Help with sea currents around Britain

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Conseanway

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Hello Everyone

This is not necessarily boat related but I figured you guys would be the best people to ask.

Next year I am attempting to become the first person ever to swim the length of Britain. The 1000 miles swim will take me two months and I'll be doing the equivalent of the channel every day.

My question is how can I find out which way the main currents flow. South to North or North to South? Should I start at Lands End and head up or John O'Groats and head down?
If I keep quite close to the shore will the currents effect me as much?

Any tips on this would be great and if there is anything else you think I might need to know then I'm all ears.

Cheers.


Sean Conway
 
I'll assume you're not a troll.

The tides change direction every 6 hours or so, so if you pick the right time of day, you can have the tide in your favour. There's a book called 'Reeds Nautical Almanac' which has the tide vectors for given times.

So... erm... I wonder why nobody's done it before...
 
You need to work out your strategy to make maximum use of the tides. In some places they will be weak, in others strong. Great if you swim with the tide as it can give you a lift of up to 10 miles or more across a 6 hour cycle - but equally knock off a similar amount is swimming against it. Most critical will be getting around headlands where the tide and sea state could have even more dramatic positive or negative effects on progress.

Probably does not matter which end you start as you will meet the same tidal flows.
 
There aren't constant currents flowing in one particular direction. They reverse twice a day due to the tides. Small boat sailors have to pay a lot of attention to them to avoid futile attempts at going the other way - you'll be needing to do exactly the same thing but even more so. How fast can you swim? If it's less than about two knots (1m/s) then you will be basically unable to make any progress against a foul tide. On the other hand, if you do your planning right, you could be being swept along at three or four knots even if you just tread water.

There are various sources of tidal flow information; the official and comprehensive sources are the Admiralty Tidal Stream Atlases.

To answer your specific question, you could go in either direction, but you will find your timetable is decided for you more than you were expecting. Sailors are the experts at working the tides, so feel free to ask for help with how to actually work out your plans.

Pete
 
I would suggest that for a project like this the easiest and by far the most efficient way to do this would be to buy a GPS plotter with tidal flows installed. That will give you the direction and rate of tide for any time you want, including in the future for planning. You can do it with an almanac but it takes a lot of effort and some skill.
 
vyv_cox said:
I would suggest that for a project like this the easiest and by far the most efficient way to do this would be to buy a GPS plotter with tidal flows installed. That will give you the direction and rate of tide for any time you want, including in the future for planning. You can do it with an almanac but it takes a lot of effort and some skill.
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Good point. Although I wouldn't suggest a plotter as he's got no need for the hardware. If he has an iPhone or iPad then I'd suggest Imray's TidesPlan app (and paying a quid or two for next year's tides as an in-app purchase). This has a currents mode that I believe uses Admiralty data and gives you little arrows growing and shrinking and turning round as you page forward through time.

Pete
 
I don't really have any empirical data, just a feeling in the water, that a clockwise course round the UK would be easier (tidewise) than the other way.
For example, doesn't the Gulf stream flow round the top of Scotland?
 
having spent a summer carrying out tidal flow measurements on the lower Clyde it was found that the measurements taken differed from those found in the tidal atlas and varied depending on rainfall wind and tidal state. These trials were carried out to a depth of 30M i.e. 1,3 & 10M drogues being dropped and monitored daily for up to 12 hours and up to 2 miles off shore
there were days when tidal current had no effect over surface movement and the surface drogues 1&3 metres would travel at speeds of up to 3.5 knots in one direction all day and on other days the surface drogues would circle round a course about 1.5 miles long while the deepest drogues nearly always traveled in the direction of the tide but very seldom at the suggested speed varying both up and down.
 
alahol2 said:
I don't really have any empirical data, just a feeling in the water, that a clockwise course round the UK would be easier (tidewise) than the other way.
For example, doesn't the Gulf stream flow round the top of Scotland?
Click to expand...

I think he proposes to swim the length of it not right round it

I don't think it matters much which way he goes. If he is going in summer perhaps there's some slight advantage to swimming north from warm waters at their coolest in spring to cold waters at their warmest in autumn. The winds will matter a lot but only in that half the time he'll probably be swimming through a wind over tide chop whichever way he goes.

If he does it though very well done, sounds a serious challenge.
 
as if you can swim the channel[distance]with out rests every day its ridiculous sorry
would you not need days of rest inbetween doing sections?
what about bad weather?
what if the winds blowing in the wrong direction?
you need to do much more reserch and it will take more like 6 months! i m o

how long can it take a yacht to do it with the wind and engines doing all the work and favourable conditions ? 1 month?...2 months?

welcome btw :)
 
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For a broad picture, this is the ideal time of year to scrounge an almanac from a yachtsman, as they go out of date Jan 1st.
Among all the other stuff are tidal charts referenced to HW Dover, which will give you a basic idea. That does not go out of date, but of course HW Dover changes and last years times will be wrong.
You can get tidal atlases of many areas either in print or on plotter software.

I think it's a mad idea, but good luck.
 
Niander said:
as if you can swim the channel[distance]with out rests every day its ridiculous sorry
(1) would you not need days of rest inbetween doing sections?
(2)what about bad weather?
(3) what if the winds blowing in the wrong direction?
you need to do much more reserch and it will take more like 6 months! i m o

how long can it take a yacht to do it with the wind and engines doing all the work and favourable conditions ? 1 month?...2 months?

welcome btw :)
Click to expand...

In the event of (1), stay in a pub
In the event of (2), stay in a cafe
In the event of (3), either will do.
 
You could do with some good chart/ tidal software to calculate how it is best to go.

Off the top of my head, I would say South to North, certainly along the south coast long short drift is West to East I would suggest that the Gulf stream type thing means that generally the best set is South to North.

Not saying you cannot go the other way but that you MIGHT get more time with a favorable tide if you went that way...

OK I am guessing here but I would think , your main questions will be east coast or west coast? Which is going to be shorter miles? Not just straight lines but between 25 mile day "hops". Where do you cross the Severn or Thames? Or the Humber The Wash? Etc etc

Also what sort of support craft will you have? You might find it cannot stay with you all the time needing a small one & big one?

If you sit down with the charts (maps might do) and work out your hops I think quiet quickly the best way will answer itself.. My guess is start at lands end, then go up the west coast (there are more distilleries) :D.

Good luck
 
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If he spends a lot of time in pubs and cafes he wont do it in 2 months will he...:)

I also think its more than 1000 miles where did you get that figure from?

also are you going over the top ? or taking the cheat[sorry shortcut] that is the caledonian canal?
 
bitbaltic said:
Once again I am pretty sure the OP said he wanted to swim the length of Britain (whatever he judges that to be) not circumnavigate it.

The Cally canal is therefore irrelevant.
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Yes and know just trying to think of the geography, if going up the west coast, would it make it shorter than "island hoping" further north? Easier swimming... Although could be considered cheating but, if swimming north South or south north was goal that would work...

Certainly the planning in this project alone is a challenge, what ever route is attempted it deserves respect...
 
I think to get an idea of what this man is proposing to do one needs to look at his website. The imagined mileage is taken from an overland cycle route with the roads being replaced by canals and waterways with a couple of canoes in attendance! Tides will the least of his worries, finding 22 mile stretches of north south water inland each day will be much more bothersome. If he truly intends to swim the length of Britain surely the east coast must be shorter than the west?
Good luck with the venture, someones got to do it!
 
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