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Thiel
Post subject: Re: Practical Nuclear Merchant VesselPosted: September 27th, 2017, 8:06 pm
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While all that's true you're way overstating the effect. It's noticeable, but it's the kind of thing that takes days to learn, not years. The placement of the bridge on a modern merchant vessel has very little to do with the ergonomics or whatever it's called and all to do with maximizing cargo capacity. Most ships have them aft because the engine is placed back there and placing the superstructure over the engine saves the most space since you can't have cargo under the superstructure.

The new mega container carriers have their engine casing and superstructure separated in order to maintain legally required sight lines forward when fully loaded. If not for those regulations they would probably have placed them over the engine room like they did on the previous generation ships like Mærsks E-class ships. Their engines are placed as far forward as they are because they need the full hull depth and a fair amount of buoyancy forward and aft of the very heavy engine(s) to avoid undue stresses on the hull, especially when they're lightly loaded.

Radars go on top of the superstructure primarily because they're not allowed to have more than a degree or two of blind spots and building a short mast on top of the superstructure is cheaper than tall mast on the bow. That said it's not actually uncommon to see radars mounted forward. We're well beyond the point where commercial radars can compensate for a few hundred meters off-set, and current regulations does allow for it.

With all that said I do agree that the bridge will probably be placed somewhere between a third and two thirds aft from the bow for the above reasons.
Front control has some serious structural implications on larger ships that aren't easily overcome. After all you're basically hanging a large weight at each end of a stick. Keeping the bending moments in check is basically impossible

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Wikipedia & Universe
Post subject: Re: Practical Nuclear Merchant VesselPosted: September 28th, 2017, 11:54 pm
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Thiel wrote: *
With all that said I do agree that the bridge will probably be placed somewhere between a third and two thirds aft from the bow for the above reasons.

Front control has some serious structural implications on larger ships that aren't easily overcome. After all you're basically hanging a large weight at each end of a stick. Keeping the bending moments in check is basically impossible
So, what's the best compromise?

I suppose I should use a real-life example to illustrate what I'm envisioning. Sevmorput has pilotage forward, and it carries freight. Does that layout become unfavorable the more you scale up?

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odysseus1980
Post subject: Re: Practical Nuclear Merchant VesselPosted: September 29th, 2017, 3:34 am
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The Sevmorput is a good example to use as a design base.


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Thiel
Post subject: Re: Practical Nuclear Merchant VesselPosted: September 29th, 2017, 8:25 am
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It depends on what restrictions and requirements the ship has to live up to. Sevmorput is designed to carry LASH barges around the high Arctic. And she was designed in the Soviet Union. That has some fairly major effects on the design.
The forward superstructure is a result of the LASH barges. They're loaded and discharged over the stern so she can't carry any cargo forward of the superstructure. Being built in the Soviet Union also meant the economic calculus looked very different. Being essentially state owned meant she didn't have to make any money as long as the entire supply chain she's part of generated a net plus.
The new Mega container carriers are restricted by the need to maximize their cargo capacity, air draught restrictions, depth restrictions and sight line regulations as well as structural limitations.

So instead of trying to shoehorn any given feature in you should establish what your requirements are.
  • What kind of cargo does it carry
  • What routes does it serve
    • Air draught restrictions
    • Draught restrictions
    • Length restrictions
    • Manoeuvring requirements
  • Legislative requirements
    • Survivability requirements
      • Collision bulkheads
      • Flooding resistance
      • Stability
      • Back-up power
    • Safety requirements
      • Shielding
      • Containment
      • Training/Manning
Being a nuclear ship I'd expect there to be some pretty severe survivability requirements. The Sevmorput's reactor is designed to survive a small plane crash for example.
Putting the reactor is the front is probably not advised since that's where you usually hit things. I'd also expect it to have a very large auxiliary powerplant in order to maintain power for cooling in case of a scram, pumping capacity in case of a leak and maybe even back-up propulsion so you don't end up drifting onto a rock somewhere.
Oh and large cofferdams around the reactor space in case someone rams you.

