Container ships and tankers
Discussion
Midship accommodation vessels are far more comfortable in a seaway, however on tankers there is a safety case for aft accommodation. Midships accommodation is right over the tank deck giving a strong risk of hydrocarbon vapour encompassing the accommodation block in still air with all the associated risk of explosion. Bulkers have accommodation all aft to leave a clear working deck for grab cranes or conveyors leaving them free to move to load the vessel minimising hull stresses.
On an amusing note while a cadet on a midships tanker we got caught in Hurricane Frances in 1980, the storm was so intense it swept away the flying bridge (the walkway between aft and midships accommodation) with the result that we (deck officers) were stranded for 3 days with seas washing over the deck. Obviously we consumed the contents of the officer’s pantry and then got hungry. This was much to the amusement of the engineers aft who rubbed it in by waving sandwiches and drinking cans of Tennants from the cross alleyway at the front of the aft accommodation where we could see them…. Those were the days!
On an amusing note while a cadet on a midships tanker we got caught in Hurricane Frances in 1980, the storm was so intense it swept away the flying bridge (the walkway between aft and midships accommodation) with the result that we (deck officers) were stranded for 3 days with seas washing over the deck. Obviously we consumed the contents of the officer’s pantry and then got hungry. This was much to the amusement of the engineers aft who rubbed it in by waving sandwiches and drinking cans of Tennants from the cross alleyway at the front of the aft accommodation where we could see them…. Those were the days!
Ships are designed around their cargo or the job they do.
In the olden days (no offence Mykap
) accommodation, bridge & E/R were all separate.
Nowadays engines & accommodation are usually stuck on a pointy end as the hull is for cargo and that's what makes the money, in most cases it's at the back because that's where the oily bits are, it's cheaper to have it all in one place, it's less far for the engineers to walk and away from breaking waves at the bow (unless steaming backwards).
Of course there are exceptions, the triple E containership pictured above has midship accommodation, probably for reasons of visibility, stability, rigidity or similar, I'm sure PH has a resident naval architect who can explain it better.
Some ships have fwd accommodation due to the nature of their work:
There are pros & cons to living at the front, you tend to bounce around more and it makes steering in narrow channels more interesting, plus you're more exposed to weather, but this makes working on the deck safer & more sheltered.
In the olden days (no offence Mykap
) accommodation, bridge & E/R were all separate.Nowadays engines & accommodation are usually stuck on a pointy end as the hull is for cargo and that's what makes the money, in most cases it's at the back because that's where the oily bits are, it's cheaper to have it all in one place, it's less far for the engineers to walk and away from breaking waves at the bow (unless steaming backwards).
Of course there are exceptions, the triple E containership pictured above has midship accommodation, probably for reasons of visibility, stability, rigidity or similar, I'm sure PH has a resident naval architect who can explain it better.
Some ships have fwd accommodation due to the nature of their work:
There are pros & cons to living at the front, you tend to bounce around more and it makes steering in narrow channels more interesting, plus you're more exposed to weather, but this makes working on the deck safer & more sheltered.
Edited by DJFish on Tuesday 21st March 17:39
The bridge is generally close to the accommodation, not separate, with a few notable exceptions such as heavy lift vessels but even on those there is usually somewhere for the master to rest as he can be called to the bridge at any time (as I know very well).
On midships tankers officers (deck) were midships and engineers aft. Cargo ships with split accommodation ran along the same lines, I sailed on the Illyric and Icenic which were set up so with a cargo hold between the accommodation blocks. Midship designed general cargo ships often had 3 or 4 hatches forward and 1 aft but the disadvantage was always the requirement to have a shaft tunnel which took up cargo space. Solution - put it all aft maximise cargo space. Yes all ships are now designed for maximising cargo including forward accommodation supply vessels as the aft deck is the working area (together with the various cargo tanks below) arranged so the vessel can stay head to weather and work the rig for the maximum time.
Just to add, the new ULCS (Ultra Large Container Ship) as shown in the pictures have their accommodation midships for strengthening the vessel. The large number of hatch openings in a container ship’s structure has to be compensated by very heavy scantlings in the upper deck and side coamings. This task becomes increasingly difficult with an ultra-wide ship of twenty or more rows. This design allows the construction of a strong transverse joint - stronger than the ones between the holds between the vessel’s sides.
Visibility restrictions also come into play, the new panamax ships have dimensions of 366m LOA and 49m beam, the canal visibility requirements are on laden vessels, that the view of the water surface from the conning positions may not be obscured by more than 1 x LOA forward of the bow. For vessels in ballast, this figure is limited to 1.5 x LOA. Container vessels may under certain conditions exceed the above limits, up to 2 x LOA, max. 500m. Given the vessels can be up to 366m long a rethink on bridge position was required. There is also a restriction to 12000 TEUs ((Ton Equivalent Unit) containers) in the new locks.
