* Regulation is non-existent in the cruise industry. You shop for the venue with the most lax regulations of the ≈200 countries in the world.
* The equivalent is insurance. Insuring a $2B ship carries pretty good due diligence. A ship simply failing is rare. Of course, ship insurance doesn't care about employee rights, safe food, medical care, or other things one might expect to keep people safe. It's about protecting the capital expense. If everyone on the ship dies, but the ship survives, that's okay!
* Welds are quite strong -- it just extends the metal. This is especially true when the baseline quality of the metal is not high.
On something heat-treated SAE AISI 4130 steel (what e.g. fancy steel bicycles are made of), you see significant weakening. There is a heat-affected zone where the normal tempering is taken off, and the joining material isn't the fancy CrMo of the baseline material.
I'm not a nautical engineer, but I doubt cruise ships are made of overly fancy steel. When you're making a 180,000 ton ship, your best bet is to use cheap steel, and if you need more strength, to simply use more of it. A good weld should be every bit as strong as the cheap steel around it, and the heat-affected zone is a lot less important if the steel isn't heat-treated or tempered in any way in the first place. It will harden the steel a bit, of course, but it shouldn't be the same level of impact.
It's also worth noting you already have welds, and things need to be engineered for welds. It's not hard to reinforce the welds. Indeed, on a bike frame, the welds are where the stresses are highest, and you get around that by making the tubes a bit thicker (or, for fancier bikes, thicker just near the welds -- that's what a butted bike tube does).
I think cruises are horrible, horrible things for a whole slew of reasons, but none having to do with the ship sinking Titanic-style.
And the original hull wasn't made of a single piece of steel in the first place, it is already a patchwork of steel plates welded together, isn't it? And I think it is assembled as vertical sections like the one being added.
Yeah, exactly how a ship is built will differ, but generally you build up fairly large structural blocks, and then assemble (uh, a lot of welding) them together.
Depending on the ship, shipyard, and I imagine a host of other factors, you might assemble a ship directly out of the order of ~50-100 blocks, or you might pre-assemble into order of ~10 "mega-blocks" which then get assembled together.
Not exactly full sections, but very large sections. For example the crane in shipyard building the largest cruise ships can lift 1200 tonnes to 90 metres height...
"none having to do with the ship sinking Titanic-style."
It's rare, but not nonexistent. The Costa Concordia springs to mind. Schettino ended up with all the blame, but it did seem to be that there was some degree of institutional incompetence as well. But not with the construction AFAIK
EDIT: oh hm, maybe you're right; like the Titanic it collided with something and water began to pour in, unlike the Titanic it was close to shore so the whole ship did not sink.
IIRC when watching documentary about the second to last gen nuclear submarines - engineers figured out that welds themselves were stronger than the steel plates themselves.
>Welds are quite strong -- it just extends the metal. This is especially true when the baseline quality of the metal is not high.
This is not the case at all. A weld almost always weakens the base material. And you don't just use whatever steel is the cheapest to build a ship. You use what is appropriate to the use case. There are cheaper and more expensive options within that category, but you make it sound like you can just grab whatever is cheapest in the yard that day.
There's so much that goes into material selection and handling that this comment confidently hand waves away.
Welds weakening the base metal is a myth that is disproven literally day 1 of any welding course. There are metals that don't like the heating and will weaken, but if the weld breaks before the base metal, someone fucked up real bad.
Of course shit welding can cause weakening of the material but thats true of everything. Anything that is worth welding that also is important will use metals that have strong welding properties that make the weld stronger than the base material.
This is misleading or wrong. In general, the weakest part of a steel weld is the heat-affected zone. Not the rest of the base metal. Not the weld.
The heat-affected zone is caused by the weld. Ergo, welds to weaken the base metal.
In most cases, this also doesn't matter. I think all but one of the things I've welded, even a bad weld would have been way more than strong enough, and for many, even the tack weld would have held fine. Welds are very, very strong, and it's usually cheap and easy to use sufficiently strong materials that all of this is moot.
But for something like an ultralight bike frame, racing car, or airplane, it is something you do need to worry about.
* The equivalent is insurance. Insuring a $2B ship carries pretty good due diligence. A ship simply failing is rare. Of course, ship insurance doesn't care about employee rights, safe food, medical care, or other things one might expect to keep people safe. It's about protecting the capital expense. If everyone on the ship dies, but the ship survives, that's okay!
* Welds are quite strong -- it just extends the metal. This is especially true when the baseline quality of the metal is not high.
On something heat-treated SAE AISI 4130 steel (what e.g. fancy steel bicycles are made of), you see significant weakening. There is a heat-affected zone where the normal tempering is taken off, and the joining material isn't the fancy CrMo of the baseline material.
I'm not a nautical engineer, but I doubt cruise ships are made of overly fancy steel. When you're making a 180,000 ton ship, your best bet is to use cheap steel, and if you need more strength, to simply use more of it. A good weld should be every bit as strong as the cheap steel around it, and the heat-affected zone is a lot less important if the steel isn't heat-treated or tempered in any way in the first place. It will harden the steel a bit, of course, but it shouldn't be the same level of impact.
It's also worth noting you already have welds, and things need to be engineered for welds. It's not hard to reinforce the welds. Indeed, on a bike frame, the welds are where the stresses are highest, and you get around that by making the tubes a bit thicker (or, for fancier bikes, thicker just near the welds -- that's what a butted bike tube does).
I think cruises are horrible, horrible things for a whole slew of reasons, but none having to do with the ship sinking Titanic-style.