Correcting list. how to pls.

mobi1
4th February 2010, 04:37
Having a chat with a buddy about correcting list on a ship with only port and stbd ballast tanks ...this assumes you cannot easily shift cargo... I say that if the ship is listing to port say 5 degrees the worst thing you can do is take on seawater ballast in the starbord ballast tank as that might suddenly cause the ship to roll violently to starbord, maybe shift the cargo and capsize the ship.

I would think the best course of action is to flood the starboard tank to lower the CG , even if you sacrifice some freeboard. Once you've lowered the CG then you can alternatly ballast the starboard and port tanks to get the ship on an even keel. Then you can deal with any cargo issues.

Would appreciate any input ...Thanks !

mobi1
4th February 2010, 06:41
Is it the case that a major contributing factor to the loss of the tug VALOUR off NC in 2006 was due to incorrect ballast pumping ?

Thanks

non descript
4th February 2010, 08:55
Firstly a warm welcome to you on your first posting – do enjoy the SN Site and all it has; secondly in answer to your question, it rather depends on what is causing the list. - In your added text it is, if you will forgive the pun, “leaning” towards a discussion on the “Angle of Loll” causing the list rather than an “Unequal Weight Distribution” – the latter is correct merely by sifting weight to the high side; the former is far more serious and is discussed here… (http://www.shipsnostalgia.com/showthread.php?t=12416) (and corrected as you say, by adding weight to the lower side first)

R58484956
4th February 2010, 12:29
Greetings mobil and welcome to SN.
On P&O we transferred oil to bring ship upright. Bon voyage.

mobi1
4th February 2010, 17:04
Hi Tonga ....thanks for that ...being an engineering type we decided to try this with a model .

Sure enough .....ballasting the starboard tank first could create a sudden and violent swing of the ship (model) to starboard which we could see might put the starboard deck under water and potentially sink the ship. What did seem to work well was as you said was to ballast the low side (port) actually quite substantially ( amount X ) and thus lower the center of gravity (COG) at the loss of some freeboard on the port side ......then ballasting the starboard side with about 1/3 X the amount of water. This further lowered the COG, but increased the freeboard on the port side .... it then became a matter of judiciously ballasting starboard and port to bring the ship (model) on to an even keel without creating any roll and not as much overall loss of freeboard as one might expect.

Re this from a previous post ..................

The absolutely vital thing, is the one John T already touched upon with such accuracy, one MUST get rid of the list by adding weight below the metacentre (M) – so put ballast in the double bottom and put it in the listed side first, or else the ship just flips over and turns turtle.

Removing the extra cargo from the low side will just cause the ship to capsize.

I would have thought that removing cargo from the low side was fine as long as your COG was low enough ?

John Cassels
4th February 2010, 17:09
Having a chat with a buddy about correcting list on a ship with only port and stbd ballast tanks ...this assumes you cannot easily shift cargo... I say that if the ship is listing to port say 5 degrees the worst thing you can do is take on seawater ballast in the starbord ballast tank as that might suddenly cause the ship to roll violently to starbord, maybe shift the cargo and capsize the ship.

I would think the best course of action is to flood the starboard tank to lower the CG , even if you sacrifice some freeboard. Once you've lowered the CG then you can alternatly ballast the starboard and port tanks to get the ship on an even keel. Then you can deal with any cargo issues.

Would appreciate any input ...Thanks !

All depends what the initial GM was.

Think that in your second paragraph you actually mean " flood the port tank
to lower ..........) but unless the righting moment was exceptionally high, one
would not get a violent roll to starboard.
If initial Gm is reasonable , no harm in bringing her upright with ballast to stbd.

Klaatu83
4th February 2010, 17:23
I used to work on containerships a lot, where listing often became an issue due to uneven loading/discharging of the cargo. Those ships have to be on a fairly even keel to prevent the containers from hanging up in the cell guides, especially during loading. Problems sometimes arose when the longshoremen got lazy and insisted upon loading or discharging too much on one side or the other for too long. There were many instances when we had to speak to them about that before things got out of hand. In addition some ports had cranes that were too short to reach all the way across the ship (Bar, in Montenegro, comes immediately to mind as a case in point). The newer, foreign-built container ships were equipped with special trimming tanks controlled from the ship's cargo office, but on the older, U.S.-built ships we had to call the engine room and have the engineers pump ballast. However, we preferred, if possible, to control the list with the cargo, and then pump ballast only after the cargo was finished.

Ro-Ros are another case where the amount list could be critical. I used to sail on a Ro-Ro ship called the Cygnus, now re-named the Cape Taylor, equipped with a stern ramp that swiveled on a turntable so that it could be landed either to port or to starboard. Even a small amount of list could cause significant damage to the ramp and it's turntable. As a result, the ship was fitted with a sophisticated automatic ballast control system, along with an audible alarm that went off if the list exceeded one degree to either side. Needless to say that that ship was NOT originally a U.S. ship, she had been built in Japan for a German company.

mobi1
4th February 2010, 23:05
"I would think the best course of action is to flood the starboard tank to lower the CG".......is indeed a typo ....should, as per our model experiment be the port, low side, first.

