Stability

kepowee
1st December 2006, 12:48
Hi All Its 40 Odd Years Since I Was At Sea And I Often Wonder Why These Container Ships Dont Just Roll Right Over On A Stern Photo Of The Emma Mearsk I Counted The Containers 10 High Thats Got To Be At Least A 100 Ft Do They Build Them Whith An Extra Wide Beam Ive Often Wonderd About This Hope I Dont Apear Realy Thik Ken Powell

R.Philip Griffin
1st December 2006, 13:26
In the days of sail stability was covered by putting 2/3rds of the WEIGHT in the lower hold, and 1/3rd in the tween deck. And so it has remained to the present day. Now we hide it in formulas etc., but the same basic applies. On a box boat, the geographical location of every box is plotted as to where it is and the weight it contains on the computer. Of course,double handling is to be avoided, but occasionally it can't be helped. So even in these modern times, the old basic applies.

stein
1st December 2006, 14:58
I'll allow myself to butt in with an only halfway relevant quotation: Joseph Conrad: "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."
-and a bit further:
"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 and soul when he has made his ship uneasy".
It goes on, he tells us in his inimitable way what it feels like to be in a ship that is too stable. A great read. "The Mirror of the Sea". Not too relevant, but reading those "Two thirds" evoked Conrad's magnificient writing on stability immediately and I just had to quote him. Stein.

rgrenville
1st December 2006, 16:58
These modern container vessels also have a tremendous ballest tank capacity to help with stability and trim.

Pat McCardle
1st December 2006, 17:22
These modern container vessels also have a tremendous ballest tank capacity to help with stability and trim.

Anti-roll (Flume?) tanks fitted too I believe?(Thumb)

John Cassels
1st December 2006, 19:36
Anti-roll (Flume?) tanks fitted too I believe?(Thumb)

Pat, Flume tanks have nothing to do with stability.
Modern container vessels can be on the bones of their arses for stabilty
depending on the port rotation , discharge/load program , bunker situation
and a whole load of other factors. Believe me ..........

JC

Brian Dobbie
1st December 2006, 21:04
Yes lots of ballast pumped by 1000ton/hr pumps.
Heeling pump also capable of 1000ton/hr.
Plus 12,000tons of heavy oil.

brian

kepowee
2nd December 2006, 13:30
hi all thanks for all the info ken powell

hasse neren
5th December 2006, 17:03
How about this link...
http://downloads.shipspotting.be/ShippingIssues.pps

R.Philip Griffin
5th December 2006, 22:44
Can't imagin the accountants being very pleased about dragging unproductive ballast around the oceans, although if it avoids double handling of containers, maybe the ballast does become productive. Any thoughts?

Rutts
9th December 2006, 09:22
I did vessel planning for a number of years, one of our services was from Aus/NZ to the East Coast USA. The vessels sailed full northbound the majority of time. Full of meat, dairy products, meat and bonemeal and other cargos - all heavy. We worked to the rule of stowing heavy boxes down low
(7 high under deck). We could only go two high on deck as we blew the deck stack weights with a box on the third height, also these third height boxes really started affecting the stability. The vessels bunkered whist downunder, which also gave us additional stability. The crucial part of the voyage was arrival in Kingston, Jamaica. The vessel had been sailing for 17 or 18 days burning fuel, this was compensated with filling ballast tanks but the vessel still arrived in Kingston in a "tender state" having lost about 35-40cm in GM during the voyage north. Kingston cargo was always stowed on deck or down a centre bay and the stability rapidly returned with discharge of this cargo.
The problems returned if there was cargo to load back, but we never heard about those as the vessel planning for Kinstown was done by our office on the East Coast. The vessel didn't take on any bunkers until she reached Philadelphia or Houston.

gadfly05
19th December 2006, 08:39
Container ships need ballast of 15-30% deadweight ,even in full load condition because of the stability.
Now the stability calculation of a ship is done by computer .

