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Old 06-29-2004
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Michael Carr is on a distinguished road
Route Planning 101


How do you know when to depart for an ocean crossing? That's where prudent route planning comes into play.

Consider this question: When do you depart on a voyage? Do you do it when the crew is ready? Do you make that decision based upon when the boat is ready? Or when you, the captain, are ready? Or maybe you just depart because the boat anchored nearby is weighing anchor so it must be time to go.

Some boats travel solo and others travel in rallies, going en masse. So how do sailors following these diverse modes of travel resolve the go or no-go decision as well as the multitude of issues involved in choosing a proposed track and then either staying with that track or modifying it as circumstances and conditions change? These are fundamental questions for all ocean-going sailors.

At first it might seem that there is no way to come to a logical and reasoned decision. But there actually is and the first step is to define your objective. Are you departing on a race that you highly desire to win or are you heading off on your first ocean cruise? You must define the objective for your voyage. Saying "I want to safely cross the Atlantic Ocean and minimize my exposure to gale-force winds" is something quite different than "I want to enter the Around Alone Race and win." These two very different goals have both issued forth from my mouth in the past, so I know something about this topic.

Once you have articulated the object of your voyage, you can then define the type of weather you desire to experience. In saying weather I include wind, waves, ocean currents, fog, rain, low and high-pressure systems, and tropical events. Waves are probably the most critical weather element since they have the greatest potential effect on a vessel's stability and its ability to make progress toward a given destination.


Finding the appropriate weather window for your vessel and your sailing style is a critical component of route planning.
Weather window is the term usually applied to that period of time, which can be hours or days, during which weather elements are appropriate for a specific, selected transit, having considered the vessel and crew's capabilities and constraints. Accepting this definition of a weather window confirms that there is no universal weather window for all voyages, boats, and crews.

Here's an example: The appropriate weather scenario for a record-setting run west-to-east across the Atlantic on a catamaran is not necessarily the same weather situation you'd want for sailing a cruising monohull over the same course. A record-racing catamaran crew would desire strong, low-pressure systems that move with it at speeds of 20 to 30 knots, while the crew of a cruising boat would rather have a stationary high-pressure system providing consistent and steady winds. For a multihull, the strong southerlies and southwesterlies that precede the arrival of low-pressure system in the Northern Hemisphere would favor the cat's off-the-wind reaching prowess—allowing it to achieve speeds equal to and greater than the true wind. A slower moving cruiser would prefer the same wind direction, southerly, but at a lesser and more consistent strength, which is gained by using winds coming off the Bermuda-Azores high pressure instead of the winds associated with developing and growing low-pressure systems.

Once a crew has chosen a route and departed, the skipper shouldn't consider that the route is locked in place. It must be updated and tweaked daily, hourly, and often minute-by-minute in response to changing weather, vessel, and crew conditions. A chosen route is similar to the information contained in a AAA triptick in that it is for general guidance only. You still need to watch the traffic pattern, shift lanes to avoid unnecessary traffic, and even detour if conditions become unacceptable. For ocean-going sailors, the same kind of flexibility is key—a willingness to institute and make changes.

"When a person cannot make intelligent decisions, he or she usually ends up guessing, and that introduces chance into the decision-making process, which can lead to disastrous mistakes."
Although it's very often overlooked, crew fatigue is one of the most important factors in determining a route. A human body has definite limits. Sleep must be given to a tired body; lack of sleep causes numerous mental and physical problems. A tired person does not think effectively, his ability to evaluate and process information is significantly slowed and events can easily overwhelm such a person. When a person cannot make intelligent decisions, he or she usually ends up guessing. Guessing introduces chance into the decision-making process, and so mistakes are made. Sometimes such mistakes are simple and not too dangerous, but other times those mistakes can cause injury to the boat or crew, or worse.

This is why all decisions need to be made within the context of a crew's capabilities, taking into account their physical and mental condition, their experience, their training, as well as their level of fatigue. A tired crew cannot perform, and should not be made to perform. In a sense, routing is a study in situational awareness, of knowing your long-term objectives while maintaining a grasp on your immediate surroundings. It is also a challenge in observing, detecting, analyzing, and then acting as you observe and evaluate your weather, crew, and vessel.

So, now that we know all the variables and possibilities, how do we start the routing process? First consider the following initial track options:

Great Circle    The shortest physical distance over a curved surface.
Rhumbline    A course that crosses all longitudes at the same angle, but is not the shortest physical distance across a curved surface.
Bucket    A route that forms the shape of a bucket by taking the vessel north or south until reaching a desired latitude for passage, then perpendicular until near the longitude of the destination whereafter the vessel turns north or south to the destination. Sailors utilize this form of routing to minimize exposure to weather at unsuitable latitudes.
Composite    A hybrid of the great circle and rhumbline routes, the composite approach employs a limiting latitude so that sailors can avoid unsuitable weather or restrictions due to geography, ice, or political constraints.


Savvy sailors know to adapt their route planning to accommodate the many changes in weather and oceanographic conditions once underway.

Once you choose the best route option you can then begin factoring in crew and vessel capabilities and limitations. Always remember that on ocean voyages, both long and short, the route that will take the least time to sail is very often not the shortest physical route. Unlike the AAA triptick, you cannot depend on making a steady speed nor have a flat highway for an entire passage at sea.

To manage your route you need information, the kind of information that keeps you informed of past, present, and future weather and oceanographic conditions. Without information you cannot make intelligent routing decisions, especially in the dynamic environment of weather. To gather information you need systems that bring in quantities of quality and timely information. Last week's weather chart is of little use, as is today's weather chart if it contains scant information. You want weather products that are data-intensive with quality data.

OK, where do such products come from? These days the Internet is overflowing with quality weather data, and marine weather products are supplied through a number of communications systems. Some that you should be aware of are NAVTEX, Inmarsat C Safety Net, OCENS Millennium, Iridium, GlobalStar, Inmarsat A, B, M, and the Global Maritime Distress and Safety System (GMDSS).


Having access to multiple means of communication in an emergency is an important part of successful route planning says the author.

A final element in successful route planning is having access to emergency communications should you need to request assistance. An emergency position indicating beacon (EPIRB), or a GPS equipped EPIRB (GEPIRB) should be mandatory equipment for every ocean-going vessel. And I consider it necessary to carry a search and rescue transponder (SART) and an emergency VHF radio, as well as immersion suits for protection from hypothermia, a liferaft, and a watermaker. Humans can survive an amazing amount of time without food, but freshwater is another matter. It's imperative that the human body intake at least 18 ounces of water every day to maintain a basic level of function. So, even the best life raft and emergency-locating gear won't guarantee that you will be alive when help arrives. You need to keep yourself hydrated and warm.

Follow these prescriptions regarding routing and make decisions only after you've gathered all the information that you can. Do that and you should be able to make the most of any offshore passage.



Suggested Reading:

West to East Across the Pond by Michael Carr

Updating the Navigator's Tool Box by Dan Neri

Using a Weather Service on Your Next Passage by Michael Carr

Buying Guide: High Frequency Radios

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