Chinese river ship launch failure

[Angélique]

So, what's the reason for these add-ons, all so similar to each other? Did the rules for ferry ship stability dramatically change at some point of their lifetime?

Some of the above have only a stern sponson added, so there seems to be a prior lack of buoyancy aft.

Maybe the side sponsons have been added due to extra safety requirements, to provide extra stability and prevent capsizing when water enters the cardeck, after disasters such as the 1987 capsize of the Herald of Free Enterprise when leaving the port of Zeebrugge, killing 193 passengers and crew.


pic thanks to Jan Dewachter

Herald Of Free Enterprise capsizing (3D animation)

Well, no cheers now
Angel

 

[RAraujo]

Yes, the rules changed...
New SOLAS regulation Ch II-1, 8-1 and 8-2 and Stockolm agreement requirements.

 

[Boat Design Net Moderator]

Wow...

And there is another thread started slightly later regarding this launch failure here as well (threads now merged)

 

[Angélique]

check out 4:45 into this video. What are these things? Filled with water, maybe?

http://www.youtube.com/watch?NR=1&v=VPGBEI5orIg

They're airbags to roll the ship down the ramp when launching. In above vid there were to little or they were to light as you hear them bang.

Here the launch of a LPG tanker, on the Danube in Romania, on those rolling airbags - Link - Link - Link - also some problems.

( P.S. - see note about this in post #54 )

They were also used to launch the Chinese ship in the vid in post#1, info about that here - Link - Link -

More links to airbag ship launchings - Link - Link - Link -

Cheers,
Angel

 

[Angélique]

Here Marine Airbags Feb. 1, 2010 record:

Eversafe Marine Breaks World Record

On 1 Feb. 2010 Eversafe marine engineering company flawlessly launched a DWT58,000 cargo ship with Marine Airbags in Zhejiang China and this ship launching project sets the new world record of ship launching by marine airbags.
This cargo ship holds 11,800 tons is 199 meters long and 32 meter wide. It is built on a 0.87 degree concrete ramp whose end is a sluice gate. From the water gate to ship’s stern is 15 meters and the water beyond the gate is 8 meters deep. Total 76 pieces YT-6 type Evergreen Marine airbags are employed to complete this project and also two 25 tons winches.
For big ship launched with marine airbags, the scientific design from calculation is vital for success. To ensure this DWT58, 000 cargo ship’s safe launching, there are two conditions must be satisfied first: avoiding the “bow decline” during the launch process and the rush distance is controllable when ship is after launch.
Eversafe engineers are gathered to calculate the launching project of the largest ship ever be launched by Evergreen Marine Airbags. From mathematic modeling to computer simulation every step of launching process are researched carefully. From the water level to weather variety most conditions are considered for the design. When settle the arrangement of Airbags, Evesafe engineers find the stern rope must be added to control the rush of ship after launch. So 4 stern ropes are demanded to fix on the bollard of a floating dock with 45 degree angle to the ship and the time of cast anchor is also stated.
At 31 Jan. Eversafe team completed the ship raise and most block remove work. At that time two winched pulled ship from slipping and the blocks under stern remained. The highest tide of 1 Feb. is estimated to occur at 10:30 AM, so launch time is decided to be 10 AM. At 9:30 am Evergreen-Maritime team began to adjust the inner pressure of ship launching airbags at stern to be 0.12Mpa and then released the steel ropes from winches. At 9:50 Marine Airbags under gravity center and bow were inflated to be 0.15Mpa then the ship began to move slowly by riding rolling airbags. During the launch process the ship’s incline angle is increasing until the stern floated when the bow enters into deep water already. There is no “bow decline” phenomena occurred just as forecasted by calculation.
When ship advanced in the sea for a certain distance its bow anchors was casted and four stern ropes were trained. So ship moved sideways then it was pushed by two tug boats to mooring.
The success of DWT 58,000 ship launched with Marine Airbags not only creates a world record of airbag ship launching but also means the Airbag ship launching technology reaches a new altitude.¡¡¡¡
Eversafe marine engineering company is devoted to be excellent and never satisfied.

Cheers,
Angel

 

[philSweet]

Yes, I spent about three hours thinking about these contraptions engineeringwise. It reminded me about a quote regarding a dancing dog- What is amazing is not how badly it's done but that it's done at all.

