A look at The Tides for Lendy Cowes Week

by Cowes Week Ltd on 23 Jul 2017 Tide planning is a crucial part of both getting the best possible results during Lendy Cowes Week and in staying safe. For much of the early part of the regatta the scheduled start sequences will be over the low water period. With the smallest neap tides occurring on Wednesday, the height of tide at low water will progressively become higher during the first part of the regatta (low water Wednesday is 1.8m above chart datum), before slowly reducing again towards the end of the week.

On the opening day the first starts are little more than 30 minutes after local low water (0922, 1.1m) and there will be an east-going stream throughout the starting sequences. For the following three days low water will be during the starting sequence. If starting to the west from the Royal Yacht Squadron line it’s important to remember the Grantham Rocks, in front of the Green and only 400 metres west of the Royal Yacht Squadron line, are a hazard on which it’s all but guaranteed some boats will ground in the first few minutes of a race.

As a general point, if you’re sailing in shallow water to gain relief from an adverse tide, the Island shore to the west of Cowes has numerous rocky outcrops. If you hit one of these while sailing upwind it will, at best, spoil your day. When sailing downwind at speed in a strong breeze the outcome of grounding here has the potential to be serious. By contrast, the north shore of the Solent is predominately less steep to (with notable exceptions such as Lepe Spit) and softer, with the bottom either gravel or mud, particularly further west towards Lymington.

Tidal streams

Even though the regatta is timed to avoid the strongest spring tides, the flow will still be relatively fast in the Solent and surrounding areas. For those not familiar with racing here it’s important to recognise that this changes the normal priorities for determining the strategy on each leg of the course. Your plan needs to take account of the tidal stream first, with the wind as a secondary factor to consider.

A common misconception is that it’s most important to remember the times and locations at which the streams are strongest. However, the biggest gains on the racetrack are often made during the more complex transition periods when the stream is on the turn.

With a strong stream the strategy is obvious – if the flow is favourable you stay in deep water, while you head for shallow water to gain relief from an adverse tide. But the transition periods are far less clear cut, handing an advantage to any boat with good tidal data on board, providing her crew take the time to consult a tide book. An extra 0.4 knots of favourable tide for just 15 minutes translates into an easy 200 metre advantage, so it’s worth analysing the changes in half-hourly steps during these periods.

As the week progresses many of the starts will take place as the west going ebb stream changes to an east-going flood tide. As well as analysing the exact situation for the time of your start it’s also important to be prepared for a later start in case there’s a delay to the sequence.

Cross tide in Cowes Harbour

Boats entering and leaving Cowes harbour in the main channel should remember that, since the construction of the outer breakwater, there’s a strong west going cross tide in the area just to the north of the Yacht Haven, especially between two and a half hours before high water to an hour before high tide. This tends to set vessels towards the western shore of the channel.