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Generally speaking, the overall layout is the same or nearly so.
There are sometimes interesting detail differences in ships of the same class, however. For example, some of the spaces on the South Dakota class ships have been 'flipped' port to starboard. Quite often, there are minor changes in access arrangments, particularly to machinery spaces, etc., and particularly if the machinery has been manufactured/installed by different manufacturers. A pump becomes a slightly different size/shape, which moves a duct, which shifts a ladderway over, which moves a hatch, which moves a bulkhead, etc. The South Dakotas tend, for example, to have somewhat different arrangements for the evaporator rooms, the steering gear rooms, and the c.p.o. quarters, as I recall.

Bill Jurens.

Question:

As to design related of the battleships, did the RN, Germany and Japan follow what the USN did when it comes to building the sistership or did they change the layout for security reason in case the ship gets boarded?

I very much doubt it. Probably the flips were due to slight differences in the machinery arrangments. I'd have to study them in detail -- which I really have not -- and see if I can puzzle out the reasons. Some will be evident, some will not.

Question:

My next question would be is how did the USN come the final design of the Iowas and then later Montana. Did they just look at the Sodaks and say well let stretch the bow and stern and add a faster power plant along with more AA. Or did they approach this in a new way?

Very likely the Iowa design was based on the South Dakota as a 'parent' ship, enlarged. The methods of doing this were taught at the MIT Naval Architectural courses that most of the USN Naval Architects attended, and are documented in textbooks by G.C. Manning. Manning's approach was, in general, to select a successful parent vessel and then copy it with changes. The general relative layout of various spaces tends to remain the same; that way everyone sort of instinctively knows what's where regardless of exactly what ship they are on, and the layout, as it simply repeats a previously successful arrangement, is relatively risk free.


Question:

And last how come they never built more NC classes it seems that after they finished with Washington they decided to end production of that class.

The North Carolina class was never really seen to be successful in a naval architectural sense. The N.C. Class was the Navy's first try at doing a battleship in many years, and treaty restrictions (or supposed treaty restrictions) meant they were only armored against 14" guns. The South Dakota class -- having benefitted from the experience of designing the North Carolina class -- represents a much more elegant and efficient design, which is why it -- rather than the N.C. class -- was used as used as a prototype for the Iowa class. In that regard, the North Carolina class may be seen somewhat as an experimental prototype, or 'interim' design. Better than nothing, but not very satisfying.

That's not to say the South Dakota's were anything like perfect; there were access difficulties to the machinery spaces -- due to a failed experiment which located hatches in the middle of well-used passageways -- and access to the heads was in some cases less than idea, probably just because the designers simply ran out of time to work out the problems. (Sometimes 'good enough' is, well, 'good enough'.) The machinery arrangments of the South Dakotas were a real mess for quite a while, although quite late in the game the designers managed to get everything in proper order. This machinery mess lasted through the contract plans stage for the South Dakotas, and was only resolved in the final sets of drawings. In the end, the arrangement that was adopted worked very well indeed.

The design of the underwater protection system was more or less a designer's option. In my opinion, based on examination of some of the caisson tests, the alleged difficulties with the South Dakota side protection system have been greatly exaggerated. In general, detail differences in the overall geometry of the system tended to be not nearly as important as the quality of the structural connections between the various elements.

I will be away for the internet for the next ten days ago, and probably won't be able to respond to further commentaries on this memo, if there are any.

Bill Jurens

The USN construction system was very similar to the British system Phil describes. The drawings for USS Massachusetts, for example, are almost all modified copies of drawings originally done for South Dakota.

Bill Jurens