car carriers and angle of loll

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JK
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car carriers and angle of loll

Post by JK »

OK, you experts, what the heck is up with all the car carriers hanging over and staying there?
Are their stability that fragile? How are they being approved if they do this at apparently random times?
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Merlyn
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Re: car carriers and angle of loll

Post by Merlyn »

It's because the owners want to avoid dry dock charges and on a fine day they can A/F one side of the ship FOC?
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.
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Re: car carriers and angle of loll

Post by JK »

LOL
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Re: car carriers and angle of loll

Post by JK »

They're bringing the latest listing car carrier into Bilboa. It has a cargo of logs from Gabo to LeHavre. Logs are banned to be exported from Gabon.
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Re: car carriers and angle of loll

Post by Merlyn »

Gabo v Gabon?
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Re: car carriers and angle of loll

Post by JK »

Gabon
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Re: car carriers and angle of loll

Post by Big Pete »

Having sailed on Car Carriers, the last thing you want is a too stable" i.e. "stiff" ship, because it would roll like a pendulum and the cargo would break free. The ideal is a fairly small GM which gives a "lazy Roll" with no big accelerations to stretch the cargo lashings and work them free.
However, in this condition it is essential to watch the "Free Surface Affect" like a Hawk, and the Engineers and Mates have to work together to maintain the list and trim using both Fuel and Ballast Tanks in such a way as to minimise Free Surface Effect.
A further complication is "Wind Induced List", because Car Carriers are very High Sided, any wind on the side causes them to heel, pumping Ballast to correct this, can leave the vessel vulnerable to flopping over in the opposite direction when the relative wind changes. On an old car carrier with an inexperience Mate I used to get called out every half hour all night with a furious tirade that I must have transferred fuel because the List had changed and I must go down the ER to pump Ballast and correct it. The Mate just couldn't understand that every time the relative wind speed / direction changed, the List changed.
I suspect most of the problems are incurring on modern ships with "Auto Heel" tanks, where the Mates and Engineers leave everything to the Automation, and ignore the Free Surface Effect.
The Car Carrier that capsized coming out of Southampton after Bunkering, last year, obviously had a FSE problem, I am not sure if the requirement to reserve Tanks for LSFO had any bearing on this. Practically you are always going to have at least one slack LSFO and one slack HSFO tank.
I was always taught to run fuel tanks empty, and fill them in pairs P&S, when Bunkering, but many Engineers now just open the filling valve to every tank full and let the fuel flow in, leaving every tank slack unless they are taking capacity Bunkers.
Many of the Eastern European Engineers have no knowledge of stability at all.
I had a Polish Second Engineer join my ship with a brand new Chief Engineer's Certificate and a "Degree" from a "Technical University" in Poland. I asked him what he had to do in order to get his qualifications, he told me it was very difficult, he had to dismantle an air compressor and rebuild it!!
No sort of Engineering Exam / training to my mind, just a trade test for a service Mechanic/ Motorman.

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Re: car carriers and angle of loll

Post by JK »

Now that makes better sense. Thank you.
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Re: car carriers and angle of loll

Post by Big Pete »

A further point I should have mentioned is that cars and trucks have their own "Free Surface Effect", the rolling chassis is securely wedged and lashed down, but all the upper works are free to move on the suspension, which can obviously contribute to stability problems.
Similar to the old "Meat Boats" when frozen carcasses were suspended on Meat Hooks from Deck head rails, the effective Centre of Gravity of the Meat was the Deck head rail, rather than the centre of the Meat.
And of course the famous Naval Arch Stability question of the weight on the Deck of the ship that is lifted by the ship's crane/Derrick. As soon as the Crane takes the weight the C of G of the weight effectively becomes the point where the crane wire makes contact with its sheave.
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Re: car carriers and angle of loll

Post by JK »

I expected a automatic ballasting system issue, but the slack fuel tanks is surprising.
you would not expect that cars rolling on their suspension would be an issue, but when it is thousands it would add up.
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Re: car carriers and angle of loll

Post by JK »

I was just reading that investigators looked at the cargo stowage and it was perfectly done. They are struggling to explain the list.
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Re: car carriers and angle of loll

Post by Big Pete »

With Logs on open Decks it can be caused by the logs on the Weather side absorbing Sea Spray and becoming heavier, a well known problem on timber carriers, but I would think that on the car carrier the logs would have been stowed internally, on the car Decks.

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Re: car carriers and angle of loll

Post by Merlyn »

A lot of vehicles are fitted with air bags ie air suspension nowadays, maybe they were pumped up too high thereby raising the C of G? Just a thought.
Remembering The Good Old days, when Chiefs stood watches and all Torque settings were F.T.
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