The RYA's former Yachtmaster chief examiner, James Stevens answers your questions of seamanship. This month, which is the best route to Guernsey?
Ian and Jenny are in Salcombe planning a cross-Channel passage to St Peter Port on the east coast of Guernsey.
They are on board their 60-year-old 28ft (8.5m) gaff cutter Florence.
Florence will sail at about 5 knots on a reach in a moderate breeze.
She’s not so quick close-hauled but her main weakness is a small ancient engine which gives 4 knots at best.
The forecast is SW Force 4 occasionally 5 decreasing 2-3. It’s also a spring tide.
The tidal streams are strong around the Channel Islands so Ian and Jenny are planning to try and avoid a foul tide towards the end of the trip.
When the tidal stream in the English Channel is NE going, the tide runs along the north and south coast of Guernsey and north up the east coast past St Peter Port.
The stretch of water between Guernsey and the neighboring island of Herm to the east is called the Little Russel and the tidal rates here can be as much as 5 knots.
On the SW-going tide in the English Channel the stream in the Little Russel is south-going.
Taking the northern route around the island and down the Little Russel to St Peter Port from Salcombe the distance is about 70 miles.
The southern route taking Guernsey on the port side is 73 miles.
Which way should they go?
This one will be well known to West Country sailors as Guernsey is the nearest Channel Island to Devon.
Ideally Ian and Jenny would arrive at the north end of the Little Russel at slack water just before the tide turns south.
In the real world this is only possible either with a strong engine in settled conditions when the ETA is predictable or in a very steady wind.
On the day, with a decreasing wind and a weak engine, trying to calculate exactly when Florence is going to arrive is almost impossible.
Too early and there’s a huge foul tide coming up the Little Russel which would defeat Florence’s little engine.
Too late and there’s a long slow passage along the north coast against the tidal stream.
The best option with this boat in these conditions is to take the longer southern route.
Providing they approach with the east-going tide, the time of arrival off Guernsey is not critical and the flow to St Peter Port is favourable.
In a motor yacht or larger modern sailing yacht with a powerful engine, timing the arrival accurately at the entrance of the Little Russel is possible and therefore quicker, but the penalty for getting this wrong in a little yacht is a long slow few miles against the stream and a late arrival in Guernsey.