Is there a formula for how you do this assuming you have enough freeboard .....like if you ballast x amount into the low port side do you then ballast 1/3 x into the starboard, as with our model ,and then so much back and forth being careful not to right the ship to quickly creating a roll to starboard ???? or is this really a matter of slowly edging the CG on to the center line ?

John Cassels
5th February 2010, 09:29
For a ship to list due due to cargo then you have an "upsetting moment ".

From this upsetting moment , one can calculate the moment required to bring
her upright.

As TONGA will verify , this is very simplistic but a basis nevertheless.

As he has already mentioned , flooding the low side first in order to increase
metracentric height would be in order if the vessel had already gone to the
angle of loll

Lancastrian
5th February 2010, 16:38
Read all about it - http://www.globalsecurity.org/military/library/policy/navy/nrtc/14057_ppr_ch12.pdf

vectiscol
5th February 2010, 17:02
One might have to be selective about which type of tank to fill. For instance, a double bottom tank might have much larger free surface effect than a wing tank.

chadburn
5th February 2010, 18:34
The effect of free liquid in a compartment of a floating vessel is to reduce the effective metacentric height, the amount of this reduction being obtained from the following formula:-
reduction of metacentric height in feet = i/V . Where i is the moment of inertia of the free surface of the liquid about a longitudinal axis through it's centre of gravity in foot units, V the volume of displacement in cubic feet. If GM be the original metacentric the value when reduced in consequence of the free liquid becomes in feet. GM-i/V

John Cassels
5th February 2010, 18:58
The effect of free liquid in a compartment of a floating vessel is to reduce the effective metacentric height, the amount of this reduction being obtained from the following formula:-
reduction of metacentric height in feet = i/V . Where i is the moment of inertia of the free surface of the liquid about a longitudinal axis through it's centre of gravity in foot units, V the volume of displacement in cubic feet. If GM be the original metacentric the value when reduced in consequence of the free liquid becomes in feet. GM-i/V

Are you sure about that ?.

Free surface moment of inertia with regards to metracentric height is
concerned with the athwartships axis and not the longitudnal axis.

Lancastrian
5th February 2010, 19:41
Which proves that stability should be left to those who understand it - not the engineers! [=P]

The athwartship breadth of a compartment has a great influence on the reduction in GM caused by the free surface effect. This influence is shown by the following formula:
Rise in G = b cubed x l divided by 12(35W)

Where b = athwartship breadth of compartment, l = fore-and-aft length of compartment, W = displacement of ship.
As indicated by this formula, the free surface effect varies as the cube of the breadth (b) but only as the first power of the length (l). Because of this relationship, a single bulkhead that cuts a compartment in half in a fore-and-aft direction will quarter the free surface effect.

Billieboy
5th February 2010, 20:44
Spent an awful lot of time setting up Trimming systems on the Bremen Express class container ships, so that the mates didn't have to think about keeping the ship upright. Most important variables were; which tanks the chief was going to use for fuel.

Duncan112
5th February 2010, 20:49
One might have to be selective about which type of tank to fill. For instance, a double bottom tank might have much larger free surface effect than a wing tank.

I remember the Naval Architecture lecturer going through this with us - the best way to flood the low side was if you were fortunate enough to have inner and outer double bottoms (as per Bank Lines Cora class) you should flood the inner DB on the low side only to reduce the free surface effect that would be caused by flooding a full half width DB.

Fortunately I was never on a ship that developed a list that was not controllable by non standard methods so cannot vouch that the theory worked in practise.

In response to Lancastrian, stability is extensively dealt with in the statutory certificates and non statutory further qualifications for Engineer Officers.

Lancastrian
5th February 2010, 20:58
In response to Lancastrian, stability is extensively dealt with in the statutory certificates and non statutory further qualifications for Engineer Officers.

Well it wasn't in my day! Some of those I sailed with didn't understand why filling a port settling tank from a starboard double bottom might cause a list!

chadburn
5th February 2010, 22:47
The statical stability curve is an important factor affecting stability. the curve is generally assessed by the values of the metacentric height, the maximum ordinate of the curve and the range of the curve.
For small angular displacements of the ship from the upright the effort required to heel the ship is directly proportional to the metacentric height. at greater angles other factors affect the effort to heel the ship. These factors are governed by the form of the ship, its interesting to assume that the centre of gravity of the ship coincides with the metacentre, when the metacentric height is zero and the ship will theoretically just stand upright. If the curve of statical stability be drawn for this state of matters, such a curve will obviously be governed by the "form" of the ship. it will be found for different ships that these "form" curves as they may well be termed vary very considerably. The form curve is influenced by freeboard, the shape of the vessel above and below the waterline and by the erections above the weather deck.(Smoke)

John Cassels
6th February 2010, 00:04
Oh dear Chas , your last post is really confusing the issue here.