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Tobius
Post subject: Re: Practical Nuclear Merchant VesselPosted: September 30th, 2017, 1:30 am
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Quote:
While all that's true you're way overstating the effect. It's noticeable, but it's the kind of thing that takes days to learn, not years.
ANSWER 1

ANSWER 2.

ANSWER 3.

[Why did the ACX Crystal U-turn into the American destroyer?

It takes years. It is called Human Factors. Ergonomics helps but it does not obviate, but knowing how the animal works is far more important in system design than economics drivers. Otherwise why bother with crew simulators, collision drills and refresher training and masters examinations for watch officers or the COLREGS for what could be automated course steerage? Notice that in every case of the four mentioned; the incident happens because someone did not LOOK with their eyes to see where they go or what is in front, to the side (abeam), astern or what aspect the confounded turn of what is near them is doing? Oil tankers are really lousy to handle (aft spot and steer) in this Human Factors regard. What really torques, though, is that in at least two cases, it is those expensive Ticos and Arleighs that are dinged up at $300 million + a pop. I might add that a submarine was almost also ruined in a fifth incident. I know it is the responsibility of the smaller ship to dodge, but let us be realistic. Oil tankers, for example, are supposed to have collision alert detection systems, and at least give warning at another ship's close approach.


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Post subject: Re: Practical Nuclear Merchant VesselPosted: October 5th, 2017, 5:13 am
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Thiel wrote: *
It depends on what restrictions and requirements the ship has to live up to. Sevmorput is designed to carry LASH barges around the high Arctic. And she was designed in the Soviet Union. That has some fairly major effects on the design.
The forward superstructure is a result of the LASH barges. They're loaded and discharged over the stern so she can't carry any cargo forward of the superstructure. Being built in the Soviet Union also meant the economic calculus looked very different. Being essentially state owned meant she didn't have to make any money as long as the entire supply chain she's part of generated a net plus.
The new Mega container carriers are restricted by the need to maximize their cargo capacity, air draught restrictions, depth restrictions and sight line regulations as well as structural limitations.

So instead of trying to shoehorn any given feature in you should establish what your requirements are.
Point taken. I said I didn't want to get married to a specific design before drawing, and here I am getting married to a specific design.

I suppose the idea for forward pilotage came partially from a lot of near-future cargo ship designs in concept art having this feature. It would seem to offer maximum forward visibility and maximum cargo capacity, but if the tradeoff is severe structural complications such as the bending moments you mentioned, I'll probably avoid that. Here are some of the designs I saw with the forward pilotage:

http://cs-001.123.is/9f252ce7-7a35-4501 ... 4b3_MS.jpg

http://www.marinemec.com/ugc-1/fullnews ... banner.jpg
Quote:
  • What kind of cargo does it carry
  • What routes does it serve
    • Air draught restrictions
    • Draught restrictions
    • Length restrictions
    • Maneuvering requirements
  • Legislative requirements
    • Survivability requirements
      • Collision bulkheads
      • Flooding resistance
      • Stability
      • Back-up power
    • Safety requirements
      • Shielding
      • Containment
      • Training/Manning
I'm envisioning a standardized range of large container vessels in different sizes (e.g. from 3,000 to 20,000+ TEU) sharing a common hull shape/design and as much parts commonality as is feasible. Ideally, I'd like the hull base to be adaptable for non-container (e.g. bulk-carrying or RORO) variants, but I can scratch that idea if it's not doable for some reason or another. In the case of my AU or a US AU, the crew would consist of merchant mariners, and the reactor(s) would be operated by a special class of nuclear-trained mariners (i.e. "Merchant Nukes"), who would attend Nuclear Power School with a similar legal status to DOE civilians, albeit with a slightly different pipeline tailored to their specific job. I'd imagine the powerplant itself having the same survivability requirements and features as e.g. Sevmorput, Otto Hahn, Savannah, etc. (which you outline below).
Quote:
Being a nuclear ship I'd expect there to be some pretty severe survivability requirements. The Sevmorput's reactor is designed to survive a small plane crash for example.

