” digital raydome on our mizzen mast.

On our previous boat we found the MARPA function struggled in choppy seas because the flux gate compass wasn’t giving a stable enough heading reference. For Speedwell we’ve fitted a new autopilot that includes a rate gyro so we get much better heading reference that give more reliable MARPA results.

The cockpit mounted plotter has turned out to be really useful in practice. On passage it provides route information without having to go down below and for collision avoidance having an AIS and radar display visible to the helm has made life less stressful. For pilotage the plotter provides a plan in the cockpit (though we don’t rely on just the GPS position for close work) and we can have this in split screen mode with the forward looking sonar display to check for unexpected rocks. The 9inch diagonal screens of our plotters are the smallest in the Raymarine C-Wide range but we’ve found that this is large enough for the cockpit plotter, except possibly in split screen mode with the forward looking sonar when a larger size screen would probably make things clearer.

The plotters have built in GPS receivers, but we use the AIS transponder as our primary GPS source. The cockpit mounted plotter gets a good fix on its internal receiver so that gives us a back-up position fixing system (the plotter at the chart table can struggle to get a fix on its internal antenna).

There is a good range of interfaces on each chart plotter, including Rayamarine’s various flavours of SeaTalk and three NMEA ports, so we’ve been able to interface all of our systems together without any specialist interface equipment, although I needed to experiment a little with connections to get it all working (the best set up seems to be to use one plotter – in our case the chart table one – as a data hub and have everything wired to that, except that video has to go directly to the plotter on which it is displayed).

AIS

AIS is a great tool for collision avoidance, especially in areas of heavy shipping like the TSSs in the North Sea. Or original plan was to fit an AIS receiver but when I contacted Digital Yacht to find out about their systems they mentioned that they had some ex-display Class B transponders for sale at much the same price as their standard receivers, so I bought one of those.

A class B transponder is required to have its own GPS input so the Digital Yacht unit came with a GPS antenna and can provide position data to the chart plotters. Because of this there was no need to buy a dedicated GPS receiver, which helped to save some cost. The GPS antenna is a small button unit that is mounted in the aft deck (rather than on a rail mount where it would be vulnerable to snagging in ropes).

The AIS transponder has a dedicated VHF antenna mounted on the mizzen mast (the VHF radio-telephone antenna is on the main mast).

We’ve found AIS to be a useful tool, giving good information about large ships (and letting us measure our performance against AIS transponder equipped yachts for a bit of fun). Because ours is a transponder we’re also visible to other vessels (although whether or not commercial shipping pays much attention to this is an open question) and friends can follow our progress on AIS reporting web sites like marinetraffic.com .

Forward Looking Sonar

We enjoy exploring out of the way places and finding small anchorages, so we’ve had an Echopilot forward looking sonar fitted. We chose the FLS Platinum Video system and use the cockpit plotter screen as the display. This gives us a big display that can read from anywhere in the cockpit and avoids the need to find space for a dedicated FLS display.

Echopilot systems use the same ultrasonic frequency as Raymarine depth sounders so there is the potential for interference between the two systems. Because we’ve fitted separate displays for speed and depth we can turn off the depth sounder if it is interfering with the FLS when we’re gunkholing or turn the FLS off and the depth on when we’re on passage. In practice we’ve not seen much evidence of interference between the two systems.

In our first season since the re-fit we’ve been using the FLS when piloting into anchorages on Scotland’s west coast. The pilot books for this area give good detailed information about approaches and leading lines so so far the FLS has just been there for reassurance that we’re in good water but it has been nice to have in some tight spots.

The display is fairly easy to get used to, although the graphics are a little old fashioned. It can be configured with the horizontal offset from the bow to the sensor so that distances off are measured from the bow but there is no depth offset so it always displays depth below sensor (I would prefer to have a depth below keel readout, as we have from our traditional depth sounder) so we have to remember that the FLS isn’t giving absolute clearances.

The control box for the FLS is a little larger vertically than standard instruments which made it tricky to find a good location in which to mount it. In the end we fitted a blanking plate over a cut-out that had previously contained the second autopilot controller then surface mounted the FLS controller on that. A smaller unit would have been easier to fit.

Navtex

We’re replaced the old paper printer Navtex with a McMurdo Nav6 dual channel system. The antenna for this is on our mizzen mast and the receiver itself is at the chart table. The receiver interfaces to the other instruments so that it can also act as an instrument repeater, as well as using GPS position data to automatically select the most appropriate Navtex stations. The Navtex receiver is on its own circuit breaker so that we can leave it switched on all of the time, receiving the latest information.

When we’re under way we usually have it set to display position, speed, depth and log so all of that information is available at the chart table while the plotter is left in chart display mode. We can switch to Navtex display to check for updated weather and navigation information, and this is the display mode that we used at anchor.

The unit stores all received transmissions in memory then provides options to filter out the data types that you’re not interested in. The interface takes a little getting used to but then works well, it’s certainly easier to find the latest weather forecast this way than working through a long print out.

Communications

Speedwell came with a relatively new Icom VHF DSC radio which we’ve retained. This is connected to an antenna on the main mast. The radio is below decks, just inside the companionway. A cockpit speaker allows us to keep a radio watch on deck.

Our longer term plans include some ocean crossings, for which long range communications would be sensible. We probably won’t be buying an SSB radio until we’re planning a long crossing but during the re-fit we had earthing plates fitted and had insulators fitted in the main backstay so that we can use that as an antenna in the future.

Autopilot

The original autopilot was largely in working order although one of its two control heads had stopped working. However this system only provided basic course keeping and didn’t provide a stabilised heading output for the radar so we decided to replace it.

We’ve fitted a Raymarine SPX-30 autopilot with a single ST6002 control head in the cockpit. We’ve kept the original linear electric ram although this does have a new stainless steel tiller arm connecting it to the rudder stock as the original mild steel item was badly corroded. I was warned that it’s not uncommon for an old autopilot drive unit to fail shortly after an upgrade of the course computer but so far our system is working fine (though I’ll consider buying a spare drive unit before we head off to remote places).

The new autopilot has built in rate gyros for improved course keeping and this also means that it provides a stabilised heading output to our plotters which improves MARPA performance.



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