How Does a Tide Clock Work?

You might think a tide clock is a magical device that somehow can tell when the tides will at their lowest or highest; and it may seem improbable that such a device could be truly accurate. However, tide clocks do just this, with some fluctuation that is to be expected. Very few clocks are exactly precise, and the tide clock is no exception--but it is correct enough to be incredibly useful for those who need to know where and when the tide is going to be.

Knowing this information is pertinent to anyone who lives near the water, whether you’re a surfer trying to catch a wave, a boater trying to make it into port or someone who loves to keep an eye on the comings and goings of the water.

What Causes the Tides

The simple answer to what causes the tides is the Moon. The Moon is large enough and close enough to have its own gravitational pull, however it is not significant enough to act noticeably on land, but it does affect our oceans because the water doesn’t have the same density of mass as the Earth and so can be “pulled” by the Moon. The Sun has a similar effect on the opposite side of the Earth, and it’s this complex play between factors that affects the tides.

This is called tidal force, and it causes the water the bulge toward the Moon, which creates the tides as the Earth rotates. The tide doesn’t necessarily move so much as the Earth rotates while the tide is still pulled toward the Moon. This cycle, from one high tide to the next, happens in 12 hours and 25 minutes for most of the world’s coasts.

How a Tide Clock Works

A tide clock works a lot like a regular clock, but with High Tide marked in the 12 o’clock position on a regular clock and Low Tide marked at the 6 o’clock position. The biggest difference, however, is that a tide clock makes a full rotation at approximately 12 hours and 25 minutes. This length of time is the average amount of time that passes from one high tide to the next, with a low tide in the middle.

Tide clocks will have fluctuations throughout the year but will in general be pretty accurate. It’s not recommended to change the time if you notice a discrepancy because it will even out over weeks and months, and adjusting the clock can result in a bigger variation in tide prediction. Most tides are regular enough that a tide clock, once set to your local tide, will be a good indicator of when the tide is coming in or out.

The tides move with the Moon, so they rotate on a more or less lunar cycle. The Moon takes about a month (28 days approximately), so you’ll notice a higher and lower tide than usual during the new or full Moon.

How to Read a Tide Clock

The tide indicator is a single hand on the clock, that rotates around the face clockwise, just like a regular timepiece. High tide is marked at the top of the clock and low tide at the bottom, with the hours until each around the sides. The numbers on the clock go from 5 to 1, counting down the hours until the tide. A glance at the clock can show you how long until the tide changes, with the hand indicating whether it will be going into low tide (right side of clock) or high tide (left side of clock).

Reading a tide clock is simple enough as long as you keep in mind the direction that the hand goes. If the hand is going toward the bottom, it’s tracking how long until low tide and if it’s moving to the top, you can tell how long it will be until high tide.

How to Set a Tide Clock

You’ll want to make sure that you have everything you need to set a tide clock. You’ll need to get a tide calendar and find the port closest to you, but if you don’t have a tide calendar, you can use the Marine Weather Forecast to get the information you’ll need to proceed.

In the calendar, you’ll see when high and low tides are predicted for the port that you’ve chosen. Here, you can see how strong the tide will be with a number called the Tidal Coefficient. The tidal coefficient measures the magnitude of the tide, with a high coefficient representing a very high (or low) tide incoming.

You’ll need a high tide coefficient, at least 85, so that you can set your clock with the highest accuracy. The coefficient ranges from 20 to 120, so the closer you get to 120, the more accurate you’ll be. Picking a time when there is a new or full moon will help your accuracy since you’ll be going with the highest tide of the month.

Once you’ve found the time that the tide will be the highest, turn the hand to High Tide and wait until the preselected moment comes. When the tide is said to be at the highest, put the batteries in and let your tide clock start doing its job!

Though this method takes some time, it is the traditional way of setting tide indicators. You might also find apps or modules that can help you set your clock online. These typically work by having you input when the tide is at its highest and then, with calculations done behind the scenes, it spits out an image of where your clock’s hand should be positioned to be an accurate tide keeper.

Do keep in mind that because the average time between high tide to the next high tide is actually 12 hours, 25 minutes and 14 seconds, you’ll need to check your clock against a tide calendar periodically to make sure that it’s still running accurately. Fourteen seconds may not seem like a lot, but it amounts to 15 minutes a month and that can cause your clock to get out of sync with the tides.

If the tide is not corresponding to your clock, you can adjust it with a tide table to be more precise. Check every month or so on the accuracy of your clock, and adjust accordingly. The time between tides is an average that best represents the ebb and flow of the tides, but it may not be exact every day--on average though, the tide follows the schedule with regularity.

Bramwell Brown’s Tide Clock

The latest in Bramwell Brown’s collection is the Tide Clock. This gorgeous clock will look familiar to fans of their timepieces, as it features a clean face with delineated marks in order to tell the time, and a window at the top for rolling scenes to play by as the tide ebbs and flows. New to the clock, however, is a smaller tidal clock with a single hand in the bottom portion of the face that tells how long it will be until low or high tide. Easy to read at a glance, the tide clock features whether the tide is rising or falling on the respective left and right sides of the face and how long until the next tide.

In the above portion of the clock, you can watch the tide recede and advance through a beautifully illustrated harbour that animates with changing scenery. Watch as boats float through the water and waves with a lighthouse that flashes to warn seacrafts about the approaching coast.

Keeping with Bramwell Brown’s impeccable craftmanship, the clock is hand-assembled with meticulous care and the frame is made from powder-coated steel that you can request in one of four colours. The clock is heirloom-quality and able to be serviced over its lifetime so that you can have it forever or pass it on to the next generation.

A Caveat on Tide Clocks

Before purchasing a tide clock, it’s a good idea to check on how regular the tides are for your local coast. There are a few areas around the world that don’t have a consistent pattern, and a tide clock cannot be set with accuracy for these spots.

If you live near Southampton or the Isle of Wight, you’re likely not going to be able to use a tide indicator because of the double tide. The double tide is due to the English Channel, and is caused by the oscillation of the water that occurs twice in a day to create two high tides, a short low tide and a significant fall between the two high tides.

Other areas, specifically near the River Thames, have tidal parts. Since the river bed is not a smooth, even surface, the friction created causes the tide to recede much slower than it comes in and this can vary quite a bit from day to day. In cases like these, a tide clock would not be of much use.

Perfect for those who enjoy coastal living: take a look at our Tide Clock