Ship modification - stretching

[phavoc]

The article here on Bloomberg (https://www.bloomberg.com/news/articles/2019-12-04/why-cruise-lines-keep-cutting-their-ships-in-half-for-stretching) talks about the economics of stretching cruise ships. In one of the cited examples they talk about while they have the ship cut open to add a new section they are taking advantage of the time in drydock to overhaul it's engines - going from seven older ones to four more modern ones that also meet new environmental guidelines.

We know that this process is also done with warships and cargo ships - though warships, with their armor and other military-specific needs, the process is more expensive and time consuming.

While Traveller is mostly an RPG game, some like to model or participate in more strategic things. of which these sorts of modifications would be more likely. So what's the consensus of how they would cost-model something like this?

 

[Condottiere]

I believe there is a hard and fast rule that the hull can't be altered.

 

[Anonymous]

Original Trillion Credit Squadron provided rules for refits of components. RAW hull size increase would have been allowed under "unlisted components" but I suspect that was an oversight and it's actually illegal. It was forbidden to change the armor, hull configuration, or number and size of bays, or increase the displacement of drives or spinal.

I don't understand what the Mongoose refit rules actually allow or how to compute the cost and time.

Thinking about the engineering of it, you can stretch the hull, or glue 2 hulls together, or glue a bulge on it. Gluing vehicles together, while it sounds stupid, has historical precedent.

 

[phavoc]

Here is another article that talks about it, but what I find more useful is a picture of the ship cut in half with the new section floating nearby. In this particular example the ship appears to be on a floating barge instead of in a drydock, and the new section is also floating. http://www.cybercruises.com/cruisecolumn_aug24.htm

I found this section particularly interesting: "As Costa Cruises takes on more newbuildings with more verandahs, news has now broken that the Costa Europa will be going on ten-year charter to Thomson Cruises. To be renamed Thomson Dream, at 53,872 tons she will become their largest ship and also the roomiest, with a passenger space ratio of more than 36 gross tons per passenger. This compares to just 26 for the Thomson Destiny, an ex-Royal Caribbean ship, and 27 for the Thomson Celebration and Thomson Spirit, ex-Holland America ships."

When you look at most designs you find the standard stateroom. I've played around a bit with the stateroom concept as I wasn't satisfied with the previous system. At first I had come up with pre-set designs (five types, with each new type scaled up in size, cost and amenities). But then I realized this wasn't sufficient because it still didn't provide the flexibility I was looking for. Then I realized that rather than trying to define the specific space I should instead define the cost per ton of the different classes. Once I did this it made it easy-peasy to scale up / scale down depending on what I was looking for. So now luxury suites for yacht owners, slightly less luxurious ones for passengers, and plain ones for crew could easily be put onto the same ship, just with different costs per ton that went along with size.

So with the cruise liner issue above, the statement of the passenger space ratio means you may have a ship full of more luxurious suites, or more comfy stateroom with more on-board amenities. Basically a GM could come up with a larger liner, with larger rooms (and richer passengers) to sustain a whole host of adventures on.

 

[Condottiere]

I think the term is welded.

Tends to work when you have the front and rear of the same class.

After that, then you have to worry about plumbing and centre of gravity.

 

[phavoc]

Original Trillion Credit Squadron provided rules for refits of components. RAW hull size increase would have been allowed under "unlisted components" but I suspect that was an oversight and it's actually illegal. It was forbidden to change the armor, hull configuration, or number and size of bays, or increase the displacement of drives or spinal.

I don't understand what the Mongoose refit rules actually allow or how to compute the cost and time.

Thinking about the engineering of it, you can stretch the hull, or glue 2 hulls together, or glue a bulge on it. Gluing vehicles together, while it sounds stupid, has historical precedent.

Yeah, I toss out that rule because it defies logic and reality. In the past warships have been up-gunned, but typically the ships retained their main armaments mostly because of the time it took to actually MAKE a gun (literally years). Plus the turrets and machinery for them had an upper limit on what you could do before you would have to gut the entire thing and start over. Which, at that point, it made more economical sense to simply build a new hull.

 

[Condottiere]

The C-141 Starlifter was the workhorse of the Air Mobility Command. The Starlifter has fulfilled a vast spectrum of airlift requirements through its ability to airlift combat forces over long distances, inject those forces and their equipment either by airland or airdrop, re-supply employed forces, and extract the sick and wounded from the hostile area to advanced medical facilities.

The C-141B is a stretched C-141A with in-flight refueling capability. Stretching of the Starlifter consisted of lengthening the plane 23 feet, 4 inches (53.3 centimeters), which increased cargo capacity by about one-third - 2,171 extra cubic feet (65.13 extra cubic meters). Lengthening of the aircraft had the same effect as increasing the number of aircraft by 30 percent. The C-141 was the first jet aircraft designed to meet military standards as a troop and cargo carrier.