 

[troy2000]

Didn't really 'sink'; the idiots just stuffed it arse-end into the water at too steep an angle. Even I could've told them that wasn't a good idea...

But for some reason, they didn't check with me first.

 

[Angélique]

Yes, the rules changed...
New SOLAS regulation Ch II-1, 8-1 and 8-2 and Stockolm agreement requirements.

Thanks, just checked the timeline...

1987, the Herald of Free Enterprise, 193 dead was a clear warning, and even before this disaster the stability problems when water enters the uninterrupted all over the ship cardecks were well known. But they waited for the 1994 Estonia disaster to change the rules. Of the 989 people aboard only 137 survived.

The Sinking of Estonia

Who's gonna blame China for mishaps

Cheers,
Angel

 

[RAraujo]

They were different types of accidents...

Anyway "a posteriori" it's always easy to say what should have been done. Are present regulations safe and fool proof? Yes, until another accident happens... Neverthless we have coming a long way since Titanic and subsequent first version of SOLAS and shipping is a heavily regulated industry but sometimes the sea, and the human being, refuses to cooperate.

The unsinkable ship is still to be built...

 

[daiquiri]

Anyone knows what is the inflation pressure inside those bags?

Edit:
Ok, found it. They work with pressures up to 1.4 atm - surprizingly small. Looked like rolling bombs at first glance, but they are actually less inflated than car tyres.

 

[Angélique]

The roll-on roll-off ferry type built as those ferries was already under fire before the disaster of the Herald of Free Enterprise, which was more than seven years prior to the Estonia disaster, because of the large continuous car decks over the whole length and breadth of the ship to enable quick on and off load.

Once such a ship makes water the all over the ship free float liquid surface rapidly decreases the stability and causes a very rapid capsize. Both disasters, the Herald of Free Enterprise and the Estonia, started with water entering trough the bow door causing the above.....

‘‘ Are present regulations safe and fool proof? Yes, until another accident happens... ’’

The lesson here to learn is that one doesn't have to wait for a second accident to change the rules..

Cheers,
Angel

 

[Angélique]

Back to the bags...

- whats the empty weight of a ship like the one in post#18 per cm² bottom surface . . ? ?

- how much of the bottom surface is covered by the bags . . ? ?

- is the 1.4 atm just pre-pressure or working pressure when loaded with the ship . . ? ?

- if 1.4 atm is pre-pressure, what's the pressure when max loaded . . ? ?


• The quick question is, does such a ship weight less than let's say 0.5 kg per cm² bottom surface . . ? ?


Cheers,
Angel

 

[daiquiri]

1.4 atm is (according to the site linked below) the max working pressure, so with the ship pushing down on the bag.
http://www.blueoceantackle.com/ship_launching_air_bags.htm

 

[powerabout]

did anyone mention the megayacht in bangkok as well?

 

[Angélique]

From Daiquiri's link . . . .

4-layer bags that are 1.5m dia x 15m long contain a rubber content that is not less than 51%. The air-bags can safely hold 156-tons with a safe working pressure of 0.08MPa while rolling. When standing still the highest lifting pressure is 0.10MPa while holding 194-tons.
~~~~~~~~~~
6-layer bags that are 1.5m dia x 15m long contain a rubber content that is not less than 51%. The air-bags can safely hold 234-tons with a safe working pressure of 0.12MPa while rolling. When standing still the highest lifting pressure is 0.14MPa while holding 272-tons.

LONGEST EFFECTIVE FLAT LENGTH IS 18.0 METERS

OK, while rolling it's 0.12 MPa (~1.2 atm), it says that gives a ø 1,5 m x 15 m bag 234-tons carrying capacity.

That seems to be a bit optimistic as . . . . 234,000 kg / 1.2 kg/cm² / 1,500 cm = 130 cm

Which means that the ø 1,5 m x 15 m roll on top and bottom surface is flattened to 1.3 m wide to carry the 234 tons at 0.12 MPa.

Flattened roll hight will be: (π x 1.5 m - 2.6 m) / π = 0.67 m

Flattened roll wide will be: 0.67 m + 1.3 m = 1.97 m

That seems to be a bit flat to roll well, even if the roll will deforme well while rolling.

It's even a bit worse because the surface lost in pointed ends is not included in the calculation.

But what's the weight of that ship in post#18 . . ? ? - I need an NA to estimate that

Cheers,
Angel

PS - it doesn't show well, but . . . π = pi