Putting the reactor is the front is probably not advised since that's where you usually hit things. I'd also expect it to have a very large auxiliary powerplant in order to maintain power for cooling in case of a scram, pumping capacity in case of a leak and maybe even back-up propulsion so you don't end up drifting onto a rock somewhere.

Oh and large cofferdams around the reactor space in case someone rams you.
Fair enough. I'll go ahead and scrap the front-placed reactor idea along with the bow pilotage. I've been looking at a number of proposals for cargo ships, and a particular one known as the "Quantum 9000" caught my eye as a potential design inspiration. The actual proposal features considerable space amidships under the superstructure to house massive C-type LNG tanks, and it looks like that space could be adapted for a reactor plant with an auxiliary generator and all the survivability features you describe.

Q9000 Image: Note that I'm speaking in in terms of the general layout, not literally this specific ship.

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Thiel
Post subject: Re: Practical Nuclear Merchant VesselPosted: October 5th, 2017, 5:41 pm
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I don't think a split layout is going to make sense on a ship of that size without the need for forward tankage. You're losing an entire cargo hold that way.
I'm not sure how well hull shapes scales, you'll have to talk with Ace about that.
Combined RORO and container carriers are a thing and there's been more than a few conversions so that should be entirely doable. Whether it makes economical sense is an entirely different question I can't answer.
Using the same hull for a bulk carrier however, doesn't make sense. You can't carry bulk cargoes on deck for obvious reasons, so having a hull optimised for deck cargoes doesn't make sense. Plus there's usually no real time pressure. It doesn't matter if that load of scrap or grain arrives in a week or three weeks as long as it's on time.

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Tobius
Post subject: Re: Practical Nuclear Merchant VesselPosted: October 5th, 2017, 6:04 pm
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[ img ]

[ img ]

Shakes head. Do I need to explain why those bridges have "wings" so someone can run to the side to look astern to see what hit them; or why the "windshield" above the stem is designed the way it is above the bows in these concept drawings? (Reduce wind resistance.) Unless one understands what is intended, (fuel economy and volume utilization uber alles.) one cannot adjudge the rightness or wrongness of the solution proposed. All I will say is; remember the truck example? I would not adopt those solutions at all without positive controlled nose steer (powerful bow thrusters for directed applied yoke forces.).

Look, these problems have been examined.

[ img ]

(I credit this image to Hawkeye of this forum.)

That wind over deck problem and cargo handling (airplanes in that case) was to be solved by sticking pilotage on a flying trapeze bridge that scooted up and down like a pogo stick. It did not and would not work. How do we know?

[ img ]

She has a pilotage control platform starboard below the flight deck and an observer station port, but she never saw what killed her, so she could not turn to avoid it.

I think a container ship needs a man in the loop direction station from which steerage 360 can be exercised. Nothing to that requirement I know suggests that a walkway above the container deck that is an actual weather or walkway bridge with coms, sensors and steer controls will interfere with cargo deck-space container utilization or load unload facilitation by H cranes. It does not have to be hull up superstructure at all to do what is needed. It can actually be wind spoiler shaped to mitigate the sail effect on the hull if needed.


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Thiel
Post subject: Re: Practical Nuclear Merchant VesselPosted: October 5th, 2017, 7:20 pm
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Nah, bridgewings are a feature on pretty much all ships. They're used when docking because you need a clear view of the ships side when doing that

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Tobius
Post subject: Re: Practical Nuclear Merchant VesselPosted: October 5th, 2017, 7:38 pm
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"They're used [when docking] because you need a clear view of the ships side when doing that [almost anything]..."

Docking and/or collision avoidance, for example. Just sayin...


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