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Tuesday, November 10, 2009


Lots of acknowledgements: Maureen, your cake has been deployed to great effect - thanks!. It will sustain us most of the way to the Cape.
Doug, thanks for Henry. He has a new waypoint and we'll get the jelly snakes out in a few days. Morro - thanks for work-around for USB thing - we use similar technique to start and try to disable or kill the serial ballpoint mouse as well - the real problem arises when the thing crashes without warning or explanation having apparently been running perfectly for days. CF18 now disconnected from USB and just running Airmail and iridium and SFSG. Daren't fiddle with it in case I destroy iridium set up and can't restore. Will be interesting to monitor success or otherwise of toy netbook which is now doing the USB and SoB. Basic problem there is that netbook has truncated screen and cant get Bottom edge of SoB screen with important cursor info. But a work around for the time being. Only using it because have separate 12v charger for it - have three toughbooks of different vintage but all have to share same charger.
Norm - tks for kind words and the other bit. I think you may have read correctly between my lines. Would appreciate your keeping posts a bit shorter - half a page or so - as sailmail can only cope with 11kb at a time and Steve has to break up his sends to us. Haven't turned left yet - won't be for about a week somewhere down between 25 & 30 S
Allan - ok - you redeemed yourself! But you're still a DOF! Glad the engine works - sounds a bit like a bigger version of mine.
Chris J - Andy? Actually, I hope we don't get anywhere close enough to Tristan for VHF but good to have your info - thanks.
Sue - Berri doing fine - El Pinko behaving - now getting cooler so not so scratchy under fur.

Lows and highs part 1

0700/10th position 1526 02456 trip 133/24 2595 to Cape Town

Still a'hooning, heading south along longitude 24.58 W to get down to where we hope the back of the high will be. To continue yesterday's explanation for the non-sailors, south of about 35 degrees the westerly winds begin - you're in the top of the roaring forties. in the forties, a line of low pressure systems tramps around the globe at various intensities and frequency. A southern hemisphere low rotates clockwise and draws air in towards the centre - think water going down a plughole - and the closer you are to the left front quadrant of the system you are the stronger the wind. The combination of the anticlockwise high to the north and the clockwise low to the south tends to promote and intensify the westerly winds where the two meet and the trick for us is to trek along the bottom of the high and the top of the low.

More on this later - must send it and get on with ritual. Post on ritual to follow too.

Latest Position

A distant barn door - perhaps

For the non-sailors and the meteorologically challenged: the weather in the central South Atlantic tends to be dominated at this time of year by a high pressure system that is centred broadly south of St. Helena. It stretches across from the S. American coast almost to Africa and sometimes down to about 35 south at its biggest. We won't go into why it's there and definitely not into coriolis force but a high in the southern hemisphere is a system in which air descends from the upper atmosphere and radiates outward from the centre in an anti-clockwise direction. There is always a soft windless patch in the centre. That means that the wind on the western side of it blows down the S American coast from the north or north east and on the other side, up the African coast from the south. Along the southern edge, it blows from the west, roughly along latitudes 25-30 south.

It follows that to get from the NE corner of Brazil(where we were a week or so ago) across to Cape Town, it is much easier to head south or SSE down the western edge of the high and turn left or east as you get towards the southern edge, taking advantage of favourable winds all the way. If you try to take the straight line you are likely to be heading into the southerly wind on the eastern side - and also the Benguela current which flows north up the African coast. We are now trying to smooch the best course from here to the Cape by cutting the corner around the south western edge of the high but not losing the wind by getting too close to the centre. This big arc is also closer to the great circle or shortest distance across.

Sailing to Australia by this route has its inherent penance. A bit like an out and back marathon, where the entire first half is sheer brain and tissue damage just getting you to the turn around point, you set out from Falmouth for Australia by going south west to get around West Africa and the effective turning point as you pass west of the Cape Verdes at about 27 W. And then you have to go a long way east to get the best angle to cross the convergence zone and the SE trades - a zig and a zag so far, plus another zig to get across and down to the base of the S Atlantic high which is what we are doing now. But - big but - yesterday morning I now think it safe to say, grabbing the nearest bit of wood, we made the final turn for home and we are heading SE towards Tristan da Cunha and the base of the high. Yeeebloodyhaaa! And so far, nothing difficult - just 'orrible in the CZ and uncomfortable for the arse bone down here. We may still have to trek a bit west on the way, to adjust our course around the high but I think we're looking towards a very distant barn door south of Hobart.

Appendages please, everyone!