Would the Titanic Stabilize Well in Rough Weather?

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Aaron_2016

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The cruise ship Astoria (aka the Stockholm) has a very strange looking stern. I think it has something to do with her stability.






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Georges G.

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In addition to increasing buoyancy, a well-designed sponson ducktail has additional benefits including:
  • Increases waterline length which reduces resistance underway.
  • Shifts the longitudinal center of buoyancy aft reducing dynamic squat.
  • Improves wake field and hydrodynamic flow.
  • Reduce pitch motion due to increased longitudinal moment of inertia.
 

Doug Criner

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The bow, if inspected closely, might look a bit strange too. I believe this ship is the former Stockholm which collided with Andria Doria off New York in 1956. Andria Doria sank and Stockholm lost her bow, which was later replaced.
 

Jim Currie

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It is usually futile, and sometimes dangerous, to attempt to cure a rolling problem by working ballast. Think free surface and virtual rise in the position of "G".
Ships crossing the North Atlantic invariably encounter bad weather from the south west. This is because Low pressure areas track north east over the area. The wind in these systems blows anti clock wise round a center which itself moves north east. The ones which have the highest winds usually move very quickly... sometimes as fast as 40 knots. Because of these factors, the direction of the wind is constantly changing and does not blow from a fixed direction for any length of time Therefore the element of "fetch" is of less importance than the speed of passage of the low because eventually, the wind and the forward progress of the system will feed each other...usually in the south wast quadrant. That's where the highest seas will occur. However, the long, (sometimes 1000 feet) swell are generated at a great distance... as much as 2000 miles away and from an entirely different system. These can become very high and are most prevalent from the SW. Vessels travelling west of the GC Europe to N America tracks invariable meet the worst weather on the port bow so pitching rather than rolling is the problem. Travelling eastward, the weather was ion the starboard quarter. The steering was a problem.
 

Rob Lawes

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Yeah, she's currently the worlds second oldest passenger liner in ocean going service although I doubt too much of the original Stockholm remains.
 

Georges G.

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It is usually futile, and sometimes dangerous, to attempt to cure a rolling problem by working ballast. Think free surface and virtual rise in the position of "G".
How do you get a substantial free surface effect if you fill up one set of water ballast tank at a time until it overflows through a side or deck discharge port?
 

Jim Currie

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How do you get a substantial free surface effect if you fill up one set of water ballast tank at a time until it overflows through a side or deck discharge port?
Georges, Free surface effect has nothing to do with the content of a compartment. I have no idea what you are writing about. In fact, the Herald of Free Enterprise event is a classic example of what happens when a well deck or card deck is flooded due to taking on a volume of water. This was 30 years ago..... almost to the day.
Free surface effect does not depend on water volume or depth within a compartment. The minute you start filling a ballast tank, or a deck becomes flooded, free surface action begins. It continues until the tank is pressed-up. Don't take my word for it here is the technical position from my Ship Stability & Naval Architecture text book:


"
Free surface 2017-05-02 001.jpg
 

Rob Lawes

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I served on HMS Echo and HMS Enterprise, the Royal Navy E Class Survey ships and they were fitted with an interesting design of stabalizer. Instead of the common fin type that extend through the hull, Echo and Enterprise have a water counter balance system.

Imagine a U shaped tube which is half full of water. As the tube is tilted to right or left, the water will naturally find its level within the tube. Now imagine if you bung the ends of tube up. When the U is then tilted left or right, the water will only move a little until the air is compressed but it won't find it's natural level. Instead of blocking the tube ends, the system we had used air compressors to pressurize the system and delay the flow of water between one side of the U and the other. This would counter balance the ships roll by adding more weight to the opposite side. Then as the ship rolled back the water would reverse direction, the air would be bled out and the system re-compressed to delay the roll to the other side.

It gave the ship quite a lazy roll in most sea states. We were sceptical about how efficient it was until one day at anchor, the stokers took the compressors off line to work on one that had failed. The ships roll became so violent that we had to weigh anchor and move into sheltered water and try again.
 

