Maskelyne v Harrison – the longitude show in London

Harrison's third clock
Harrison’s third clock

 

We finally managed to take in the excellent Ships, Clocks and Stars exhibition at the National Maritime Museum, Greenwich, which runs only until 4 January. Among other things, it puts the record somewhat straighter on the eminent 18th century Astronomer Royal, Nevil Maskelyne, chief villain of Dava Sobel’s best selling nautical history of the race to measure longitude at sea. Maskelyne was the man who conspired against John Harrison, the genius who built the first true chronometer, or so the narrative goes in Sobel’s book, Longitude.

Not so, it is clear from the detailed story set out in the exhibition, Continue reading “Maskelyne v Harrison – the longitude show in London”

Charts, pilots, weather – Scotland, West of Ireland to Scillies

The cost of a portfolio of paper charts for the British Isles is enormous, so we ignored advice in magazine articles and pilot books to stock up on large scale charts and relied mainly on electronics. (See this link to earlier posts: electronic navigation ).

We have:

C-Map NW Europe – chartplotter.
Memory Map UK and Ireland – laptop.
Navionics UK and Holland, including Ireland – iPhone.
Antares, Bob Bradshaw’s ultra large scale inshore charts for West of Scotland – laptop. (We tried them out in some very tight little anchorages, and they seemed very accurate). Continue reading “Charts, pilots, weather – Scotland, West of Ireland to Scillies”

Marine survey accuracy

Data published by the International Hydrographic Organisation shows up a surprising fact: the UK and Ireland are below Turkey in the league table of survey quality by area of national waters. Spain, Portugal and France score much higher than the UK. Continue reading “Marine survey accuracy”

Med charter disaster?

Since looking into chart accuracy following the Orkney cruise (see previous article) I’ve spent a couple of months in the Mediterranean. It’s much worse there.

I vaguely knew that, but previous sailing in the Mediterranean had been without chartplotters and on the earliest occasions without GPS. More recently, chartplotters seem to be standard on charter boats as well as private yachts. We amused ourselves by doing some checking. Continue reading “Med charter disaster?”

Orkney Roulette

Not long after a jack-up rig called Octopus ran aground in Stronsay Firth in the Orkneys in 2006, we were feeling our way into a bay at nearby Stronsay. We crept through shoals and reefs relying on chartplotter and echo sounder, in strong winds and bad visibility, confident that our plotter would get us through: after all, we had checked it frequently on our passage up the English and Irish coasts and through the Hebrides, and had been pleasantly surprised never to find the GPS positions more than 50 metres out on the chart.

So confident had we become in our first chartplotter that a few days earlier, in fog rolling off the island of Hoy so thick that the boat’s bow was only just visible, we used it, along with the depth sounder, to find our way at dusk into the harbour of Stromness, which involves a tight turn round a reef at a point where the tide can run at up to 8 knots into Scapa Flow, right across the entrance to the inlet leading to the town.

If only we had known more about the quality of the local charts ….. much later, I came across a Marine Accident Investigations Branch report on the grounding of the jack-up rig Octopus, under tow by the tug Harald, which popped up in a web search for something else. (MAIB Report 18 2007).

Continue reading “Orkney Roulette”

How to mimic big ship equipment

To cut back seriously on paper charts, the greater vulnerability of equipment on a small craft to accidental damage would have to be taken into account, including lightning strikes. For small boats it is already possible to buy, at a price, extremely robust electronic systems, including waterproof laptops that withstand impacts (costing several thousand pounds), and high capacity lithium battery back-up packs;  small back-up generators have also become cheaper in recent years and can be accommodated on many mid-sized cruising yachts.

At a cost, robust weather and shockproof  electronic navigation with reliable backup systems should therefore be quite close to achievable now on a yacht. Even if we fall well short of the rigorous standards of an ECDIS system, we will not be carrying 100,000 tonnes of crude oil or thousands of containers, so perhaps we can be allowed to be rather less tough on the backup specifications. Similarly with training: new courses may be necessary, but perhaps not the 40 hours plus specified for ECDIS for commercial ship deck officers.
Continue reading “How to mimic big ship equipment”

Paper-free chart tables

The idea of a paperless chart table is usually dismissed out of hand, and the very suggestion makes some old hands fume. But if a 100,000 ton bulk carrier can now be paperless, then it is hard to maintain that it will always be a mad idea for experienced yacht owners.

Continue reading “Paper-free chart tables”