Voyager Notes: Section 1: Planning a Voyage, an Atlantic Circle

From the ASA's 108 standards, skills 1 and 2

1.Plan a passage across the North Atlantic or Pacific and state the advantages, disadvantages and hazards of various routes, utilizing Ocean Passages for the World, climatic charts, Great Circle plotting charts, plotting instruments, etc.

2.Plot a series of rhumb lines on a Mercator chart to approximate a great circle route.

Our plan is to sail from Newport, RI to Horta, Azores using a 35 foot seagoing sloop.  

The Azores are most of the way across the Atlantic and on the route to Gibraltar and the Med. It is over 2300 nm from New England which is about 16 days at an average speed of 6 knots or 20 days at an average of 5 knots. I'd plan on 20 days!

Let's discuss charts. We will use a Mercator Chart, pilot chart, and a Gnomonic chart. Each has it purpose.

 At the outset, let's make Plan A: the top shows two of the possible planning tracks. On the Mercator Chart, the pictured pilot chart, the great circle route plots as a curve, white pins. The great circle route goes into the cold reaches of the North Atlantic north of the Gulf Stream. The warmer and somewhat longer route is plotted as a curve to the south of the rhumb line. Advantages are warmer water, a fair current, and favorable wind direction and strength. The dark pins mark the route this sailor prefers, Plan A.

Pilot Chart for North Atlantic in June

The catalogue of pilot charts shows average conditions for each month.  Other considerations are things such as hurricane season in the Atlantic, July through November.  Hurricanes are most likely in August through October which makes those poor months for North Atlantic voyaging.  Other oceans have other severe weather seasons.  Seldom discussed is the risk of prolonged periods of calm.  No wind is a severe condition for a sailing vessel.

 A view of the big picture. 

A closer look at the Gnomonic chart comparing the Great Circle Route (straight line with flags) to the straight line on a Mercator chart (curved line marked with pins). The pined route keeps the heading constant at 093 degrees True. On the top chart, our desired route is planned out to be below the rhumb line defined by the blue pins (see above chart). It is longer and more comfortable.

Once we arrive at Horta, Azores, what are we doing next? Aside from cruising the islands, how about another voyage? Maybe an Atlantic Circle? (If you can get the book Atlantic Circle by Kathryn Lasky-Knight, do so. True story about a young couple a long time ago in a small boat and eventually with a little kid.) 

Using pins on the Gnomonic chart, the Atlantic Circle is detailed. The regulator of the trip is the Atlantic Hurricane Season, July through November. One must not be too far west as hurricanes brew off the Coast of Africa. Madera, The Canaries, and Cape Verde Islands  are for lingering until the crossing season starts in late November or early December. A first landfall in Barbados, for example.  That starts the Caribbean cruising circuit which ends somewhere in May with a run to Bermuda and then into home waters off New England.

The Atlantic Circle