Mark Baber

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«What's the basis of your opinion, Sahdowraven?»

What do you mean by Sahdowraven, Mark?
I tough you were asking me what was the source of the diagrams I posted …
Shadowraven posted a message saying simply that "The ship probably would have experienced difficulty in harsh weather." I was asking him/her what the basis of that opinion is.

You then responded to my message with one that says "Derrett, Bowditch…" and I was asking you what you meant by that.
 
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Georges G.

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Georges, Free surface effect has nothing to do with the content of a compartment. I have no idea what you are writing about. In fact, the Herald of Free Enterprise event is a classic example of what happens when a well deck or card deck is flooded due to taking on a volume of water. This was 30 years ago..... almost to the day.
Free surface effect does not depend on water volume or depth within a compartment. The minute you start filling a ballast tank, or a deck becomes flooded, free surface action begins. It continues until the tank is pressed-up. Don't take my word for it here is the technical position from my Ship Stability & Naval Architecture text book:
Jim, I must also admit that I have no idea what you are writing about.

You wrote;

«Free surface effect has nothing to do with the content of a compartment.»
«Free surface effect does not depend on water volume within a compartment»

fse111.png


I have the regret to say that Free Surface Effect depends not only on the liquid content of a slack compartment, but also on its density. It depends as well on the water volume or the dimensions and shape of the slack tank (length x breadth). I agree that the free surface action begins the minute you start filling up a ballast tank. But when the tank is «full», water acts just like a static weight.

I rough seas, if the vessel keeps rolling synchronously after having firstly alter course and speed, you will have no other choice but to fill up available water ballast tanks and at the limit, hoving to. My point is to avoid the risk of a substantial virtual rise of GM due to free surface effect, you will have to fill up in sequence one set of water ballast tank at a time until it’s full before pumping in the next set. On Titanic, the cellular double bottom water ballast tanks, just built similar to a product tanker, made taking ballast very safely in rough seas. But again, I would fill up ballast tanks in sequence, one set at a time until totally filled before pumping in another set.

Here is a sequence example that I would use on Titanic. Since you now know how to calculate the Free Surface Effect, you can make up the calculations for each and every steps to see if the vessel would survive.

Wing WBT;
1. fill up #7 P & S / #8 P & S to capacity, then and only then…
2. fill up #6 P & S / #9 P & S to capacity, then…
3. fill up #5 P & S / APT to capacity,

Center WBT:
4. fill up #8 P & S to capacity, then and only then …
5. fill up #6 P & S to capacity, … then
6. fill up #9 P & S to capacity, …
7. fill up #7 P & S to capacity, …
8. fill up #5 P & S to capacity, …
9. fill up #4 P & S to capacity, …

Making sure not filling up a Fresh Water Tank with sea water, stay within shearing forces & bending moment limits and not finish trimmed by the head …
 

Georges G.

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Erratum… It depends as well on the water «surface area» or the dimensions and shape of the slack tank (length x breadth)! :oops:
 

Jim Currie

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Erratum… It depends as well on the water «surface area» or the dimensions and shape of the slack tank (length x breadth)! :oops:
Yep! That's what I was trying to tell you. Are you questioning the wisdom of the Naval Architects who very clearly, as I illustrated in my post of No.30, emphasised the futility of what the Bowdich advice you quoted earlier? That's why it is called "Free surface".

As for the s.g. of the liquid in the tank and surface tension of liquids? Yes, I am aware of that, but you really must concentrate on responding to a rebuttal of what your earlier posted...I re-quote :

"1. Use water ballast (not another kind of liquid)to alter the KG of the vessel".

Incidentally, that is a very incomplete suggestion. Unless the reader had in-depth knowledge of ship stability, he or she would not know how it would alter the KG of the vessel in question.

The original question was whether Titanic or Olympic had any artificial means of reducing motion in a sea way. They did not.
 

Georges G.

