Tides affect our sailing so what’s the difference between springs and neaps
Click the links below to see today’s high and low tide times.
The difference between neap and spring tides is the earth’s oceans are controlled by the gravitational pull of the sun and moon.
When the sun is on one side of the earth and the moon on the other the two cancel each other out to some extent giving a weaker tide called ‘neaps’.
However for a few days once a fortnight the moon travels around the earth to pull in the same direction as the sun. Combined together they cause the tides to be pulled up that bit higher and pushed down lower. These are the ‘spring tides.’
The tables give both the time of high and low water.
Also displayed is the ‘height of tide.’ The lowest possible tide ever is called LAT (lowest astronomical tide) and any residual depth of water is called CD (chart datum). So on our chart we have little numbers giving us the depth and on to this we add the height of tide given in the daily tables.
So if the chart has the number 10 out to sea and the tide tables give 6.0 as the height of tide, add the two together to get a depth of approximately 16 metres.
It is important to check whether your boat’s depth gauge(or echo sounder as they are called) is set to tell the depth measured from the surface or from the bottom of the keel.
Tidal heights are also affected by the weather.
A low pressure allows the high tide to come up that bit higher which is why we sometimes get flooding during a winter storm.
On the other hand a high pressure forces a low tide that bit lower resulting in a sailor run aground scratching his head as he checks his arithmetic.
Also the constant movement of the tides sweeps sand along underwater which gradually silts up estuaries, and as charts are not always kept up to date.
So err on the side of caution, and if in doubt wait for a local fishing boat to go by and show the way into harbour.