Getting on the water for an afternoon is fun, and something most of us can do easily. But an overnighter or a cruise calls for a little more preparation, with careful attention to navigation along the way. You need a plan to reach the other side of the horizon – before you leave the dock.

Learning to plot a course using charts and electronics – and maintaining that course in the face of tides and currents – takes practice, and it never hurts to watch someone else first. So in order to learn, we are going to look over the shoulder of a fictional friend we will call Bill, and see how an experienced boater might approach a weekend trip.

The journey from Norfolk, Virginia, to the town of Cape Charles on the eastern shore of the Chesapeake Bay is about 33 nautical miles. It requires navigating busy harbors, traveling through miles of open water and cutting across shipping lanes.

Bill wants to see the Eastern Shore, and decides a weekend trip to Cape Charles would be a good way to start. Because it will include crossing Chesapeake Bay at its widest point, about 16 miles of open water, much of it out of sight of land, he needs to plan ahead of time.

PLANNING A TRIP

The first thing Bill does is check marine weather forecasts and call a marina at Cape Charles to reserve a transient slip. That done, he lays out the appropriate chart and examines his route options. The chart will give him much of the information he needs, including the quickest route, the proper compass headings, depths and the location of the navigation markers he can expect to see along the way. He can also use it to calculate the length of his journey and how much time it will take, allowing him to target optimum light and weather conditions.

Bill decides it would be quickest to go straight to Cape Charles from Thimble Shoal light, which is 3.5 miles outside his harbor. It would also give him some open-water navigation practice, which he always values. Since the first 13 miles will be in familiar local waters, he concentrates on the open Bay portion. He can follow the buoys to Thimble Shoal light, so he starts his planning from there.

Bill could lay out a course straight from there to the light at Old Plantation Flats at the entrance to Cape Charles. The direct route would be 15.8 miles. About half way there, he would cross the main ship channel up the Bay. However, if he were to aim for one of the buoys marking that channel, say Bell 22, he would add only a little more than a mile to his course, but he would have a nice check on his progress at about the halfway point. That would give him confidence that he was on course, and it would break the route down into shorter legs. Making the trip in shorter legs will minimize the effects of any errors in steering.

First he lays out the course lines on the chart, then he uses a parallel rule to get his headings from the magnetic compass rose on the chart (his boat's compass is fully compensated, so he can steer magnetic courses directly). Above the line on the chart, he writes the compass course toward Cape Charles. Below the line, he writes the distance of that leg of the journey (see photo). He now has a great deal of information in one place, in a format that does not depend on his boat's electrical system.

USING A GPS

Of course, electronics can also be useful. Bill wants to maintain his skills piloting by chart and compass, but he also owns a hand-held GPS, so he prepares to use that too. He uses the chart to determine the latitude and longitude of (1) the entrance to his home waters (Hampton Roads); (2) Thimble Shoal light; (3) bell buoy 22; and (4) the entrance to the well-marked channel to Cape Charles. He enters these into the GPS as waypoints, which form a route. He gives this route a name (or number). When he gets underway, he will bring up that route and the GPS will indicate the course to the next waypoint along the route.

Bill does not have a large suite of electronics aboard his boat, but he would do many of the same things if he had a chart plotter or a laptop loaded with navigation software. It would be easier to place the waypoints, the large screen would be nice and he would want capabilities such as radar if he were going long distances. But Bill knows his hand held, if used properly, can do a fine job for short hops, and he has so far resisted the expense. Maybe someday.

TIME AND TIDES

With his route laid out and the distances measured, Bill can calculate the times it will take to run each leg, and the time for the whole trip. He will use this formula:

Time = Distance / Speed

He estimates a boat speed of 7 knots. By using the formula, he calculates that the leg from Thimble Shoal to Bell 22 will take about an hour and a quarter. The leg from there to Old Plantation Flats will take an hour. He knows from experience it will take him a little over two hours to get to Thimble Shoal and he estimates another half hour to run the channel into Cape Charles. Rounding the numbers up a bit, that totals about five hours for the whole trip. He should be able to do the whole trip by daylight (Bill avoids operating after dark if he can). He has been monitoring the marine weather in the days leading up to the trip and it looks good the whole weekend.

Finally, he checks the tidal current tables In Reed's Nautical Almanac for the coming weekend, though he could have done so online or using navigation software. It would be ideal if he could ride the last of the ebb out as far as Thimble Shoal and then catch the beginning of the flood as he goes up the Bay. But let's say it is not going to work out that way this time. Perhaps he will be fighting an ebb current in the Bay of about one knot. This will vary slightly from one part of the Bay to another, and also can be modified by wind conditions, so he decides to deal with that when the time comes.

Saturday morning arrives and Bill is prepared to go. His water and fuel tanks are full and his holding tank is empty. He has food, drink and safety gear aboard. He turns on the GPS, puts it and the marked chart near the helm, and turns on the VHF. He can use this to check the weather from time to time if he wants to. Everything is ready, so he heads out.