On midships tankers officers (deck) were midships and engineers aft. Cargo ships with split accommodation ran along the same lines, I sailed on the Illyric and Icenic which were set up so with a cargo hold between the accommodation blocks. Midship designed general cargo ships often had 3 or 4 hatches forward and 1 aft but the disadvantage was always the requirement to have a shaft tunnel which took up cargo space. Solution - put it all aft maximise cargo space. Yes all ships are now designed for maximising cargo including forward accommodation supply vessels as the aft deck is the working area (together with the various cargo tanks below) arranged so the vessel can stay head to weather and work the rig for the maximum time.
Just to add, the new ULCS (Ultra Large Container Ship) as shown in the pictures have their accommodation midships for strengthening the vessel. The large number of hatch openings in a container ship’s structure has to be compensated by very heavy scantlings in the upper deck and side coamings. This task becomes increasingly difficult with an ultra-wide ship of twenty or more rows. This design allows the construction of a strong transverse joint - stronger than the ones between the holds between the vessel’s sides.
Visibility restrictions also come into play, the new panamax ships have dimensions of 366m LOA and 49m beam, the canal visibility requirements are on laden vessels, that the view of the water surface from the conning positions may not be obscured by more than 1 x LOA forward of the bow. For vessels in ballast, this figure is limited to 1.5 x LOA. Container vessels may under certain conditions exceed the above limits, up to 2 x LOA, max. 500m. Given the vessels can be up to 366m long a rethink on bridge position was required. There is also a restriction to 12000 TEUs ((Ton Equivalent Unit) containers) in the new locks.
Edited by Mykap on Wednesday 22 March 15:21
Edited by Mykap on Wednesday 22 March 15:23
Edited by Mykap on Wednesday 22 March 15:25
I must precis this with the fact I am not a naval architect, but I have been in technical discussions with the top bods at Maersk Ship Design….. Genuinely very nice people they are too… nicest customers I have ever dealt with.
The accommodation is at the back as others have stated, due to the fact that commercial vessels are designed with efficiency uppermost in the operators mind, maximum cargo/minimum ship = max profit.
The newer much larger E-class vessels have the accommodation block about 60% of the distance from the bow due to some basic reasons. Some engineering, some logistics…
Matey boy captain on the bridge would like to know where they are going visually. Whether they could do this with cameras mounted on the bow and a video link, I know not… if you are sat right at the back of a vessel 400 metres long, your visibility is seriously compromised.
The above mentioned E-class vessels (and beyond) start to cause a problem, to get the commercial efficiencies of shipping stuff from China, they have to go at a fair lick, 25-29 knots, all the time, apart Suez obviously. This takes serious horsepower, hence the largest diesels ever made. 109,000-horsepower Wärtsilä-Sulzer RTA96-C. Which having stood next to it at Odense shipyard, I can assure you, it is MASSIVE. So massive, I found myself sniggering. Everything is almost comic book huge…
https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-S...
At the time, the limitation was the ability of the engine manufacturer to make a bigger (read longer) engine. The machine tool size to actually machine the parts, and the ability of controlling suitable tolerances being one issue. All this power has to go through one propeller, which is 140 tonnes of high grade cast bronze. The foundry capacity is now a problem, as is transporting said propeller to the shipyard. For the E-class vessels, the route from foundry to shipyard involved chopping down some trees at the side of the road. This did not go down well in Germany…. Especially for a vessel which was supposed to have impeccable green credentials…
So for a bigger vessel (more efficiency of operation) you need to get more power, so you need another engine. If they are at the back - this completely buggars up the extremely efficient hull design, as you need 2 propeller shafts, 2 rudders, and all the associated hardware. As above, efficiency is everything with these vessels, especially when you are burning nearly 300 tonnes of fuel a day. Fuel is their biggest expense.
The discussion at the time was a bigger vessel, (15,000 TEU+) would need a larger engine, or 2 engines. They couldn’t get the efficiency of the rear of the hull to work with 2 engines, so they gave up. I didn’t suggest remapping it….You need the propeller to be as efficient as possible in relation to the vessel, hence the somewhat dramatic lines of the stern on the modern vessels. This compromises the ability of the naval architect to get the massive engine installed, so it has to go further away from the stern. Hence the desire for an 1100 mm diameter propeller shaft nearly 100 metres long. This is in 5 pieces.
