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A Day in the ITCZ

October 13, 2011

Day 15

Local Noon Position (1119):
By GPS: 09.22.31N by 143.28.13W
By Sextant: 09.24.60N by 143.29.50W

Celestial Nav Note: the sun was solidly behind cloud for the 0930 shot but just visible enough at noon and 1430 to get a tentative running fix, represented above.

Course: 350 degrees true
Speed: 5 knots
Wind: 10 Knots NE
Sea: 1 foot S
Sky: 100% occluded. Low cloud all around. Very dark cell ahead–am trying to slip behind it. Bar: 1012
Temp: 79 degrees

MILES
Since last noon: 68
Total for passage: 1635
Daily Average: 117

Mileage Note: the following question came in yesterday and is answered at the bottom of this post. “When you refer to making a certain number of miles a day, are you referring to nautical miles or statute miles? You talk about knots, so I assume nautical, but don’t know.”

DAY SUMMARY

Winds were light and variable over night, and in the morning our course made good on the chart plotter screen looked like a child’s doodle, a collection of figure eights and a lazy S going nowhere. For a time wind was light from the south, then light from the north; I would dutifully rise, adjust sails and the vane, and race back to my bunk only to wake an hour later and find Murre gliding in the opposite direction. I finally gave up and slept. In the early morning before dawn, heavy rain for several hours with no wind.

Daylight brought a view of nothing: low, featureless cloud in all directions, a close horizon, and drizzle. Winds were light from the south and then southwest but couldn’t fill the sails, so at 0930 I started the engine. Which brought wind: by noon we were under full sail in a NE breeze of 10 knots…which slowly, slowly faded to nothing three hours later. But threatening to motor, I have decided, is good luck. So in the late afternoon and after an hour of flat calm, I began to rig the autopilot and we were immediately gifted with ENE winds at 10 knots (which are still blowing nicely as I type).

The sky has been a crazy collection of cloud all day: towers pouring rain; low, flat cells with torn or hazy edges that just drizzle, and when the sky opens, a hodgepodge of cumulus in all direction.

During one moment of sun, I noticed that the near water had about it a coppery-orange glow, and then as I stared, the glow expanded in size and became coppery-green at the center but hung right above the water’s surface. It could only be a water-top rainbow, but I half expected a space ship to slowly descend through the cloud.

A short while later I was relashing the main boom vang when I noticed just off to port and in the water below me a large portion of the water that had suddenly turned a light, effervescent, sherbet blue. Panic. It could only mean one of two things. The first was that we had just discovered a subsurface, uncharted reef, and I held my breath. Seconds later a great rush of bubbles broke the water’s surface, and the light coloration rapidly moved away from Murre. It blew a short distance away, and its companion, whom I had not seen, blew almost simultaneously some fifty feet behind us. The boat had barely any way at that point, so most likely is that these two whales were coming back up from depth and hadn’t noticed Murre until the last moment. The only distinctive feature, beyond their black coloration and their size (think school bus) was a tiny, hooking dorsal fin, like that of the Minke or Bryde’s whale. Two deep breaths and they sounded.

Tonight, a full, butter-colored moon rises over an inky sea and a swell from the north. Below it, Jupiter shines warmly, and around in all directions, stars, an open sky, just whisps of cloud at the margins.

Could it be? Have we escaped?

_=_=_=_=_

Question: “When you refer to making certain number of miles a day, are you referring to nautical miles or statute miles? You talk about knots, so I assume nautical, but don’t know.”

Answer: I’ve only ever met one sailor who insisted that the unit of measure for navigation at sea was the statute mile. Our two boats were anchored in Turtle Bay, on the Pacific side of the Baja Peninsula, next to a very brown town, and his wife was serving up a lovely Christmas dinner of roasted chicken and potatoes with red wine, so I thought it impolite to disagree at the time. But he was wrong. Sea miles are, by definition, nautical miles.

I’m not sure why the statute mile was invented, but its 5280 feet don’t relate to anything salty that I know of. The 6076 feet in a nautical mile, on the other hand, trace off one small part of a great circle which, in total, is the measure of the globe. One nautical mile equals one minute of latitude and 60 nautical miles (60 minutes) equals one degree of latitude. We get to 60 by dividing the earth’s rough circumference (21,600 miles) by the 360 degrees in a circle.

So, if I’ve made it from 08.00.00N to 09.00.00N, I’ve traveled 60 nautical miles (assuming my course is due north). Just so, when you see (as above) that my noon position by GPS was 09.22.31N and my Sextant reading gave me 09.24.60N, you know the sextant has missed the mark by just over two minutes/two miles (24.60 – 22.31 = 2.29 miles).

By the way, a knot is a unit of speed equal in distance to one nautical mile. Leave it to the sailor to invent two same-sounding words for similar ideas that bear no etymological relationship. *Nautical* is from the Greek *nautikos*, of or pertaining to ships, and *knot* references the old device used by sailing ships to measure speed, the chip log–a spool of line with knots tied at regular intervals whose end was tossed over the ship’s side and her speed measured by the number of knots that reeled off the line in s set period of time.

I hope that answers the question, Judy. Thanks for asking; it was a fun exercise.

end

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