Sunday, February 12, 2017

Momentum and motion

One of the more disarming and difficult-to-describe dangers we experience as mariners is how dangerous motions are often slow-moving ones.

 I've been rolled off my feet in a relatively rapid roll on a 700-foot ship. I've also lost my footing and gone flying in a slow and deep roll where I didn't have handholds or a bulkhead to brace myself on- and yes, in a long, deep roll, putting a foot on the wall to stay upright or to keep walking is a thing.
I've never been launched vertically, thank God. I know that it can happen, but in the times I can think of where vertical motion at sea has been an issue, it was a matter of being in reduced G, light enough that my center of gravity shifted rather than achieving liftoff. Several times, I've been clutching my mattress, and a combination of roll and heave was enough to lift my mattress up over the lip of my bunk and send me surfing across the room.
 It's very disconcerting.

 More often these days, for me, vertical motion is an occupational factor, not a danger to life or limb, but I'm very aware that this can change in an instant. We moor against ships, generally with a high angle between us and the much taller vessels we're moored alongside. Mooring techniques are a series of compromises- keeping an equal strain on all lines, a good 'lead' on spring lines, and breasting or head/stern lines that keep us snug to the other ship. If we have those things, we're in good shape... and it's not rocket science, it's basic seamanship. Describing these things is more difficult than actually doing them. 

     Momentum counts. When, through swell or roll, there's relative vertical motion between your vessel and another- whether it's another vessel or a dock or whatever, no hawser or series of hawsers is likely to have enough ass to hold you hanging in the air.
   The slow speed at which this happens at times can be disarming. Listening the other day while the hawsers were singing (approaching their maximum stress modulus) while bunkering in a swell (and 45kt winds), I realized we were in a situation where I truly did not want to be. Do I want to slack lines, bail out, or keep watching?  Each is an option, each has costs.
 Should I slack lines, it allows for momentum to build between our two vessels. Lines can go from singing to snapping. Should I sit and keep watching, it means that the warning that the lines are giving us is being ignored. Will it get worse? That's a gamble. Should I bail? At some point, I need to come back, and if we're already getting banged around, sailing off in that situation presents its' own dangers. All the same, that's sometimes the best thing to do. Experience, judgement and self-preservation make for good decision-tree price points.
   But yeah, the slow speed at which momentum and motion becomes an issue is disarming. Thing is, when you're dealing with thousands or tens of thousands, sometimes hundreds of thousands of tons in motion, much like having sex with Bill Cosby, there's just not much you can do about it once it's started.

Here's a picture of us bunkering in a swell, on a beautiful day where a 400,000 (seriously, there was 70 foot of draft on that ship)  ton ULCC was just barely rolling, but when you're 250+ feet wide, a little roll translates into some respectable motion, and that, coupled with the swell, made for a 10-15 foot heave.
 (Note. I estimated that the writing on the hull was 25 feet tall. It is probably about 15-20)

 A more recent video from another mariner showed a pilot boat trying to get alongside a rolling container ship, and the pilot door being submerged in the process, much to the consternation, I'm sure, of all involved. The principle issue on this next vid is the lack of communication between all parties- something I'm unfortunately deeply familiar with (one of my pet peeves is when I have to shut down a fuel transfer because no one will answer radios, sledgehammers against their hull, blowing the air horn, etc. I just don't get it). However, my point in showing it to you isn't from a comms and safety perspective, just to show you how slow that roll is, and how there us just fuck all that can be done as a proximal solution to dealing with it for the man on the scene. It's not quite slow motion, but it might as well be for all that there's much can be done on the spot.

Now, this is a fair-sized container ship, and a relatively sedate roll. But there wasn't shit that that poor sailor could do about getting thigh-deep at that moment. At least he had a good handhold.

 I occasionally have nightmares where we snap all our mooring lines when alongside a ship, and I have to watch the slack being pulled out  of the cargo hose as it comes tight, stretches and snaps. Obviously, overseeing an at-fault spill is one of my deepest fears. Second only to a loss-of-life incident, although, judging by my dreams on a longer timeline, showing up for school in my underwear might still be the longest-running deep fear I hold. Jury's still out on that one, but about 10 years of dreaming that when I was younger has to mean something.


Anonymous said...

That Bill Cosby statement made me blast my morning beverage out of my nose. I'm stealing that for future usage.

Anonymous said...

While serving aboard the Forrestal in '91, we were doing an UNREP when the oiler steaming parallel to us lost her gyro. Her stern began swinging wildly, collision alarms were going off, and, needless to say, all the hoses popped in mid-transfer (CV-59 was one of the last of the oil-burners active). Scary as hell, and a hell of a mess. Fortunately, we avoided a collision, & injuries were minimal & minor.
--Tennessee Budd