Stability Decay - Educational

Hi All,

I’m working on a series of short videos on ship science. Stability, rudder sizing, ship life expectancy, etc. This video is on Stability Decay: how a boat loses stability over its lifetime. This video covers the source of decay, how to minimize decay, and recommended maintenance. I welcome any constructive feedback.

Video Link:
[video]https://youtu.be/5qiR4ceUsqM[/video]

Weight growth has always been a problem which can go unnoticed for a long time until something unexplainable happens but then it can be too late. The stealth character of weight growth can be pretty dangerous. A weight growth during the lifetime of a ship for alterations and additions and ‘natural’ weight growth due to accretion of paint is a fact of life. A possible figure might be based on as much as 1/2% per annum of the light weight (Watson) of the intended ship life.

For war ships also a second margin, the board margin, is applied. This an allowance for addition of changes in weight due to future alterations and additions such as new weapon systems.

A dramatic example of the phenomenon of unchecked weight growth is the El Faro. It underwent notable work over its life, including a lengthening in 1992-93. In 2005-06, the ship was converted from work in Alaska to its last duty on the Jacksonville to Puerto Rico route. Though the ABS did not consider that work major, it increased the draft of the ship by two feet, according to testimony. That raises the question how major is major.

The operator also welded 100-ton fructose tanks to the deck in 2014. With those weight changes there would need to be changes to the ship’s trim and stability book and the CargoMax software program used to determine the stability of the ship but this was not done. During smooth weather conditions the stability problem will not immediately be noticed. However, under extreme circumstances it will become very evident. The increase in weight of the El Faro according to Watson could, at the end, have amounted to more than 20% of the light weight…

[QUOTE=Dutchie;194250]…In 2005-06, the ship was converted from work in Alaska to its last duty on the Jacksonville to Puerto Rico route. Though the ABS did not consider that work major, it increased the draft of the ship by two feet, according to testimony…[/QUOTE]

…who or what increased the draft?

  • ABS moved the load mark up and adapted the valid draft marks?
  • With equal payload, weight growth pushed the old marks below the water line?

The lenghtening of the ship in itself is beneficial for the draft since after such conversion the ship will have an increased displacement which decreases the draft. The increased draft could be due to the conversion work carried out in Alaska. The testimony about the increased draft was made during the second week of the hearings when the ship’s stability was discussed.

True, the lengthening should diminish the draft; but then what with the stability and the dynamics? However, for these big works, they certainly made the necessary calculations and asked for the right certificates.

I understood that after the “minor” works and with the aging of the ship, the draft increased by two feet… and the ABS did nothing or was not aware.

The Plimsoll mark under water will not sink a ship in port, but it is a highly visible sign to everybody passing by, that there could be problems offshore.

IMO rules call for inclination experiment to be carried out when light weight changes more than 2%: imo.udhb.gov.tr/dosyam/EKLER/MSC-Circ.1158.pdf

I have some experience with “cheating” on this requirement though:
In the early 1980s all rigs working in Norwegian waters were required to undergo a new check on their stability. Nearly all lost substantial deck load capacity (Abt. 800 m.t. on average for Aker H4 MODUs)I was involved in preparing two rigs for the check.
Knowing what had happened to other rigs we removed all items that could be called “removable” from Lightship to a new post called “Semi-permanent Variables”, thus lost only 3-400 m.t. off the variable deckload on paper.
NOTE: This did not increase the risk however, as all additional weight was accounted for, only in a different way.

Some years later I was Manager for a Betlehem Mat-supported rig which had a known weight problem not recorded in the Stability Booklet, since the “equivalent sister” rule had been applied when new. (Built in USA)
We needed to add living quarters to use the rig in S.E.Asia and knew that if we were forced to do a lightweight survey we would loose much of the already small Variable Deckload capacity.

The added weight was under-reported to stay within the acceptable limit and accepted by ABS Class.(Again this was not a danger to stability, but the load line was regularly exceeded, as it had been for years)

PS> A few years later I was engaged as Consultant for the buyer when that same rig was sold and returned to the GoM. A bit a of a dilemma, as I “met myself in the door”, so to speak.

Moral of the story: It is possible to bypass nearly any rule, but it should never be to the detriment of safety.

