Well, the ship you are talking about is completely something else then what you are describing here as "answer", sorry to say, but I disagree.
1. I spoke at the beginning about the lengthening of the original "Alfonso III" passenger ship. The second passenger ship of the Spanish "Transatlantica" line was in service in late XIX century and in 1895 she was lengthened by 18.5 meter, to a total of 160 meter, maintaining ther beam of 16.5 meter. The third ship with the name "Alfonso III" was built in 1927, as stated in the beginning, and served as basis for this German aircraft carrier "Prinz Alfons". She had the dimensions of 152,4m x 18,6m x 10,9m and a total displacement of 14.400 tons. By my "intentions" to use the hull and increasing her dimensions, that would alter her length by 50 meter (to 202,4m) and afterwards bulges of 1,5m on each side would make the underwater part of the hull broader by some 3 meter, to a total of 21,6m. And, as I said before, shaped at the front and rear ends in a most hydrodynamic form, like the bulges in submarines. The length vs. beam proportion would have been 9,37, with the larger portion (with the bulges) well below the CG of the hull with superstructures. If we take a look at HMS "Glorious", transformed by the RN from a battlecruiser into an aircraft carrier in the 20s, we had there a length of 239,8m and a hull width (beam) of 24,7m, giving a ratio of 9,7. Not sooo much different, I'd say.
HMS "Glorious" had an installed power of 90.000 shp for a max. displacement of some 22.720 tons, giving her a max speed of 32 knots. My example here would have had a displacement of some 16 to 17.000 tons and a total power of a bit over 50.000 shp. Max speed? Mavbe some 28/29 knots.
Design of the bulge shape welded onto the side of DKM "Prinz Alfons" (based on a design by Wikipedia under the tag "anti-torpedo bulges"):
The 1895 ship you are describing, was lengthened by 13%
The Alfonso III you are using as base, you lengthen her by about 33%. A lengthening of, relatively speaking, 2,5 times more then what you are describing for the 1895 ship. So no, that proves nothing about this working.
You increased the beam of the ship with anti torpedo bulges. These are mounted below the waterline, if your schematic is to be believed. This means that the addition of the bulges actually has actually an slight negative effect on the metacentric height of the ship, although that might be offset by the higher center of bouyancy and an better stability curve (Due to increase in width of the waterline when the ship reaches an angle, increasing the forces needed to increase the angle further) They work very well as torpedo bulges though! They just do not that much for the ships stability or strength.
2. Now the strength part of the lengthening process I suggested. The most important features on any hull are stability and resistance (toughness). Stability to suffer as little as possible from the forces a ship has to endure, by the forces os the waves, mainly, but also by the wind and its own weight under motion. The main notion here is the "hull girder" and that is a science to itself, to study them and to design ships with the most counter-measures against these vibrations (plus the ones created by the Diesel engines). Now the lengthening of the ship. That is done for long is a fact and in the attached picture we can see that some quite big new portions are sometimes added. And obviously thye naval engineers know how to incorporate the new sections into the existing hull and how to insert the needed metal stringers to ensure the necessary resistance.
I don't fully follow what you are saying here. But oh hey, you mention that naval engineers know how to add big hull sections in a ship. Hello! I'm an engineer, I studied to know stuff like this, and, oh, yes! I indeed know how to tackle the lengthening of a hull. This of course requires a look at the ships construction, but that would be way too much work for just a simple shipbucket drawing. There are a few rules of thumb though, which I kept in mind when I made my earlier post:
- The forces in a ship are in 99% of the ships the largest amidships. If you lengthen an existing ship, you have to ensure that at every part of the ship, it can take the larger forces this new ships shape puts on the ships structure. If a ship was designed properly, the margins on strength are not massive, so the ship can take as much cargo as possible as as much of the displacement as possible is not the ships structure. So, in other words, if you lengthen a ship, near the midship sections it will need major reinforcements.
- In seagoing ships, the largest stresses are most of the time resultant from the vertical forces. Waves, cargo, the weight of the ship itself etc. This means the ship bends slightly under the forces, and the top and bottom are under the most stress (compressed and extended in turn) so the higher up or the lower down in the ships structural frame, the more reinforcement they need. But also: The higher a ships structural frame, the more distributed the stress is, so the lower it becomes relative to the amount of weight used.
- When lengthening an existing ship, you try to keep the existing arrangements intact. So you for example try to keep the entire power assembly the same, as the requirements set on the rigidity of the ship by a longer propeller shaft or the layout of the weights of the engines could result in changing a lot more inside the ship then just the lengthened section.
- If your ship doesn't have the reserve strength for the increased stresses, you either reinforce the ship (increasing weight and increasing the amount of work massively)
There are several ways of attaching the edges of a new section in such a way that it resists all forces acting onto a ship's hull, including the longitudinal ones, the transverse ones and also the heave and surge motions during harsh sea conditions. Since we are at this, one aspect to have also in (big!) consideration is the different types of vibrations the hull girder has to endure. The usual construction methods used to strenghten a hull such as to break down the vibration waves obviously are beneficial to the overall strength of the hull and the ship it self. Why in motorsport a monocoque type of chassis is much better than the old spaceframe chassis? Same reason, pieces welded together in such a way as to resist the twists and bendings occuring at high speeds in corners.
Vibrations is an entirely different issue. Too large or too low strength does influence vibrations in a ship, but "construction methods used to strenghten a hull such as to break down the vibration waves obviously are beneficial to the overall strength of the hull and the ship it self. "is just entirely not true.
As for what I would do (which can be seen in the lengthened cruise ship, btw) when lengthening a ship, is cutting the ship at midships, where the hull is parallel so it is easy to add in a section. You strengthen that new section for the now larger length and forces, so the amount of modifications for the fore and aft sections are limited. If possible (and in most cases of ships lengthening this was done) I would keep the engine spaces intact, putting all that in the section aft of the 'cut' so you do not run into issues with the machinery.
In your proposed rebuild, you did not insert the new sections amidships, meaning you will have to modify the ships entire shape to make it line up without adding resistance due to the hull now being bumpy. (You could do this by adding well designed bulges over a length larger then the extended section, if they extend above the waterline and all the way to the flat bottom of the ship, effectively building an entirely new underwater hull around the former hull). You put completely new machinery on board, with more power and a different arrangement. That means everything below the waterline and all intakes, uptakes etc above the waterline are all new. You rebuild the bow into a clipper bow.
All in all, the resulting ship has possibly, the below sections (in green) mostly unmodified from the original ship.
- The aft section is rebuild due to the larger forces, new rudder, new propellers, newer higher diameter propeller shafts which likely sit at an different angle to have the machinery as low as possible in the ship. Also, at least 30% of its length is new underwater hull due to the added bulges.
- The inserted lengthened sections are of course new
- the midship section is reinforced and rebuild with new bulges, new machinery, modified deck layout due to new intakes and uptakes.
- The bow was rebuild into a clipper bow.
- Next to the extended section, bulges are added and flared into the underwater hull of the original ship.
Looking at your carrier drawing, the green sections above the waterline have new window positions, new deck heights. In other words, these are also modified quite a lot. In other words, the green section forwards below the waterline is the only section of the entire ship that MIGHT get away with not being completely rebuild in your aircraft carrier. Thus my conclusion that the lengthening of this ship makes the entire carrier unfeasible. So no, I am not sure if you are truly aware of the problems occuring, but the above description might help a bit.