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Saturday, 24 February 2018

Shaping our course

We have a large blue volume on board published by the British Admiralty with the imposing title "Ocean Passages for the World". It is full of general information for modern mariners detailing the appropriate routes to follow between different ports of the world. The final one third of the book, rather anachronistically, even has the same information copied from previous volumes tailored to the operation of large square rigged wind ships such as plied the world's oceans up to the middle of the twentieth century. Our "wind ship" is not so large, but our desire for the favorable winds and the avoidance of calms is the same.

Of course such a book can be based on climactic conditions (which are relatively constant over time) but cannot hope to present the best route in relation to the daily changes to the weather superimposed on that climate.

The following few rather pedantic paragraphs explain why our route has meandered to right and left rather than simply heading off towards our destination. Unlike our New Zealand to Chile voyage a year ago, there are no storms to avoid on this route but we DO want to avoid calms and make the fastest passage possible.

On most summer days, the winds off Valdivia in the south of Chile blow out of the south. It was so when we left but with a threat of contrary winds approaching from the west a few days after our departure. This led us to parallel the coast and make for the north as quickly as possible rather than head straight for our destination. While this strategy of outrunning the weather system worked fine in the short term, it still made sense to continue on this initial course well to the north, thus remaining relatively close to the coast for some time after. A region of high pressure and associated very light winds is a constant fixture well off the Chilean coast in the summer months - worth the extra distance to keep moving quickly in the better winds nearer the coast.

As we got north of 25 south latitude, the threat of calms from high pressure offshore diminished and the new issue was where to cross the equator. This is a bit of a compromise. The winds from tropical South America out to French Polynesia blow out of the southeast consistently and with moderate strength. This provides steady progress but, coming from dead aft and without great force, don't move our boat at its best speeds. North of the equator, the wind angle and speed provide 30% more boat speed but there is a catch. In the far eastern part of the tropical North Pacific, these excellent winds are often interrupted and the band of calms near the equator can be very wide, even approaching the limits of the fuel we could spare for motoring.

Initially, we were looking at crossing the equator in 110 west longitude to take advantage of higher speeds generally available on the other side. About five days ago, it started to become clear that winds would be very light for about 900 miles from 5 south latitude to 10 north if we held that course. That situation would dissipate within two weeks and, at any rate, didn't extend past 120 west longitude. The obvious path to avoiding the calms in both time and space was to turn left and keep ourselves in the southern hemisphere trade winds progressing steadily until a route direct to Hawaii can promise us useful winds. The planned equator crossing is now at 125 or 130 west longitude with the associated right turn coming within a week.

Now a digression . . .

As we move along here through starry night and day and night again, unable to say for sure on what day we will arrive in Honolulu, I often think with amusement at the idea of delayed flights. I know there is always room for improvement but ...

On those rare occasions that international air travelers are inconvenienced to the extent of a few hours, I'd love to bring them out here for a few days to show them the immense distances that the airlines have simply annihilated in our modern world. As to the airlines charging "so much" for such a cramped seat, it is easy to forget that the real product is transportation - moving hundreds of people many thousands of miles in a few hours, in safety and mostly on time. The cost in "constant dollars" has actually decreased considerably since the inception of long distance travel in the 1950s and is now less than what we pay for groceries alone to provision one of our sea crossings.

Benjamin Franklin made a number of Atlantic crossings as part of his diplomatic efforts to forge the new republic. Sea travel at the time, absent the weather forecasts we benefit from today, was often uncomfortable and uncertain to an extent totally unappreciated today. Franklin would have seen Mary Anne's and my voyages in Traversay III as reasonably fast and comfortable but could only have rolled on the floor laughing at air travel complaints.

. .

As I write, we are just past three weeks into our voyage. Honolulu is perhaps four weeks ahead. The nearest lands are Easter Island 1100 nautical miles to the south of us and Clipperton Island an equal 1100 to our north. The Galapagos are some 1200 nautical miles to our east northeast. We were similar distances from land on our New Zealand to Chile passage last year but Oh how different is the gentle tropical sea we experience now from that cold stormy southern ocean!


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At 2018-02-24 06:43 (utc) our position was 09°01.63'S 109°45.76'W

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