The statement about the draft was made during the second session of the hearings held in May 2016 and covered shipboard operations, cargo loading, lashing and stowage operations for the accident voyage, as well as examine the vessel’s analysis of stability and weather conditions forecasted as compared to what was encountered.

I wanted to look for more specific information about the changed draft but I can only find transcripts of the first hearings that were made public. Anyway it seems that the information about the increased draft was accepted by the Board and not challenged. On the other hand the board members did not strike me as to have much expertise on such matters but maybe I am wrong…

The weight growth continued also during the last fatal voyage as probably tons of piping was put on board which was to be installed by the Polish work force. Would that weight been installed high or low in the ship? That question never came up.

I was somewhat perplexed to read about this draft increase.

Grossly, the float line surface (say 75% of 241m x 28m) was about 5000 m2.
The draft increase of two feet then corresponds to a weight increase of about 3000 metric tons…

[QUOTE=Urs;194296]I was somewhat perplexed to read about this draft increase.

Grossly, the float line surface (say 75% of 241m x 28m) was about 5000 m2.
The draft increase of two feet then corresponds to a weight increase of about 3000 metric tons…[/QUOTE]

Same here. As she was a slender ship especially up front, I estimated the blocking factor Cb as 0.62 which gives a figure of 2500 tons. Never mind it still is a lot and the question is how that weight was distributed over the vessel. She had stability problems as the former captain Jack Hearn told the board.

The ro/ro containership [I]El Faro[/I] and sister ship [I]El Morro[/I] could be very tender and slower to recover from rolls when heavily loaded, a characteristic that led its officers to add more margin of safety when calculating the effects of loading, a former captain testified Tuesday to the Coast Guard marine board of inquiry investigating the Oct. 1, 2015 sinking in Hurricane Joaquin that killed all 33 crew.
Capt. Jack Hearn, who worked on TOTE Maritime ro/ro ships for years in the Alaska trade, recalled the differences when he moved to TOTE’s Sea Star Line division and sailed on the Ponce-class ships for the Jacksonville, Fla., to San Juan, Puerto Rico, service.

In a straight ro/ro configuration, the TOTE vessels “were excellent ships…they handled well,” Hearn said. The combined ro/ro with container cargo is “more of a different animal, especially in rough weather,” he told the board.

"The ship was very tender,” a tendency he could feel with rudder commands, recalled Hearn who served on the line in 2007, 2009-2011 and 2012, when he charted a course to avoid Hurricane Sandy in October of that year.

When the ships rolled, they came back with “a very slow return,” Hearn said. “You could feel the ship as it leaned over.”

It seems that after the conversion to Ro-Con it was not the same ship anymore. That coming back with a ‘very slow roll’ is a sign on the wall. In my opinion the ship was in fact unstable or close to it.

I love to get my hands on the information about what caused that enormous weight increase. Those transcripts must be around somewhere…

49 CFR 801.31 governing NTSB activity states that “Within approximately four (4) weeks after a public hearing concerning an investigation, the Chief, Records Management Division, will make available to the public the hearing transcript. On or before the date of the hearing, the Chief, Records Management Division, will make the exhibits introduced at the hearing available to the public for inspection or commercial copy order.” It is not clear whether this regulation pertains to the transcripts of an MBI.

I’ve uploaded the one thing in the docket, which is the transcript of an NTSB conference call: http://bit.ly/2jfxR9S This is not sworn testimony, and employees of Tote, ABS, and Herbert Engineering are present as members of the NTSB investigating panel.

Cheers,

Earl

[QUOTE=Dutchie;194299]She had stability problems as the former captain Jack Hearn told the board.

It seems that after the conversion to Ro-Con it was not the same ship anymore. That coming back with a ‘very slow roll’ is a sign on the wall. In my opinion the ship was in fact unstable or close to it.

…[/QUOTE]

A ship can feel very tender to the crew and still be within legal required minimum. For example in ballast I might have a 4.0 meter or higher GM and ship has a 12 second roll which feels like a snap roll to the crew and gives a poor ride in rough seas. Loaded with a GM of, say 2.0 meters or a little less is a 18 second roll which feels normal to the crew.

Arriving in port with minimum fuel and minimum ballast close to the legal minimum required GM of under 1 meter the ship has a 26 second roll peroid. The crew and the pilot will comment on this as it feels “top-heavy”

The ship is not technically unstable in any of those cases but the ships feels much different in each case.

