by78
General
It's a photoshopped image that digitally reduced the gaps between all the modules to give an idea of what they would look like if they had all been welded together.
CV-18 Fujian/003 CATOBAR carrier thread
- Thread starter Jeff Head
- Start date
It's a photoshopped image that digitally reduced the gaps between all the modules to give an idea of what they would look like if they had all been welded together.
the fact that cargo ship tend to be lopsided general,y has little to do with speed. It has to do with the fact that cargo ships operate at either nearly fully laden, or in ballast. The bulb is designed to produce the most benefit when the ship operates at laden draft, but must not produce too much excess wave and drag when the ship is in ballast and parts of the bulb is above water plowing a furrow of its own.
But that is not the only reason why a bulb may be designed to be lopsided. Thee are instances of Large fast ships designed to operate with a very narrow range of drafts, and the bulb will almost always be submerged just like on a aircraft carrier, that also has lop sided bulbs. For example the 29 knot cruise ship/ocean liner Queen mary 2 has a distinctly lopsided, upswept bulb.
So analysis by analogy can’t provide definitive conclusions.
The majority of box ships, bulkers and tankers have bows like this where the point is upward.
The Queen Mary has a bulbous bow where the point is upward.
This is the kind of bulbous bow I would expect for boxships and tankers, although some would be shorter.
Whereas for an aircraft carrier like Queen Elizabeth II, the point in the bulbous bow is at the center.
That bulb does not point up.
This bulb does not point up, and it has its point at the center.
The CMA CGN containerships being made by Jiangnan don't feature a bulb at all. Certainly rules out those ships.
Again, The bulb on box ships point upward, and tend to have a rather sharp prowl of its own, because the bulb must provide the maximum benefit when it is submerged When the ship is at deep load, but must not create too much Additional drag cutting through the surface of the water when it is partly exposed at shallow draft. However, the fact QM2, a ship of broadly similar size, similar top speed as a large Aircraft carrier, and also Designed to operate within a narrow range of draftS just like an large aircraft carrier, suggests the aysymmetry of the bulb is not diagnostic of whether the hull it is attached to is meant to be operated in a manner consistent with a carrier.
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It's rather how much of the time the bulk of the hull is submerged. For a box ship, bulker or tanker, they are in that time, most of the time, whereas warships don't go fully loaded most of the time. Once again, this is the bulb for the Gerald Ford.
This bulb doesn't point up like a boxship or tanker's would. This bow has a very good chance it doesn't belong to a box ship, tanker, membrane type LNG carrier, or the ice breaker membrane type Yamal LNG carrier being specifically made for Russia. I took some time to match it with as many CSSC, CSG and CSIC built ships.
These are bows made by CSSC for Maersk ships. Compare that.
Only other ship I can think of that can be made at Jiangnan with a bow like that is potentially an ice breaker.
This one is the latest Russian Elbrus. But many ice breakers don't feature any bulbs at all including Jiangnan build Xuelong 2. I may think that the Jiangnan built Xuelong 3 might follow Xuelong 2's design more than the Elbrus.
Tankers either have an upturned bow or a short stubby bow. There are also tankers without a bulbous bow. This photo shows both bows common in tankers in one single shot.
Entirely on the contrary, commissioned warships only ever operate at or near full load displacement. If they use up consumables And become lighter, they take on water ballast maintain theOr near maximum displacement. Their underwater damage resistance is usually calculated to be at maximum at their designed combat displacement. Look at the boot top of warships. You never see the commissioned warships ridding high with their boot top much farther than normal above water.
A similar state does apply to passenger ships, such as cruise ships and ocean liners. They also ballast down when lightened by usage of consumables such as fuel, this is why you also never seem the riding high in the water with boot top conspicuously high above actual waterline.
Many box ships, on the Hand, do operate very light much more often, such as when transiting between different service route. The state is also called ballast, which means the ship rides as high as stability and immersion of the rudder and propeller will allow. Go near major ports, you see perhaps 1 in 5 cargo ships Move around the port running in ballast, with boot top half way up their freeboards. Off shore, you see perhaps 1 in 10 in that state.
A similar state does apply to passenger ships, such as cruise ships and ocean liners. They also ballast down when lightened by usage of consumables such as fuel, this is why you also never seem the riding high in the water with boot top conspicuously high above actual waterline.
Many box ships, on the Hand, do operate very light much more often, such as when transiting between different service route. The state is also called ballast, which means the ship rides as high as stability and immersion of the rudder and propeller will allow. Go near major ports, you see perhaps 1 in 5 cargo ships Move around the port running in ballast, with boot top half way up their freeboards. Off shore, you see perhaps 1 in 10 in that state.
Warships don't hold over 200,000 tons of cargo for an empty weight of say, only 60,000 tons.
That's because the empty weight of warship isn't that much different from its fully loaded weight. A Type 054A might be standard loaded fully loaded at 4,000 tons. At empty it may only be 3,600 tons. A freighter with an empty weight of 4,000 tons, can have a deadweight of around 10,000 tons, and when fully loaded, displaces around 13,000 to 14,000 tons. Big difference.
When a merchant ship is riding high, its not hauling cargo, its not loaded with fuel and its not running on a contract. When its fully loaded, then someone is paying for this.
When a container ship is running high on the water, its either not running a delivery, or its doing a run that's losing money, which means it will recoup its cost going outward by charging you the cost of both runs in one run.
For example, some ships head to this country on empty, load the cargo, and then head back. If this happens, the cargo freight is 2X the cost designed to cover both in and out runs. A ship has to be fully loaded from Country A to Country B, then fully loaded back to Country A in order to have the lowest freight and fuel cost.
They don't operate light as its main business model, because if a box ship operates light, its losing money. And because of that, they don't operate very light much more often, because you are simply going bankrupt. If you are operating light, for one way trips, like say, transporting freight from the US to Puerto Rico or Hawaii, and there is nothing to ship back to the US from Hawaii or Puerto Rico, then one trip isn't making money and while the other is making money and the shipping company will charge you the cost of both trips for one trip. So instead of say, $1000 for a 20 ton container, you have to charge $2000. But if you are shipping two major countries directly that has much trade with each other, say China to US and back, you make money both trips and you can charge only $1000 per container.
Operating like the way your describe is the exception for the shipping business not the norm. Like for example. you are making Jones Act ships. If you are going to be servicing islands that have no outward export business, you are going to be using much smaller freighters.
Good try because going back to the shipyard at hand, Jiangnan Shipyard does not make Jones Act ships or is in the business of making small freighters to service some small island in the Pacific. The ships they make are those that go between Europe to China or China to USA. It does not make the kind of ships where you expect to be transiting on empty. Major container ships, like those with over 20,000 TEU are guaranteed to be servicing routes where the two points have significant in and out business which means the shipping business line will try to ensure the ship will be fully loaded as much of its time as possible.
Back to the question. How many warships do you see with a bulbous bow typical of very large merchant ships like this? Go ahead, find me a picture.
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That’s a good point. A Chinese paper from 2013 described an optimized Kitty Hawk hull. Same block coefficient of 0.58, but longer with a waterline length of 319.2m (more than a Nimitz) and a displacement of 85.4kt. The waterline beam was kept the same at 39.4m.
I roughly estimated the block coefficient of the Nimitz at 0.63. Based on the diagrams from the paper, such a blockier hull requires upwards of 20% more power to maintain 35kt.
Source: Rapidity optimization of the aircraft carrier based on the minimum resistance, Wang et al.