The point is that - for all intents and purposes - statical stability curves and
the information obtained from them is a function of the transverse axis , a sort of cross section if you like.

If the COG coincides with the metacentre , it's not just " interesting to assume" that the metracentric height will be zero , it's a fact. Not only is
the GM zero but the righting lever as well.
You might also point out that in this state , any external force which may
then cause the vessel to heel will produce an angle of loll. this is caused
by the COB moving out to the low side and when the metacentre again
coincides with the COG , the vesel will come to rest at this angle and with
a zero righting lever.

I think this was what Mobi1 was asking in the first place.
There is a formula for calculating the angle of loll , but will have to do some
major digging out to find it.

Lancastrian
6th February 2010, 10:14
Angle of Loll. tan theta = square root 2GM over BM
(Its difficult to copy and paste forrnulae!)
Where theta = angle of loll, GM= a negative initial metacentric height and BM= BM when upright.

I still don't understand why mobi1 is experimenting with models to find the answers which can easily be found in any good book on the subject.
And conditions of loll should of course be avoided in the first place

chadburn
6th February 2010, 12:20
I am presuming the point of the exercise Mobil 1 is doing is to put away "the book" and start off with a clean sheet which is what Engineers do, sometimes a new approach to a problem will emerge with a new solution and sometimes it does not. It's based on the old adage of "Nothing ventured, Nothing gained" or in today's world "thinking outside the box" or the book in this case.(Smoke).

joebuckham
6th February 2010, 12:29
I am presuming the point of the exercise Mobil 1 is doing is to put away "the book" and start off with a clean sheet which is what Engineers do, sometimes new approaches to a problem emerge and sometimes they don't. It's based on the old adage of "Nothing ventured, Nothing gained" or in today's world "thinking outside the box" or the book in this case.(Smoke)

i would expect that the empirical approach to this "problem" was employed many times over many years before the final formulae were arrived at.

chadburn
6th February 2010, 13:23
It still should not prevent Engineers looking at a fresh approach yet again to a "problem" in today's world or in the future that's how we make progress when new technology kicks in.

Lancastrian
6th February 2010, 13:44
Sounds like re-inventing the wheel.

mobi1
6th February 2010, 17:54
The reason I got interested in this is that my "buddy" is shortly going to be doing his 150 ton orals and I have been secuded to pepper him with questions one of which concerned the biz of correcting list. Yes i do have an engineering background .....i am, as a hobby, a self taught marine mechanic for VP and mercruiser and have found that regardless of what is in the books/manuals there is nothing like hands on practicle. Hence the model experiment ..... what i was trying to get at formula wise is a result of our little experiment ...... with a list to port at angle of lull if we filled the stbd tank first we could create a violent roll to starboard with could put the stbd deck under water...... I am sure the roll would be less violent on a ship but am sure the result would be the same and might capsive the vessel.

We were however able to significantly ballast by (X) the low port side, much more than we thought possible reducing freeboard for sure but not effecting the angle of lull much at all. This of course lowered the COG ..... we could then start ballsting the starboard high side .... as we started to do this the model started to right itself, however not wanting to create an upsetting to stbd moment we stopped after 1/3 X volume on the stbd side .....we now had gained some freeboard on the port side so we again ballasted the port side thus further lowering the COG ...... from then on it was a matter of smaller amounts port and stbd until the ship was level ...... I can see that all this would have to depend on tank arrangement, amount of freeboard you have to play around with, sea conditions, etc ...... Perhalps in reality this is very much a masters knowledge of and feel for the ship and understanding of moments of force etc. What I was hoping for was a simple formula that if you could ballast the lower port side by X volumn and still maintain some freeboard then you could safely ballast by 1/3 X on the stbd side and then slowly back and forth to right the ship ?

I think this was not done properly on the tug Valour ...a factor which contributed to its loss.

Finally ...thanks to all for your input !

Cheers !

mobi1
6th February 2010, 18:08
Although my buddy is a wiz bang z drive tug boat operator he does not seem to think this will work in actual practise on a large ship ...Oh boy !!!!! these young guys are so hard to convince !!!!! us old guys can't of course be right !!! LOL :rolleyes:

chadburn
7th February 2010, 14:22
Sounds like re-inventing the wheel.

Thankfully Engineers have re-invented the wheel many times and we have moved from round stones all the way through the various stages to Alloy wheels fitted with Dunlop 205/55/18's.
One of the best examples of Engineers re-looking at previous idea's is the Ships Bow, from the straight Stem pointy bit at the front through to the Bulbous (of which there are many types not just one standard design) through to the point when they put previous Bow design "book" aside and came out with the remarkable X Bow. Most Engineers like to keep busy they haven't got time to stare out of windows.[=P]

mobi1
7th February 2010, 18:29
Thanks for that Chadburn ..........your tag line

"From Grey Funnel to any Funnel, just show him/ me the money Mabel"

kinda reminds me of one by an old marine mechanic pal with 40 years in the biz

" Any grease is better than no grease at all ! " ......(Thumb)

X bow you say .....I'll have to check that one out .....sounds a bit like the bows on the WestPac Express ......with the under surface wings .... big issue with the whale foundation in Hawaii re slicing whales in half ..in the end the high speed Hawaiian superferry died an economic death.

