The Joys of Bow Thrusters

My initial reaction when I first saw a bow thruster on a 40-foot sailboat was to laugh my docksiders off. I’d spent a lifetime threading awkward boats with single props into tricky berths and could imagine no sensible reason for compromising sailing performance by drilling a hole the size of a baby’s head through the bow of a perfectly good boat. As thrusters became more common and I watched
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My initial reaction when I first saw a bow thruster on a 40-foot sailboat was to laugh my docksiders off. I’d spent a lifetime threading awkward boats with single props into tricky berths and could imagine no sensible reason for compromising sailing performance by drilling a hole the size of a baby’s head through the bow of a perfectly good boat. As thrusters became more common and I watched competent people using them, it finally dawned on me that for hard-to-handle boats, or even easy-to-handle ones stuck in marina berths from Hell, they do make sense. Then came the true moment of revelation.

I was crewing on a friend’s big, light-displacement boat that drew a quarter of nothing from stem to stern, except where her keel and rudder plunged to unimaginable depths. They gripped the water well, but only when the boat was moving faster than two knots. Below this speed the keel stalled. Any wind worthy of the name would then blow the bow away like a potato-chip bag. Docking the boat in an offshore breeze would have been nearly impossible for the owner and his wife without their bow thruster. This projected from the hull on a pod at the touch of a button and made docking an otherwise impossible boat a viable proposition.

Bow thrusters may have no place on well-mannered, heavy-displacement boats with a fair helping of static lateral resistance, but many of today’s boats have no forefoot to speak of, along with skinny foils that don’t grip the water well at low speed. In tight quarters where they can’t gather enough way to get the keel working, larger boats can embarrass even the most competent skippers. Bow thrusters have come of age.

Last month I spent a day playing with a hefty boat of a type I’d had problems maneuvering in the past. This one, however, had a thruster. There was even a remote wireless unit to control it with, so I had no excuse not to find out what bow thrusters can do.

An alternative to spring lines

As it happened, the boat was berthed in a tricky corner rafted up to a sister ship. I couldn’t see how we were going to squeeze her out of there without either springing off the other boat’s cleats (not kind) or deploying the thruster. My mate let go all the lines except the stern and I gave a good long blast on the thruster, wondering how well it would work. The bow positively galloped out. We slipped the remaining line and away we went, having proved a thruster is a viable, if noisy, alternative to a spring line.


Docking alongside in an offshore wind

For many skippers, this is the crunch. No boat is easy to tame when she’s “blowing off,” and a light boat will humiliate you by slip-sliding away to leeward as soon as it loses way.

Without a thruster: The best short-handed scenario is often to cram the midships section alongside as best you can while the crew steps off and secures the boat with a short line from a midships cleat. On some boats this works just fine, but not on all, and the line has to be very short indeed for it to work well. Failing that solution, the conventional approach is for a solitary crewmember to hop off as best he or she can and secure a bow line. By the time this is achieved the stern is blowing away, so the crew trots aft along the dock and the skipper either throws or hands a stern line across; all very well if the boat has enough lateral resistance to stay put for a few seconds and the crew are sprightly enough to do what’s needed. A thruster, however, offers a real alternative. My friend with the big boat and his wife had developed a singular system, and we decided to give it our best shot.

With a thruster: The secret is not even to try to steer the bow in. Instead, the crew scrambles off the boat with a stern line. Once this is secured, it doesn’t matter what happens because the stern won’t go anywhere. Even if the bow blows right out perpendicular to the dock, you need only power up your little friend in the bow and the boat will walk back alongside in defiance of the laws of nature.

We selected a berth barely long enough for our 40-footer. As I threw the engine astern to take off way, she shimmied her hips in like a halfback making a break as the mate hopped ashore with the stern line. In the brief interlude that it took to whip in the slack and make fast, the quarter had already blown three feet off the dock and the bow was halfway to Christmas. No problem. I produced the WiFi remote control like a rabbit from a hat, hit the button that pointed to where I wanted the bow to go, and in she came. The wireless controller let me mosey up to the foredeck, keeping the bow in as needed, pick up the bow line and hand it to my pal. He made the end fast, I took in the slack and secured it, and that was that. The rest was simply details.

Singlehanded docking

The owner of the boat I was using had recently found himself singlehanded when his only crew was taken ill. This left him the job of docking his substantial boat alongside as promptly as possible and, guess what? Half a gale was shrieking off the dock as he came in. The bow thruster was a big help, but it was the wireless remote control that really set him free. To berth a big boat singlehanded always calls for the highest levels of seamanship. In a heavy cross-wind from the wrong direction, it can be nearly impossible without shoreside help. With the wireless remote, however, all that is needed is to have a stern line ready and a bow line draped from its cleat to a point amidships where it can be reached from the dock. The boat is then hooked up to the berth any which way – even stern-first if need be – until the skipper can clamber off with the stern line in hand and the remote in his pocket. Even if the boat has blown off six feet by the time he secures his line, all he has to do is mop his brow, hit the thruster, and drive the bow in. He grabs the waiting bow line and secures it. Springs and shortening up the stern can wait until later.

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