Fastnet Race navigation: tactics for the new finish

With the Fastnet Race due to finish in Cherbourg for the first time in 2021, Christian Dumard offers his expert advice on the challenges competitors are likely to face

The new Rolex Fastnet Race course, finishing in Cherbourg instead of Plymouth for the first time this August, offers more options on the way back from the Fastnet Rock with different possible routes.

The new Fastnet Race course is likely to become more open if the wind shifts, with possible tactical options along the English or French coasts.

Meanwhile, the current will be critical around the Casquet and its TSS, Alderney, and the Raz Blanchard (also known as the Alderney Race). You must make a few key choices after rounding the Fastnet and when entering the Channel.

South of the Scillies?

The first main choice in this part of the Fastnet Race will be whether to sail south of the three Scilly TSSs, or through the middle of them. Most of the routings tend to take you through the middle. A few routes favour the southern option, to avoid light wind zones or, for example, to play a wind shift along a stationary ridge. Routing software will be good at finding the ways through.

The main decisions to be made will usually be in the Channel, where there will be very strong currents a few miles from the finish.

The parameters to be considered are:

• The wind shifts.
• The difference of wind speed, depending on the time of the day, along the English and French coasts.
• The current around the Casquet and the Raz Blanchard. It will have a huge impact on the possible options.

Channel wind direction

With easterly winds, the wind tends to decrease along the English coast during the afternoon and increase during the second part of the night. The opposite happens along the French coast, where it increases in the afternoon and decreases during the night.

The law of quadrants and its effect on seabreezes, as described by David Houghton more than 30 years ago, works well on both coasts. Timing is critical; the models tend to be good at spotting the diurnal wind variations along the coast, but understanding why the routing takes you in the northern or southern part of the Channel, depending on the time of the day, is important.

With westerly winds, the opposite happens if you have sunny conditions. The wind will increase along the English coast in the afternoon and decrease during the second part of the night. Likewise, the reverse occurs along the French coast.

Playing the current

Depending on the time, the current can be more favourable in the south or in the north of the Channel. In this example (below) the current is stronger along the southern French coast.

Currents are very strong around the Casquet, Alderney and the Raz Blanchard and can reach up to 8 knots. Anticipating the current will often be the key factor; the current changes quickly and an error of 30 minutes in your timing can ruin a good option. You need to assess the risks of being stuck for five hours if your ETA to the Casquet is close to the time when you expect the current to reverse.

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