Lancastrian
7th February 2010, 20:52
Most Engineers like to keep busy they haven't got time to stare out of windows.[=P]

But its still a wheel. Were they engineers or naval architects? Jealousy will get you nowhere.

joebuckham
7th February 2010, 21:21
bathing regularly in salt water is supposed to be good for thin skin(==D)

chadburn
7th February 2010, 22:39
Naval Architecs will have normally studied and have Degree in Engineering.[=P]
Engineers cannot stand salt water it causes corrosion and drives those who apparently do, quite mad.(==D)
MOBIL1, the job of the Engineer is to keep it all running, no matter how, owners tend to get annoyed when they have to send for Tugs. Incidently I only use Mobil 1 in the family cars, now that is a good oil

Billieboy
8th February 2010, 08:18
Difference between Naval Architects and Marine Engineers:-

One is wetted surface area, the other is power/weight ratio. Both can calculate a moment, but only one bothers about the reciprocal.

mobi1
8th February 2010, 08:45
Ah ha CHADBURN ......you must be on the money! ..... I see like many great marine engineers you hail as did old Capn’ Cook from Yorkshire ! I surmise after reading volumes about Cook ...(I also have a collection of Webber’s drawings ) ..... that Cook with his keen interest in all matters scientific was indeed in the days of moments of force by wind and water, apart from being possibly the world’s greatest navigator, also ipso facto, a great marine engineer !

I digress .... but only to admit that I am only a small boat “engineer”? .....Like a hands on tecky friend of mine used to say when he answered some boatowners complex question about riser cooling ......” Well , I don’t have a degree in engineering nor have I taken a marine mechanics course, but I did stay at a Holiday Inn last night !!

Engineering types are even valuable on small boats ....... Well do I remember the time, out on the salty brine, with a friend ....the CAPTAIN of a 26 ft Owens vdrive which suddenly lost rudder control ...... Oh my God shouted the CAPTAIN ..."what shall we do” ...... Of course I felt like saying “ I haven’t got the foggiest idea ..you’re the captain ..you tell me” however by then his wife was tearing a strip off him a mile long for taking her out in ....I think she used the words “floating wreck” ........ anyway I opened the aft hatch above the steering and could see that the tiller arm was rotating freely on the rudder post. So I grabbed a pair of vice grips from my tool box .... I always bring tools along ..... no use asking the captain for his tool box ..... I know why these guys never carry tools ...they wouldn’t know how to use them anyway ...... so I get in to the aft compartment , lock my vice grips on the rudder post and yell “OK captn” ...... So he turns around to yell at me and confuses port with starboard so for the first 50 feet or so we are on a zig zig course barely missing the fuel dock ........ Oh well maybe I just just mixed things up for fun ..LOL ...anyway we made it back to the marina with his wife swearing that “hell would freeze over before she would ever go out in that derelict again !!!!”

Oh ...and did I fail to mention ........ I was born in Sheffield some 63 years ago.... (Thumb)

chadburn
8th February 2010, 16:56
Mobil 1, Interesting you should mention the great Capt Cook who spent his formative years in the area where I now live (North Yorkshire), the latest Space Shuttle which took off this morning is called "Endeavour" and has as one of it's crew a Dr Nicholas Patrick he also spent his formative years in this area and he has on board with him a replica of the flag Captain Cook flew on his "Endeavour" when he set off into the unknown on his round the world voyage in 1768. It's a small world(Thumb) , well it will be from up there(Jester) I at one time was involved in Offshore Powerboat Racing where things broke due to the stress and strain, ingenuity was a basic requirement for we the Engineers mainly because of the pressure of not wanting to miss the post race party where there was a bit of "lolling" due to the free drinks.(Thumb).

John Cassels
8th February 2010, 19:34
So Chas , are you trying to tell us that if engineers who happen to loll are then able to incease their waterline area , they will manage to become
upright ?.

mobi1
8th February 2010, 20:14
Definition of ........................ loll about (some place)

to lie, lounge, or droop some place. The tired travelers lolled about all over the hotel lobby until their rooms were ready. They were still lolling about at three in the afternoon.