Hopefully someone else will be along shortly with some more or better knowledge. My exposure to the above is nearly 10 years out of date…
The accommodation is at the back as others have stated, due to the fact that commercial vessels are designed with efficiency uppermost in the operators mind, maximum cargo/minimum ship = max profit.
The newer much larger E-class vessels have the accommodation block about 60% of the distance from the bow due to some basic reasons. Some engineering, some logistics…
Matey boy captain on the bridge would like to know where they are going visually. Whether they could do this with cameras mounted on the bow and a video link, I know not… if you are sat right at the back of a vessel 400 metres long, your visibility is seriously compromised.
The above mentioned E-class vessels (and beyond) start to cause a problem, to get the commercial efficiencies of shipping stuff from China, they have to go at a fair lick, 25-29 knots, all the time, apart Suez obviously. This takes serious horsepower, hence the largest diesels ever made. 109,000-horsepower Wärtsilä-Sulzer RTA96-C. Which having stood next to it at Odense shipyard, I can assure you, it is MASSIVE. So massive, I found myself sniggering. Everything is almost comic book huge…
https://en.wikipedia.org/wiki/W%C3%A4rtsil%C3%A4-S...
At the time, the limitation was the ability of the engine manufacturer to make a bigger (read longer) engine. The machine tool size to actually machine the parts, and the ability of controlling suitable tolerances being one issue. All this power has to go through one propeller, which is 140 tonnes of high grade cast bronze. The foundry capacity is now a problem, as is transporting said propeller to the shipyard. For the E-class vessels, the route from foundry to shipyard involved chopping down some trees at the side of the road. This did not go down well in Germany…. Especially for a vessel which was supposed to have impeccable green credentials…
So for a bigger vessel (more efficiency of operation) you need to get more power, so you need another engine. If they are at the back - this completely buggars up the extremely efficient hull design, as you need 2 propeller shafts, 2 rudders, and all the associated hardware. As above, efficiency is everything with these vessels, especially when you are burning nearly 300 tonnes of fuel a day. Fuel is their biggest expense.
The discussion at the time was a bigger vessel, (15,000 TEU+) would need a larger engine, or 2 engines. They couldn’t get the efficiency of the rear of the hull to work with 2 engines, so they gave up. I didn’t suggest remapping it….You need the propeller to be as efficient as possible in relation to the vessel, hence the somewhat dramatic lines of the stern on the modern vessels. This compromises the ability of the naval architect to get the massive engine installed, so it has to go further away from the stern. Hence the desire for an 1100 mm diameter propeller shaft nearly 100 metres long. This is in 5 pieces.
Hopefully someone else will be along shortly with some more or better knowledge. My exposure to the above is nearly 10 years out of date…
Mykap said:
There is also a restriction to 12000 TEUs ((Ton Equivalent Unit) containers) in the new locks.
TEU stands for Twenty-foot Equivalent Unit, as a 20ft container is the baseline measure in the shipping world. Container shipping capacity is measured in TEU, so a 15000 TEU ship can carry (oddly enough) 15000 20ft containers, or 7500 40ft containers, or a combination (there's also high cube 20's, 40's, normal and high cube 45's, 48's and 53's but they complicate the math a little)Modern commercial ships are all about cost saving and efficiency. One way to reduce costs is to shrink the crew - the 18,000 TEU, 400m Maersk Tripple E has a crew of only 13. On container ships this together with the desire to maximise cargo deck space led to the all aft accommodation and engine layout. However there are also rules on wheelhouse visibility, not a problem for a tanker or bulk carrier as there is not much sticking above the deck, bit of a problem for the larger container ships, hence the separated fwd accommodation/bridge arrangement, as its obviously been calculated that the loss of deckspace is offset by the ability to stack containers higher forward ie its a case of maximising your container capacity whilst complying with the rules.
Interesting stuff. Although it begs the question, why use all this old school hard to handle massive engineering?
Why not have a diesel electric powertrain using a collection of smaller and easier to distribute, and maintain generators, all powering azipod props? Like on large passenger ships. All "off the shelf" kit, very fuel and space efficient, and easy to get 100k plus combined horsepower. All with no ridiculously huge bespoke engines, propshafts, gearboxes, propellors, rudders, etc to worry about. Not to mention the lack of redundancy, maintainability, and maneuverability associated with such oversized systems.
Why not have a diesel electric powertrain using a collection of smaller and easier to distribute, and maintain generators, all powering azipod props? Like on large passenger ships. All "off the shelf" kit, very fuel and space efficient, and easy to get 100k plus combined horsepower. All with no ridiculously huge bespoke engines, propshafts, gearboxes, propellors, rudders, etc to worry about. Not to mention the lack of redundancy, maintainability, and maneuverability associated with such oversized systems.