gadfly05
19th December 2006, 08:45
How about this link...
http://downloads.shipspotting.be/ShippingIssues.pps

Yes , very useful .
thank you .

hasse neren
20th December 2006, 12:16
Hi Gadfly05, here is one more link about container problems. From a nice forum called SHIPSHUNTERS.
xsbb.nl/phpbb/viewtopic.php?id=shiphunters&t=680878

Trevorw
21st December 2006, 00:23
Have you ever carried timber as a cargo? We loaded pit props in Archangel, holds full and twenty feet high on deck. The run back to Grimsby was hairy! If you put the wheel hard over too quickly, she would heel over and take an age to right herself! I think we termed it as being "tender" All I can say is I was very glad when we lost 25% of our deck cargo in heavy weather in the North Sea - she handled much better then!

gadfly05
30th December 2006, 18:35
Hi Gadfly05, here is one more link about container problems. From a nice forum called SHIPSHUNTERS.
xsbb.nl/phpbb/viewtopic.php?id=shiphunters&t=680878

Thank you a lot ,hasse neren.
I will show all these pictures on the class to my students,and tell them "SAFETY, THE FIRST".
(==D)

RobW
2nd January 2007, 12:10
Further to above, understand most Maersk containerships are fitted with fin stabilizers. Certainly the 8,000 teu "S" and "A-class" vessels have them.

Some of the early large panamax boxships were fitted with these (eg OCL Liverpool Bay-class) although don't think any other owner apart from Maersk fits them these days.

Do bear in mind that very few containers are actually weighed at the container terminal by the carrier itself. Therefore under-declaration of weight is common - the cause of a number of accidents whereby heavy boxes are unwittingly stowed high up in the deck stow.

mclean
2nd January 2007, 18:28
Further to above, understand most Maersk containerships are fitted with fin stabilizers. Certainly the 8,000 teu "S" and "A-class" vessels have them.

Some of the early large panamax boxships were fitted with these (eg OCL Liverpool Bay-class) although don't think any other owner apart from Maersk fits them these days.

Do bear in mind that very few containers are actually weighed at the container terminal by the carrier itself. Therefore under-declaration of weight is common - the cause of a number of accidents whereby heavy boxes are unwittingly stowed high up in the deck stow.

Rob, I was involved in the stowage of vessels using the container terminal in Vancouver in early 70,s, and can say that every container into the terminal, aws weighed by the terminal operator. Due to the massive increase in container traffic, Can only assume that this is no longer practical? regards Colin

RobW
3rd January 2007, 10:40
Yes that's certainly true. I worked at a terminal in the UK in the 80's and 90's and can honestly say only a handful of boxes were weighed - mainly any container that the haulier suspected had been over-loaded. One box actually fell off a trailer doing a sharp turn and landed on our agency car which was alongside a ship at the time (fortunately with nobody inside it). When the box was weighed it rolled in at a mighty 50 tons ! Bear in mind the maximum permissible weight was 28 tons.
With the huge volume of box movements these days there just isn't time to put containers over a weighbridge. The big ships on the transpacific trade can exchange up to 5,000 containers (load/discharge) at one port and get turned around in only 2-3 days.

Peter B
3rd January 2007, 21:51
The first series of container ships built by Maersk, the A-class from 1975-76, had stabilizers and I believe that has been the case ever since.
In fact, the "Emma-class" currently being the worlds largest box ships, have two sets.

RobW
4th January 2007, 10:46
Yes that's certainly true about the A-class looking at their GA plan - but this idea never seems to have caught on perhaps to keep costs down as fin stabilizers are an expensive addition. Almost all modern containerships are built to standard designs and none seem to have option for fin stabilizers.

Peter B
4th January 2007, 10:57
RobW: In my comment, I was referring to Maersk vessels only, and as far as I am concerned, stabilizers has been common practice in Maersk since the A-class. Sorry for any confusion about that.