What do you think Chadburn ...... I doubt he'd ever get upright , unless of course he fell in the swimming pool ! I suspect then that previously imbibing copious amounts of 80 proof blue label would help! Ah ha ! I thing another experiment is in order......(Thumb)

chadburn
8th February 2010, 22:23
[QUOTE=John Cassels;400870]So Chas , are you trying to tell us that if engineers who happen to loll are then able to incease their waterline area , they will manage to become
upright ?.[/QUO

John& Mobil 1, Like ships, we are not all built the same it depends on his "underwater" profile(EEK) and the height of the erections above his weatherdeck(Thumb) Blue label, no, Moet & Chandon was the drink at those event's as they were sponsored prize giving parties. The late great Roger Clark was alway's in attendance as he ran his own powerboat called "Vita Power". Not a lot of people know that.(Jester)

Billieboy
9th February 2010, 10:47
The late great Roger Clark was alway's in attendance as he ran his own powerboat called "Vita Power". Not a lot of people know that.(Jester)

Was that the Roger Clark from British Vita Ltd.? British Vita used to make 100% of all vacuum hoses on British Rail and 98% of all squash balls used in the World. How's that for useless information?

John Cassels
9th February 2010, 13:58
Was that the Roger Clark from British Vita Ltd.? British Vita used to make 100% of all vacuum hoses on British Rail and 98% of all squash balls used in the World. How's that for useless information?

By gad Sir , you are a mine of information , but here's one you don't know ;

what colour is a London red bus - bet that's got you stumped.

Bye the bye , how is the weather up at your neck of the woods ?.

mobi1
9th February 2010, 15:44
Re formula to correct list ...... found this

http://www.fas.org/man/dod-101/navy/docs/swos/dca/stg4-08.html

but seems to me that pumping the entire 3200 gals of fuel from port to stbd before moving the fork lifts is stupid ...... don't you want fuel and cargo evenly distributed as much as possible so you don't have any opposing moments stressing the ship.

Ah yes ........ re Captn Cook ..... I was lucky enough to be sitting at my favorite pic-knick table having lunch 2 weeks ago ...just 100 yards up the beach from the mouth of the Waimea River and exactly at the spot Cook came ashore in 1778.

Anyway ...if any of you are Cook aficionados , I have a few of Webber’s drawings which I had syncron scanned from probably the best surviving copy of Cook’s Atlas on the planet, which happens to reside at the Special Collections branch of the UBC library. I have these on disc ......12MB files so the resolution is superb ..... but not suitable for Internet transfer. If any of you are interested I could send along a copy disc which you can take to some archival printer ..... I had mine printed up on Arches water color paper ...... the curator at UBC could not tell the diff between the originals and the copies. The descriptions by Cook of the drawings, such as Night Dance ( below ) are fascinating indeed ......

http://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~24154~870168:A-night-dance-by-women,-in-Hapaee--

Lancastrian
9th February 2010, 16:13
Re formula to correct list ...... found this

http://www.fas.org/man/dod-101/navy/docs/swos/dca/stg4-08.html

but seems to me that pumping the entire 3200 gals of fuel from port to stbd before moving the fork lifts is stupid ...... don't you want fuel and cargo evenly distributed as much as possible so you don't have any opposing moments stressing the ship.

- (http://www.davidrumsey.com/luna/servlet/detail/RUMSEY%7E8%7E1%7E24154%7E870168:A-night-dance-by-women,-in-Hapaee--)

Moving the fuel was not enough to correct the list. 3200 gals is peanuts. Sometimes tanks are emptied for cleaning. Its only a fictitious example to show how to work the formula! Like I said, leave it to those ....

Billieboy
9th February 2010, 19:52
By gad Sir , you are a mine of information , but here's one you don't know ;

what colour is a London red bus - bet that's got you stumped.

Bye the bye , how is the weather up at your neck of the woods ?.

Effing cold, brass monkeys all over the place! Got my electronics looked over this afternoon and met a new female Israeli/Dutch/Canadian Cardiologist who is also an electro-cardiac physiologist, (she says when to change the batteries on pacemakers), been here three weeks, says it's just as cold as Toronto!

Seems that after about six to eight weeks, if I'm fit enough, they will change around the third wire from inside the heart to outside. Have to dump some five to ten kilos of excess fluids first!

mobi1
10th February 2010, 06:45
Moving the fuel was not enough to correct the list. 3200 gals is peanuts. Sometimes tanks are emptied for cleaning. Its only a fictitious example to show how to work the formula! Like I said, leave it to those ....

Thanks ....... "3200 gals is peanuts" .... no kidding ..... I think 3200 gals would just about keep some boats at top speed for about 30 minutes.

Anyway, I guess you missed the point ..... but, as you say ...." leave it to those who know better" or was it "leave it to those who think they know better" like my wife, for example....(Thumb)

chadburn
10th February 2010, 17:08
Billieboy, john, obviously not World Rally Car Driver fans or fans of Micheal Caine otherwise you would have recognised both of my last two comments.
Mobil 1, Think, Lanc/ Neville Chamberlain and "I have in my hand a piece of paper"/(formula) and I will stick with it till Hell freezes over, see my point. It's called tunnel vision.

mobi1
10th February 2010, 20:22
Precisely ......My “buddy” past his 150T Orals ...... as an aside the examiner told him that over 50 percent get the list question wrong because they don’t see beyond this type of example of the “formula”......(Thumb)

Lancastrian
10th February 2010, 21:47
Peace in our time! I'm surprised Engineers, even of the aspiring 150T variety show such disrespect for formulae!
[=P]

ray bloomfield
11th February 2010, 13:59
....I always bring tools along ..... no use asking the captain for his tool box ..... I know why these guys never carry tools ...they wouldn’t know how to use them anyway ......

