Another vid of a sister ship that has some views of the cargo and bow.
You have articulated my thoughts on the troll exactly.
On VLCC’s it was possible to see the movements of the hull in a seaway. Tapping a handrail resulted in a pitch change in the sound as the hull flexed. These container ships are the same size as VLCC’s and I can’t see that the hull would respond differently.
Besides the extra impact forces you mention, the load on the lashings could change from one end of the container to the other end. I feel that there is little accurate data to support the calculations made to form lashing plans. I’m not aware of a single strain gauge ever going to sea in one of these behemoths.
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VLCC hull bending due to waves is easy to watch in severe weather. The main deck may deflect 0.5 m up/down when the waves pass. Container ships with large hatch openings are, in addition to bending, subject to torsion/twisting of the sides of the hull fwd/aft. Wave impact loads on the bow above waterline at high speed is completely different. There it is compressed, trapped air between the moving bow and wave surfaces that ‘explodes’ with a loud bang after having elastically or plastically deformed the ship’s plate between stiffeners at the bow. The whole ship shakes and vibrates and you have to slow down. I have seen all types. The ONE Apus incident – container stacks shifting – is of course due to incomplete lashing/securing of the boxes and violent motions due to too high speed in severe weather.
Anyone have the vessel’s position and track at the time of the event?
The first information at FleetMon gave the data of the container-loss (then 50 containers !):
at position 33°15’N, 172°35’E — at November 30, 11:32 UTC
This Screen from MarineTraffic shows the path up to the incident
From (https://twitter.com/MarineTraffic/status/1334475858464083968)
The course off Tokyo was NE, the great circle to Long Beach.
At one point, the course changed to ESE. To avoid a bad weather zone?
The container loss was at the end of this ESE course, before going South
Just now, ‘One Apus’ is in the Kobe Bay, accompanied by two tugs.
That position seems too far south.
report that a significant number of shipping containers were lost overboard during severe weather on the night of Monday 30th November 2020 at 2315LT approximately 1600NM North West of Hawaii, USA.
Roughly it looks like 1600 miles NW would be about 40 N / 175 W
The given position is 1720 NM from Honolulu; at bearing 301°, about NW…
Then, the vessel was already far South of the great circle to Long Beach.
On the MarineTraffic screen, the incident was South of the Tokyo Bay (at about 35°)
Passing south of that low makes sense. More favorable wind and sea direction than trying to go north. Don’t know the forecast track but typically a low there would be headed for Unimak.
Somethings not adding up. Isn’t that position showing about 1 or 2 meters seas?
The update said weather at the time was reported as wind force 4 on the Beaufort Wind Scale, corresponding to 13-18 mph winds, with north-westerly seas of 5 to 6 meters and a “long high swell”.
40 N / 175 W is a better match.
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I searched the position in reply to @fredwx.
He will probably give us more detailed informations…
Seems like Marine Traffic would have the right info. - 35 N could well be 5 to 6 meters as well.
Based on the position via Urs of 33-15N 172-35E at 1132 UTC it appears that the vessel encountered SW shifting NW winds of forces 6-7 with significant wave height of about 4 meters at that time.
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Sounds like it might be similar to the MSC Zoe. Excess stability and synchronous rolling.
Which doesn’t take high seas.
We lost the entire stack off the hatch aft of the house on an APL C8 off the BC coast approaching Juan de Fuca due to rolling in long greasy but high swells. The twist locks and lashing eyes were ripped off the hatch and there was no other damage to the hull or deck except for minor damage to the port rail. The boxes were airborne when they went over.
The sound was like that when a train pulls the slack out of the couplings, boom, boom, boom, boom and that quick it was all over. The C8s had a nasty motion in some seas, the forebody would move in what felt like a vertical figure 8.
The worst were quartering seas whether on the bow or stern. Pitching combined with the rolling made for a wicked, miserable ride.
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Which is what we had heading south about a day out of Seattle, quartering stern.
I used to work on tugs that ran the outside between Juan de Fuca and SE Alaska and remember the incredible swells we would get off Vancouver Island if there was a deep low out west.
Let’s face it (https://owaysonline.com/rolling-of-ships/ ) :
Every vessel has a natural rolling period, which is inversely proportional to the square root of the GM and directly proportional to the beam B of the ship, if you believe it and know a little mathematics.
Synchronous rolling is caused, when the rolling period becomes ‘synchronous’ with the period of wave encounter. When this occurs, the ship will heel over and in exceptional circumstances be rolled further over by the action of the wave. It is terrible.
Parametric rolling occurs when the pitching period is either equal to or half of that of the rolling period. Large roll angles may occur quickly in head or stern seas or nearly head or stern seas. The roll angle may increase from a few degrees to over 30 degrees in only a few cycles. Imagine THAT!
It is caused - wake up!! - due to a combination of various factors such as low initial stability, large flare around the water line, waves as long as ship’s length, sufficiently large wave amplitudes, period of encounter half the rolling period, low hydrodynamic roll damping , sleeping Master, lazy crew, bad luck and that you don’t understand all above.
Parametric rolling is produced by the pitching motion on vessels which have a very fine bow together with very wide and flat stern like large container ships which have a large flare forward and a flat after ship. Imagine THAT! Pitching causes rolling going sideways through waves.
In irregular waves however synchronous and parametric rolling and pitching of any type are irregular and may thus occur at the same time making you afraid, if you are sober and awake.
Actually, only way to avoid it is to reduce the period of encounter, i.e. to slow down or change course. If you are in a hurry at sea, you shouldn’t be there. Enjoy the fresh air and the view.
I was going to ask about this “parametric rolling” term until I saw the juvenile, vindictive response. Then I saw this link which explained this is peculiar to container ships. Lacking any past information, I supposed this might be related to “free surface effect” we were taught in damage control but is a different thing altogether. Thank you for the link!
Can you please just call ONE and any relevant agencies and let them know your findings. It would speed up their investigative process immensely. Seems like you have it totally, accurately figured out.
“I think the real cause of the incident is going much too fast in severe weather and in the night. The bridge is far away from the bow and the crew doesn’t know what goes on at the front of the ship. They just sit and sleep on the bridge.”
“They were just going too fast in severe weather. Parametric rolling - ROTFL!”
“Yes, parametric rolling is a new trick to fool marine incident investigators, when ships and cargoes are damaged at sea.”
“Sitting/sleeping comfortable on a bridge high up at mid-length of the ship (i.e. at center of rolling, pitching and heaving) is not good seamanship.”
“The ONE Apus incident – container stacks shifting – is of course due to incomplete lashing/securing of the boxes and violent motions due to too high speed in severe weather.”