Dispatch 7: Science and Seamanship

8th August, 2012


The DS-6 Top Float and it's Hard Hats

Physical oceanography is a unique combination of heavy industry, fine-tolerance science, and precise seamanship.  That to me is one of the most interesting aspects of this work.  The Dutch and American technicians, along with JCR’s deck crew, were routinely craning over the side 1,000-meter-long moorings, anchors that weigh two tons and top buoys producing some 1,500 pounds of flotation, not to mention all the scientific instruments affixed in between and the additional flotation set near the bottom of the mooring to help keep the wire straight—then landing the entire structure on a precise bottom site predetermined by the scientists.   Nothing of this could be accomplished without the ship and the equally demanding seamanship, which brings us to the remarkable displays of ship handling we’ve been seeing by Captain Chapman, who came on this ship twenty years ago as third mate.

 

'Watching from the aft window of the bridge, I felt like applauding, but that’s just not done; besides, it probably would have embarrassed this modest man.'

We’ve grown used to demonstrations of his skill, but several days ago we were treated to a particularly exquisite one.  When I, among others, complimented him, the Captain said, “Well, it’s the machine, you know.”  He was referring to the so-called Dynamic Positioning System, which we’ll get to in a moment.  It’s a fine tool, but it was definitely not just the machine that drove JCR on that particular occasion, or the others.  But it demonstrates the braided relationship between science and seamanship.

 

Hooking The Top Float

By the nature of their work, research vessels must routinely do things conventional ships that steam from point to point need never do.  She can stop in the middle of the ocean, fair weather and foul, and hold position within a few meters while the various ocean-measuring instruments are deployed and/or recovered; she can be directed to slide sideways; and she can spin around in her own length.  It’s a remarkable thing to see a big ship perform such nautical anomalies.  They require a specialized propulsion system.  Like other ships, JCR has a conventional propeller on a single shaft driven by Diesel electric motors.  But she’s additionally equipped with “thrusters” recessed in the hull to protect them from ice, one some twenty meters forward of the transom and another about an equal distance aft of the bow, that can be rotated 360 degrees to deliver thrust in any and all directions (“azimuthing,” in technical lingo).  The main propeller is controlled by a conventional transmission and throttle, while a video-game style joystick on the Dynamic Positioning System console operates the thrusters.

 
Though that’s just a cursory explanation of the system’s potential, it’s enough to get us back to but one example of the Captain’s skill and its relationship to the performance of ocean science.   Ideally, the Captain will position the ship such that when the technicians trigger the acoustic release, the top float will bring the mooring structure to the surface away off the starboard bow, because on this and most other research vessels, gear is recovered on the starboard side of the ship.  But it doesn’t always work that way; nature’s forces, current and wind, don’t always sympathize with well-laid plans.  So on this occasion, the current dragged the top float to the port side on the way up.  And the additional flotation, in the form of plastic-encased glass spheres (“hardhats”), came up on the other side of the ship.

Retrieval
Among the worst of the lurking potential mishaps is to run over the wire, in which case not only have you destroyed the wire and its attendant instruments, you’ve likely disabled the ship by winding the wire around the prop.  I’ve seen that happen on another ship; it’s ugly and costly.  So now, not only was the top float on the wrong side of the ship, but the wire between the top float and the secondary floatation arched around the bow to the starboard side.  Captain Chapman deftly extricated himself from the immediate danger by backing away from the gear.  The picture of calm, he twisted the joystick to spin the ship 180 degrees.  Then he backed the ship—against the wind and current—to position the top float on his starboard side where it could be hooked and retrieved by the deck crew, while avoiding that string of secondary floats looped around the stern onto his port quarter.  Finally, he steamed slowly forward, towing the mooring to string it out straight behind the ship for ease of recovery.
 

Jim, Murph & Dan, The WHOI Mooring Team
 
Watching from the aft window of the bridge, I felt like applauding, but that’s just not done; besides, it probably would have embarrassed this modest man.  Jim Ryder and Steve Murphy from WHOI, two of the best mooring techs in the business who’ve seen their share of ship handling in most all oceans, were also impressed.  So was Bob.  So was everyone who recognized the skill inherent in the act.
 
“Nice job, Captain,” said Jim at dinner.
 
And as I was leaving the dining room, I heard the Captain again reply, “Well, it’s the machine, you know.”
 
Right, anyone could have done it.
 
- Dallas
 

Captain Chapman