Oi!! Not all captains are on big ships with egg on their cap with someone to polish their shoes, tuck them up at night etc etc. So please dont tar us all with the same brush. Interesting thread though.

mobi1
11th February 2010, 15:08
No disrespect intended gentlemen, but things may not always be, as in pieces of paper, as they appear to be ...my handle, for example, is not that slippery ...its more like the whale with a Star Wars twist.

I am still trying to draw the connection between Mini Coopers and swimming pools ?

May The Force Be With You.....(Thumb)

Billieboy
11th February 2010, 15:22
No disrespect intended gentlemen, but things may not always be, as in pieces of paper, as they appear to be ...my handle, for example, is not that slippery ...its more like the whale with a Star Wars twist.

I am still trying to draw the connection between Mini Coopers and swimming pools ?

May The Force Be With You.....(Thumb)

Well mobi1, it depends on how many elephants you can get into them!

mobi1
11th February 2010, 16:31
My apologies ...yes .... I should have phrased things differently ..... the “captains” I had in mind are power boat types ..... (sailing types are usually excluded).... who may know the purpose of a tool but are sadly lacking its application to marine engine systems. Having subscribed to Rat’s Toad Hall theory of boating for many years, its been my experience that these “there is no replacement for displacement” types, usually with exhaust diverters and without a kicker, venture out in the open ocean without a clue as to how, for example, change an alternator or raw water pump belt.

Now I don’t know a heck of a lot about computers, but then my life may not depend on that, unless, for example, I inadvertently delete my wife’s favorite tourtiere rec________________

Oh my God !!!!

mobi1
11th February 2010, 16:51
Ah Billieboy !!!!! Good point ....I had completely forgotten ....(Thumb)

chadburn
12th February 2010, 13:30
Just to clear up my #37 for those who are unaware, Roger Clark was the foremost World Rally driver G.B. has had to date and a really nice chap, for those who have had a sense of humour bypass.
"Not a lot of people know that" was a quote from the film "Get Carter" starring Micheal Caine, a saying which was also used by Eric Morecombe.
In regards to Engineers ignoring formulae, Engineers realise that the stability of a ship depends on so many different properties of that ship that the possibilities of variation are limitless and it is not always wise to move from one ship to another as so many varying factors occur "one size does not fit all" as the saying goes.

Lancastrian
12th February 2010, 17:20
In regards to Engineers ignoring formulae, Engineers realise that the stability of a ship depends on so many different properties of that ship that the possibilities of variation are limitless and it is not always wise to move from one ship to another as so many varying factors occur "one size does not fit all" as the saying goes.

Complete waffle. The stability of any ship depends on it's metacentric height, which is determined by formula.

Caine is a popular subject for impressionists and mimics, having a voice and manner of speaking that are distinctive, yet fairly easy to imitate. Most Caine impressions include the catchphrase "Not a lot of people know that." Peter Sellers (http://en.wikipedia.org/wiki/Peter_Sellers) initiated this when he appeared on BBC1 (http://en.wikipedia.org/wiki/BBC_One)'s Parkinson (http://en.wikipedia.org/wiki/Michael_Parkinson) show on 28 October 1972 and said:
“ Not many people know that. This is my Michael Caine impression. You see, Mike's always quoting from the Guinness Book of Records. At the drop of a hat he'll trot one out. 'Did you know that it takes a man in a tweed suit five and a half seconds to fall from the top of Big Ben to the ground?' Now there's not many people who know that! ” The line had been used earlier in Spike Milligan (http://en.wikipedia.org/wiki/Spike_Milligan)'s script for The Last Goon Show of All (http://en.wikipedia.org/wiki/The_Last_Goon_Show_of_All), performed on October 5, 1972.[20] (http://en.wikipedia.org/wiki/Michael_Caine#cite_note-19)
In 1983, Caine was given the line to say as an in-joke in the film Educating Rita (http://en.wikipedia.org/wiki/Educating_Rita_%28film%29).

John Cassels
12th February 2010, 20:50
Sorry Chas , I can't let you get away with that.

