Bookmark and Share Email this page Email Print this page Print

January/February Issue 238: Rounding the Horn

Dec 29, 2016
The four-masted barque Priwall.

The four-masted barque Priwall.

Wikipedia

From the time it was discovered in 1616 by the Dutchman Willem Schouten, and named for the town of his birth, Hoorn, Cape Horn has held the image of doom and redemption, heartache and tragedy in the minds of mariners. More than 1,000 ships met their end there, with more than 15,000 sailors lost.

Cape Horn, located at 55° 58’ S by 67° 17’ W, is the southern headland of Horn Island, Chile. The first Europeans to see it were father and son Isaac and Jacob Le Maire, successful Dutch merchants. The shorter and dangerous approach to the Cape, the Strait of Le Maire, is named in their honor.

Rounding Cape Horn from east to west was a serious business, yet captains who knew their stuff and had good ships with good owners routinely made passages from Europe to the West Coast of Chile in less than three months. No country did this better than the Germans, and no company was more successful than that of F. Laeisz and Sons. The company’s “P-Line” ships — barquentines, four- and even five-masted full-rigged ships — hold all the records for the fastest passages with the least loss of life. It was Laeisz’s ship, Pamir that was the last commercial sailing ship to round the Horn in 1949.

Many ships fought for months trying to make it to the West, finally either succeeding, wrecking or turning around. Captain Bligh aboard Bounty spent 31 days making 85 miles to the West before he turned to go to Tahiti by sailing around the Cape of Good Hope. In 1740, George Anson spent three months getting around Cape Horn.

The distance run was at least 1,200 miles. Not only did the captains have to fight the strong westerlies, but also a powerful southern ocean current setting to the East. Ocean Passages of the World says among other things, “When the wind is strong and opposed to the tidal streams, the overfalls are overwhelming and very dangerous, even to a large and well-found vessel.”

The record holder for the fastest rounding of the Horn was made by the cargo-carrying school ship Priwall in 1937. It took five days and 14 hours. Priwall was a 20-year-old, four-masted barque of 3,100 tons, built at the Blohm and Voss Shipyard in Hamburg for the Laeisz Line. In the 1930s it had a crew of 72, of which 55 were cadets.

Priwall’s master was Captain Adolph Hauth, 39, the youngest of the Cape Horn masters at the time. He already had 25 years experience. He took command of Priwall in 1937, outward bound to Valparaiso with general cargo and coming back with guano. This was his third rounding of Cape Horn on a passage that took 72 days from Hamburg to Talcahuano, Peru. The rounding was made in early November and the ship took the dangerous shortcut through the Le Maire Strait on a strong northwesterly.

Let’s join our intrepid captain on Oct. 31. We will use the 2016 NA. Our height of eye is 20 feet. We are taking a lower limb sight of the sun. It is true that at the time of the passage, stellar observations were taken sometimes to ascertain longitude, but the tried-and-true method was to DR and to find LAN latitude. DR at the time of the sight is 49° 54’ S, 65° 53’ W. Priwall is beginning to make the turn west, rounding the Horn. Noon sight time is at 1607 GMT and the Hs of the lower limb of the sun is 54° 17’.

A. What is the latitude? 

A: Latitude is S 49° 55.8’

Edit Module

Old to new | New to old
Jan 22, 2017 02:32 pm
 Posted by  JaO

Hello,

I have different result. LAT = 49 54,9 S.

My calculation:
Hs=54 17'
Dip - 4,3
App.alt 54 12,7
Main +15,5
Ho 54 28,2

DEC S 14 23,1'

Noon sight:
90 00,0
- 54 28,2
ZD=35 31,8
LAT=ZD+DEC

35 31,8
+14 23,1'

LAT= 49 54,9'

What is wrong, please?

John

Feb 11, 2017 03:32 am
 Posted by  Sean C.

John,

I see only one, very minor mistake in your calculations. The daily pages of the Nautical Almanac give GHAs and declinations for each whole hour. However, our sight was taken seven minutes past the hour. We will need to correct for the change in declination over this time period.

At the bottom of the daily page for October 30th through November 1st, the 2016 N.A. gives a d correction for the Sun of 0.8'. This is the average change in declination over the course of an hour for the three days on the page. (Actually, IIRC, it is calculated for 00h UT on the middle day of the page, but don't quote me on that.) By inspection, we can see that the declination of the Sun is increasing toward the south. Therefore, we will need to add the correction to the declination. But we need the change for seven minutes of time, not for the whole hour.

So, we turn to the increments and corrections pages and look up the table with a heading of "7m". Under the "v or d Corr" columns, we see that a d correction of 0.8' corresponds to 0.1' for seven minutes of time. We add (again, because the declination is increasing) 0.1' to the Oct. 31st 16h declination of S14°23.1' to get S14°23.2'.

Everything else in your calculations matched mine. So, with the corrected declination, I got a latitude of 49°55.0'S. Which, of course, only differs from your answer by +0.1'...the same amount as the d correction. This PARTICULAR difference is within the limit of accuracy to be expected when using a marine sextant, so it is essentially inconsequential. HOWEVER, in the case of a larger d correction and/or a larger number of minutes having elapsed since the whole hour at the time of observation, the error in latitude could be larger.

I am not sure why Mr. Berson's answer differs by +0.8'.

Add your comment: