Flexi Steel

Yes, slow down, alter course, or both. I saw the movement shown in that video literally a thousand times and sometimes far more movement ... like I wrote earlier, in bad weather that door at the end of the tunnel would be out of sight half the time. I never saw anyone praying that the ship would not break and aside from a few WW2 surplus Liberty ships I can't recall any that broke in half because of steel formulation. Even then it was cold embrittlement.

There is much more to the issue than you are apparently aware.

Well, considering that 70 to 80 percent of a modern ship's hull is made of steel defined as high tensile (compared to mild steel) there are a few who might disagree with you. The other 20 or 30 percent is glass, plastic, non ferrous metals, and a thousand other materials so it is unlikely an entire ship would ever be built of HT steel isn't it?

Moonen just sold a high tensile steel hulled 37m yacht. I guess they don't agree either.

Yeah, that started a whole new era of investigation into how bulkers were loaded and offloaded as well as how they were inspected.

At that time there was something like one bulker a week vanishing without a trace. It finally got so embarrassing that the IMO had to do something. Until then no one gave a darn because they were mostly FOC ships with native crews.

Look how long it took the Derbyshire families to produce some movement.

If it doesn't bend, it breaks

Large ships, especially box arriers, tankers and bulkers are flexing a lot. And they have to, otherwise they will break apart, as mentioned and shown above. This can happen not only while on cruise, it can also happen while loading or deloading cargo. Large cargo vessels not only have strain gauges, their bending and flexing is permanently measured and recorded, i.e. Laser detector systems. The central pathway in the lower hull is the most favorite position for these measurement systems. I can tell you, it looks really scary on a 1.000 ft bulker at seastate 9 or 10 down in this tunnel. The other end of the tunnel will come totally out of sight .

But not only the magnitude of its flexing, also the frequency and the point of flexing is measured. Normally a large ship is not flexing around a single frame or position of the hull. It is more like a wave running through the ship. If during a storm or high seastate, the amplitude, frequency and position of flex is reaching a state, where a resonant vibrancy is building up, means the ship cant flex back before the next impact arrives (like a large group of soldiers marching over a long bridge in lock step), the crew on the bridge has to change the parameters, causing the resonant vibrancy, like changing speed, course and / or trim of the ship. If a resonance is tolerated for a longer period by the crew or if it is developing due to a bad construction or naval architexture, the occurance of fatigue and cracks / failure is just a matter of time.

The other big problem with cracks due to flexing is the usage of cheap steel, i.e. steel made out of scrap metall with to much copper or other " bad ingredients" in it. This type of scrap metall is very common when using recycling steel from cars and other consumer products. Grade A ship building steel will (normally) not have this problem. But some well known ship building nations are also well known for using this scrap metal based cheap steel in order to make more profits.

On the BP chartered tankers the strain and immersion gauges were connected to a computer console in the wheelhouse that looked like another radar pedestal. The display could be varied to illustrate the maximum allowable strain and approach to slamming. The only problem was that once the silly mates could see what the limit was, it became a goal. It was a video game for them to keep as close to the target as possible.

The one motion that made me a little bit nervous was the "ringing" caused by slamming of the bow. The whole ship would ring like a bell for a long long time. You could feel the "boing boing boing boing" and listen to all the loose bits rattling until the whipping stopped.

We spent a week in a typhoon once near the dateline enroute to China and got blown back several hundred miles by 80 to 100kn winds and seas about the same height. Hove to and between the rolling that launched the sat antennae overboard, broke all the HF antennae, and destroyed part of the house and much deck gear, the scariest part was the slamming and the noise. Thank heavens the hull flexed as much as it did.

New Thread Marmot?

Well, the picture clearly shows the stern broken off, not midship, not in half. Interesting picture btw, I wonder when it was taken, must have been before Andrew 92, as I have always known the sapona with the stern submerged.

This blog post is far from accurate... The sapona sits in about 15' not 30' making it a great snorkeling spot. Some people still climb to the crumbling deck to jump in the water...

No, it actually broke almost midships, there is an entire section that crumbled and submerged into the water.....in between the stern and the foward half that is shown out of the water in the old picture. I believe it broke at the rear bulkhead of the midships cargo compartment. The propellor is still there resting on the bottom, I'm surprised nobody salvaged that as I believe it is bronze.

Here is what I have gathered from researching these ships:

The MOL Comfort, together with its sister vessels, were the first containerships classified by ClassNK to utilise ultra-high strength steel with a yield strength of 470 MPa (the unit of stress pressure) in their hull structures to to reduce the steel weight of the ship by avoiding extreme plate thicknesses. The reinforcement on the hulls of the sister ships was performed by MHI to twice the level required by ClassNK.

The company has filed a claim in the Tokyo District Court for compensation from Mitsubishi Heavy Industries (MHI) for the cost of having to strengthen the hulls of six sister ships, after inspections by ClassNK found “buckling-type deformations” on their bottom shell plates.


Investigators also discovered 20-millimetre buckling deformations on the bottom shell plates of the six sister vessels, which were all called in for hull strengthening, and enhanced to twice the strength level required by ClassNK and the International Association of Classification Societies.

In 2007, the vessels were the first in the world to use high-tensile steel, which was supposed to enhance the reliability of hulls against brittle fractures through reduced plate thickness, according to an MHI report.

In modern container ships, the hatch side coamings are subjected to the highest stress levels of all structural members in the ship due to the large openings in the strength deck that are necessary for loading and unloading of containers in the cargo holds. In order to cope with this problem, plate thicknesses up to 90 millimetres (3.5 in) are used to keep the stress levels acceptable. MOL Comfort's sister ship, 2007-built MOL Creation, was the first container ship classified by Nippon Kaiji Kyokai to utilize ultra high-strength steel with a yield strength of 470 MPa in these structures to reduce the steel weight by avoiding extreme plate thicknesses.

These are pulled from various articles BUT:
In 2007, these vessels were first in the world to use ULTRA high-tensile steel
Used reduced plate thickness
Company doubled the plate thickness on all of the sisterships
Buckling of 20MM was found on the hull plates of all 6 sisterships.

The Sapona

Are you kids talking about that cement hulk South of Bimini? It's been 20 years but I understood navy aircraft used it for gun practice Long, Long ago..

Yes, and yes the Navy did during the WWII era. It seems like the Navy wasn't too good of a shot back then. LOL

http://www.mlit.go.jp/common/001029660.pdf

The Ship was built using YP47 steel (yield stress: 460 N/mm2) in the hatch coaming to mitigate against toughness degradation that could occur when using extra thickness plates.

I don't see how anyone can attribute this loss to high tensile steel - that was not where the failure began and it was the last part to break.

https://www.mhi.co.jp/technology/review/pdf/e443/e443028.pdf

The green parts are where HTS was used. Those were the last parts holding the ship together before the final break.

From what I've read and seen in the pictures. All of the damage and breakage of the ship occured solely in Cargo hold 11. I don't know if this was because of a design flaw and it wasn't strong enough structurally in that section. The other thing is they might have built the ship in 2 seperate sections and then welded it together in that area, I do not know. Once it broke off there, the bow piece and stern piece of the ship stayed afloat for days. The bow piece might have even made it to shore via tow if it did not catch on fire.