Although every ship may be different , they all have their own stability
booklet containing all stability data , cross curves , conditions but all
based on the same principle.
To say that it's not wise to move from one ship to the other due to so many
varying factors is just not true.

mobi1
13th February 2010, 08:32
OK ...maybe I am missing something here ...but re the preposted formula dealing with the example of the fuel and the forklifts ....sure ..works there ..but what of instead of KM of 23.5 and KG of 19.75 you use numbers that are close to zero diff .....then shifting major weight transversly before lowering the COG could be bad news........ :confused:

Lancastrian
13th February 2010, 14:02
And what if the captain was wearing red, white and blue braces?
If you have a very small or zero GM you are in an unstable condition and that would need to be rectified before you do anything else. But that doesn't invalidate the use of proven formulae.
Perhaps if you really want to understand stability, instead of trying to pick holes in what appears to be a transatlantic Naval exam syllabus, you should take a course in the subject, or at least get a good book.

mobi1
13th February 2010, 17:23
Certain aircraft carriers have an inherent list to starboard; not a lot of people know that. Perhalps I could ask the design engineers on the Nimitz to lend me their stability formula books, they should have some "good" ones, or maybe they should take the course with me ?

“Nimitz class aircraft carriers possess an inherent list to starboard that their list control systems (LCS) are typically unable to correct while under Combat Load Conditions. As a result, it has become necessary to use fresh water ballast in a number of inner bottom voids and damage control voids to augment the LCS. Maintaining liquid ballast in damage control voids is unacceptable, as it reduces the design counter flooding capability of the ship, and thus reduces ship survivability”.

I bet the Department of the Navy wished someone had "poked holes" in their formula.....;)

Lancastrian
13th February 2010, 19:00
Not surprising if you stick an island on one side. The fomulae still hold good!
When in a hole, it is best to stop digging.

mobi1
14th February 2010, 17:13
Re digging holes ....... quite possibly ....but then again I am learning lots ! Fascinating subject !

Granted .....The formula works, theoretically, for low angles of list but apparently does not for high. Pls keep in mind that this thread started in regard to correcting an angle of loll situation ..as in filling high or low side ballast first.

FROM THE TEXT ...................

A Righting Moment is created by the ship to keep itself upright. In this case, the force is equal to the ship's displacement (WF) and the distance is the ship's righting arm (GZ) at each particular angle of heel.

RM = W X GZ


The Righting Arm (GZ) changes with inclination of the ship. Using the relationship derived in Unit 4.01 for small angles of heel:


GZ = GM X SINo


NOTE: This relationship holds true for angles less than 7°-10°

Text about loll ...........................................

At some angle of heel (say 10°), KM will increase sufficiently equal to KG (distance from the keel to the center of gravity), thus making GM of vessel equal to zero. When this occurs, the vessel goes to neutral equibrium, and the angle of heel at which it happens is called angle of loll.<br /, In other words, when an unstable vessel heels over towards a progressively increasing angle of heel, at a certain angle of heel, the center of buoyancy (B) may fall vertically below the center of gravity (G). Note that Angle of List should not be confused with angle of loll. Angle of List is caused by unequal loading on either side of center line of vessel.

Its this last sentence I don’t get .....why can you not load a ship to create an angle of loll ...what’s the diff between that and having timber cargo shift or get water entrained at sea ?

Lancastrian
14th February 2010, 17:28
Why would you want to? Ships should be loaded to ensure they retain an adequate GM throughout the voyage, allowing for any changes than can be expected.
List is caused by an off centre weight which can be counteracted.
Loll is caused by being unstable and can only be remedied by increasing the GM.

james killen
14th February 2010, 19:13
There seems to be reams of opinions about what to do about a listing vessel.

I have NOT read 'em all.

However, before we begin, the cause of the list should be known.

It could be due to a negative GM when the vessel is upright and the ship has taken a list to where the GM has again becomes positive.
In this instance to fill a tank on the higher side could be suicidal!
The vessel may roll to the other side and, there being a very low GM and possibly not much range where the GM remains positive, the moment of inertia may be sufficient to cause the vessel to roll through her righting range and continue on over!!!!
Providing the free surface of the lower tank(s) does not too adversly effect the GM the tank(s) should be filled first - one at a time, smaller tank(s) first!
When they have been filled the high side tanks may then be filled.
------------------
If the list has been caused by a shift of cargo/breached tank etc and the GM is sufficient and will not be too adversly effected the high tank(s) may be ballasted.

The effect of free surface MUST be taken into consideration in both cases.

non descript
14th February 2010, 19:57
There seems to be reams of opinions about what to do about a listing vessel.

I have NOT read 'em all.

.....

Then that is a great shame Sir; for it would seem that we already have a consensus about how to cope with the Angle of Loll. Whilst it is of course Chinese New Year, there are some disadvantages in reading the last page first (Jester)… - Of course allowing Tigers to move to the highest deck, when the GM is almost zero is also not good idea, regardless of the Year….particularly if they are fat Tigers who have eaten all the animals on the lower decks…(EEK)

mobi1
15th February 2010, 07:46
Good one Tonga ......... Tigers up top after dinner lowers the GM maybe to zero .. no righting arm so if to many Tigers on the port side .....then maybe wet Tigers. VG explanation.

In this situation I guess you better ballast the port side pronto or chase the tigers below or hope enough of them roll of the port side thus producing a righting moment before its ball game over.

Speaking of Tonga ..... Love to go - maybe some day. You may know this, but suspect a lot of people may not ! Believe Cook picked up Omai thereabouts. He was a young strapping native lad Cook took back to England.

