Map Display

Saturday, 11 June 2016

On weather and fatigue ...

Mary Anne and I notice our levels of fatigue, and thus irritability, go up and down with the weather to a much greater extent than in port or on the land. So where does this fatigue come from? Don't we simply go about our daily routine of cooking, sleeping and watching "Sharpe's Rifles" and "Hornblower" videos while the autopilot sails on?

The obvious starting point for fatigue is that people are adapted to sleep at night and work in the day. We, on the other hand, are up and about at all hours on a kind of twenty-four hour fragmented sleep schedule. There is much to do cooking [think cooking in a moving RV on a gravelly pot-holed road!], repairing, and obtaining and studying weather information. Also, our systems for generating electricity and for making fresh water are not automated and thus require attention every day.

And then there is actual sailing - the factor whose effort IS very weather dependent.

When people go out sailing for an afternoon, they might have one person in command, another steering and others handling the control lines of each sail. We have one person for all these functions [the other is probably sleeping]. In constant conditions such as we experienced in the northern hemisphere tropics, hardly anything needed adjustment each day, let alone during a four hour watch period. Fatigue never surfaced.

By contrast, yesterday during the passage of a type of weather system called a "trough" wind directions shifted and then shifted back a number of times. Wind strength changed radically up and down as squall after squall passed by. Each alteration [and there were many during each four hour watch] required sail to be added or removed and the angle of the sails to the boat adjusted. Failure to take any of these actions would either stress our rigging or arrest our progress. Fatigue and Irritability!

On shorter voyages where we can carry fuel to motor a significant portion of the distance, these frustrating weather system passages can be dealt with by motoring for a half day or day until the winds again settle down. On a long voyage like this though, each use of precious and irreplaceable fuel must meet a sterner test than simply the avoidance of frustration.

* * *

I'll revisit now a subject I touched on a few years ago: "How does the availability of weather information affect the modern offshore sailor?" After all, it is not as if we can look at the forecast and decide not to go sailing today!

Before small boats were equipped with long-distance communication equipment, the route was chosen relying on fixed historical weather statistics while actual departure date was based on a shore sourced forecast. By contrast, on this trip we are always looking a week into the future and making decisions based on that information.

Gale or storm avoidance: Our choice to [in the end] sail north of Fiji rather than south was in order to avoid a gale warning.

Seeking more favorable winds: Our current track towards a transit of Vanuatu north of Espiritu Santo rather than south of Efate offers a slight advantage and reduces the risk of calms. Earlier in the voyage, our route toward the south rather than to the southwest off California avoided calms.

Efficient use of limited fuel: In a fixed area of high pressure or in the inter tropical convergence, useful wind might be more than a week away. In this case, it may make sense to motor to where the wind IS. It might also be that you are becalmed and favorable winds are to be found just ahead of you. If these favorable winds are of a transient nature and will be replaced shortly by calms, you might motor ahead in order to avoid "missing the bus." On the other hand, if wind is going to arrive tomorrow and remain in the area you will be sailing through, you might as well loaf slowly along under sail today and save the fuel.

These are just a few examples of the kind of decision that detailed weather predictions can inform.

* * *

In other news, we went from June 10th yesterday to June 12th today as we crossed the 180th meridian into the eastern hemisphere. The actual date line was a few days ago but our onboard flexibility with time zones allowed us to put it off until convenient.

The tiny French island of Futuna graced our horizon for a few hours yesterday.

And pleasantly, a two to three meter swell had been rolling in from the south for several days causing Traversay to bounce about very enthusiastically. This has now been toned down considerably as the large mass of Fiji to our south blocks swell from far away.

Even more pleasantly, when Mary Anne wrote the last blog posting, the temperature was 34C in the cabin; it has now dropped to 30C in the day and 29C at night.

-----
At 6/11/2016 21:48 (utc) our position was 14°47.07'S 179°38.11'E

1 comment:

  1. Following your progress with great interest. Happy Birthday to you, Larry.
    Clive and Susan

    ReplyDelete