CROSS TRACK ERROR

The first 13 miles are in the confines of the port of Norfolk and Hampton Roads. This is a well-marked and busy area that is familiar to him. Being outbound, he keeps close to the green marks on the starboard side of the channel. There is quite a bit of commercial traffic of various kinds. It is both courteous and prudent to give them a wide berth: courteous because those pilots are earning their living and prudent because most are not as maneuverable as recreational boats. Bill knows, for example, that an empty barge is more difficult for a tug to control than a full one, so he keeps well clear of it.

Like any careful mariner, whenever he passes close to a fixed object in the water, such as a buoy or a daymark, Bill checks the water flowing around it to see what the current is doing at that place. He sees that the current is ebbing out of the harbor at perhaps half a knot. That will give him a slight boost on the way out. But as he gets out into the Bay, the ebb will work against him.BiotechnodesignsClick for an illustration of Cross Track Error

He follows the buoys out of Hampton Roads. He continues to steer up the well-marked main ship channel until it turns toward the sea at Thimble Shoal light. At the light he turns toward the northeast and puts the boat on his predetermined compass course of 042. There will be no more buoys to guide him for another 10 miles. He knows that he will be crossing the gradually building ebb current, though at maximum it won't be more than a knot.

There are two ways he can compensate. Since it will take him about an hour and a quarter to run this leg, a one-knot current will push him a mile and a quarter south of his course (the direction of the ebb). So Bill could aim for a point a mile and a quarter north of Bell 22, knowing he will actually slide a little sideways and end up near where he wants to go. The amount the current will carry him sideways to his course is known as "cross-track error."

The GPS can automatically determine the cross-track error and display it in a form that is easy to follow. Bill switches the screen to a "highway" format (see photo). Now he just has to steer to keep the highway looking like it is going straight ahead. If he stayed with the compass screen, he would need to turn periodically to keep the boat pointed at the next waypoint. That would cause the boat to follow a curved course, which would add distance (and in the case of a sailboat, might require a disadvantageous tack).

Bill decides on a combination of the two. He sets a new compass course of 038. This, he calculates, should compensate for the current. Periodically he will check the GPS to see if that course will accomplish the goal. If not, he can easily adjust the course by steering for a moment to "straighten out the road" and then steer that new course by compass. Bill is keeping up his steering skills, without becoming dependent on the electronics. He is only too aware that electronics on a boat can fail for a number of reasons – and always at the worst time.

STEERING BY COMPASS

There is a technique to steering by compass. From the point of view of the helm, the compass appears to swing back and forth. But Bill knows that the compass is relatively motionless, and it is the boat that is swinging back and forth. If he were to concentrate on the compass and try to correct each little movement, he would be constantly sawing at the helm. He has learned that his boat swings back and forth a small amount, but usually averages a fairly consistent course. He tries to maintain that course with the least movement of the helm.

In addition, he has to maintain a lookout. He is watching for other vessels and obstacles in the water, such as crab pot buoys or floating debris. He wants to enjoy the trip, too. Bill is constantly scanning the water. He can get a sense of his direction by the angle of the wind and the waves to the boat, one more reason he checked weather conditions studiously. He watches the horizon to see how much the bow of the boat moves one way or the other. This is much easier if there is some fixed object or land on the horizon. Periodically he checks the compass to see if he is maintaining the correct course. He learned long ago that staring at the compass and trying to make it stand still was a fast road to frustration.

When he arrives at Bell 22, Bill shifts to the next leg. A glance at the base of the buoy will tell him how the current is doing. If he still has more than minimal current, he will do the same kind of quick calculation he did on the last leg. He may pick a new aiming point upstream from the channel entrance. Or he may just check the GPS (which has automatically switched to the next leg) occasionally to keep him on track. This leg is a little shorter than the last, and in a little while he is able to make out a thin line of trees on the horizon ahead.

Old Plantation Flats light is ahead and he can steer for it, which is easier than following a compass course. It would be easy to relax and just aim at the light. But that would let the ebb current carry him down onto the flats south of the light. To avoid that, he continues to check his highway display on the GPS.

When he enters the marked channel, he follows the three R's: Red Right Returning. He is careful to keep the red buoys on the starboard side of the boat. Navigation here is easier, but he can't relax too much. He has two or three more miles to go, and the water on either side of the dredged channel is shallow.

Finally he arrives at the marina and secures the boat. Now he can kick back and relax, or go ashore and explore a new place. Tomorrow he will do it all over again – in reverse. He simply needs to add 180 degrees to his compass courses and invert the GPS route to get back home.

Gene Bjerke, whose work has appeared in Cruising World, Chesapeake Bay, Good Old Boat and Multihulls magazines, regularly crews on square riggers near his home in Virginia. He has been boating for 45 years and has made the trip from Norfolk to Cape Charles many times.