A Navigator's Guide to Passage Planning
A smart voyager identifies unique ocean features that can move you more swiftly over the bottom or set your plans adrift. A feature from our July 2010 issue
West Coast Wisdom
Downstream and upstream passagemaking along the U.S. West Coast are anything but two sides of the same coin. During the decade I spent cruising and racing off Southern California's rocky continental borderland, I figured out why so many West Coasters end up sailing around the world. It all stems from what adds up to two friendly headings out of four. Sailing south and east puts smiles on crews' faces. Conversely, crashing into the down-coast current and bucking the prevailing down-coast westerlies are no one's idea of a picnic. Fortunately, every wily West Coast navigator has a few secrets that make climbing back up the hill a little easier. For example, take the back eddies and diminished down-coast current that exists inshore, where the punishing westerlies are also somewhat diminished. This is another chance to use the beach hugging and motorsailing I mentioned earlier to improve progress up the Baja coastline. Early morning coincides with the least down-coast wind, and like surfers looking for waves, sailors headed up the coast prefer the glassy conditions that end up getting blown out by the afternoon.
Making use of countercurrents is an art in itself, and one of the most fascinating opportunities to do so occurs in between the two trade-wind belts that circle the globe. This equatorial countercurrent snakes its way across the Pacific. Situated between the northeast and southeast trade-wind belts, the inter-tropical convergence zone offers a reliable easterly setting current in a tropics dominated by two westerly setting equatorial currents. Originally called the Doldrums, this zone of flat seas, hot sun, and occasional punch-packing thunderstorm is a good place for cruisers with fuel to spare to make some miles against the dominant trade winds and equatorial current.
Charts, Moon, and Tide
One of the big epiphanies for an apprentice navigator is the realization that the current and tide, though related, are far from directly proportional. In fact, in many areas, the tide can be dropping while the current is rushing into an inlet, and the opposite can also be true. Add to this the cyclic nature of the phases of the moon and there's good reason for every passagemaker to carry both tide charts and current tables or a digital rendition of each.
Carefully timing a coastal passage can do more than simply add a couple of hours of fair current to a cruise. My favorite example of putting current diagrams to good use, and feeling like you just outwitted gravity, can be encountered during a passage from Newport, Rhode Island, to the Lower Bay of New York via Long Island Sound. By timing your departure from Newport to coincide with the last part of an ebb, a crew can scoot out of Narragansett Bay, pick up a flood current rushing toward Long Island's Plum Gut, and be well into the sound when the set turns foul. Add an easterly breeze to the equation, and a harbor midway down Long Island Sound can be reached in one tidal cycle. Plus, in this part of the sound, ebbs and floods are often measured in tenths of a knot rather than in whole numbers.
The second session of smart current planning calls into play the time it will take to reach Hell Gate, a tidal strait in New York's East River. It's a calculation that's based upon the time when the flood turns into an ebb at this point. This isn't when the tide is high at Hell Gate; it's when the flow up the East River and in from Long Island Sound actually reverses. Just as with the run from Newport, a flooding current can be ridden right to the slack-water point, and then the ebb will carry you down the East River into the Upper Bay and Lower Bay of New York. Picking favorable current conditions can cut the transit time in half, and the slower a vessel is under power, the more valuable this natural lift phenomenon becomes.
As one voyages around the world-or close to home-a veteran cruiser translates lessons learned into nautical wisdom, cues that warn about hazards ahead or deteriorating weather conditions. He or she pays heed to coastline features as well as bottom contours, soundings, and other benthic attributes. By understanding their influence on sea state, and merging the information with the surface weather maps and the 500-millibar forecast, a sailor can construct a very informative sea-state perspective. The process blends the science of the oceanographer and meteorologist with the art of effective seamanship, and the outcome is a safer, more enjoyable voyage.
Ralph Naranjo is a seasoned ocean voyager, author, and CW contributor.