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German planes are here: viewtopic.php?f=16&t=133&start=1170

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Nobody expects the Imperial Inquisition!

Thank you very much, Rhade, very friendly of yours! Suddenly being in the Shipbucket community is cool. Thanks to you and to others, of course.

After that big work Ultraking and BB1987 have spent to show me with great details the errors in my DKM "Prinz Alfons" design and taking into account other points which have been pointed at by other members as not correct, I spent in the meantime many hours working in detail to get the issues correct. Okay they may not be 100% okay, but I dare say that the (re)work done is satisfactory. But before I show you the ship as it "left the yard" after all thye works were done, I want to go first into some correlated issues.

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"):



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.



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.

This to explain that I am very well aware of the problems occuring when augmenting the length of a ship. The corrected DKM "Prinz Alfons" will be shown at next.

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.
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.

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)
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.

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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

Acelancelot,

The technical issues you've described in a lenghty form sound correct and since I'm no expert in this field, your point of view stands. Being so, let's terminate this story.

Thank you Ace.
I am enjoying reading the pro's and con's to lengthening a ship. And where it should or should not be lengthened from. The information for us that like to play with AU ships is very good.

What I draw from your remarks is that the best time to lengthen a ship is when it is still on the drawing board.

Craig48. There are 100's of merchant ships in the size that you are looking at converting. They may not be Spanish to start with, but during the early 1930's a lot of small shipping companies went broke and were forced to sell off their assets. The ships they owned. So it is quite possible for the Spanish Navy to purchase the size of ship it needed and convert it without having to do the major work you have given your conversion.

And the point of that would be..... what exactly? I basically told you your background story (the lengthening of that particular ship) doesn't really make sense, so redrawing the hull would improve your drawing but make it exactly nothing better as an AU story? I have actually said very little, apart from anything to do with the lengthening, about the drawing itself. That is a whole another story, so I am not certain why this "challenge" would be the answer to that.

In short, I'd rather spend my time drawing on my own entry for the carrier challenge, as I am sure you'll understand.

_________________
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

Project "Prinz Alfons" eliminated from this topic.

The middle part of Europe, in the already described scenario where all the ships would fit into. Basis for this was the "Amsterdam Treaty" (following the AGNA with England) and six months later the "Vienna Treaty". As already said before, the basic idea for these treaties was the economic side (reduced taxes on the exported goods ("sales tax") and no taxes when crossing the borders for goods produced inside the signing countries). With Poland a similar treaty was signed one year later (late 1938), when this country got fully reassured of the real intentions of Berlin... London gave here a "helping hand" reassuring Warsaw... In mid 1939, in total secrecy, an adenda to these treaties was signed, regarding the military cooperation between the undersigning countries. This cooperation included several agreements to produce German defense items in the other countries (complete, under license, or partially to be then sent for final assembly to Germany). It was under these circumstances that Bulgaria agreed to allow a naval base at Varna for the DKM. It was as well under these agreements that nearly all river boats for patrolling duties ("Schnellboote") were produced either in Austria, in Tchekoslovakia, in Hungary and in Romania and Germany acquired those it needed at 4/5 of the real cost (which in itself was lower than if made in Germany due to lower manhour costs). On the other hand, Germany assured all the undersigning countries assistance in their territorial defense.

Under the above described circumstances, in mid 1938 the German government laid out a definitive plan for its DKM, taking into account two aspects:
1. The defense of its own shores and those of the states with which the treaties of cooperation had been undersigned (this latter part lead to an interesting naval development in itself...); and
2. With lower priority, to show a presence in the international waters. Not too ostensive, but enough to show that Germany was rising slowly from the ashes of the "fire" lit by means of the "Treaty of Versailles".

Under these aspects, the core of the DKM would include:
- 2 battleships with 4x3 38 cm guns, max. displacement 33.500 tons
- 2 "pocket battleships" with twin turrets for 38cm artillery
- 5 heavy cruiser with 18.000 tons, 4x3 28cm guns
- 6 midsized fast cruiser with 4x3 20,3cm guns, 8.500 tons
- 6 midsized fast cruiser with 3x3 15cm guns, 6.700 tons
- 18 different class destroyers with either 4x3, 3x3 or 4x2 15cm main artillery guns, max. 3.800 tons
- 28 escort and tender ships with either 12,7cm or 10,5cm DP guns as main armament.

These units were to be deployed sucessively into three main fleet:

- Nordatlantic fleet based at Wilhelmshaven;
- Baltic fleet based at Kiel
- Black Sea fleet based at Varna, Bulgaria;

Due to circumstances maybe later detailed here, this port of Varna became suddenly of great importance, in the wake of the Soviet invasion of Finland and the build-up of the "Baltic Alliance", which due to the circumstances grew to a much bigger size and role than first planned. The Varna shipyards had suddenly plenty of orders to fulfil, building vessels for several countries belonging to said alliance.

1. The two battleships were "Bismark" and "Tirpitz", after several deep changes to accomodate four triple turrets instead of three;
2. The two smaller battleships were "Scharnhorst" and "Gneisenau"
3. The five heavy cruiser were "Graf Spee", "Hipper", "Blücher", "Scheer" and "Prinz Eugen"
4. The first six fast cruiser were (approx.) those of the Leipzig and Königsberg-classes
5. The second batch of six fast cruiser were (approx.) those of the "Dichter" (poet)-classes
6. The destroyer were being built gradually using yards in Germany, the Netherlands, Poland and Bulgaria
7. The necessary auxiliary ships to form the three fleets were also made not only in Germany, but at least by 2/3 by foreign yards, according to general German layouts.
8. A fleet of 60 submarines was also built between 1936 and 1943 but completely in German yards.

Complementary note: The Baltic fleet got their task from beginning of December 1939 on, when the USSR invaded Finland; the Black Sea fleet was put together in its first form following the formation of the "Baltic Alliance" and as the counter-attacking forces pushed back gradually the Soviet forces. Foreseeing an arrival at the Black Sea, the high command of the "Baltic Alliance" accepted the assistance of the nations with shores at the Black Sea which belonged to the number of countries having signed beforehand defense agreements with Germany (Romania and Bulgaria) and accordingly armed forces from the "Baltic Alliance" began to be deployed there, to build up a claw to attack the Soviets from the southern flank, Finland and the Baltic States (with the masive assistance from the part of Germany) attacking from the north and Poland and Hungary (also with assistance from the part of Germany) from the middle sector. The "North Atlantic fleet" was in January 1940 partially deployed high up in the Arctic, to assit the Finish troops trying to defend Petsamo and later on attacking the Russian port of Murmansk. While the land troops had a very hard time to make progression through the heavy snow, the ship's artillery and mainly the aircraft embarked on "Graf Zeppelin" did a remarkable job.

These events also led to a massive build up of a vast fleet of river boats of all kinds, a part we will go also go into detail further on. Let it also be said that from the moment on when the USSR attacked Finland and the "Baltic Alliance" was put together, the USA though not intervening directly did it indirectly, supplying vast amounts of pre-treated crude and - most importantly - gave the "Baltic Alliance" a credit line of USD 1 billion. (This part is a relatively small part of the real world's "Marshall plan" taking place beforehand...).