"As the wave crest travels along the hull, it results in flare immersion in the wave crest and the bow comes down. The stability (GM ) varies as a result of pitching and rolling of the ship. .
The similar action takes place as the bow goes down in the next wave cycle resulting in synchronous motion which leads to heavy rolling up to 30 degree in a few cycles. This type of rolling is known as Parametric rolling."
I wonder what clown invented the above.The stability varies ??? The combination of buoyancy and wave excitation forces push the ship to the other side ??? (it) leads to heavy rolling up to 30 degree in a few cycles ???
Actually, the only way to avoid damages in severe weather is to look out and listen, change course, slow down or avoid the bad weather all together. 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.
All these technical terms on here can boggle the mind. Had decent weather forecasts(Not as good as todays forecasts) and best I could do loaded was about 10-12 knots. Avoid the weather as best you can. ETA was a guess anyway. Fucked up part of retirement is I wait for bad weather, and can’t move.
Then please, either find another way to amuse yourself online or stick to threads about tugboats.
You claim to have built ships yet you haven’t heard of a phenomena thats been studied in the shipping industry for the better part of a century? I learned about parametric rolling almost 20 years ago in college, the IMO was putting out papers warning about it more than 15 years before that, and studies exist going back to the early mid 1900’s. Originally in relation to smaller ships at that.
It’s not a trick, its a name given to something that a Container ship captain should be aware of so shit like this doesn’t happen. Thats what we do when we study a recurring phenomena, we give it a name.
(Also, the bridge is too far back to see the bow so the Mates had no idea what was going on up there?? I wonder how they ever got anywhere at all, or ever tied up to a dock !!..must be impossible since they couldn’t see anything from the bridge. My goodness, if only someone had invented a way to see something not right in front you, like a camera…)
Anything parametric makes me ROTDL.And please do not suggest you can see the focsle or stern from the bridge of ONE Apus behind all those container stacks on deck.
He offers € 1 000 000:- to anybody proving him wrong, Try to win it!
Fuck off Mr Steamer sir. Enjoy your miserable life. The tugboat guys always kept their eye on the weather. Again, fuck off with your negative comments regarding fellow mariners, no matter what business they operate in.
Let’s see; 14,000 TEU is about 7,000 forty-foot boxes to check at say, 1 minute per box for the mate to look at the lashing and cones. Is 117 hours or almost 5 days. Then another 5 days for the Master to go out and double check so he doesn’t go to prison…Then add a few more days so the crew can comply with STCW rest rules. As a container ship officer I LOVE THIS IDEA!! We get to stay in port now for 14 days instead of 2!
What if it was the Kraken under cover of the storm?
Is there a clause in the insurance just in case a giant squid attacks the ship?
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Looks like I’m not the only one that think it is time to limit height/weight of boxes on deck:
The other subject taken up is the increasing wave height/period (that MAY have caused Parametric rolling) caused by climate change:
If I count right there are at some places 9 containers stacked on top of each other. Quite a squeeze. The lashings are calculated for a maximum permissible acceleration of 0.8 g or 7.848 m/s^2.
I made a quick calculation that shows that at the top of the stacks by a roll of 30° the acceleration is 9.7 m/s^2. To be sure I will recalculate it.
I agree with the general point of the article that safety at sea requires basic labor protections for all mariners. Seems obvious.
I think it’s unlikely that anyone purposely exceeded weather limits to stay on schedule. As was mentioned, the ship was most likely being routed professionally. Limits and margins are calculated in advance.
More likely technical errors and a combination of factors than a simple, deliberate violations of limits.
I have had the weather routers miss stuff. It’s not prudent to just follow the recommended route without careful checking.
At what roll frequency??
Roll of 16.42 s.
I assume the ONE Apus has a crew of 20 and that all is automatic aboard. The crew only sleeps, works and watches videos aboard or work out at ship’s gym. One man is on the enclosed bridge at sea while some deck crew walks around checking the lashings of the deck cargo. They climb up/down/walk across on the 30+ fixed, deck lashing rods platforms, etc The engine crew walks aft and keeps an eye of the engine room far aft. There is no view of the sea from any crew cabin as the view is blocked by deck cargo. I always wonder why you but the bridge where you cannot see the bow or the stern. Must be very boring being locked up like that. Maybe nobody noticed that heavy weather was coming up? I assume nobody aboard had ever heard about parametric rolling and experienced it.
Recalculation gave as result that at a roll of 30° the acceleration is less, 7.56 m/s^2. The required 7.848 m/s^2 for the lashings is reached at 31°. I don’t know how much tolerance is available before they really break.
What I think could be a serious problem is lateral jolting by wave impacts. As far as I know lateral jolt has not been studied yet anywhere. The acceleration caused by a jolt (not m/s^2 but m/s^3) is much more serious then by a roll. Steel bars and deck fittings could easily snap under these circumstances.
In general the design limits of lateral accelerations assume prudent seamanship.
A word of advice. Don’t feed the troll because he is growing and growing and undermining bit by bit the quality and professionalism of this forum. Be aware!
Video I found showing the maiden voyage of the loaded One Apus. can clearly see the lashing of the containers and I think I saw a camera on the forward mast.
https://www.youtube.com/watch?v=xm5PxsPEGlM&feature=emb_rel_pause