It was a busy time at the Hamburg, Germany, shipyard of Blohm & Voss in the 1930s. Hitler and his cohorts were re-arming the nation and Germany was flexing its military muscles. The shipyard was turning out submarines, battleships and all sorts of naval weaponry that would be soon used in WWII. Every now and then, however, an interested observer might see the sharp ends of a sailing ship under construction, amidst the ships of war.
Indeed, Blohm & Voss were responsible for building some of the most magnificent sailing ships ever known. The company was the go-to builder of the famous Laeisz family of vessels — square-rigged ships of the great “Flying P-Line” like Peking, Pamir and Passat that are, to this day, considered the sine qua non of engineered sailing vessels. Magnificent workhorses of the sea whose job it was to haul freight from Hamburg around Cape Horn to Valparaiso, Chile, bringing back nitrates to Europe. For more information about those ships and about Blohm & Voss, see Alan Villiers’ book The Way of a Ship.
It was during the late 1930s that three sister sailing ships were launched at the shipyard. They were all about the same size and all were rigged as barques (square sails on the fore and main, fore and aft sails on the mizzen). All were about 290 feet in length. Two of these sailing ships have particular interest to us. One was Albert Leo Schlageter, now known as the Portuguese tall ship Sagres III, and the other Horst Vessel, better known today as the USCG barque Eagle.
Sagres is the third vessel of this name in the Portuguese Navy. She was used as a German training vessel and in 1944 slammed into a Russian mine in the Baltic. She was out of the war, and the U.S. confiscated the vessel and in 1948 sold her to Brazil for a nominal $5,000. She sailed in Brazil under the name Guanabara. In 1961 she was sold to the Portuguese and named Sagres after the peninsula to the south of Portugal where Prince Henry the Navigator had his navigational academy. In 2010 Sagres did an around-the-world voyage, covering 35,000 miles.
Let’s join her on that voyage. We will be using the 2015 Nautical Almanac. On the day of July 19, at a dead reckoning position of 38° 25’ N by 62° 50’ W, the navigator is hoping to get a star sight. There have been intermittent clouds all day and he’ll be glad if he can get one shot. The height of eye is 25 feet and the sextant altitude, Hs, is 78° 20’. He is looking to shoot Alphecca in the constellation of Corona Borealis.
At 00:07:10 GMT (July 20), the navigator gets a shot through the clouds of Alphecca. Find the local hour angle of the star and using Volume II of HO249, calculate the intercept. Then plot.
A. What is the time of civil twilight in GMT?
B. What is the local hour angle of Alphecca?
C. What is the intercept?
D. What is the azimuth?
A. 00:01:20 GMT July 20
C. Intercept is 8.1 nautical miles away.
D. Azimuth is 193 degrees.