DIY tidal plotter

This clever little instrument pre-dates the computer age by some years but retains its place on the chart table by virtue of its usefulness.

The original idea came from an article by Jim Andrews, author of Twelve Ships A-Sailing, many years ago, although his was a far simpler device made from drawing paper.

I developed his idea using Microsoft Powerpoint to provide the smart appearance.

Use the tidal plotter as a quick guide to HW at your usual cruising ports. Here, HW Dover (in the blue rectangle) is at 1pm. This means HW Boulogne will occur at approx the same time (remember local time is 1400), HW Holyhead will be 1230 and HW Cowes will be 1330

The main display is on each side of an A4 piece of card, covered with sticky-back plastic.

One side shows HW at ports relative to HW Dover, the other shows Change of Tidal Flow relative to HW Dover.

Use the reverse of the plotter to shot that change in tidal flow relative to HW Dover. Here, when HW Dover is 1155, the Alderney Race is SW-going. In an hour’s time – at 1255, the Land’s End tidal flow will be N-going

The central disc is divided into 12 segments as for a clock face.

Vyv Cox is a chartered engineer and has been sailing for more than 50 years

All you need to do is rotate the clock face so that the time of HW Dover is at the 12 o’clock position.

The appropriate times for all other ports can then be read directly against the clock face.

All the data was sourced in Reeds Almanac. Some care is needed with the change of tidal flow times as this can vary considerably between inshore and offshore locations quite close to each other.

My version includes the Irish Sea, English Channel and French, Belgian and Dutch coasts, but the same method can be used anywhere.

Vyv Cox

Heed the chart warnings!

The Oa of Islay is renowned for unpredictable, turbulent waters. Credit: Imray

I remember a time when we were motoring close inshore on a flat calm past the Oa of Islay.

Brian Black has survived nine Arctic seaons since the mid-1990s and often finds himself getting out of tricky situations at sea

The chart could not have been more clear – here were overfalls. The West of Scotland pilot warned of their danger, but apart from some swirling in the water all seemed well, but not for long.

Suddenly huge mushroom-shaped seas were rearing on every side.

At first I was able to steer and avoid the worst of them but as they grew in intensity they cascaded as solid water onto the coachroof.

This is an evil part of the world, renowned for its dangerous waters and my experience that day was a lesson indeed.

These were clapotic seas doing little more than bearing their teeth. I dread to think what it would be like with a stiff wind against the tides that swirl around the island.

In future, I’ll take chart warnings more seriously.

Brian Black

Confident crew

Smooth mooring is all about practice. Credit: Andrew Sydenham

Managing the crew during docking is one of the most important things to get right, yet skippers often forget this.

Polly Philipson is the digital marketing manager for Grenada Bluewater Sailing and has experience in the sailing industry

Go over each person’s responsibility individually, and then together as a team so everyone understands the order of events.

If there are extra crew that are not needed, make sure they know to remain seated and quiet.

During docking, clearly communicate with your crew and be ready to give additional instructions if things do not go to plan.

Remember, if you’re not happy with the docking manoeuvre then simply start again. There is no pressure to get it right first time.

It’s far better to reassess or retry the manoeuvre. No-one will think any less of you as a skipper for doing so – quite the opposite.

The more you practise docking the better you will be able to respond to different situations.

Get out and try different boat handling manoeuvres with varying wind and tide conditions – the better you know the boats limitations the easier it will be to dock it.

Polly Philipson

Compass checks

Think about where you install new gear, it could have an affect on your compass

Many years ago, when sailors depended on log and compass and used to get lost a lot, we sailed south from Ireland for France.

I didn’t expect to weather Land’s End in one tack so I was delighted when it appeared on the port bow, and congratulated myself on my fine helmsmanship.

Norman Kean, FRIN, edits the Irish Cruising Club’s Sailing Directions. He and wife Geraldine sail a Warrior 40

On the way home, we sailed north from Land’s End heading for the Smalls, which failed to appear when expected.

Hours later my daughter (then 11) sighted the Tuskar. We were 9 degrees off course.

Now, 28 years later, she still tells the story of the night Dad couldn’t find Wales and she found Ireland!

The culprit was a stereo speaker, which I had installed on the cabin side of the bulkhead too close to the compass.

This resulted in a 9E deviation when heading north and 9W when heading south. We had been heading 9 degrees west of our supposed course, both ways.

It is a sad reflection on human frailty that when the unknown factor acts to our advantage, we congratulate ourselves on being so clever, and it is only when it screws up the plan that we wonder what the hell is going on.

This basic psychological fact is still out there in today’s world of GPS and chartplotters.

Always question a surprising observation, even – especially – when it’s a pleasant surprise!

Norman Kean