Bill is in Plymouth in September planning a passage to the Med. He has decided that the first leg is to sail to Camaret near Brest in Brittany. His yacht, Aries, is a 12m cruiser racer. He has three crew.

The forecast gives a low off south-west Ireland with SE 5-6 winds becoming 6-7 and veering south later for sea area Plymouth. The long-term forecast is for unsettled weather, so Bill is anxious to set
off and sail south as soon as he can.

The course to the northwest corner of Brittany is 195º true, and the distance is about 115 miles. From there he is planning to sail south down the Chenal du Four, a tidal passage inside the offlying Islands, for about 14 miles before turning to port towards Camaret.

The tidal stream in the Chenal du Four will be 4 knots, and it is midway between springs and neaps Bill knows that on a close reach Aries will sail comfortably at 8 knots so he reckons that he will be in the lee of France by the time the wind freshens and veers. He can then take the favourable tide down the Chanel du Four to arrive as soon as possible in Camaret.

His alternative plan if he is faced with a strong southerly, is to continue west to the Isle of Ushant and ride out the strong winds in Lampaul in a west-facing bay. All things considered, should Bill continue with his route or should he stay put?

The forecast is unsettled, should you leave harbour?

A It is an ambitious plan which could go badly wrong. Aries will sail comfortably at 8 knots on a close reach in good conditions but as the wind freshens the sea state will slow the speed. Progress will be slower when close-hauled hard on the wind. It is going to be very uncomfortable, even on board a 12m yacht.

In a southerly 6-7 the Chanel Du Four in wind against tide condition is going to be rough and difficult. In spite of the strong tidal stream the speed through the water in the short steep seas will be slow.

The plan to continue to Lampaul as a port of refuge is flawed because the bay is open to the west. The forecast of veering winds will bring southwesterly then westerly winds in the next day or two, making Lampaul untenable.

My view is that Bill should stay in Plymouth until the wind has veered to the west or even better, the northwest. This would then give a fast, more comfortable point of sail with a freeing wind, and the Chenal du Four will be much safer.

Even with wind prediction models available on the internet, skippers can never be certain of the precise time the wind will begin to veer, so passage plans need to acknowledge this and include some flexibility, especially if the change brings the direction further forward onto the yacht’s bow.

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