Understanding how bow thrusters and docking systems work is key to stree-free landings

Few things can instill fear into a sailor like docking a boat in a stiff cross breeze with a group of spectators gathered under the auspices of catching a line, but who really just want to see how much fending off will be necessary.

Considering that all docking used to be done under sail power, it's certainly easier to dock a boat today than it was then. And now even more so as bow thrusters and docking systems become more commonplace on sailboats.

Bow thrusters are nothing new but as the technology has advanced it has become easier to retrofit boats with bow thrusters. Undoubtedly many a sailor has decided to do just that after watching the skipper of a gargantuan powerboat ease onto a face pier with the just the slightest kiss of the dock. Unfortunately bow thrusters don't work the same way on sailboats as they do on dual-engine powerboats with no keel to get in the way of sideways motion. With a little bit of thought and practice however, a bow thruster can certainly make docking or any kind of maneuvering in tight quarters, a bit smoother.

The first thing to keep in mind when using a bow thruster is that it is one more mechanical system that could potentially fail at the worst possible time, so you should not become too reliant on it when docking. It's good to practice docking and leaving the slip without the bow thruster so you know you'll be able to if necessary.

The other thing to remember is how a bow thruster works. Without a bow thruster, the bow of a sailboat can only move as a reaction from the stern. The rudder causes the stern to move and the bow reacts by moving the opposite way. When you move the boat with the rudder, the stern will move more than the bow and when you move the boat with the bow thruster the bow will move more than the stern. This action and reaction relationship dictates how you can best move the boat using a combination of the rudder, throttle and bow thruster.

A bow thruster can be most useful when coming into or leaving a slip. A short blast to the left or right can keep the bow straight and under control. The key is to get a feel for how long to apply the bow thrust. It is almost always better to start with a shorter blast rather than a longer one, but if you're dealing with a particularly tricky wind or current situation, you should be ready to apply longer additional bursts.

You can also use a bow thruster to pivot the boat, perhaps around a piling or even around the end of a pier in very tight quarters (Fig. 1). Prop walk, in which the propeller rotates the boat as well as move it forward or aft, is one of the factors that complicates docking, but the effect can be used in conjunction with a bow thruster to move the boat more efficiently. Pivoting in a small area is difficult if not impossible without a bow thruster (unless you employ the use of some craftily placed dock lines), but can be done relatively easily with one. To pivot a boat with a right-hand prop (one that turns clockwise as you look at it from the stern), turn the boat to starboard in forward gear with a short burst of power and a burst on the port-side bow thruster. This will serve to kick the stern out and move the bow in. Then, keeping the boat turned to starboard, give a short burst of reverse, along with a burst from the port-side bow thruster. You can repeat this process until you've pivoted as far as you need to go. You can pivot the opposite direction using the same theory, but the boat won't pivot as easily when it's working against the prop walk.

When pulling up to a face pier, particularly one in which you don't have a lot of room to make a long run up to it, it can be difficult to know when to turn, so it can be helpful to have the ability to go a bit sideways, also known as crabbing. By counteracting the bow thruster against the direction of the rudder you can go part sideways and part forward, while keeping the boat more or less parallel to the dock (Fig. 2). Steer moderately away from the dock and apply the bow thruster on the side of the boat farthest from the pier while moving forward. In other words, if the dock is to port, steer to starboard and apply the starboard bow thruster. The boat won't go completely sideways, but it will gradually make its way over to the pier.

Docking systems
For all the benefits bow thrusters have, they are still limited in what they can make a sailboat do. Now some manufacturers are offering propulsion docking systems that make even docking neophytes look good. The systems employ a pivoting sail drive and bow thruster controlled electronically by a joystick in the cockpit. By physically turning the propeller to face the direction it needs to be, the prop walk issue all but disappears.

The systems-Beneteau's is called Dock & Go and Jeanneau's is called 360 Docking-are offered as options on some of those manufacturers larger boats, but the technology has been so popular it is only a matter of time before it is commonplace on most production boats and certainly larger charter boats.

The most important thing to remember about using these systems is that it is important not to over think docking, said Wayne Burdick, president of Beneteau USA.

"You need to divorce yourself from all those fears," he said. "You just have to learn to be very gentle. It is very intuitive."

When in the docking mode, everything is controlled via the joystick. The wheel is locked in a neutral position so all steering is done the same way you might play a video game.

"If I just slightly move it forward, it will engage at the lowest idle," Burdick said. "The more I push it, the more it accelerates. You can get it all the way to 2,200rpm just with the joystick."

Unless there is a strong wind or current to contend with, though, you want to keep the joystick movements relatively subtle.

In addition to pushing the joystick in any position, you can also rotate a knob on the joystick to help rotate the boat. By simply rotating the knob, the boat will stay in the same place but pivot around its center of rotation. You can also use the knob to compensate for wind or current when trying to move the boat sideways parallel to a pier.

Burdick said most people pick up the system quickly, and they feel confident using it after an afternoon of practice.
"If they can concentrate for an afternoon in an area where they don't feel threatened by steel piers and in a basin where you can just turn the boat, they have it down," he said.