Equipment – tide by tide

Wrong-headed satellite precision claims

I’ve had quite a few emails recently from Orca, a navigation equipment and software firm, boasting about the 3 metre location accuracy of their equipment as a major selling point. It’s a waste of marketing effort, as far as I’m concerned.

Three metre satellite accuracy – available nowadays even on some top of the range phones – is no use when round much of the British Isles chart positions can be far less accurate.

Orca equipment and software do look temptingly attractive on paper, and I have no doubt that their 3 metre claim about their GNSS equipment is accurate. But that’s not how we should be thinking about satellite positions in practical navigation.

*Passing through the Thames Array – one of the few places in the estuary where we trust the chart.*

In many places we sail, such as the Western Isles, the West of Ireland and, much nearer to home, most of the Thames Estuary, it’s particularly risky to expect your charts to be able to match anything like that standard.

In the Thames Estuary, 3 metre satellite accuracy is irrelevant for a small boat that needs to keep out of the main channels and use swatchways and other routes less frequented by commercial traffic. The only short cut I know where the chartplotter positions are reliable is through the Thames Array windfarm, which you’d expect to be charted and updated to high precision.

But generally, the depths are changing all the time and charts cannot keep up outside the main ship channels. Valiant efforts are made by amateurs to track the changes, especially East Coast Pilot and Roger Gaspar’s Crossing the Thames Estuary

They publish plenty of examples of rapidly changing profiles of the sea bed. Recently they noted how several yachts had gone aground together on the Sunk (I think it was) because they followed their chartplotters.

Last year (2021) we crossed the Sunk in May and by August when we came back to the Solent an alert had already been put out by Gaspar that the sand had shifted the swatchway since the spring. No published chart of the Thames Estuary, paper or electronic, can keep up with that pace of change.

Ireland has been updating the once notoriously old surveys of its West Coast, and charts were supposed to have been much improved by the last time we visited. But inshore, for instance along the Connemara coast, we still assumed 100 metres error, to give ourselves a safe margin. In some places, that meant focusing on old methods, and ignoring the plotter.

In the west of Scotland, Bill Bradshaw has done a great service over the last 15 years or so with his Antares charts of anchorages. We have used them, and hope to again, but they are not official charts. In fact, one thing they have done is expose how out of date other paper and electronic inshore charts actually are, based on surveys sometimes unchecked since the 19th century.

I’m not criticising the Orca products, which I’m sure are fine, and I will try out their app next season. It’s the marketing message that I take issue with.

Update, Jan 2023: Bill Bradshaw gave an excellent talk in London this month on his charts, and on the deficiencies of official charts in Scotland. It was organised by the Little Ship Club and the Royal Institute of Navigation (of which I’m a member).

Beachcombing for weathered teak

Every river I know with saltings has timber rubbish stranded near the high tide line, usually broken and ignored. A close look, however, tells a better story. Today’s flotsam is often a fragment of a very old boat, and the best of all is a piece of long-lasting teak.

It will look like scruffy, broken, unidentifiable, grey rubbish. But examined closely there may well be usable sections that can be cut into smaller pieces of timber. Old teak, cleaned and oiled, has a rich colour and patina that is impossible to reproduce with new wood.

It took 20 minutes strolling along the saltings high up the River Medina on the Isle of Wight to find what we were looking for: a chunk of teak, probably a fragment of a boat’s coachroof. It was about 6 feet long and jagged, but there were several undamaged sections within it.

Above is one of them: a mounting plate for a new chronometer and barometer on the saloon bulkhead. The teak was cut, the edges rounded, and then it was rubbed down and oiled.

These two instruments were retirement gifts, forgotten in a cupboard for a while, now handsomely displayed.

February – survey nerves

Insurance surveys don’t come round very often, but it’s a finger chewing time when they do. What’s going to be found and how much will it cost?

We’ve been lucky with our insurers, who haven’t insisted on a survey since we bought Spring Fever in 2009. Our current insurers gave us a year’s notice that we’d need one this winter.

The survey has just been completed by Adrian Stone of Cowes. The good news is that the main work needed is a job we have been contemplating anyway, which is replacing the standing rigging.

It still looks acceptable on close inspection, but one of the risks with stainless wire and fittings is sudden failure, as likely from a hidden crack in a steel piece as from the wire itself. Some insurers are said to ask for replacement every 10 years but our standing rigging has lasted a full 13 seasons.

Other than, that Spring Fever has come out well from the survey for a 34 year-old boat with one significant exception: the P-bracket that holds the prop shaft has come slightly loose, and will have to be reinforced, a small job but an awkward one that will need an expert to do. The loose bracket has caused heavy wear on the cutlass bearing on the shaft. Other than that, the recommendations were minor.

Four years ago we commissioned a really big job, repair of delamination around the keel. If that hadn’t been found in late 2017 it would have been a big shock to find it alongside new standing rigging, but we got it out of the way. We also had a new engine installed in 2019.

It’s been expensive over the last four years, but keeping the boat up to scratch brings real reassurance when things get tough out there. The survey has been delivered to the insurers, Topsail, and the policy renewed.

