| Tidal flows are an important part of navigation at sea | | | | the yacht through 360 degrees and checking the |
| and have to be considered when plotting your course | | | | differences on the yachts compass reading to an |
| to steer. | | | | actual calibrated compass. This process is normally |
| The gravitational forces created by the sun and moon | | | | undertaken by a qualified marine surveyor. |
| on the rotation of the earth, affect the rise and fall of | | | | Wave action. Similar to Lee way the wave can affect |
| ocean water, this is called tide and happens twice | | | | the yachts course to steer and should be considered. |
| each day. | | | | Charts |
| Such rise and fall of water levels causes changes in | | | | When using your chart to obtain tidal flow information |
| the depth of the water level and produces oscillating | | | | the table can normally be found in a convenient clear |
| currents. These are known as tidal streams. Wind can | | | | area of the chart. It will refer to an alphabetical list |
| further influence water levels and intensity of tidal | | | | given the information in respect to the letters of the |
| stream. | | | | alphabet. On the chart its self you will find what are |
| Learning to sail requires in-depth knowledge of | | | | called "tidal diamonds" these are diamond shaped |
| seawater levels at all times. You should therefore | | | | marks on the chart, with their specific letter of the |
| remain aware of high and low water affects your | | | | alphabet shown inside the diamond shape. The location |
| yachts course to ensure safe navigation. | | | | on the chart of each tidal diamond gives you the |
| The information you require can be found in yachting | | | | information required from the table for the specific |
| nautical almanacs issued annually, shown on charts, | | | | area of ocean. When plotting your initial course you |
| and booklets issued by local yacht clubs for its | | | | can then see which diamonds information can be used |
| members. The tables show the tidal flows direction, | | | | along the path of your course for the correction to |
| speed and depth of the tidal stream, at a given date | | | | your course. |
| and time of the year of every standard port. This is | | | | You must check the date on your chart being used |
| then plotted on your chart from your passage plan | | | | and if necessary apply the correction for the year the |
| start datum, this will create what is called a tidal vector | | | | chart is being used. |
| and closing that vector off with a third line will give you | | | | Tides |
| to a given time to travel the degrees of correction, plus | | | | The tidal differences caused through the cycle of the |
| or minus, you will have to make to your course to | | | | sun and moons influence are called "Spring and Neap" |
| steer. | | | | tides. Spring tides are the highest and Neap the lowest |
| Other considerations to your course to steer are; | | | | in the tide cycle given in feet or metres. It is a gentle |
| Lee way. The affect the wind will have on your sailing | | | | progression from Neap to Spring tides where you will |
| yacht, which will vary to the wind speed and direction. | | | | see the gradual increase in tidal flow as you get closer |
| Deviation. The influence the yachts infrastructure has | | | | to the Spring tide. The highest and fastest tides are |
| on the yachts compass. This is obtained by spinning | | | | normally two days after a full moon. |