El Faro’s sisterships built for Matson, the Lurline and Matsonia, were also converted to Ro/Ro Containership and are still active. Any changes in the configuration would be accounted for in a revision of the ships stability program.

I don’t have the qualifications to comment on the stability questions. I did work in Commercial management for a ConRo owner. We always booked a “basic cargo” first load port, discharge last port. Each vessel had a specific bottom capacity and we booked to provide block stow, reducing lashing cost while providing secure weight & countering the container deck load. As a practical matter we could calculate the basic cargo weights in advance exactly and from history expected on deck container weights. Bookings fixed for the bottom early, containers late booking with poor advance weight information. Wide weight variables on the RoRo decks, we often left containers behind last load port when stability became a question. ConRo ships are special and need special handling. I know very little about the Puerto Rican trade and can’t say if the same practices applied to El Faro.

Having been in many capacity planning situations I never saw commercial mangers question the Cargo Superintendents recommendation in the planning stage. Final decision on cargo acceptance was always in the hands of qualified professionals. Without reading the entire transcript can’t say what Totes practices were. They are questions that should have been asked.

Boats3

[QUOTE=Dutchie;194250]
During smooth weather conditions the stability problem will not immediately be noticed. However, under extreme circumstances it will become very evident. …[/QUOTE]

I don’t agree with this, everywhere I’ve worked it standard practice to check the calculated drafts against the actual drafts upon arrival and prior to departure. Differences of 0.1 meters are not a matter for concern but more than 0.2 meters is something that would warrant investigaion.

Also a GM much lower than calulated would immediately be noticed in smooth weather conditions because the ship would heel sharply in turns or by wind heel. Also small shifts in weights; fuel, ballast or cargo would cause large changes in list.

This is from Stablity and Trim for the Ship’s officer:

Effect of GM on rolling. The first point to be made quite clear is that GM is by no means the only factor involved in the manner in which a ship rolls, although it is an important one. We know that with increased metacentric height a vessel will roll more quickly; that is, her period of roll in seconds will be short. The effect of GM on amplitude is less well known. It should be clearly recognized by ship’s officers that a stiff ship in heavy weather not only has a short period of roll but also a large amplitude. Conversely, a tender ship is apt to have a long period of roll with small amplitudes.
To understand the reason why a large GM produces large amplitudes, we can compare a stiff ship with a raft. The raft as a type of vessel represents the acme of stiffness. And how does a raft behave in waves? Does it not assume exactly slope of the seas, thus inclining to large amplitudes? The stiff ship attempts to do the same. She is quick and alive, responding immediately as a wave rolls up her side and under her bottom. The stiff ships bobs about like a cork. The tender ship, on the contrary is sluggish. She lags behind the motion of the waves and thus tends to roll to lesser amplitudes.

Evidently many ship’s officers get this wrong.This is Captain Jack Hearn from the hearings:

Second, he testified that the El Faro and her sister ships were “tender ships” after their conversion to con/ros and deployment on the busy route, with heavier cargo on top and a smaller GM margin. Once competitor Horizon Lines stopped operating to Puerto Rico, “cargo was increasing, both volume and tonnage, we were picking up the available cargo that we could fit on the ship. We were going to full load,” he said. He testified that after noting ship behavior that caused him concern, he asked for a minimum GM margin of 0.5 feet, which he thought suitable for normal weather. “I was observing a very slow return, the ship becoming even more tender on arrival when it was when it left,” he said. “You could even feel the ship [heel] over from a rudder command alone [in fine weather], [B][U]let alone rolling with a heavy swell.[/U][/B] We felt it important to build in a safety margin to preserve stability [for rough conditions].” In the event of heavy weather, “I wouldn’t hesitate to call operations and see if we could go a different route or take some cargo off and go for about a foot [of GM margin],” he said.

A tender ship would be expected to heel over from a rudder command, however that doesn’t mean it will roll in a heavy swell.

The tender ship, on the contrary is sluggish. She lags behind the motion of the waves and [B][/B][U]thus tends to roll to lesser amplitudes[/U].

It’s not just out of a book, it’s very evident while watching the behavior of the ship in a sea.

