How do container ships float and not fall over? They look too top heavy?
Answers:
There's much more below the water line that you don't see. Looks can be deceiving. Take it from me, I know.
They have ballast tanks that balance the ship.
The displacement of the ship in water, I think
ships stay on water not because of the weight on top but how it ditributes its weight on the bottom
its simple, to every action there is an equal but opposite reaction, so when the container ship pushes the water down, the water pushes it back up. to get more push from the water the ship has a massive base, this base spreads the weight of th ship over a large area, thus the "pressure" on the water is reduced.
the push (buoyancy) applied by the water is dependent on the surface area of the ship's base, larger the base bigger the push. (actually its density not surface area, but to keep the things simple we can assume that it is surface area).
All you see is the containers above deck and don't see the stacked 4 high containers that are below deck in the hold.
boats have things called keils to stop them going **** up or down as the case maybe
The amount of containers you see on the top of the ship is around only 15% of the weight of the containers AND the ship. There is very little superstructure, practicallity means lighter ship to increase load capacity. The amount of ship you see above the water is around 3-5% of its total height, ergo there is significantly more ship under the water than above, much like an iceberg. Looking at this in its entirety, most of the weight is under water, so it is highly unlikely to "fall" over, this makes it bottom heavy. If it was top heavy it WOULD roll over. Simple physics.
The holds are usually full of illegal immigrants.
First in ship building they will measure the stability of the ship, and the stability is the most important thing in the ship, with out stability you will see the ship is tilted or unstable, they will calculate the CL (center line) and the CG (center of gravity) and the CB (center of buoyancy), and when they put the load on the ship they will arrange so they can stabile the ship trim by bow and by aft, considering it will not exceed the draft line limit.
stability and displacement
most are below the deck
you should see whats on the bottom, it's called ballast
Containers may be the same size in volume, but the heavy ones (20+ tons) are place low and the light ones (<8 tons) are put on top.
Put simply, assuming you know what a floating thermometer is in a tropical fish tank, it bobs about in the water, if you lay it on it`s side the heavy end will sink, obviously, but because the total weight of the thermometer is less than the weight of the water it displaces, it floats, A container ship works on the same principal, the weight of the ship below water is more than the weight above water but less than the weight of the water it displaces,as with the floating thermometer.
There is a line around a ship, level with the water which is called a plimsole line, a ship is always at this level when at sea, It is the balance point of the ship, this level is kept by of balancing the weight of the cargo with the weight in so called `ballast tanks` which are located at the lowest point within a ship and are either filled or emptied of water to keep the ship balanced at all times.
They do look top heavy. They have a lot of ballast. Sometimes they do lose some of the cargo, there have been some strange boxes washing up on shore like a load of rubber duckies, and many pairs of sneakers.
There is a line on the side of the boat, near the water line, which no boat is allowed to have below the water line. This is calculated by the naval architect to be the maximum safe loading possible. If that line is in the water, the boat is too heavy.
Now you will find that below the water, there is a lot more boat than you would imagine, and in this area is ballast tanks, fuel tanks, storage tanks, and main machinery, basically to counter balance what is above the water, and keep the centre of gravity as low down as possible.
If youre really interested, look into metacentric heights. Its a fairly straightforward calculation to work out whether the boat is in trim or not.
DEEP KEELS AND BIG BALLAST TANKS AND STABILISERS IN ROUGH WEATHER . THERES A LOT OF SHIP BELOW THE PLIMSOLL
When a container ship is fully loaded, what you SEE on top is only a third or even a quarter of it actual Payload. Most of the weight is inside the Hull and below the waterline.
ballast and design
If you watch the news then you will see that they do fall over and sink.
The main reason is to do with the centre of gravity. All the heavy stuff, Engines , Ballast , Fuel, Black, grey and fresh water is all in the lower compartments of the ship. If you look at the bow or stern of the ship you will see some numbers that will tell you how far the lowest point is. And it is not as far as alot of people seem to think.
These types of vessel are very unstable . along with the large car carriers. Case in point the one that rolled on its way from Japan to the USA , or the one that rolled over in the English channel a year ago. They are only as good as the Stevedore's that load it and the skipper that masters it.
The vessel has got limits and if they are pushed then it will sink. As some one once said. " It is made of steel and WILL sink"
on the hulls of ships there are markings called plimsoll lines these indicate the ships displacement in the water. if the water is not within the markings then the boat would not be stable.this line is arrived at using the mathematical laws of displacement
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