Buoyancy Ballast

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Andy H
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Buoyancy Ballast

#1

Post by Andy H » 25 Mar 2015, 00:32

Hi

Most people are aware of (predominately) Merchant ships sailing with ballast, especially when empty, to help with the stability/handling of the ship etc.

However Buoyancy Ballast was almost as equally common and I'm interested in finding any set rules etc concerning numbers/volume etc.

The only info I have come across is from a book called The Blockaders by A.C.Hampshire (which looks at the role of the Northern Patrol/AMC's etc in the economic blockade against Germany in both WW's).
The author states (Pg184) that the AMC Scotstown (17,000Grt) had arrangements for more than 17,000 ballast oil drums when she was sunk, whilst the (on Pg189) AMC Andania (13,950Grt) had a quota of 15,000 oil drums when she met her fate. Earlier on Pg180, he makes note of the 14,000 ping-pong balls on board the AMC Carinthia (20,227Grt), which was below the 'recommended number'!

So any information about recommended levels of buoyancy oil drums or ping-pong balls, either totals or number per ton etc, would be appreciated.

Regards

Andy H

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Mark McShane
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Re: Buoyancy Ballast

#2

Post by Mark McShane » 30 May 2015, 15:44

Hi Andy,

There is surprising little about buoyant ballast in Admiralty files, here what I have managed to find from files I have,

Extracts from
Board of Inquiry into sinking of...

Laurentic & Patroclus...
A notable feature in both ships was the very considerable length of the time they remained afloat after receiving severe damage. The measures taken to increase buoyancy in armed merchant cruisers may be responsible for this and ships may well be saved after considerable damage is received if suitable measures are taken in the ship and help can be quickly forthcoming.
Laurentic...
Although buoyant and other ballast apparently achieves the purpose of keeping the ship afloat and upright it also effectively prevents the shoring up of bulkheads.
Dunvegan Castle...
The buoyant cargo consisted 225 steel drum, 2700 wooden barrels and 440 tons of wood.
Springbank...
It was evident that the only method of attempting to keep the ship afloat was by using the pumps. The use of shores for shoring up bulkheads was impracticable on account of the holds being filled with buoyancy drums.
It is recommended that ships with large holds which are filled with buoyancy drums should have these compartments permanently shored.
Instructions for Fitting Out A Mercantile Vessel as an Armed Merchant Cruiser
Instructions re stowage of buoyant cargo in certain of the larger hold compartments to reduce permeability may be given at the time of fitting out but Admiralty instructions will be sent as soon as practicable regarding this stowage.
Although not much it appears they were a double edged sword, they were of some use in keeping ships afloat with limited damage, they prevented proper damage control measures and were of no use when significant damage was sustain such as the multi torpedo hits on the Laurentic and Patroclus.


Fitting out seems to have been done on a case by case series as each ship came in to their fitting out ports. Would be interesting to know how the buoyant cargo differed between the fitting out ports in UK and elsewhere dependent on what was available to hand.

Mark


John T
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Re: Buoyancy Ballast

#3

Post by John T » 30 May 2015, 17:49

Andy H wrote: Most people are aware of (predominately) Merchant ships sailing with ballast, especially when empty, to help with the stability/handling of the ship etc.

However Buoyancy Ballast was almost as equally common and I'm interested in finding any set rules etc concerning numbers/volume etc.
Was it used on ordinary merchant ships or only AMC'S ?

I understood it as being part of the fitting of Armed Merchant Crusers but not regular merchants
(or does a load of timber counts?)

Mark McShane wrote: Although not much it appears they were a double edged sword, they were of some use in keeping ships afloat with limited damage, they prevented proper damage control measures and were of no use when significant damage was sustain such as the multi torpedo hits on the Laurentic and Patroclus.
Wasn't the buoyance ballast the very reason why Laurentic and Patroclus where hit with such large number of torpedoes ?
(three and six hits repectively if I got it correct for uboat.net)
Had they not sunk after the first couple of torpedoes without this "padding" ?


Cheers
/John

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Mark McShane
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Re: Buoyancy Ballast

#4

Post by Mark McShane » 30 May 2015, 18:13

John T wrote:Wasn't the buoyance ballast the very reason why Laurentic and Patroclus where hit with such large number of torpedoes ?
(three and six hits repectively if I got it correct for uboat.net)
Had they not sunk after the first couple of torpedoes without this "padding" ?


Cheers
/John
Hi John,

According to boards of inquiry Laurentic was considered to be beyond saving lost once engine room and other hit compartments were flooded, Patroclus was still thought to be able to be saved after the first two hits, everything else after that made the sinking inevitable.

John T
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Re: Buoyancy Ballast

#5

Post by John T » 31 May 2015, 09:44

Well, my comment are most on the "double edged sword" part of you previous post-
Mark McShane wrote: Although not much it appears they were a double edged sword, they were of some use in keeping ships afloat with limited damage, they prevented proper damage control measures and were of no use when significant damage was sustain such as the multi torpedo hits on the Laurentic and Patroclus.
The intention with buoyance ballast where to improve compartmentalization,
and by filling the space it it's always a trade off between blocking flooding and blocking "proper damage control measures".
Mark McShane wrote: Hi John,

According to boards of inquiry Laurentic was considered to be beyond saving lost once engine room and other hit compartments were flooded, Patroclus was still thought to be able to be saved after the first two hits, everything else after that made the sinking inevitable.
But without the extra boyance, would not the ships had sunk earlier or at least shown the sub captain (Kretschmer ) signs of sinking, that the work was done and he could move on without wasting further torpedoes on them.
I just think one side of the double edged sword greatly outweighed the other and the reason the ships received so heavy damage was due to that they remained afloat.


Cheers
/John

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