Coming soon on your phone – one metre accuracy

It seems that while my phone is accurate to an error of considerably less than 10 metres, the industry is heading to even better precision of a tenth of that level, and soon. This post looks at why that means satellite accuracy on all devices including smartphones is reaching levels where there are diminishing returns for small boat sailors.

In general, 5 metre satellite accuracy has been available on smartphones for a considerable time now. I give links at the end to industry, US government, academic and consumer articles that give more detail on how accuracy has been developing (and see also my earlier post ‘and a phone to steer her by’).

One of the secrets of the top performers such as the high-end Samsung phones, which can achieve 2 metres, is that they now have dual frequency satellite aerials so they can make the best use of the latest improvements not only in the US GPS, but the Russian Glonass, European Galileo and Chinese Beidou satellite systems. Nowadays, phones will often have as many as 40 satellites in the sky from which to choose the best signals.

…and a phone to steer her by

Mobiles have had a bad press as navigational tools, but if I were forced to choose one single piece of electronics to take to sea it would be my phone. That’s not a popular view among professionals.

Instructors, coastguards and rescue services learn of many cases where boat owners, especially of powerful motor yachts and RIBs, set off for the open sea with nothing beyond a chart app on a mobile phone, and no knowledge of the underlying skills needed to navigate safely. For the Royal Yachting Association, mobiles are well down the list of recommended priorities, because of the risk that they will be used badly. Textbooks give stern warnings that you must not use them for navigation.

April – third mate missing

We moved the boat back to our mooring in Cowes this month, but on the way our autopilot lost its sense of direction.

Whenever we are just two on board the autopilot is an extra member of the crew, and an essential third mate on longer passages.

Battles over flares

In one corner, the Royal Yachting Association, declaring pyrotechnic flares are obsolete. In the other, the UK Maritime and Coastguard Agency, pointedly renewing for another 2 years its ruling that flares are mandatory under the Safety of Life at Sea (SOLAS) convention, though softening it a little round the edges.

What does it actually mean for a typical small yacht? The crucial issue here is that SOLAS distress signals are only a legal obligation for yachts above 13.7 m or on smaller craft licensed for commercial use, including sail training. They must carry flares. This means if you charter a yacht, it has to have them. The RYA has, however, won a dispensation allowing private yachts from 13.7 to 24 metres to at least dispense with parachute rockets, easily the least useful and most hazardous in use of the flares. Continue reading “Battles over flares”

Bowsprit – pronounced bow, bo’ or bogh?

How do you pronounce bowsprit? I’m usually against language pedants, who try to foist the views of Victorian grammarians onto the 21st century. But this word is my one little obsession, ever since getting a letter into Yachting Monthly on whether the first syllable of bowsprit should rhyme with dough or cow.

I was reminded by contemplation of this lovely boat recently.

I can’t remember why or when, but I learnt to pronounce bowsprit to rhyme with dough as a child. In fact, the similar word bowline is always pronounced like dough. Continue reading “Bowsprit – pronounced bow, bo’ or bogh?”

New engine calculations

A new engine is a big challenge, not just financially but in the thought process running up to the decision.

Our Volvo is 30 years old and we had it taken out and largely rebuilt 10 years ago. It has been reliable since then but this winter it has been increasingly difficult to start, and the expert verdict was that the valves probably needed regrinding. Continue reading “New engine calculations”

What to do with an old liferaft

It’s 17 years old, requires expensive annual servicing and it’s cheaper to buy a new one: here’s a fun way to dispose of the old one, on a pond:

Useless marina internet

Marina internet is a waste of time. It’s fun doing a live blog of a cruise, but it was so difficult to get web access on our 900 mile round trip to the Morbihan this summer that I failed to file anything en route, and will do a single post later.

021 — How we got marina wi-fi in Vannes, but nowhere near the boat. (The jacket shelters the tablet from the rain).

Every single marina over 4 weeks advertised wi-fi, and only one actually delivered it in practice at a decent speed, with the rest either intermittent and unworkably slow, available only a few yards from the marina office, or simply not showing up on my tablet’s wi-fi source list. Some marinas openly confessed to technical problems, others were incredulous at our inability to log on. At most marinas, it was a cheek to advertise wi-fi at all. Maybe sailing magazines should be taking this on as a campaign.

There were cafes and restaurants, of course, but we went to drink and eat not write in a corner. I’ve also filed posts in the past from my phone using 3G, but we seem to have consistently chosen places where the 3G signal was poor, so that didn’t solve the problem either.

Fitting out at Ardoran, 4 -11 May

We arrived at Ardoran Marine on 4 May to stay at one of the three chalets the boatyard owns, with a few days fitting out planned. (Peter, Christine, Tony, Elaine and Nigel). Ardoran stores boats in an old quarry behind the main workshop, and we found Spring Fever in excellent condition, dry inside and well cared for, with the anti-fouling done ( a present to ourselves because of the 500 mile drive to reach her.) Continue reading “Fitting out at Ardoran, 4 -11 May”