Learning about Great Circle Navigation
02 December 2017
And another fairly similar day passes. The wind still blows from behind and we still are sailing goose-winged, pretty much where we want to go given what we can safely sail on this gybe. We will likely gybe to port during the next couple of days, to compensate for a slight northing in our course. The forecast is looking good for the next few days but we need to watch a bit of softer wind on the north of the Trades in a few days time, giving another reason to put in a bit of southing.
We are learning to sail a great circle route based on a gnomonic projection chart. That means that the shortest route from us to St Lucia is not a rhumb line but a curve with a constantly changing bearing. On our gnomonic Atlantic passage chart the course is plotted as a straight line, but across curving lat/long lines, and so every day we will have a new and slightly different course. Well, thatâs the theory anyway â�" lets see which island we end up in. With the wind dead downwind itâs all fairly approximate anyway.
Highlights from the last 24 hours:
- Now under 1,350 miles to go - No flying fish in the cockpit (Bibi happy) - No fish caught, though the lure we had out was bitten right off by something big - A good fast sail for the last 24 hours â�" all pretty much in the right direction - hopefully the mid-day stats are good for us today - B&K managed to produce a lovely crispy fresh iceberg lettuce â�" not bad 12 days out - Grahamâs freshly made rustic bread - Water maker still working (so we can have showers) - Happy hour watching the sun set with chilled country music, snacks and soft drinks (a glass of vino would be so nice, but we continue to be a dry boat) - A supper of butternut squash and chorizo pasta - A fast steady sail through the bright moonlit night
On the Republic of Barracuda we get to set our own shipâs time so we have democratically discussed what we want it to be. We have decided that we like to have happy hour in daylight and supper at twilight. Then we start the night watches in the dark, at 20:00 shipâs time. We also want the sun to rise near the end of the last watch â�" ie around 07:30 shipâs time. So taking all that into account we are currently still on UTC(z)-1hr. We know we should have moved on but it just makes sense for us and for Barracuda.
Distance run in the last 24 hours: 143 nautical miles
Cumulative distance run since ARC start: 1,648 nautical miles