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Jim You and your Naval Architects should modernize, study and amend your stability incantations by reading not only Nathaniel Bowditch American Practical Navigator but also through Captain D.R. Derrett Ship Stability for Masters and Mates written with grateful help and comments afforded by the following personnel in the Maritime Industry. Taking note that those experts agreed and signed their names to «Use water ballast changes to alter the KG of the vessel. This should alter GMt and hence the natural rolling period to a no-synchronous value.»
  • Captain Sergio Battera, Vice-Chief (Retired) Pilot, Co-operation of Venice Port and Estuary Authority.
  • Julian Parker, Secretariat, The Nautical Institute, London.
  • Tim Knaggs, Editor of the Naval Architect, Royal Institute of Naval Architects, London.
  • Gary Quinn, Head of Testing Services, Scottish Qualification Authority (SQA) Glasgow.
  • Roger Towner, Chief Examiner, Department for Transport/Maritime and Coastguard Agency (DfT/MCA), Southampton.
  • Captain G.C. Leggett, Area Operations Manager (Surveys and Inspections), Maritime and Coastguard Agency, Liverpool.
  • Captain Neil McQuaid, Chief Executive, Marcon Associates Ltd, Southport.
  • Malcolm Dann, Partner, Brookes Bell Jarrett Kirmann Ltd, Liverpool.
  • Captain I.C. Clark, Maritime Author for The Nautical Institute, London.
  • Darren Dodd, Managing Director, Saab Tank Control (UK), Wokingham.
  • Colin Jones, Stock Control Manager, DPM Ltd, Liverpool.
«1. Use water ballast (not another kind of liquid)to alter the KG of the vessel»

I agree that you will have no other choice but to use salt water ballast in the middle of the ocean. Nothing new here. Since the FSE formula integrates liquid density, you will also have no other alternative but to apply sea water density. On other occasions, ballast could’ve been taken in a fresh water harbor prior sailing to expected rough seas. An oil tanker continually manipulates liquid cargo and segregated ballast of various densities. So that’s why I posted a working example using oil; to point out that the liquid density is of prime importance and cannot be ignored.

«The original question was whether Titanic or Olympic had any artificial means of reducing motion in a sea way. They did not.»

Declaring that an Olympic class vessel had no means of reducing motion in at sea is, borrowing your own expression, pure hogwash! She could have easily altered course and speed but to the evidence, it was not in Capt Smith’s priorities! It does not seem yours either. She could as well have taken ballast to increase her drafts, reduce her KG thus rising her GMt and hence the natural rolling period to a no-synchronous value. The cellular wings and double bottom water ballast tanks of an Olympic Class, made taking ballast easily and safely in rough seas. But again, it would have to be done in sequence, one set at a time to reduce the Free Surface Effect to insignificant value and by a mariner who understood the phenomenon.

Jim, like it or not, erratum understood or not…

Rise of GM = GG1 = wd / W₂.
Loss of GM = FSE = lbᶾ / 12 x 1/W₂ x δ x 1/n²
  • where w equals the mass of the water ballast pumped in
  • where W₂ equals the initial displacement added by the mass of the water pumped in
Captain D.R. Derrett...
 

Jim Currie

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Jim You and your Naval Architects should modernize, study and amend your stability incantations by reading not only Nathaniel Bowditch American Practical Navigator but also through Captain D.R. Derrett Ship Stability for Masters and Mates written with grateful help and comments afforded by the following personnel in the Maritime Industry. Taking note that those experts agreed and signed their names to «Use water ballast changes to alter the KG of the vessel. This should alter GMt and hence the natural rolling period to a no-synchronous value.»
  • Captain Sergio Battera, Vice-Chief (Retired) Pilot, Co-operation of Venice Port and Estuary Authority.
  • Julian Parker, Secretariat, The Nautical Institute, London.
  • Tim Knaggs, Editor of the Naval Architect, Royal Institute of Naval Architects, London.
  • Gary Quinn, Head of Testing Services, Scottish Qualification Authority (SQA) Glasgow.
  • Roger Towner, Chief Examiner, Department for Transport/Maritime and Coastguard Agency (DfT/MCA), Southampton.
  • Captain G.C. Leggett, Area Operations Manager (Surveys and Inspections), Maritime and Coastguard Agency, Liverpool.
  • Captain Neil McQuaid, Chief Executive, Marcon Associates Ltd, Southport.
  • Malcolm Dann, Partner, Brookes Bell Jarrett Kirmann Ltd, Liverpool.
  • Captain I.C. Clark, Maritime Author for The Nautical Institute, London.
  • Darren Dodd, Managing Director, Saab Tank Control (UK), Wokingham.
  • Colin Jones, Stock Control Manager, DPM Ltd, Liverpool.
«1. Use water ballast (not another kind of liquid)to alter the KG of the vessel»

