1883 The set of tides at half ebb and half flood
From the David Rumsey Collection.
HHA Tidal Surges
14AUG24 there was a surge, it built up very quickly as can be seen from the graph. Two stream measurements were made from a yacht taking the difference between STW and SOG. HHA Tide Data for the period here, times are BST. HW 0700 3.3m, LW 1245 1.4m, HW 1930 3.3m Range 1.85 average (neap …
Priming and Lagging
Each port has an ‘Establishment’, being the hour of the day (GMT) at which the High Tide occurs at the ‘Full and Change’ of the Moon. At Harich this is xxx. As the Moon moves through her quarters the time at which HW occurs changes. After the New Moon the Moon ‘waxes’ or enlarges through …
Log Calibration
A yacht’s log records the distance travelled through the water and, from that, derives speed (there are other types of log such as Doppler which work differently). Because the log wheel is subject to the marine environment, such as weed, it ought to be tested often and calibrated to be reliable. Many sailors are perhaps …
Sea Words And Phrases Along The Suffolk Coast- Edward Fitzgerald
Fitzgerald collected words and phrases from local sailors and fishermen which were published in the East Anglian. The full text is available here. This is a short selection:
SYH Berth Survey June 2022
As part of a plan to survey sections of the marina for depth, it was necessary to establish the difference in tidal height between SYH and the tide gauge at Harwich (HHA). The HHA gauge gives predicted and actual tide for every ten minutes on a 24-hour basis: the data can be read into a …
Roman Weather Lore
A fictionalised account of the departure of the legions from Britain is given in the ‘The Count of the Saxon Shore by Alfred John Church’, set in the early fifth century. An interesting snippet from this, the time was mid-October: But I must say, saving your presence, that it is against all rules of a …
Elevation and Depth data
Also see Walton on the Naze tides – variation LIDAR is a Laser-based surveying technique that provides elevation data across a land area. There are various types of survey data that can be downloaded and then processed to show a given area. The raw data will include buildings and vehicles, this is the DSM version. …
Tides and Waves
A brief analysis of North Sea physics – in depth technical explanation of how the North Sea works including surges, wind, circulation and future climate change.
Air pressure, Sea Level and Surges
Standard air pressure at sea level is 1013 mb or Hectopascals, Changes in air pressure affect sea level, This effect has implications for the sailor since each A 10mb change in pressure results in a 0.1m opposite direction change in sea level which can be calculated easily. This is enough to make a difference at a river bar or marina entrance although any change should be within the safety margin allowed by the prudent sailor.
Walton on the Naze tides – variation
Also see Elevation and Depth data. Walton on the Naze is the standard port for our part of the East Coast despite the major port being Harwich. Times and heights are similar between the two ports but with Walton having slightly greater heights. Tide readings and tables for thirty years ahead are available from the …
GPS-GOTO vs CTS
It is easy when sailing to set the GPS system to GOTO waypoint and then steer to match the Bearing (BTW) with the Course over Ground (COG,) or set the autopilot to do so. Provided that Cross Track Error (XTE) is managed, and the course can be made, then the boat will travel directly to …
How Boats Move
Sailing Wind related terms
Sea Direction relative to the boat
Bearings Relative to the Boat – Points
Relative Bearings – Points – An excellent system that all sailors should know.
Sailing Terms
Commander William Hewett
Sounding by lead and line
Acoustic depth sounders appeared in the twentieth century, earlier for ships than yachts. However, from at least biblical times depth was found by lead and line.
Traverse Board
Knots by Log and Line
We use knots as a measure of speed on the water. How does this work, and how did it come about? The history of the “knot” is intimately tied to the method used for measuring it and this presents a variety of conflicting and confusing sizes and units. Conversions to metric units are given where …
1752 John Mount Sailing Directions
Tides by Full and Change
Watches, Bells and the Ships Day
How many bells at what time in a watch – What were the watches – Dog Watches – How was the day reckoned?
What’s the Point of a Compass?
The magnetic compass has developed, not as quickly as one might think, over the last seven or eight centuries. Mariners have been navigating the seas out of sight of land for much longer than this: directions had to be based on the bearings of the Sun and stars although local use could be made of …
Collision Regulations
Great Britain has led the World in many things, mostly good: maritime safety is but one example. Before the mid nineteenth century, local …
Confused helm instructions
Robert Fitzroy had overcome the confusion caused by “Larboard” and led the change to using “Port”. However, all was still not well. Until 1930 helm orders were tiller not oriented. Putting the tiller to port, would turn the ship to starboard but a wheel to port would turn the ship to port: the opposite effect. …
Port and Starboard
Once we’ve realised that Port is on the left only when facing the pointy end (not Italians – see later) we take these terms for granted. However, those of a curious bent might wonder how they came about . About ninety percent of us are right handed. Since roman times , at least, we have …
Felixstowe sea temperature
From Channel Coastal Observatory graph showing temperature range by month for 2018-2020 data. Month Degrees C January 6.7 February 6.1 March 7.6 April 9.7 May 12.6 June 16.2 July 18.4 August 19.9 September 17.6 October 14.3 November 9.9 December 7.7 Some data here on temperature rise. There are better figures for Sizewell somewhere. About 0.75 …
Tidal level at Woodbridge
Tide gauge (sometimes a bit on the drag) Highest level was 3.35 (2013?) 1953 the flooding reached up Cliff Road to the bend by the entrance to the Maybush car park. This is about 4.0m AOD (hard to be exact without measuring – lost OS BM on wall) which makes a height of tide of …
Tide and Wave predictions and data
Tide Predictions Harwich Haven Authority/Leisure produces annual tide tables as well as a tidal atlas. The tide does not turn at HW or LW anyway in Swimscapes Bay. The tidal stream turns to flood north about 4-4.5 hrs after HW and to ebb north about 1.5 hrs before the next HW. In time I’ll work …
Wrinkles in practical navigation by Captain S.T.S.Lecky
Squire Thornton Stratford Lecky , 1917 edition of Wrinkles, explains tides and instruments, lovely language.