Straighten Up!

You can get from one place to another the fastest by going in a straight line, which is an advantage airplanes and boats hold over those boring old land vehicles such as cars. Once beyond the restriction of channels we boaters don’t need those twisting, turning roads, and can point the bow at the destination then go in that straight line. Or can we?

Try as we might, rather than cruising in a straight line, most boaters travel in a series of long, slow S-curves. And with each and every curve your boat carves, additional distance is being added to the trip. Let’s say, for example, you’re making a 60-nautical-mile cruise at 20 knots. The math is simple: You’ll be at your destination in three hours, right? Yet when you look at the clock on arrival, it says the journey took three-and-a-half hours. That’s because your boat made hundreds of S-curves along the way, as the bow drifted to port and then you corrected course back to starboard or vice-versa. The net result? It may have been a 60-mile cruise but your boat actually traveled 70 miles to get there.

Unfortunately, none of us – not even the best autopilot in the world – can steer a boat in a perfectly straight line. Sure, you can get pretty close in a well-marked channel in dead-calm water, but most of the time boats are regularly knocked off course by environmental variables like waves, currents, and gusts of wind. Add to that operator inattention and/or an absence of visible marks to steer by. We can, however, take several measures to minimize our cross-track error (XTE in navigational parlance) and keep that boat as straight as possible.

Electronic Assistance

Aside from your eyeballs and your hands on the steering wheel, the most valuable weapon you have in the battle to maintain a straight course is your chartplotter. In order to best use it, however, it does need to be on the proper navigational screen. Many people look at the chart view with the boat icon on it, see that the icon is oriented in the proper direction, and go on their way. This is a recipe for inaccurate steering. Remember, the chart is a tiny representation of real life. If that little boat icon you see on screen were to scale, it would be a microscopic dot. In reality, you have to alter course by huge measures in order to see the change. In most cases even 5-degree changes to port and starboard, making one big S after another, won’t make a visible alteration in that icon’s direction.

Switch to a nav screen showing a compass rose or “highway”-style display, on the other hand, and you’ll be able to see tiny adjustments in the course line right down to a degree or two. Or you can steer by numbers. With course over ground displayed next to the target bearing you can see changes down to a single degree quite rapidly.

Wait a sec – what about steering via compass? In some cases a large, well-positioned, quality compass can provide as good an indicator to steer by as any chartplotter. Today, however, the vast majority of boats depend more on digital means for navigation, and a decreasing number have such a compass aboard. If you have that 10-inch Ritchie at the helm we applaud you, but that’s become the exception rather than the rule.

Remember that as you strive to maintain that perfect course, as a matter of safety your eyes should spend most of the time trained on the horizon, with the exception of 360-degree scans. You’ll only want to give the chartplotter (or compass) quick, occasional glances. That means you need to be very good at holding a straight course visually before you can hope to apply the advantages of these aids.

Visual Indicators To Steer By

Once you have your course set and bow pointed in the proper direction, it’s time to choose a visual indicator to steer by. Large, fixed, easily visible items are the best ones to look for. Landmarks like towers or tanks, lighthouses, distant points, fixed markers, bridges, and similar items won’t move and should remain visible (barring the onset of fog, heavy precipitation, or darkness) from the moment you spot them until you reach your destination.

Of course, you won’t always have one of these items within view. In that case, the next thing to look for along the horizon is a distinct point in a cloud formation. Though clouds move, they usually move slowly compared to your other options. Don’t plan on steering for that bulge or hole in the clouds forever, because as it moves you’ll get thrown off track. Instead, glance at the formation and then down at the electronics or compass intermittently. As the cloud begins to lead you astray, look for a different oddity or irregularity you can steer for that’s closer to the mark.

If there aren’t any clouds, you might be able to spot a boat on the horizon to steer for. Again, remember that it will be moving and represents a temporary target. Sailboats are naturally better than powerboats in this regard since they tend to move slower, but at long distances even a cruising powerboat can give you a brief mark to steer by.

When there aren’t any visual indicators, you’ll have to simply pick a point on the horizon as well as you can and head for it. In this case, assume you’ll be unable to hold a perfectly straight course for very long, and glance at your electronic helper regularly and often to make sure you remain on track.

Combatting Bow Steering

One of the most common ways we get knocked off course and into that big S is bow steering. Simply put, this is when the bow of your boat slews off in one direction or the other in reaction to waves. One way to minimize the effect is by being sure your boat’s trim is properly set. You won’t want your boat to run with the bow kissing the sky, nor do you want the bow to be forced down into a negative angle. All boats are different but, as a general rule of thumb, for planing V-hull powerboats, the farther down the bow runs, the more significant the bow steering effect will be. If you find it to be a problem, try trimming up a bit and you’ll likely discover that it takes a lot less work to keep the boat on course.

The other thing a captain can do to combat bow steering is simply to pay constant attention to the motion of the boat and counter-steer against waves as rapidly as possible. A savvy helmsman paying close attention will be able to predict the boat’s reaction to waves as he or she sees them approaching and will be ready to counter their effects as they happen.

The Results Of Straightening Up

With all these nautical nuggets tucked away in the gray matter, can we now make that three-hour cruise in exactly 180 minutes? Not a chance. No matter how good a job you do at steering, you’ll never make that boat go in a perfectly straight line. But you can make one heck of an improvement.

To keep the math simple let’s not worry about other variables such as currents and winds and just stick to the accounting for those big S-curves. Let’s say you make one full “S” every 100 yards, and each curve to port and then to starboard adds 10 yards, for 20 total yards of error. That’ll add 20% to the distance you travel and thus to your travel time. Twenty percent of 180 minutes is 36 minutes, so this 60-mile cruise will take 3 hours and 36 minutes.

Now let’s say you work hard to steer as straight as possible and correct the S-turns as fast as you can. You manage to shrink that error by half, so one of those curves takes you 5 yards to port and then 5 yards to starboard. Now, you’re travelling 110 yards to make each 100 yards of forward progress. Add 10% to your travel time instead of 20% and that three-hour cruise will take you three hours and 18 minutes.

Remember that all boats are different, especially when it comes to bow steering effects and how quickly you might be able to correct for them. Boat size, steering systems, hull type, propulsion systems, and other variables come into play, so the same captain minding the wheel the same way might make huge S-turns running one boat and tiny ones running another. But if you can get those S’s down to 10 yards of error for every 100 yards traveled, you’re doing a darn good job. Congratulations, skipper! You’re now travelling the straight and narrow path. Sort of.