This blog post has been a while in the making so I hope you you all enjoy it and find it interesting. A while ago I promised to talk about tides and the route I would end up taking across the channel, well the time has finally arrived for me to do just that.
When I was getting ready to swim to the Isle of Wight a couple of years ago, I noticed that there was a cut off time of 2 hours for the swim. This wasn't a problem for me as I can swim 4km in just over an hour but the reason behind it was different than I thought it would be. I thought that the organisers just wanted to keep us all together for safety, however it was down to the tides. Any longer than 2 hours and swimmers would be swept past the beach and potentially in to the English Channel.
You can see from the line I took that the tide had a small effect on my swim, I swam in a reasonably straight line and finished close to the pier (albeit a long way out due to the fact it was low tide). The person who took the longest, just shy of 2 hours, finished up at the opposite end of the beach.
When I was getting ready to swim to the Isle of Wight a couple of years ago, I noticed that there was a cut off time of 2 hours for the swim. This wasn't a problem for me as I can swim 4km in just over an hour but the reason behind it was different than I thought it would be. I thought that the organisers just wanted to keep us all together for safety, however it was down to the tides. Any longer than 2 hours and swimmers would be swept past the beach and potentially in to the English Channel.
You can see from the line I took that the tide had a small effect on my swim, I swam in a reasonably straight line and finished close to the pier (albeit a long way out due to the fact it was low tide). The person who took the longest, just shy of 2 hours, finished up at the opposite end of the beach.
This is a short distance in comparison to the channel, in fact it is about 9 times shorter than the channel; imagine how much the tide in the channel can carry you. One of my work colleagues is a keen sailor and lent me a book about the tides in the channel, he lent it to me about 3 months ago and I have only just got round to properly looking at it.
Covering the basics (aka my simplistic understanding of it): The moons gravitational pull creates the tides. Over the 28 days it takes to orbit the earth it creates “Springs" and “Neaps” depending upon where the moon is in relation to the sun. If the moon and the sun are in line on opposite sides of the earth we experience higher high waters and lower low waters, this is know as a “spring” tide which is what I have chosen to swim the channel in. If the moon and the sun are at right angles to each other the earth experiences lower high waters and higher low waters. The tides work on about a 6 hour period, for 6 hours they will go one way and then 6 hours later they will be going the other way.
Covering the basics (aka my simplistic understanding of it): The moons gravitational pull creates the tides. Over the 28 days it takes to orbit the earth it creates “Springs" and “Neaps” depending upon where the moon is in relation to the sun. If the moon and the sun are in line on opposite sides of the earth we experience higher high waters and lower low waters, this is know as a “spring” tide which is what I have chosen to swim the channel in. If the moon and the sun are at right angles to each other the earth experiences lower high waters and higher low waters. The tides work on about a 6 hour period, for 6 hours they will go one way and then 6 hours later they will be going the other way.
Photo from the Macmillan Reeds Nautical Almanac 2001 (© Nautical Data LTD 2000)
As you can see there are a lot of arrows and numbers, each box tells you what the tide is doing relative to when high water is. So the top left box is 5 hours before high water and the bottom right is 6 hours after high water. The arrows show which way the tide is going and the numbers tell you the speed.
If we look at 2 hours after high water in more detail you can see that the tide is flowing from the bottom of the UK upwards, the first number tells you how fast the tide flows at "neap tide” the second number how fast the tide flows during a "spring tide”.
If we look at 2 hours after high water in more detail you can see that the tide is flowing from the bottom of the UK upwards, the first number tells you how fast the tide flows at "neap tide” the second number how fast the tide flows during a "spring tide”.
Photo from the Macmillan Reeds Nautical Almanac 2001 (© Nautical Data LTD 2000)
So at the tip in France where I’m hoping to land during a spring tide 2 hours after high water the tide is flowing at 3.3 knots represented by the18,33. 3.3 knots is 3.798 miles per hour, now that doesn’t sound that fast but in swimming terms there aren’t too many people who can swim that fast. My average swimming pace at the moment is about 2 miles an hour and by the time I’m near France I’ll be amazed if I can still keep that speed up. If I’m swimming against the tide at this point I would be getting pushed backwards at nearly 2 miles per hour.
Of course I’m not swimming with or against the tide, I’m swimming across it which means that I’ll be getting pushed sideways making my course more of an “S” shape rather than a straight line...
Of course I’m not swimming with or against the tide, I’m swimming across it which means that I’ll be getting pushed sideways making my course more of an “S” shape rather than a straight line...