Practice at our company Cargo Superintendent compared calculated and actual drafts several times loading. This due to the wide variance booked vs actual weight of the containers on deck. Many phone calls back to the office on cut list, what to leave behind . He was having simultaneous conversations with the Ch Officer and Master on stowage lashing ballast and bunkering for the voyage. All three had to be in agreement and the Commercial department followed there decision . Point is stability on a ConRo is a very special thing and it takes long experience and cooperation to operate successfully.

I doubt if the investigation understood the relationship between the various parties involved. I was involved in a small way after the Bow Mariner parcel tanker accident. Read the full report. It totally missed the relationship superintendent - Vessel. Obvious safety was ignored cleaning tanks with the blame put on the crew. No mention of why the crew was pressed to clean with too little time to do it properly. UK investigation of the Hoegh Car carrier that lost stability in the Thames few years ago found the core issue. Commercial in the home office changed rotation which changed stowage and instructed the Superintendent to do it, over objections. Super instructed the 3rd world ships officers who did not object, they never do, afraid for their jobs. Result is ship nearly capsized flat calm while turning.

Investigation without full details on who actually controlled El Faro’s stability is focusing on the machine when the human factor was probably to blame. This opinion with no facts, take it for what it’s worth.

Boats3

[QUOTE=Boats3;194330]Practice at our company Cargo Superintendent compared calculated and actual drafts several times loading. This due to the wide variance booked vs actual weight of the containers on deck. Many phone calls back to the office on cut list, what to leave behind . He was having simultaneous conversations with the Ch Officer and Master on stowage lashing ballast and bunkering for the voyage. All three had to be in agreement and the Commercial department followed there decision . Point is stability on a ConRo is a very special thing and it takes long experience and cooperation to operate successfully.

Boats3[/QUOTE]

Traditionally loading the ship did not require hands on minute by minute involvement by the master. When I sailed on box boats some years ago the master was was only peripherally involved and was sometimes ashore. The master’s authority with regard to ship safety and ability to manage his own time has been seriously eroded.

In the case of the El Faro neither the captain or the mate had " long experience" with ConRO.

[QUOTE=Kennebec Captain;194327]I don’t agree with this, everywhere I’ve worked it standard practice to check the calculated drafts against the actual drafts upon arrival and prior to departure. Differences of 0.1 meters are not a matter for concern but more than 0.2 meters is something that would warrant investigaion.

Also a GM much lower than calulated would immediately be noticed in smooth weather conditions because the ship would heel sharply in turns or by wind heel. Also small shifts in weights; fuel, ballast or cargo would cause large changes in list.

[Snip]

It’s not just out of a book, it’s very evident while watching the behavior of the ship in a sea.[/QUOTE]

As observed by Joseph Conrad, First Mate of the [I]Highland Forest[/I]:

"So seemed to think the new captain, who arrived the day after we had finished loading, on the very eve of the day of sailing. I first beheld him on the quay, a complete stranger to me, obviously not a Hollander, in a black bowler and a short drab overcoat, ridiculously out of tone with the winter aspect of the waste-lands, bordered by the brown fronts of houses with their roofs dripping with melting snow.

This stranger was walking up and down absorbed in the marked contemplation of the ship’s fore and aft trim; but when I saw him squat on his heels in the slush at the very edge of the quay to peer at the draught of water under her counter, I said to myself, “This is the captain.” And presently I descried his luggage coming along—a real sailor’s chest, carried by means of rope-beckets between two men, with a couple of leather portmanteaus and a roll of charts sheeted in canvas piled upon the lid. The sudden, spontaneous agility with which he bounded aboard right off the rail afforded me the first glimpse of his real character. Without further preliminaries than a friendly nod, he addressed me: “You have got her pretty well in her fore and aft trim. Now, what about your weights?”

I told him I had managed to keep the weight sufficiently well up, as I thought, one-third of the whole being in the upper part “above the beams,” as the technical expression has it. He whistled “Phew!” scrutinizing me from head to foot. A sort of smiling vexation was visible on his ruddy face.

“Well, we shall have a lively time of it this passage, I bet,” he said.

He knew. It turned out he had been chief mate of her for the two preceding voyages; and I was already familiar with his handwriting in the old log-books I had been perusing in my cabin with a natural curiosity, looking up the records of my new ship’s luck, of her behaviour, of the good times she had had, and of the troubles she had escaped.

