Day 22 - Bermuda to Guernsey

Stravaig'n the Blue
Wed 15 Jun 2022 17:48
Position: 48:08.0 N 011:44.9 W
Position timestamp: Wednesday 15 June 2022 14:00 (UTC)
Distance travelled in last 24 hours: 147 NM (average speed 6.1 knots)
Reduction in distance to destination: 146 NM
Shortest distance to destination: 334 NM

We have been motoring for the last 24 hours and our ETA is still late on Friday evening. Since lunch time we have had 8-12 knots of wind on the nose. This is slowing us and is forecast to continue through the night. However, tomorrow, the wind should veer to the south which will allow us to hoist our sails and, motor-sailing, catch up on lost ground.

We are 222 miles west of Ile d’Ouessant (Ushant) and 240 miles WSW of The Lizard - not quite within sniffing distance of land. We are however picking up French maritime authority VHF radio traffic and there’s been a noticeable increase in commercial shipping around us.

The water depth is about to reduce dramatically as the seabed shallows towards the English Channel and the Bay of Biscay. According to our charts, the depth currently is over 5,000 meters but that will reduce to 100 metres or so in the next few hours. In strong westerly winds the seas build dramatically as the water depth reduces. Fortunately, today, the winds are light and from the east.

The straight line route or, in nautical parlance, the rhumb line from Bermuda to Guernsey is 2973 miles. To sail this, the boat’s heading would be 073 degrees throughout the passage. The rhumb line passes north of the Azores and the biggest risk to taking this route is the light winds of the Azores high pressure system. This system isn’t always a significant presence and it isn’t always right over the Azores but running into it can mean being becalmed or motoring for days on end.

The shortest route between Bermuda and Guernsey is the Great Circle route which owes its existence to the fact that the Earth bulges at the equator and isn’t a perfect sphere. The Great Circle route involves starting out from Bermuda in a more northerly direction, 053 degrees, and then progressively altering course to follow the shortest path to Guernsey, the arc of a circle, which the chartplotter knows all about. The Great Circle progresses north so fast that two thirds of the way into it, you are already at the latitude of Guernsey and the final third is basically heading east.

The down sides to the Great Circle are having to alter course continuously (although once a day would give a good approximation to a circle), the fact that it gets colder much quicker and the high risk of running into (or having to detour to avoid) the high winds of upper North Atlantic low pressure systems as they make their way towards Europe. The upside is that it is shorter. How much shorter? At 2906 miles it is 67 miles shorter, about 2.2% or half a day off a 25 day passage. No a lot then.

As we have experienced on this passage, the reality is that the weather dictates your routing. Our initial weather routing had us following the Great Circle route for the first two days before it took us south. Since then we have tracked the rhumb line, sometimes north of it, sometimes south, as we have chased better winds, beaten into north-easterlies and detoured south to avoid high winds, finally ending significantly south and passing right through the Azores to avoid Tropical Storm Alex. Currently, we are 25 miles north of the original rhumb line and 70 miles south of the original Great Circle.

Apart from having to put up with the unrelenting drone of the engine, all is well.