Edited by dvs_dave on Monday 27th March 06:05
dvs_dave said:
Interesting stuff. Although it begs the question, why use all this old school hard to handle massive engineering?
Why not have a diesel electric powertrain using a collection of smaller and easier to distribute, and maintain generators, all powering azipod props? Like on large passenger ships. All "off the shelf" kit, very fuel and space efficient, and easy to get 100k plus combined horsepower. All with no ridiculously huge bespoke engines, propshafts, gearboxes, propellors, rudders, etc to worry about. Not to mention the lack of redundancy, maintainability, and maneuverability associated with such oversized systems.
Cost. Why not have a diesel electric powertrain using a collection of smaller and easier to distribute, and maintain generators, all powering azipod props? Like on large passenger ships. All "off the shelf" kit, very fuel and space efficient, and easy to get 100k plus combined horsepower. All with no ridiculously huge bespoke engines, propshafts, gearboxes, propellors, rudders, etc to worry about. Not to mention the lack of redundancy, maintainability, and maneuverability associated with such oversized systems.
Edited by dvs_dave on Monday 27th March 06:05
Big marine diesels are quite efficient compared to small ones, and easy to maintain
D_T_W said:
Mykap said:
There is also a restriction to 12000 TEUs ((Ton Equivalent Unit) containers) in the new locks.
TEU stands for Twenty-foot Equivalent Unit, as a 20ft container is the baseline measure in the shipping world. Container shipping capacity is measured in TEU, so a 15000 TEU ship can carry (oddly enough) 15000 20ft containers, or 7500 40ft containers, or a combination (there's also high cube 20's, 40's, normal and high cube 45's, 48's and 53's but they complicate the math a little)DJFish said:
Some ships have fwd accommodation due to the nature of their work:
I recently followed the link on the interesting wiki thread about the great lake freighters, have fore & aft can lead to "A bizarre incident" https://en.wikipedia.org/wiki/SS_Daniel_J._MorrellLots of catastrophic losses involving Great Lakes freighters. Very often total and sudden structural failure. They're not required to be built to anywhere near ocean going specs so are very long and slender, have no watertight bulkheads, and are very low to the water. Essentially glorified barges.
Great Lakes sailing conditions can very quickly get very violent and dangerous with very high choppy seas and winds.
Most recent and mysterious total loss was the SS Edmund Fitzgerald which resulted in some major changes to Great Lakes shipping regs. Wiki has an interesting write up on it.
https://en.m.wikipedia.org/wiki/SS_Edmund_Fitzgera...
Great Lakes sailing conditions can very quickly get very violent and dangerous with very high choppy seas and winds.
Most recent and mysterious total loss was the SS Edmund Fitzgerald which resulted in some major changes to Great Lakes shipping regs. Wiki has an interesting write up on it.
https://en.m.wikipedia.org/wiki/SS_Edmund_Fitzgera...
dvs_dave said:
They're not required to be built to anywhere near ocean going specs so are very long and slender, have no watertight bulkheads, and are very low to the water. Essentially glorified barges
You're right, they're not ocean going vessels, but that isnt why they are long and slender - they're slender because of the width of the locks they need to pass through. Condi said:
dvs_dave said:
They're not required to be built to anywhere near ocean going specs, so are very long and slender, have no watertight bulkheads, and are very low to the water. Essentially glorified barges
You're right, they're not ocean going vessels, but that isnt why they are long and slender - they're slender because of the width of the locks they need to pass through. They are generally built to "Seawaymax" size for the Saint Lawrence Seaway. Although there are apparently plans to upgrade the SLS to at least Panamax in the next 20 years or so. That might see an end to specifically built Great Lakes freighters as there will be no longer be need for such a customized size of ship anymore. Just buy any old Panamax and be done with it.
Nanook said:
dvs_dave said:
A misplaced "so".
They are generally built to "Seawaymax" size for the Saint Lawrence Seaway. Although there are apparently plans to upgrade the SLS to at least Panamax in the next 20 years or so. That might see an end to specifically built Great Lakes freighters as there will be no longer be need for such a customized size of ship anymore. Just buy any old Panamax and be done with it.
No-one is really building Panamax anymore, and many are being scrapped, even at only a few years old!They are generally built to "Seawaymax" size for the Saint Lawrence Seaway. Although there are apparently plans to upgrade the SLS to at least Panamax in the next 20 years or so. That might see an end to specifically built Great Lakes freighters as there will be no longer be need for such a customized size of ship anymore. Just buy any old Panamax and be done with it.
Gassing Station | Boats, Planes & Trains | Top of Page | What's New | My Stuff