 

[Condottiere]

In game terms, you could add in a plug in the middle. and maybe roll a dice to see if there's now a structural flaw in the hull.

Changing the hull has never seemed something you could dick around with.

 

[phavoc]

The C-141 Starlifter was the workhorse of the Air Mobility Command. The Starlifter has fulfilled a vast spectrum of airlift requirements through its ability to airlift combat forces over long distances, inject those forces and their equipment either by airland or airdrop, re-supply employed forces, and extract the sick and wounded from the hostile area to advanced medical facilities.

The C-141B is a stretched C-141A with in-flight refueling capability. Stretching of the Starlifter consisted of lengthening the plane 23 feet, 4 inches (53.3 centimeters), which increased cargo capacity by about one-third - 2,171 extra cubic feet (65.13 extra cubic meters). Lengthening of the aircraft had the same effect as increasing the number of aircraft by 30 percent. The C-141 was the first jet aircraft designed to meet military standards as a troop and cargo carrier.

Lengthening aircraft (at least non-fighters) is extremely common. Nearly the entire -700 series of Boeings are stretched versions of the original aircraft, albeit some have new wings. But essentially the just keep adding plugs in front/behind the wings to make a bigger aircraft. Sometimes that's all they have done. Other times newer models will include bigger engines, which sometimes requires new landing gear for more height because the engines are physically bigger.

 

[Anonymous]

Some ships were upgunned before/during world war 2. Certainly at least one cruiser class from 15 to 20cm but the name escapes me. Floaty boats have stability and bending issues not so prevalent on ground vehicles or spacy boats. Any major structural modifications on floaty boats usually involves work below the water-line as well. The up-gunning of tanks was common.

These days we should consider stretching floaty ships as "commonplace".

 

[Anonymous]

Lengthening aircraft (at least non-fighters) is extremely common. Nearly the entire -700 series of Boeings are stretched versions of the original aircraft, albeit some have new wings. But essentially the just keep adding plugs in front/behind the wings to make a bigger aircraft. Sometimes that's all they have done. Other times newer models will include bigger engines, which sometimes requires new landing gear for more height because the engines are physically bigger.

Any such change will also affect the center of gravity which means you have to modify the wingy bits too. Except for the 737 max where you try to trim the aircraft in flight to compensate for larger engines, but use a badly implemented computer system, and crash.

 

[Condottiere]

Let's be frank, the Japanese preplanned to upgrade their "light" six inch triple turret cruisers with dual eight inchers.

I can't recall if that made them top heavy.

 

[Anonymous]

Let's be frank, the Japanese preplanned to upgrade their "light" six inch triple turret cruisers with dual eight inchers.

I can't recall if that made them top heavy.

Warships these says are usually designed with that in mind. They last 30+ years and war changes.

 

[phavoc]

Lengthening aircraft (at least non-fighters) is extremely common. Nearly the entire -700 series of Boeings are stretched versions of the original aircraft, albeit some have new wings. But essentially the just keep adding plugs in front/behind the wings to make a bigger aircraft. Sometimes that's all they have done. Other times newer models will include bigger engines, which sometimes requires new landing gear for more height because the engines are physically bigger.

Any such change will also affect the center of gravity which means you have to modify the wingy bits too. Except for the 737 max where you try to trim the aircraft in flight to compensate for larger engines, but use a badly implemented computer system, and crash.

For an aircraft you can offset that by adding plugs in front and behind the wing box (where the wings connect to the body of the plane). To save money they typically try NOT to make modifications to this section, since if you do you have to design new jigs and new production process - a very expensive thing to do. So the center of gravity can be handled this way.

Though one thing that needs to be considered when you lengthen the fuselage is the rotation of the craft when it's taking off. There have been a few cases where pilots forgot and rotated too fast and scraped the tail against the runway. Oops!

Let's be frank, the Japanese preplanned to upgrade their "light" six inch triple turret cruisers with dual eight inchers.

I can't recall if that made them top heavy.

If the larger turret was taken into account during the design process then no, it would not make them more top-heavy. Depending on the factors they might have ballasted the ship with 6" guns to add additional weight so the ship operated to design specs with a lighter turret. They would have needed to include the larger gun size when they designed the barbette and turret foundation (assuming one was needed, of course). There are a number of ways to handle this. Naval designers usually did a good job if they had all the information available to them (the Vasa being a notable exception - though in its' defense it was not thought to have been designed by people who really knew how to design a big-gun battleship of its day).

 

[Anonymous]

Modifying planes involves a lot of paperwork and certification. The reason Boeing tried to use a computer to stabilize the 737 max after they enlarged the engines, is not primarily the fabrication cost of the wingy bits but having to re-certify the plane, and operator complaints about legally required pilot training for the new model.

