The bridge crew, composed of three mates and the captain, have finished docking us. They got one final flurry of excitement before the rest of the team settles in to unload.
During the cruise, the bridge crew had a little less excitement for the most part, but an incredibly important and constantly shifting job nonetheless. They’re responsible for getting the Thompson where it needs to go, and while that requires fewer people on watch than it used to, it’s a complicated procedure.
The R/V Thompson’s bridge is decidedly hi-tech. I initially expected what I assumed to be the typical nautical arrangement – a sort of small helm, a throttle lever, a large compass and three to five people milling about looking stressed.
Instead, there’s a single row of computer screens with a bunch of LED buttons below them and three dials beneath an old-fashioned (and upside-down) compass. At any given point the bridge is watched by only two people, a mate (Pete, Christine, or Todd) and an AB (able-bodied seaman). Visitors are welcome when nothing’s going on, and the atmosphere up there is just as relaxed as anywhere on the ship.
The primary job of the mates, 3rd Mate Pete told me, is to make sure the Thompson stays her course. There’s more to it than standing behind a wheel and driving the ship, and there’s a lot more to it than just punching a destination into the autopilot.
Pete explained that, under normal conditions, the Thompson is always fighting the wind and the swell. If we want to go for a point due East, then – say we turn the ship to 90º on the compass – and the wind was blowing from the South, we’d actually wind up going Northeast. How far off course we’d go depends on the strength of the wind. Either way, because we usually wanted to follow a specific track rather than just arrive at a waypoint, we couldn’t do that.
Instead, we point a little into the wind, or at least turn a little to counteract it. Technically, then, the Thompson isn’t pointing exactly where she’s going. In the above example, she’d point a little further South – 93º, maybe – and her “course made good” would be a track due East. The autopilot will compensate and do this, but it needs near-constant supervision to make sure we don’t deviate too far.
The mates also take celestial bearings to confirm the GPS coordinates, Chief Mate Christine told me – weather permitting, that is. Generally they use the position of the sun, limited only by the roof of the bridge blocking their view. A device is mounted on a gyro post at either side of the bridge, lined up between the two holes that act as a sort of sighting system, and the number is read off the compass at the bottom. It’s like the long thin hole in a compass case, and used for the same purpose.
Celestial navigation also helps determine true North and South, which can be used to compensate for the magnetic compass’ slight deviations. Not only are the magnetic poles slightly different from the “true” ones, a massive steel and iron beast like the Thompson can cause a magnetic compass to aim a little off. To effectively “undo” the magnetic deviation, magnets and strips of iron are placed very carefully around the magnetic compass to counteract the error.
To follow her course, the Thompson uses two Z-drives and a bow thruster to maneuver. The Z-drives are screws – that’s propeller in sea-talk – mounted on rotating pods, giving multidirectional thrust instead of using a rudder. The bow thruster, or BT, isn’t used for propulsion but for precise movements.
This modern configuration makes the ship a lot more nimble than she looks. To dock, for instance, we just backed in and then moved sideways against the pier – moving to port only, no parallel parking necessary. Imagine if all four wheels on a car could point in any direction. Using the bow thruster to assist with turns changes the center of the motion, too, so it’ll handle differently.
I awoke this morning to the sound of the bow thruster at full blast. My bunk is in the bow, so there’s less ship in the way to muffle the enormous whirr of the maneuvering machine. Up to this point we haven’t needed to use it except for staying on station – we need to stay in the same place when we’re tethered to forty feet of pipe intent on embedding itself on the bottom of the ocean. To preserve the core and prevent damage to the ship, the BT and Z-drives take the place of an anchor.
The mates and AB’s have brought us safe to shore with plenty of mud. We’ve always appreciated them and their job of keeping us safe, but we’re especially grateful after a long, successful cruise.