Omai became the darling of London society and was the guest at many stately residences. He was apparently often lolling about when the master of the house was away. Such was the speculation, as to the motive of certain society ladies, for Omai’s company, that Cook was ordered to “return the noble savage from whence he came”

Happy New Year .....(Thumb)

chadburn
15th February 2010, 12:48
James, that is the way to do it.(Thumb)
John, indeed, every ship does have it's own stability booklet based on the different properties of that particular ship. The measure's you can take on a Tanker will not be the same as on a Tug for obvious reason's.
Mobil 1 see Bourbon Orca in photo section re X Bow

mobi1
15th February 2010, 15:06
Bloody ugly, I'd say ......

Saw this post elsewhere which I thought raised some good points ....

"North Sea winter, steaming into the Wx on passage- with no flared bow, what stops the greenies smacking straight into the wheelhouse windows? Maybe she has monster freeboard but I used to drive 65 metre jobbies and have seen water over the top of the monkey island on many occasions.
A flared bow provides increased reserve buoyancy, is this being replaced by the volume within the dramatically raised topsides for'd?"

chadburn
15th February 2010, 16:20
I would agree Mobil1, ugly but apparently very efficient I understand, as you see the normal designs of a Bow have been put on the shelf and a completely new approach has been taken which was the point I was making about ongoing development whether it's wheels or ship design, (not unless you want to drive around in a "Fred Flinstone" car)(Jester)

mobi1
15th February 2010, 20:52
Point well taken .....perhaps in certain cases though “further development” does go a bit too far ! Pam Anderson comes to mind........[=P] [=P]

CAPTAIN JEREMY
12th March 2010, 17:53
Having a chat with a buddy about correcting list on a ship with only port and stbd ballast tanks ...this assumes you cannot easily shift cargo... I say that if the ship is listing to port say 5 degrees the worst thing you can do is take on seawater ballast in the starbord ballast tank as that might suddenly cause the ship to roll violently to starbord, maybe shift the cargo and capsize the ship.

I would think the best course of action is to flood the starboard tank to lower the CG , even if you sacrifice some freeboard. Once you've lowered the CG then you can alternatly ballast the starboard and port tanks to get the ship on an even keel. Then you can deal with any cargo issues.

Would appreciate any input ...Thanks !

If it is an angle of list, ballast the opposite side and the list will gradually diminish. There will be no violent roll in the opposite direction. If you ballast the same side you will eventually capsize as the list increases. If it is an angle of loll, then you ballast the same side first to lower the centre of gravity. In this condition there would be a violent roll possibly resulting in a total capsize if you started by ballasting the high side.

It is not only engineers who can manage liquids in bulk. After all who does the cargo work on all liquid bulk carriers? Who calculates the ship's stability and instructs the "Chief" the order of tanks to burn out!

I have memories of being held responsible for polluting Genoa harbour yacht marina (while in the dry dock), The ship was in the dock, and for a period of time the engineers had been pumping the oily bilge water into a slop barge moored alongside the dock wall. Unfortunately this vessel had a longitudinal bulkhead and as all of the slops were pumped into only one side, it capsized, resulting in the whole yacht basin being covered with a film of oil. Obviously they thought that you had to ballast the low side to alleviate the list. I had a few fun filled hours with the Caribinieri, in company with the guy who is now CEO of NCL.

Amusingly that resulted in my first command. I was the Staff Captain and as the Captain was a retired Italian captain drawing his pension, he was not permitted to work in Italy. Thus he was at home and when the Caribinierri walked up the gangway and demanded to see the Captain, Roberto Martinoli who was one of Costa's technical managers, elbowed me in the ribs and said "that is you". So my first command started with my being taken into custody by the police. That evening I faxed the personnel dept and asked them to confirm my appointment and salary, and they came straight back with it! It was a very healthy pay rise. Eventually the case was dropped, by which time I had already left Costa.

Lancastrian
12th March 2010, 18:16
Brave words Capt J. You will now be subject to an onslaught from those who think they have a monopoly on the understanding of anything to do with pumps!
[=P]

Bill1949
21st March 2013, 07:36
If you start with a port list you should ballast the port tank first to reduce FSE and increase GM.

oldman 80
21st March 2013, 10:42
First and foremost do nothing until you have determined is it list or is it loll.
That is important.
(I just noticed this thread)

trotterdotpom
21st March 2013, 14:08
I just saw this thread and thought it was about the Admiralty List of Radio Signals, however, I was pleased to see that I knew that FSE stands for Free Surface Effect and GM stands for General Manager.

On Jobst Oldendorff, carrying sawn timber, if there wasn't a list everyone wondered what was wrong!

John T

jmcg
21st March 2013, 15:49
If you start with a port list you should ballast the port tank first to reduce FSE and increase GM.

Welcome to S/N Bill - hope to hear more from you. Let us have a few details on your profile.

J