Ed is skipper of a 10m production cruiser racer Aurora, which he keeps in Weymouth. He is returning from a West Country cruise with three friends and preparing to round Portland Bill.

Portland Bill has a race which extends about 3 to 5 miles south of the Bill, and the streams at springs can exceed 7 knots. It has been described as the most dangerous extended area of broken water in the English Channel.

However, in fine weather yachts can round the Bill by taking an inshore passage no more than about 200m off the tip of the land where the sea can be fairly calm. Skippers have to be cautious in this area as there are strong south-going streams which can push yachts into the race.

On the eastern side of the race is a shoal: the Shambles Bank. Sailing between the race and the shoal is not advised, except in calm weather.

On the outbound trip, Ed took the inshore passage. As Weymouth is only about 7 miles from the Bill, Ed timed his arrival at slack water and took the subsequent west-going tide.

He is now on his way back across Lyme Bay in daylight. The wind is Northerly 15 to 20 knots. Aurora is making good progress on a beam reach and if they continue at their present speed they will arrive at the Bill at about 2 hours after the tide has turned towards the east.

It is midway between springs and neaps. Does he take the inshore or offshore passage?

How to round Portland Bill

The advantage Ed has is that in this situation the wind is northerly so the inshore passage is on a weather shore. Ed needs to monitor the wind and the forecast on the way across the bay and if possible obtain available and accurate real-time weather reports.

If the wind stays below 20 knots my view is that the inshore route is possible in these conditions. He needs to read the pilot books and almanacs carefully and study the tidal stream atlas, because once he has committed Aurora to the inshore passage there is no going back.

The crew and yacht should already be prepared for rough water, with everyone suitably dressed, harnessed on and safe in the cockpit. The washboards should be in.

Ed should approach the Bill by steering to be uptide as he approaches the strong south-going stream to avoid being swept into the race. The navigator needs to maintain a close look on the chart plotter and, if possible, radar to keep the yacht no more than about 200m from the Bill.

If these precautions are taken they should have an uneventful rounding and fast passage to Weymouth. However, if the wind was blowing onshore at 20 knots or more the only option is to choose the long way round.

Skippers also need to be extra cautious about going close inshore if there is a large ground swell running.

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