Post by davidd on Apr 27, 2019 12:33:44 GMT 12
Having (briefly only, in 1968!) worked in a dry dock, I somehow doubt the description of "opening the gate of the dock and letting the sea rush in" (my paraphrasing). Although the one I worked in was perhaps only 5% of the capacity of the South Korean one, probably even less than that, the addition of a vast amount of sea water would be, I suspect, rather dramatic and damaging if you simply "opened the gate". My memory of watching just one ship being reacquainted with the sea was that valves connected to the sea were opened (the ones I saw probably involved men winding up long threaded shafts way beneath their feet), and sea water then started flooding in through openings in the lower sides of the dock. Quite a few large fish which happened to be swimming rather too close to the intakes tended to get sucked in too, which were later shared by the permanent staff when the water was eventually pumped out again (I was only a casual staff member, so did nor get any share of this booty). Anyway, the seawater flooded in fairly slowly, so as not to erode the dock wall on far side or tear into the block work, and thus it probably took several hours to fill the dock completely (cannot remember how many hours), but I do remember that pumping out the dock took considerably longer, perhaps 6 - 8 hours. During the period the water level was dropping in the dock, the scrubbing down staff (including me) took to primitive wooden punts alongside the ship (there was plenty of room around it) and commenced the cleaning operation using tools somewhat like garden hoes (the "flat" ones, not the chopping ones). This was rather a disgusting and thankless job (I think the permanents mostly left this task to the casuals) and I recall that suspicious looking blisters in the ship's paintwork usually turned out to be the scene of some severe corrosion in the steel which had eventually to be ground out, then heavily repainted as the air dried out the surface of all structures. Once the sea level in the dock was about down to the bottom of the ship (about 6 feet from bottom of dock), the punts were hauled out and we had to wait for another hour or two to allow the remaining water to be pumped out. Then everybody descended into the bowels of the dock and got to work under the ship with a vengeance, scrubbing and scraping off all the roughness, weeds, other marine life, and "blisters", the later containing a completely black liquid, the result of oxidation of the steel. I was also surprised to learn (I did not know very much about the appearance of ships below the waterline) that ships tend to have perfectly flat bottoms, something I should have known, as there are some great scenes captured on film of ships in distress (in war and peace) which roll right over, and then can be seen that the entire bottom is flat. Anyway, with this unique experience, I have my doubts about "opening the gate of the dock" and letting the sea rush in - it would just not be possible in my eyes, both as to how they could open the "gate" (the dock I was working in had a floating gate which had to be "sunk" into the gate opening, with rubber seals to complete the water-tightness against the dock opening proper) without the weight of the outside water forcing it through the gate opening and having the sea burst through in an uncontrolled manner. Of course modern technology can be very clever, but the Lyttelton graving dock which I am familiar with was built (in the 1880s from memory) and it was developed in the age of steam, so it is entirely possible that much more elaborate and clever systems of moving water around have been developed since then.