I agree that you will have no other choice but to use salt water ballast in the middle of the ocean. Nothing new here. Since the FSE formula integrates liquid density, you will also have no other alternative but to apply sea water density. On other occasions, ballast could’ve been taken in a fresh water harbor prior sailing to expected rough seas. An oil tanker continually manipulates liquid cargo and segregated ballast of various densities. So that’s why I posted a working example using oil; to point out that the liquid density is of prime importance and cannot be ignored.

«The original question was whether Titanic or Olympic had any artificial means of reducing motion in a sea way. They did not.»

Declaring that an Olympic class vessel had no means of reducing motion in at sea is, borrowing your own expression, pure hogwash! She could have easily altered course and speed but to the evidence, it was not in Capt Smith’s priorities! It does not seem yours either. She could as well have taken ballast to increase her drafts, reduce her KG thus rising her GMt and hence the natural rolling period to a no-synchronous value. The cellular wings and double bottom water ballast tanks of an Olympic Class, made taking ballast easily and safely in rough seas. But again, it would have to be done in sequence, one set at a time to reduce the Free Surface Effect to insignificant value and by a mariner who understood the phenomenon.

Jim, like it or not, erratum understood or not…

Rise of GM = GG1 = wd / W₂.
Loss of GM = FSE = lbᶾ / 12 x 1/W₂ x δ x 1/n²
  • where w equals the mass of the water ballast pumped in
  • where W₂ equals the initial displacement added by the mass of the water pumped in
Captain D.R. Derrett...
Georges, show me where it states that these measures should be taken while the vessel is actually engaged in synchronous rolling. In fact, your example agrees with me. The following is an extract from the very publication you use as an example:

Ship Stability for Masters and Mates Fifth edition by Captain D. R. Derrett , Revised by Dr C. B. Barrass

"If free surface be created in a ship with a small initial metacentric height, the virtual loss of GM due to the free surface may result in a negative metacentric height. This would cause the ship to take up an angle of loll which may be dangerous and in any case is undesirable."

Have you ever seen what happens to a vessel when the GM becomes neutral? Have you seen the damage caused by sea water sloshing about in a partially filled tank? Have you actually seen vessels which flipped due to free surface creating a negative GM? No? Well I have, many times.
You can think on about this as long as you like but I can assure you; back in the 'good' old days, filing an empty ballast tank at sea while the ship was rolling her guts out was like playing Russian Roulette with a fully loaded revolver. We are discussing these very days.

I say again: "The original question was whether Titanic or Olympic had any means of reducing motion in a sea-way."
In fact they had but two, safe ways of doing so.
In 1912, and right up until the late 1970s, no master worth the salt would ever contemplate selectively filling ballast tanks to compensate for a rolling problem. He would simply alter course or change speed or both.

It seems that your Captain Derret and his illustrious mentors agreed with this in a roundabout way.
 
A

Aaron_2016

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Does anyone know what this stabilizing device is?

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Rob Lawes

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You only see it briefly but looking at that I'd say it was an attempt to create an automatic stabilisation device by mounting a gyroscope onto the stabilisers.

As the ship pitched and rolled the gyroscope would attempt to remain stable and would transmit that force as a signal to generate the movement of the ships stabilisers.