Water ballast in Titanic's double bottom tanks


Arun Vajpey

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Jul 8, 1999
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Is there any information available on how much (in terms of percentage of total capacity) water ballast was there in the tanks of the Titanic's double bottom before it set off on the maiden voyage?

The reason that I ask is that I read something about it in Tom McCluskie's book Anatomy Of The Titanic. He says that when the ship was almost completely empty of crew, passengers, coal and cargo, the tanks would almost be full to avoid a very high waterline and consequent risk of transverse instability. Apparently, the ballast is gradually pumped out as the ship is loaded and theoretically could be almost empty if the ship was full to capacity.

Sam Halpern's superb article Titanic's Hidden Deck gives a detailed description of the anatomy of the tanks in the double bottom including their capacities. I understand that the total capacity of those 44 tanks in the double bottom was around 5700 tons. But other than fresh water tanks, I imagine the ballast tanks themselves would only have been partly filled at the start of the voyage.

The Titanic was carrying about 2/3 of its passenger capacity; the crew and cargo were likely to a higher capacity. Based on that, I am guessing (and only that) that the ballast tanks in the double bottom contained about 20% of their capacity of water.

Can someone clarify this, please?
 

Stephen Carey

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Apr 25, 2016
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Is there any information available on how much (in terms of percentage of total capacity) water ballast was there in the tanks of the Titanic's double bottom before it set off on the maiden voyage?

The reason that I ask is that I read something about it in Tom McCluskie's book Anatomy Of The Titanic. He says that when the ship was almost completely empty of crew, passengers, coal and cargo, the tanks would almost be full to avoid a very high waterline and consequent risk of transverse instability. Apparently, the ballast is gradually pumped out as the ship is loaded and theoretically could be almost empty if the ship was full to capacity.

Sam Halpern's superb article Titanic's Hidden Deck gives a detailed description of the anatomy of the tanks in the double bottom including their capacities. I understand that the total capacity of those 44 tanks in the double bottom was around 5700 tons. But other than fresh water tanks, I imagine the ballast tanks themselves would only have been partly filled at the start of the voyage.

The Titanic was carrying about 2/3 of its passenger capacity; the crew and cargo were likely to a higher capacity. Based on that, I am guessing (and only that) that the ballast tanks in the double bottom contained about 20% of their capacity of water.

Can someone clarify this, please?
I doubt anyone can unless there's a stability booklet knocking about for these ships. Passenger vessels carry very little in the way of ballast as their "cargo" doesn't weigh very much. A 7000 passenger cruise ship with an average body weight of 70kg has less than 500t of "cargo".
It's donkeys years since I was on passenger ships, but we had a tank plan with all the DB intercostal spaces throughout the ship. The Mate would send down instructions regarding shifting of ballast, not for bodily sinkage but to alter trim and/or heel for various purposes to compensate for consumption of fuel and hotel services.
A VLCC (tanker) however has massive ballast tanks which are filled for unloaded passage to get the ship at a draught that suits fuel consumption and weather. This is pumped out as loading commences and is around 60,000t from memory, on a cargo of 250,000dwt. I have capacity plans for these ships but not on my phone...
 
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Arun Vajpey

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A VLCC (tanker) however has massive ballast tanks which are filled for unloaded passage to get the ship at a draught that suits fuel consumption and weather
Thanks. On the same subject, I have often wondered about what sort of ballast Naval Aircraft Carriers used in the 1930s and 40s when they were relatively new. I know it is only a film, but the sight of those massive ungainly looking carriers with wide flight decks and one-sided tall superstructures negotiating huge Pacific swells in Tora! Tora!! Tora!!! is etched in my mind. I know that in wartime those ships were full of crew, aircraft, ammunition etc but there must have been times when they had to be almost emptied and serviced, especially during peace. I would have thought that a high waterline in an aircraft carrier would make it very unstable.

Sorry for digressing from the core subject but we were talking about ballast in big ships, and so I hope that the mods won't tell me off.
 
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Stephen Carey

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Apr 25, 2016
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Philippines
Thanks. On the same subject, I have often wondered about what sort of ballast Naval Aircraft Carriers used in the 1930s and 40s when they were relatively new. I know it is only a film, but the sight of those massive ungainly looking carriers with wide flight decks and one-sided tall superstructures negotiating huge Pacific swells in Tora! Tora!! Tora!!! is etched in my mind. I know that in wartime those ships were full of crew, aircraft, ammunition etc but there must have been times when they had to be almost emptied and serviced, especially during peace. I would have thought that a high waterline in an aircraft carrier would make it very unstable.

Sorry for digressing from the core subject but we were talking about ballast in big ships, and so I hope that the mods won't tell me off.
When I was in warship design in my chequered career as a marine engineer, most were specified as "not requiring permanent nor temporary ballast", so you had to design for that. A warship has to be arranged to compensate for stores and ammunition usage but as we only designed up to 85m craft it wasn't necessary.
At one time - and the USN may still do it, not sure - warships used "seawater displacement of fuel tanks, in that the lighter fuel was pushed out of the top of the tank, the heavier seawater acting to preserve trim and heel. The RN had chronic problems with contamination of fuel systems by SRB (Sulphate Reducing Bacteria) and also new pollution regulations of course, and discontinued the practice.
How an aircraft carrier manages this I would think is similar to the passenger ships, with sufficient trimming ballast to maintain conditions within reasonable parameters. Nothing much changes on these ships though, and when I was in Ark Royal more years ago than I like to remember, the ship was maintained in stores, fuel and ammo regularly by RAS (VERTREP in USN terms).
As in the case of "top heavy" cruise ships much observed by armchair naval architects proliferating on social media, both they and aircraft carriers are not inherently unstable unless subject to damage of course - an occupational hazard with warships!
 
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