We did indeed pick up some following current and make good progress towards the bar. By 11.30pm last evening I could slow the ship down as we were coming near. As explained before, we have to reduce speed here otherwise the ship might hit the sea bottom due to the extra draft caused by squat. However the ebb and flood times were this time in conjunction with the ships schedule and while we approached the bar, the flood current started to come in. This caused us to loose some speed but at the same time resulted in more water over the bar and thus more clearance for the ship.
This clearance is called Under Keel Clearance or UKC and is of great interest to all those sailors who do not like running aground and that includes me. When we entered the Amazon, the UKC became as little as two feet for a short while, now with the incoming tide, we had a minimum UKC of 8 feet. A second phenomena, which also has to do with shallow water, is that the ship gets an extra speed reduction due to the fact that it has a harder time pushing the water away with the bow. When a ship moves through the sea, the water that the hull displaces has to go somewhere; it is pushed aside but also pushed under the hull. When the bottom of the hull, the keel, is close to the bottom of the sea, e.g. there is only a small UKC, then that water has a hard time flowing under the hull and that also slows the ship down. So the more UKC there is, the less friction there is and the faster the ship will travel. It also means that there is no use trying to race through a shallow area with all the engines going full-out, this friction of the hull in the water simply prevents the ship from getting up to full speed.
Thus it is a matter of finding the balance between not creating too much squat and finding the right relation between engine output and maximum speed attainable. Figuring this out is more or less a matter of experience and knowing your own ship. There are tables and diagrams available that give general parameters but as each ship is different it still boils down to the experience that a captain has had with the ship before in similar circumstances.
With a bigger UKC we managed to make a little bit more speed than when we were inbound and by 04.30 in the morning we entered deeper water again. Although the estuary is quite wide and ships can be spread out over a larger area, we had quite a bit of traffic during the night. The Brazilian Navy was out in force doing all sorts of maneuvers in the dark and a few cargo ships came by. First an empty tanker on its way to Manaus followed by a Dutch container ship going the same way. There were loads of fishermen around as well and they did liven up our watch keeping activities. Most of the time they have no navigation lights going or deck lights on; I assume to save fuel. Only when they are hauling in their catch or when a ship comes too close they suddenly switch on their lights. As most of these boats are made of wood, they do not always reflect on the radar and that can have the startling effect that suddenly a few miles ahead of you a bright light is switched on, while you were absolutely convinced that the sea was clear and free of any traffic.
Brazil has a rule on the Amazon, that smaller boats and fishing traffic have to give way to the big ships, due to the draft restrictions of these large vessels. That rule is simply enforced by the pilots by not changing course and so most fishermen have learned from experience that it is better to get out of the way of the big ships for obvious reasons. For us who are used to the regular Rules of the Road it is a bit of an unnerving experience to
witness this but it works very well. So also during this crossing we saw the fishing boats make lots of room for us, while we steadily progressed to open sea.
By 7 am. we started to leave the muddy waters of the Amazon behind and the chief engineer started up his evaporators again to make fresh water. While on the river we could not make any fresh water; due to the danger of too much silt getting into the systems and we had to rely on the full tanks and the loading in Manaus. So we had to put in a bit of rationing, going for minimal ship cleaning, closing the self service laundries and emptying the Jacuzzi’s. Also the guests had been asked to be frugal with the water consumption. Drink Beer instead of water and shower with a friend……………..
It worked all out very well and we had a day consumption of water spare in the tanks. An amount of water that you want to keep up your sleeve, in case the ship is delayed in getting into clear seawater and or having to deviate for a medivac or something. So things turned out very well and expedition Amazon was successfully concluded.
October 25, 2008 at 2:57 pm
. . . exhalation . . . (I was holding my breath). Some welcome you got at the estuary bar. It was more like DON’T wipe your feet intering into the home of the Amazon. Pretty scary to move 55,451 gross tonnage (?) over 2 feet of water. Has any HAL ship every surfed up the Amazon on the Pororoca tidal bore? Or would it be wiser to wait out this violent commotion? Thank you for including a photo of the pink Boutu piglets. I also took note of the ice bow on the Prinsendam. You did pack your tap dancing shoes for this last assignment on the Veendam, didn’t you? And 42 years is a lovely age 🙂 [ . . . plus tax . . . ]
Welcome back the working world!
October 25, 2008 at 4:54 pm
Hello captain I love your blog i read it everyday. One day I wish to be a captain of a passenger vessel, but it worries me that ship are getting to large to even carry the name ships. I hope that when the Oasis of the seas and others like her come out, that all connections to maritime tradition are not lost. how do you feel about this? Do you think the captain of that vessel would be more like a mayor and about 5% real maritime captain. Are the going to start to require a 4 rear business degree for the captain as well? If you were given the chance to be the master of a vessel that size would you take it? I really hope you get a chance to answer these questions, I have been curios for quite some time and I thought you were the right person to ask.
Joey LaMarche Seattle, Washington
October 25, 2008 at 5:17 pm
This is a great blog. I appreciate that you take the time to explain regular ship operations in simple and easy to understand terms. I always find it difficult to explain what one does on a daily basis in clear, easy to understand language, and you do an excellent job.
Keep it up!