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Titania - day 10 update: How did we get here?



16:48:15N   44:56:77W
 
Distance to destination: 942 Nm
 
Those of you following the ARC2018 online tracker  www.worldcruising.com/arc/arc/eventfleetviews.aspx will see that Titania, along with many other boats, did not head to St Lucia in a 'straight line'. There are some reasons for this, and if you're not a regular ocean-going sailor you might want to know why.
 
1. Straight lines on the map
 
If you draw a straight line on a normal Mercator map of the world across a trans-continental distance, this is not the shortest distance between the two points. That actually looks more like a curve on the flat map, due to the Earth being roughly a sphere (for those of you that are Flat Earthers, bear with me here), and is called the 'Great Circle' route. You can prove this by using a piece of string stretched across a globe. If you've ever wondered why to fly to Los Angeles from London, you fly over Newfoundland, this is the reason!
So, we were never going to appear like we're travelling in a straight line on the tracker. In fact, the tracker shows the Great Circle route itself as a black line.
 
2. Wind
 
Even if we had sailed down the Great Circle route, that still wouldn't have helped, as the wind along that route would have been too light to give us good boat speeds. Titania is quite a large yacht, weighing 50 tonnes (plus all our supplies), and needs a strong breeze to keep her sailing around the magical 10-12 knots that we can achieve. By going more south at the beginning of the crossing, we could get into these stronger winds quicker, and settle onto a faster course.
 
We get wind forecasts about every four hours, using the internet via satphone to download GRIB files which contain detailed info about wind strength and direction. With these in the navigation computer, we can predict what the wind will be doing as we travel west, and we can make sure we don't steer into a patch of light winds. Jam today and hopefully jam tomorrow.
 
3. Angles to the wind
 
Sailors quite often go further but faster in order to get there quicker. We have a number of phrases for this: VMG, dVMG, VMC... They all roughly mean the same thing: going dead downwind is slower than sailing with the wind on your shoulder, and you need to know how fast you're approaching your destination, even if you're not actually pointing at it. We monitor this through our navigation software, and it's also displayed on the instruments visible to the crew on deck. We know how Titania sails best, and so we position ourselves so that the wind is the optimal angle for us. At the moment we are monitoring our speed in the direction of St Lucia which, happily, is also the direction in which we are pointing.
 
We're within 1000 miles to our destination now. We are doing well against the other boats (not that it's a race, of course...), and hope to reach St Lucia at the weekend for some rest, recuperation and rum punches.
 
Wildlife watch: we were buzzed by a beautiful little whale today. It surfed behind us, overtook us, went under the boat, swam round the front of us, and then did it all again. They really do look like they're enjoying themselves, inquisitive and benign.
 
Ned 

4215

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