 

[DickTurpin]

Most "stretched" airplanes are redesigned and built as new planes. Private owners sometimes rebuild smaller airplanes, like my brother adding floats to his plane and extending the wings and replacing the engine with a more powerful one to compensate for the increased weight and drag. These modifications are not trivial and require an engineer to verify the proposed changes to ensure that everything will work correctly.

I see no reason not to allow spaceships to be rebuilt so long as it is done at a shipyard that can build that class of ship. As to the cost: 1% of the total cost of the new ship for an architect's/engineer's fee, the difference in cost between the original ship and what a newly-built ship of the modified configuration would cost, plus about 10% of the price of the new section to handle the extra work. The time required would be two days per million credits of the upgrade.

Note that the performance of the ship will change unless the drives are upgraded to match the new size. This might require enlarging the fuel tanks also. I see no reason why this procedure would not allow armor to be increased, it would just make the ship bigger since the easiest way would be to add it externally, and that would require engineering section upgrades to handle the additional tonnage as well.

All in all, it is probably more efficient to build a new custom ship, but I would allow players to make changes if new construction was not possible for some reason.

 

[Sigtrygg]

Look at some of the ships in TNE for inspiration for welding ships together...

I played around with deckplans from S7 and other CT sources and cut some up along bulkheads before sticking them together - lots of interesting permutations you can come up with.

 

[Condottiere]

The Seven Three Seven is a fifty year old design, and while the objective is to allow pilots to simulate handling the default model without requiring recertification, once you've rearranged the engines so that they're practically dragging on the tarmac, you may want to reboot your short/medium haul jet programme.

They've gone about as fur as they c'n go.
Yes sir!
They've gone about as fur as they c'n go!

 

[phavoc]

Most "stretched" airplanes are redesigned and built as new planes. Private owners sometimes rebuild smaller airplanes, like my brother adding floats to his plane and extending the wings and replacing the engine with a more powerful one to compensate for the increased weight and drag. These modifications are not trivial and require an engineer to verify the proposed changes to ensure that everything will work correctly.

The amount of re-certification really depends on what is being changed and how it affects flight characteristics. Flaps, new engine cowlings, installing wing tips, all set up different levels of re-certification. Adding fuselage plugs does require more certification, however its far less than a new-sheet design costs. They used to have to be signed off by the FAA (in the US) for commercial aircraft, that changed and we have seen a result of that change. Airworthiness certification will probably go back permanently to the FAA after the two Boeing crashes showed that private industry does not do a good job of self-regulation.

I see no reason not to allow spaceships to be rebuilt so long as it is done at a shipyard that can build that class of ship. As to the cost: 1% of the total cost of the new ship for an architect's/engineer's fee, the difference in cost between the original ship and what a newly-built ship of the modified configuration would cost, plus about 10% of the price of the new section to handle the extra work. The time required would be two days per million credits of the upgrade.

Yah, I don't see ships being cut and stretched outside of a normal shipyard. While it could be possible, you shouldn't see it for those ships that are licensed and/or regulated in known space. Authorities on any planet would take a dim view of a poorly-welded stretch ship breaking apart entering it's atmosphere.

Good suggestions on cost/time.

Note that the performance of the ship will change unless the drives are upgraded to match the new size. This might require enlarging the fuel tanks also. I see no reason why this procedure would not allow armor to be increased, it would just make the ship bigger since the easiest way would be to add it externally, and that would require engineering section upgrades to handle the additional tonnage as well.

All in all, it is probably more efficient to build a new custom ship, but I would allow players to make changes if new construction was not possible for some reason.

Any changes to displacement or machinery should require a re-computation of fuel and other displacement-based calculations.

I could see Traveller ships being subjected to this, and using the same economic factors that ship owners use today to determine whether or not it's economical to do so. One time to do it, as cited in the cruise ship example, was when the ship was basically needing an overhaul anyways. Replacing thirsty TL-9 engines and power plant with more modern TL-15 ones can make sense during a full overhaul. And maybe by adding the plug you take your 2-G freighter down to 1-G, but if that meets your needs then that's just fine. Where it can get complicated is if you try to increase the tonnage and you have to increase the other systems at the same time to maintain the equivalent characteristics. That's when your numbers can make or break the reasoning to do it.

A pirate who 'found' a ship floating in space with crew who 'killed themselves in some crazy firefight' might endeavor to do something like this and then offload the ship as an entirely new one. Though financing such a job might be beyond the reach of the normal pirate. Perhaps if they had friends in shipyards and licensing offices it might go a tad smoother in the resale market...

 

[M J Dougherty]

I have this idea for a referee's briefing.....