Cowes Week - Tips on tidal planning

by Rupert Holmes on 8 Jun 2012 Abderdeen Asset Management Cowes Week 2012 is being held from 11th to 18th August in the Isle of Wight.

Although these days Cowes Week is timed to avoid the Solent's biggest tides, they still play a very important part of any successful race strategy. Unlike the majority of sailing venues, the Solent demands that tidal planning takes precedence over wind strategy. For example, it's almost always the tidal stream that will dictate the favoured side of a beat to windward.

Broad principles that will be familiar to almost every competitor – and many spectators for that matter – are to stay in deep water (where the stream is strongest) when the tide is favourable, and shallow water (where the stream is weakest) when fighting tide.

However, many competitors – locals included – are guilty of focusing on the fastest rates of flow mid-tide and failing to study the detailed picture as the stream changes as carefully as they should. Granted, the key eddies that form close to shore up to two hours before the main stream changes – most noticeably close to West Cowes – are well known. But it's the many subtleties over the two to three hours as the stream changes that can hand perceptive competitors an advantage of up to half a knot.

A detailed half-hourly tidal atlas is essential to be able to identify the best opportunities at the turn of the stream, enabling even those who are newcomers to the Solent to make good gains on the many competitors who attempt to rely on memory.

How shallow? When fighting an adverse tide it's tempting to head right into the shore to minimise the strength of the tide you're fighting. This can work well on most of the north shore of the Solent, where the land is low-lying, there are few navigational obstructions and the seabed is predominately gravel or mud.

However, the Isle of Wight shore presents a greater number of challenges, including significant wind shadows under the high ground and a number of rocky outcrops. The latter means it's vital to be fully on top of your navigation here, including the current height of tide.

Every year there are competitors who fall foul of Grantham Rocks, a few hundred metres west of the Royal Yacht Squadron start line, Gurnard Ledge and Quarry Ledge. Almost all escape with no damage other than a poor result, dented pride and a bill for re-fairing the keel, but to hit one of these at speed on a downwind leg in a big wind could certainly be dangerous.
Cross tide reaching legs

It's all too easy to lose ground on this type of leg through being swept downtide of the rhumb line between the two marks, especially if the buoy at the end of the leg is out of sight. While boats with GPS can easily ensure they track in the correct direction, there's also an easy solution for the White Group dayboat classes that are denied electronic aids: use a hand-bearing compass to keep the mark behind you on a bearing that will lead you to the next mark. It's very simple and very accurate, so you can make good gains on the many boats that fail to do this. As soon as you can see the mark ahead, use this, lined-up with the land beyond, to give you a transit to sail along and making life even AAM Cowes Week website