Shipbucket

A lengthened Arleigh Burke already exists in the form of the KDX-III destroyers.

they're about 10 meters longer then a Flight IIA

Hmm. I think I mean the VLS Spruance conversions. As for the Cavours, I suppose, adding 30 meters of bow, tearing the midships X turret out, tearing out two shaft alleys, replacing the other two shaft alleys, widening the beam by about two meters, adding fuel tanks, and replacing the powerplant completely might not involve reframing from the keel up?

One does understand that the ship frame is cellular and must be redone with such modifications? That includes repositioning along the length of the keel to distribute weight and volume properly. The Spruance VLS ships especially are modern examples that illustrate the need to make these modifications.

You are not making any sense at all.
You describe 2 examples.
- The Spruance class were not lengthened. The VLS went for about 60% into the space the ASROC reloading system was already (designed so it could be swapped with the Mk 26 being developed when the Spruances were build), and for the other 40% or so went into space that was reserved into the design for the larger Mk 71 gun. No major modification of the construction was needed or done.
- I am not familiar with the Cavour modification (why would you bring in a 1910 battleship into a discussion about an 2000's destroyer), but if this could be done, that actually makes a point about the reserve strength on warships. Of course a lot of design work is done, but the Cavours were not rebuild from the keel up around the original weaponry. This means her original construction was already strong enough to get modified to this extend.

These 2 examples have nothing to do with what you were talking about: the ships construction needing a redesign when lengthened amidships. Only one of your examples was lengthened, and not in the way we were talking about. Also, your examples were modified when already build, while we are talking about a ships design being enlarged for new construction.

In other words, Tobius, what the hell are you talking about? I have no idea what you are trying to say, your examples disagree with the things you say, your sources are extremely unreliable and hell, I would even say you are adding disinformation to an otherwise great and interesting thread. May I ask why?

_________________
Drawings are credited with J.Scholtens
I ask of you to prove me wrong. Not say I am wrong, but prove it, because then I will have learned something new.
Shipbucket Wiki admin

Modern ships don't really have a keel in the conventional sense, and you can quite literally cut them in half and splice in a section with relatively little difficulty.

Warships are certainly harder then cruise ships and oil tankers but in practical terms this just means that the number of places you can cut the ship in half are more limited. Before the void swallowed it whole the old naval matters site had a section which went into some detail about the practicalities of lengthening the Invincible class CVLs as a "cheaper" alternative to the CVF program.

Yes I do use two examples.

And here is the third.

And a fourth.

Example five is a fail.

I think one understands?

The ship is a live bridge load. Lengthen it without understanding the issues at one's peril. I wonder why I have to repeat that?

Finally, examples which make some sense!
however, these examples all still apply to the modification of an existing ship, not a new build design.

While some checks and possibly some modifications are needed for this lengthening, it would hardly be a new design from the keel up! As I stated before: And I can say this as an engineer who works with those calculations and regulations almost every day. I know the stresses which a ships hull is subjected to, and I know how to build a ship that can handle that. And I know you can lengthen a ships design by just checking the bending moments and the section modulus, possibly reinforcing the midships, but keeping 95%+ the original construction. (That is 95% of the modified sections, which in itself is less then 10% of the ships length, which means 99,5% of the ships construction remains the same) Would you call that a redesign from the keel up? I would not.

so you are still making little sense, if any.

_________________
Drawings are credited with J.Scholtens
I ask of you to prove me wrong. Not say I am wrong, but prove it, because then I will have learned something new.
Shipbucket Wiki admin

so you're using the example of the structural issues of lengthening lightly built and already in many cases structurally weak cargo ships to infer the design issues with the lengthening of ships which are by design very structurally strong?


there is also the subject of lengthening during design and lengthening after the fact

which are two very different things

If you use a new build design based on existing plans (Here we use the RN Broadswords (Batch III)and the US Arleighs (Flight IIs) ), that sort of type reframings and subdivisions redistributions I suggested will be just as necessary to modify off the paper plans to bend new steel.

Reply to Hist...

Strong warships? Like the LCS (Lockheed version) that had to go back to have its hull reinforced? Or that new British destroyer that made an Atlantic speed run to show up the Americans and prove that British shipwrights had the right stuff? Wrinkled hull plates. Back to the builders to be reframed.

How about the French Charles de Gaulle? Hull frame issue there was the reactors. Or the first VLS Spruances? Guess what the VLS did to the hulls, specifically the bows? Back to the builders for reframing.

Warships, whether one knows it or not, are just as susceptible to bungled refits, stretchings, underestimated dead and live loads, torqueings and fracturing as any ship. Collins or the Upholders or the Valiants and the trouble plagued Astutes seem familiar?

Could add the Permits, Sturgeons, ands early LAs. Look, warships have shakedown cruises after a refit or SLEP exactly because of the issues I addressed above.

yeah, the RN T22 batch 2 and 3 were lengthened compared to the batch one, but that actually proves it is very doable to lengthen a ships design without much issues. No flight 2 burkes were lengthened, the Flight 2A had a bit more overhang in the stern to give more space to the helicopter deck aft. I still have no idea what you are actually saying, is it an bad idea according to you to lengthen ships? do they need such considerable rebuilding that lengthening warships is never done? you point at issues, but here you post a perfectly working example of an lengthened design that does work without problems.

As for the reserve strength of warships. Of course some ships have errors (FFG-7's had to be strengthened, the lengthened T42 destroyers had to be strengthened, as had many others) engineers sometimes underestimate the forces building up in a certain area of the ship. Note that the examples I stated here were fixed by reinforcing the deck and adding a girder to the side of the hull, hardly rebuilding the ship from the keel up again........
Also, the LCS is not build to military standards in being shock proof IIRC, so has indeed a lot less reserve strength. add to that the experimental nature of building a ship like that from aluminium and it is not weird there would be problems. it says exactly nothing about the strength of the burkes.
I have no idea how the reactors on the Charles Du Gaulle could be an hull frame issue, was she leaking radiation trough the hull? has the reactor dropped out? that ship had quite some issues when build, but the hull strength was as far as I know not one of them. VLS spruances had some reinforcing, as there was cut a big hole in their deck, one of the main components of the strength against bending moments in a ships construction. hardly a rebuild from the keel up though, just adding the removed metal in another position.

So yeah, more disinformation. Could you please start saying something actually true and useful, maybe?

_________________
Drawings are credited with J.Scholtens
I ask of you to prove me wrong. Not say I am wrong, but prove it, because then I will have learned something new.
Shipbucket Wiki admin

By new do you mean the Type 42 Batch IIIs?


Because the problems with the actual new British destroyers have nothing to do with the hulls, even then the Type 42's wearen't "reframed" they welded a strengthening beam along the hull at main deck level and called it a day.