Navigation and Trepidation

I apologise in advance as this post is one for the ‘nerds’! It’s a little sterile and technical so, if you are only mildly interested and just a casual reader, it’s probably best to give up on it now and to wait for the next, hopefully more compelling blog.

In the thick fog we are currently enduring with visibility less than 100 metres at times, it may be of interest to some (?) to understand a little of the navigation instruments and information we are working with down below at the chart table.

The instruments, facing the navigation position comprise a chart plotter to the left and a slave auto pilot control and a multi-function display to the right. The chart plotter has been configured to show two screens. On the left is the chart showing the current vessel position with a yellow arrow showing the wind direction and a blue arrow showing the tidal stream direction. The two different coloured vectors with arrows from the front of the yacht show the course steered and the ‘course made good’, that is the direction we are actually going in – this is not necessarily the same given the influence of the current and leeway. They have been adjusted to reflect an hour of progress which is helpful in planning. The chart shows depth contours and to the bottom left you can see traffic separation lanes shown in purple (we are well inside of them) and the depth of 72 metres is shown. The blue triangle to the left is an AIS target. It is the Nadir, a 95ft. Fishing vessel out of Figuera Da Foz doing 4.1 knots – this and other information is available by placing the cursor over the target. If it were a collision threat it would be shown in red and it would have registered an alarm. I would then have attached flags showing which side of us it would pass, how close and how long before it is closest so the situation can be monitored. Any doubt and the vessel can be called by name or direct using their MMSI number. In the shipping lanes you hear ship watch keepers talking to each other all the time. The black screen of the radar to the right has been adjusted to a range of 1.5 miles with ¼ mile range rings and shows a ‘guard zone’ in purple and a vessel in that zone inducing the alarm that can be seen. This is not transmitting an AIS signal as it doesn’t have a corresponding indicator on the plotter and is probably a smallish fishing vessel for which  AIS is optional. The bar at the top is configurable and currently shows our Long and Lat position, SOG (speed over the ground), course and depth, there is also another drop down bar with more information like the Long and Lat of the cursor which is actually quite useful. We tend to only use the radar at night and in poor visibility although regulations state that if you have it, you have to use it. The multi-function display to the top right can show and scroll through all manner of information and the displays can be tailored to any preference, including even the sea temperature. It is currently showing that we are tracking to the Peniche Passage which is between Peniche and a group of islands offshore. It shows how far it is away, the time of our arrival and that we have the expected slight contra current (the difference between the speed from our log impeller in the water and the ‘speed over the ground’ from the GPS) The slave auto control is just that and controls auto and standby (manual steering), shows rudder angle (useful to indicate if our sail plan is efficient – too much rudder angle would suggest we are ‘over canvassed’) the bearing of our track and we have the ability to adjust our course. We not only have this main electronic navigation system but paper charts and a GPS dongle on the computer as a ‘back up’ AND a spare computer in the metal safe (a protective Faraday cage) equipped with charts in case of a lightning strike which might ‘fry’ all of the electronic devices. Oh, and a sextant, but I doubt I would remember how to use that.

It has to be said that all of this information makes navigation a bit of a ‘doddle’ and, as it’s available, it would be foolish not to use it. In some ways, however, it does detract from the satisfaction we used to derive from navigation before all the electronic aids – plotting positions on charts, taking fixes, calculating tidal vectors, trying to identify landfalls and working out the collision potential of shipping by monitoring bearings. It is certainly safer now but somehow, not so much fun…

The electronic gizmos are all very well but they can’t detect lobster pot marker buoys and in the dark and fog, even the MK1 eyeball is of very little use. We have just run over a marker buoy, it was on my watch and the noise was such that both crew members shot out of bed in their jimjams. We were motoring and I saw the gear disappear behind the transom. There was immediately vibration from the engine and it would not ‘rev up’ as it should. I was fearing we would have to limp into port somewhere under sail but, somehow, the problem cleared itself – presumably the rope cutter did its job, the revs picked up, and the vibration disappeared. A close shave and a reminder that, even with all the electronics, there is still danger lurking out there.

When sailing hard on a starboard tack and heeling to port, the two heads (toilet) basins on Hejira can fill with water and spill over in a lumpy seaway – not good. It is therefore essential to close the seacocks before the situation arises, otherwise it is necessary to ‘luff up’, level off and allow the sink to drain then close the seacock. Another mistake that can be made on the Southerly 135 which is disastrous (it’s been done of course) is to close the wrong seacock in the forward heads as the sink drain seacock is next to the ‘shower tray pump out’ seacock and you can only locate them by ‘feel’ deep inside a cupboard under the basin. If you close the shower tray seacock by mistake and subsequently turn on the shower tray pump, the water has nowhere to go and the powerful positive displacement whale pump will split the gasket, spray water everywhere and need replacing.

We had an AIS alarm with a yacht called Alegria overnight which was heading south. This seemed too much of a coincidence as we ‘hooked up’ with a French yacht called Alegria in Angra do Heroismo on the island of Terceira in the Azores in 2016. We had drinks with them on their yacht and sailed in radio contact for a few days on our way back to the UK before our courses diverged and they headed for Northern Spain. Could it be the same yacht? They answered our radio call and we had a chat but this Alegria was a Swedish yacht heading for the Med. Co-incidences do happen, just not in this case.

Endeavouring to maintain mobile data contact along the coast enables us to regularly update our weather forecasts. As in a lot of things, timing is very important and the small weather window off Northwest Spain and into Biscay needs careful planning. There are a lot of factors at play to get the approach right from a substantial distance. There is the wind, the current, the sea conditions, our speed and the variability and likely evolution of the forecast.

Our fingers are crossed but it is currently looking as though it will be ‘bumpy’!

Richard writes:-

Radar and AIS are a revelation to me. My yacht, Esmeralda, is an elderly Hallberg Rassy 31, she has no such luxuries. Just an old chart plotter, a set of charts, tide tables and a Channel Pilot. But being in strange waters in thick fog at night reminds us of just how vulnerable you are at sea. So, these two instruments, in these conditions, are invaluable. Particularly when the dubious French contractors in Nice disconnected our foghorn, probably in retaliation for our leaving the EU!

This trip has been a great learning experience for me. With so many miles under his belt, Nick is very well informed and happy to share this knowledge. We have daily morning briefings on weather, sail and passage planning, which are discussed and explained. Decisions are then made mutually, with full knowledge and agreement, which is great.