He was right in his prophecy. On our passage from Amsterdam to Samarang with a general cargo, of which, alas! only one-third in weight was stowed “above the beams,” we had a lively time of it. It was lively, but not joyful. There was not even a single moment of comfort in it, because no seaman can feel comfortable in body or mind when he has made his ship uneasy.

To travel along with a cranky ship for ninety days or so is no doubt a nerve-trying experience; but in this case what was wrong with our craft was this: that by my system of loading she had been made much too stable.

Neither before nor since have I felt a ship roll so abruptly, so violently, so heavily. Once she began, you felt that she would never stop, and this hopeless sensation, characterizing the motion of ships whose centre of gravity is brought down too low in loading, made everyone on board weary of keeping on his feet. I remember once over-hearing one of the hands say: “By Heavens, Jack! I feel as if I didn’t mind how soon I let myself go, and let the blamed hooker knock my brains out if she likes.” The captain used to remark frequently: “Ah, yes; I dare say one-third weight above beams would have been quite enough for most ships. But then, you see, there’s no two of them alike on the seas, and she’s an uncommonly ticklish jade to load.”

Down south, running before the gales of high latitudes, she made our life a burden to us. There were days when nothing would keep even on the swing-tables, when there was no position where you could fix yourself so as not to feel a constant strain upon all the muscles of your body. She rolled and rolled with an awful dislodging jerk and that dizzily fast sweep of her masts on every swing. It was a wonder that the men sent aloft were not flung off the yards, the yards not flung off the masts, the masts not flung overboard. The captain in his armchair, holding on grimly at the head of the table, with the soup-tureen rolling on one side of the cabin and the steward sprawling on the other, would observe, looking at me: “That’s your one-third above the beams. The only thing that surprises me is that the sticks have stuck to her all this time.”"

Cheers,

Earl

[QUOTE=Boats3;194330]Practice at our company Cargo Superintendent compared calculated and actual drafts several times loading. This due to the wide variance booked vs actual weight of the containers on deck. Many phone calls back to the office on cut list, what to leave behind . He was having simultaneous conversations with the Ch Officer and Master on stowage lashing ballast and bunkering for the voyage. All three had to be in agreement and the Commercial department followed there decision . Point is stability on a ConRo is a very special thing and it takes long experience and cooperation to operate successfully.

I doubt if the investigation understood the relationship between the various parties involved. I was involved in a small way after the Bow Mariner parcel tanker accident. Read the full report. It totally missed the relationship superintendent - Vessel. Obvious safety was ignored cleaning tanks with the blame put on the crew. No mention of why the crew was pressed to clean with too little time to do it properly. UK investigation of the Hoegh Car carrier that lost stability in the Thames few years ago found the core issue. Commercial in the home office changed rotation which changed stowage and instructed the Superintendent to do it, over objections. Super instructed the 3rd world ships officers who did not object, they never do, afraid for their jobs. Result is ship nearly capsized flat calm while turning.

Investigation without full details on who actually controlled El Faro’s stability is focusing on the machine when the human factor was probably to blame. This opinion with no facts, take it for what it’s worth.

Boats3[/QUOTE]

I think it’s worth quite a bit. The culture of the NTSB, which is almost wholly shaped by the aviation industry, is to look for “probable cause” rather than “multiple causal factors.” This tends to drive their focus toward actions of the crew, and ignore that a crew in peril must play the cards that are dealt by other, outside agents, and those agents should be subject to the same depth of scrutiny as the crew. A central factor is what the crew knows about the hand they have been dealt, and the shortcomings of systems in which they place their trust.

Earl

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[QUOTE=Earl Boebert;194361]I think it’s worth quite a bit. The culture of the NTSB, which is almost wholly shaped by the aviation industry, is to look for “probable cause” rather than “multiple causal factors.” This tends to drive their focus toward actions of the crew, and ignore that a crew in peril must play the cards that are dealt by other, outside agents, and those agents should be subject to the same depth of scrutiny as the crew. A central factor is what the crew knows about the hand they have been dealt, and the shortcomings of systems in which they place their trust.

Earl[/QUOTE]

The catch-all phrase is pilot error.

[QUOTE=Lee Shore;194364]The catch-all phrase is pilot error.[/QUOTE]

Yes, and the best response comes from Nancy Leveson: “Human error is a symptom, not a cause.”

Cheers,

Earl