November 2, 2010

How Creamer did it

EVER SINCE I READ ABOUT Marvin Creamer’s voyage around the world without navigational instruments of any kind, I’ve been wondering how he actually did it. I mean, how in fact did he deduce his latitude by eyeball only?

His explanation for the great unwashed public was simple. The former East Coast geography professor said he observed when a particular star was directly overhead. At that moment, the star’s declination (published in navigation tables) equaled the observer’s latitude.

If, at the time of observation, the star was not directly overhead but at least passing over his meridian, it must have been on a line either directly north or south of him. Then he simply estimated its angular distance away from directly overhead and converted that to miles, one degree being the equivalent of 60 nautical miles.

Yeah, right. The theory is sound . . . but the practice? Can you imagine standing on the heaving deck of a small sailboat at sea, hanging on for dear life, craning your neck upwards, squinting around the mainsail, and trying to judge when a star’s meridian transit occurs? How did Creamer do that? Well, I found the answer, or some of it, in the appendix to his book.

Apparently he drew an imaginary line from the polar point to the star before its transit. He extended that line in both directions and then he waited until that imaginary line divided the sky into two equal halves.

Okay, that’s the (very) approximate time of meridian passage, but how did he tell if the star was directly overhead or not?

“The observer should fix his shoulders in a north-south direction, stare upward, fix an imaginary zenith point and then make a zenith distance judgment.”

Hmmm. He makes it sound so easy.

“Normally an observer has a bias to his left or right,” Creamer continues, “which will affect where he ‘sees’ the star. By averaging two sights, one facing east and the other west, he can fix a point for the star and estimate his latitude based on the star’s declination.”

Creamer was in his late 60s when he sailed around the world via Cape Horn without even a compass or a watch. All I can say is that he was a very special and very gifted type of navigator. He also had his fair share of good luck. That, he explained, consisted of not having bad luck at dangerous times.

After his voyage was over, he discovered that his latitude estimates were within 100 miles of true latitude 68 percent of the time, and within 200 miles 95 percent of the time.

So, what next? you ask. What act can possibly follow that, to startle and amaze us all?

Why, blindfolded, of course. Yes, now someone needs to sail around the world blindfolded. And alone, naturally. And non-stop. And be under 15 years old.

Nothing less will startle and amaze us now. I’m afraid Creamer has desensitized us.

Today’s Thought
Journeys, like artists, are born and not made. A thousand differing circumstances contribute to them, few of them willed or determined by the will — whatever we may think.
— Lawrence Durrell

Boaters’ Rules of Thumb, #115
Best keel shape. For the best windward work, a deep narrow keel is more efficient than a wide shallow one. The maximum cross-sectional width should be about 35 to 45 percent of the chord aft of the leading edge and it should be tapered smoothly to a fine edge — then either cut off bluntly at right angles or rounded to a small radius.

“How long did it take your son to learn to drive your car?”
“Oh, three or four.”
“Weeks or months?”


Phibius said...

You might find it to be worth trying Creamer's methods out yourself - I get a kick out of trying to estimate the declination of a start then checking my estimate against predictions by star gazing software on my phone or laptop. It's early days yet, but Creamer-like accuracy does not seem completely unattainable.

John Vigor said...

Well, you're right, of course, Phibius. Professor Creamer proved that reasonable accuracy was indeed attainable by eye alone. But he had lots of practice. He crossed the Atlantic three times without instruments before his eventual circumnavigation.

John V.

Dennis @ Marine Electronics said...

Stories like Creamer's are so motivational. They make one just want to get out there and try (although I wouldn't try this for the first time too far from shore).

Anonymous said...

Hi John,
Today I was doing some research for my ocean rowing memoir and I thought I'd look up Marvin Creamer whom my late husband Curt Saville and I met a couple of times in the 1980s. The first time was at a boat show where we were exhibiting our ocean rowboat "Excalibur" after our1981 Atlantic row. The second time, we were on the South Pacific in the same rowboat. Our meeting was a lot more meaningful the 2nd time because Curt had fallen overboard and dropped the sextant before I could get him back on board. Crazily, we didn't carry a spare so we really had to improvise until I remembered Marvin and his technique of voyaging without navigation instruments. The maritime net people we regularly chatted with on our TR7, ham radio, located him and we talked to him. Since we were rowing for Hiva Oa in the Marquesas, Marvin suggested we aim to get under kappa Orionus in Orion. To make a long story short, it worked! It took over 40 days of navigating with the stars (63 days total from Galapagos) until we got there but we managed to save ourselves with his method that he so patiently described to us. When Curt asked him if it was good enough for our 25' rowboat to reach the Marquesas, he said yes. He has always been a hero to us.
BTW, your description of his method is spot on. It's exactly what we did.
Best regards,
Kathleen Saville