In 1931, 26-year-old Dennis Puleston, a resident of the small English village of Leigh, decided it was high time to see the world. He had graduated from University of London after studying both biology and naval architecture and was working at a bank. It wasn’t the life he imagined as a young lad reading the exploits of Joshua Slocum and Alain Gerbault. Like his heroes, he wanted to sail around the world.
So along with a like-minded companion, Geoff Owen, they purchased a 26-year-old wooden boat named Uldra, built of teak, kauri, and white oak. Uldra was 31 feet with a beam of 9 feet, drawing 5 feet 10 inches. To protect her from the ravages of the tropics, her bottom had been sheathed with copper. Uldra had a water tank capacity of 120 gallons, two Primus stoves set on gimbals and no engine. Uldra had a gaff-rigged main and Marconi-rigged mizzen.
They tested the boat and themselves in increasingly boisterous weather until they were sure they knew what they were about. Finally with $200 saved between them, they set off for the Canary Islands.
Thus began a six-year odyssey. The world before World War II was a much easier place for a young sailor to get along and to survive without money. Along the way he operated a coconut plantation in Tortola, survived a hurricane, got shipwrecked off Cape Hatteras, crewed on a schooner from Newfoundland in the winter, searched the Caribbean for Spanish treasure, sailed to the South Pacific, got captured by Japanese soldiers in China, and did it all with his faithful dog Tiger.
All of this and more was lyrically recorded in his book, Blue Water Vagabond. Of all the “let’s go cruising” genre books, Blue Water Vagabond is far and away one of the best, capturing a time, only 80 years ago, that has long since vanished: the Caribbean and the South Pacific had not yet been “discovered,” the anchorages were empty and the cruise ships had not yet arrived.
What makes Puleston even more interesting is his career after this adventure. He settled in the U.S. and during World War II, along with Rod Stephens, helped develop the DUKW, an amphibious landing craft. He also went on to become a preeminent ecologist and was one of the founding members of the Environmental Defense Fund.
Like most navigators of the day, Puleston mostly did observations of the sun: “We both took morning observations of the sun, to determine our daily position. We had different methods of working out our sights, so there was no chance of us both making the same slip. On comparison we found that the results of our calculations never differed by more than four miles.”
So let’s join a young Puleston on the deck of Uldra, somewhere on the Atlantic Ocean, running down the trade winds.
The date is Oct. 20 and we are using the 2012 Nautical Almanac. The dead reckoning (DR) position is 25° 15’ N, 58° 16’ W. Height of eye is 10 feet and we are taking a morning sun line and we will see how the line of position matches up with the DR. We are taking a lower limb shot of the sun. The time in GMT of the shot is 12:27:35. The Hs of the observation is 31° 18.6’. We need to calculate the Ho, and then using H.O. 249 Vol. 2 reduce the sight so we can find the intercept. Then we need to plot and locate the estimated position (EP).
A. What is the Ho?
B. What is the intercept?
C. What is the EP?
A. Ho is 31° 30.2’
B. Intercept is 16.2 nm toward
C. EP is 25° 15’ N by 58° 12’ W
Back in the day everyone who went offshore relied on celestial navigation. It is true that there was no other off shore navigation system, but it is also true that once the basics were mastered, celestial navigation was a pretty reliable method of navigation. I only remark on this because in Dennis Puleston, we have a story of a young man sailing around the world and getting everywhere with his sextant, timepiece and sight reduction tables. It’s a good lesson to remember.
We have young Puleston doing a morning sun sight out on the Atlantic on his way to the West Indies. The purpose of this one line of position (LOP) is not to get a fix — for that we need two sights — but to see where the DR position is in relation to the LOP. We want the DR nearby or right on the LOP. This will confirm that the log is reading correctly and that there is no unknown current setting the vessel. It is usual for the navigator to take a morning sun line and then advance the LOP to a noon sight and create a running fix. That fix then can be advanced to an afternoon sun line. Usually that is all that many generations of navigators ever did. Many of them eschewed star sights as they were just too difficult.
Puleston is at a DR of 25° 15’ N by 58° 16’ W on October 20. We will be using the 2012 NA. and HO 249 Vol. 2 for solutions The height of eye is 10 feet. The time of observation of the Lower Limb of the sun is 12:27:35 GMT. The Hs is 31° 18.6’. We want to find the HO, the intercept and we want to plot the sight to calculate the EP.
Hs 31° 18.6’
Ha 31° 15.5’
+3rd cor 14.7’
Ho 31° 30.2’
Next we go to the daily sun pages of the NA for Oct. 20 GMT 12:27:35
GHA 1200 hrs 3° 49.1’
Inc 27:35 + 6° 53.8’
GHA 10° 42.9’
GHA 370° 42.9’
-ass long 58° 42.9’
While we are here we see that the declination of the sun at 1200 hrs is S10° 35.0’. The d correction is 0.9’ and is increasing. We see this by inspection. In the 27 minutes and 35 seconds the declination has increased 0.4’ so we have:
S 10° 35.0
S 10° 35.4’ Declination
We now can enter HO 249 Vol. 2 using assumed longitude, assumed latitude and LHA. These are the three entering arguments necessary for the solution of the celestial triangle.We go to Contrary declination to latitude and find:
Hc 31° 35’ d-36 z 121°
We go to Table 5 in HO 249 to calculate the correction for minutes of declination and find that is 21. We see that the d correction is minus so we subtract that from the Hc and we get:
Hc 31° 35
– d -21’
Hc 31° 14’
We subtract this from the HO and get:
Ho 31° 30.2’
-Hc 31° 14.0’
Intercept 16.2 Toward
We know that the LOP is toward because HO is greater than the HC and we recall that Ho MO Tow.
Next we lay out a plotting sheet and use the following as our Assumed Position 25° N by 58° 42.9’
When we plot we find that the DR is almost right on the LOP and our EP is 25° 15’ N by 58° 12’ W.