Shipbucket

I've been looking over the hull again, and I'm not certain she'll have have adequate deck room for her aircraft. There may be a revision coming that will change her dimensions. More research to do.

_________________
Redhorse

Current Projects:
Republic of Texas Navy
FD Scale F-14s

Yep. She's about 65 feet too short. Stand by for revision. I'll post it with the previous steps completed so I can pick up where I left off.

_________________
Redhorse

Current Projects:
Republic of Texas Navy
FD Scale F-14s

New dimensions, but essentially at where I left off with the old hull:



What I didn't fully grasp at the time I did the springsharp numbers for the Rio Grande is that I need a minimum of about 70 feet of deck length to handle aircraft. So I changed how I estimated it. The end result is a heavy cruiser that is 45 feet longer at the waterline than the battleships. Not uncommon during this time period, but it still irks the Naval Staff.

_________________
Redhorse

Current Projects:
Republic of Texas Navy
FD Scale F-14s

Machinery spaces are penciled in with uptake trunks above them. The hangar space is in purple on the main deck along with the conning tower position and approximate location for the catapults. On the overhead view you'll see the working radii for the 6"/53 guns (future locations of the 5"/38s).



My next steps are fleshing out the magazines (gotta have space for those projectiles and propellants), add the tripod foremast and mainmast, sketch out the bridges, and plot out a few more vital compartments (main battery plot, etc).

_________________
Redhorse

Current Projects:
Republic of Texas Navy
FD Scale F-14s

Thanks for sharing your design process, Redhorse. It's really cool to see how much thinking goes into these wonderful designs.

_________________
Republic of Lisenia AU - In progress
Republic of Lisenia in FD Scale - In progress

Hi Redhorse. I couldn't help but notice that you uttered the 'never to be mentioned' powerplant in cruiser design - turbo-electric drive. I have to ask this - have you tested this using actual turbo-electric plants? I've attached several US CV preliminary designs that used TE drive so that you can reduce them to SB scale and determine the length and beam requirements for the plant.

http://i7.photobucket.com/albums/y291/B ... -11-26.jpg
http://i7.photobucket.com/albums/y291/B ... -11-17.jpg
http://i7.photobucket.com/albums/y291/B ... -11-24.jpg
http://i7.photobucket.com/albums/y291/B ... 22-9-9.jpg
http://i7.photobucket.com/albums/y291/B ... 3-1-31.jpg

Also, use the machinery weights listed on the designs as a guide for the weight requirements. Unless you plan to restrict the design to say 85,000-shp, you're going to have at least 3,000 tons in machinery weight (my rough calculations put a 100,00-shp plant at 3,200+ tons). Compare that with the Pensacola-class cruisers which had a machinery weight of 1,765 tons and the Northampton-class which 1,945 tons - and these are dry weights!

IMHO the plant won't fit within the space that you have within the hull. Remember that the generator and motor room sizes are determined not just by the size of the of the generators and motors, but also by the equipment necessary to get that power to where the ship needs it. That equipment is largely fixed in size, with little variation for differences in power - so a generator room or motor room in a 100,000-shp plant won't be , let's say, 55% of the size of a similar compartment on a ship with a 180,000-shp plant.

Some other observations that I have made from your internal arrangement drawing.

Draft. Just going by the Mk I eyeball, it seems to be at least 24 feet. That seems a bit excessive, unless RTX is building cruisers of 11,000 to 12,000 tons standard displacement. I know they didn't sign the treaty, so thats your call.

Armored freeboard. Just as draft seems a bit excessive, armored freeboard amidships seems almost non-existant. Any flooding in the midships or after hull will allow the machinery spaces to flood from the deck above in the event of battle damage.

Double bottom. In British Cruisers, Friedman states the the double bottom is about 3 feet in depth. Checking that against US cruiser drawings in US Cruisers, that depth seems to be constant between the two navies designs. You might want to adjust yours to a similar depth.

One final observation. I've noticed that RTX designs of late are similar to their USN counterparts. This design is markedly similar to the Pensacola-class. Remember that their flush-deck hull design was adopted with Pacific Ocean operations in mind. That hull design won't cause RTX any problems in the Gulf, the Caribbean or the South Atlantic, but if they envision operations to include escorting convoys to Europe (through the North Atlantic), a raised forecastle might be in order. It would keep the battery drier and provide more internal space.

Just some thoughts and recommendations.

Wow, Spike. That's quite an analysis, and all of it well researched. Let me see if I can do it justice:

I used the internal arrangement from the West Virginia to help me determine the proportions of the machinery spaces, giving preference for available length in sketching out the bulkheads. The WV was 600 feet at the waterline, just 35 feet longer and 27 feet wider with greater distance between the outer skin and the machinery spaces than this ship. HSNA has a PDF available that I used for the measurements. I did the same thing for the previous Pecos Class, which were also TE. I like the greater compartmentation with TE, and the fuel economy at cruising speeds. I am concerned that my outboard motor rooms are cramped, but keep in mind every line drawn in SB scale is 6 inches wide.

According to Springsharp, the powerplant is rated for almost 68,000hp with a machinery weight of almost 4300 tons, so yes it's heavy. The plant may or may not fit, as you state. But Springsharp only tells you what's in the realm of the possible. The program says machinery, storage, and compartmentation space is excellent consuming only 66.7% of the underwater volume.

These cruisers will draw 24 feet as you noted, and come in at a normal displacement of 14,000 tons. Again, very heavy because I was originally hoping to arm her with 10" main guns. Here's the catch - no one makes a viable 10" gun in 1927. And (tongue in cheek here) if the US is going to build Texas a 14,000 ton cruiser...which undoubtedly would raise naval ire among Treaty signatories...the US will insist on 8" main armament. It's a tradeoff, because Texas can't built anything over 10,000 tons yet. The available shipyards are small and limited to about 4000 tons. Galveston is the only body of water deep enough for capital ships as yet, and that's because the channel and harbor are dredged to a 30 foot depth.
I don't have the armor belt depicted yet, but it is 10 feet high and runs the entire vital length of 367 feet. And I don't have all the bulkheads laid out yet since I'm depicting the process I use step by step. She's just not finished yet.

Your point about the double bottom is probably right. It's a little shallow at only 2.5 feet when the US and Brits are using 3 feet. But not everybody got it right during these years.

She might look like a Pensacola, but would be more like a Northampton since the Pensacolas came in almost 1000 tons underweight and the US sacrificed armor for speed to meet treaty restrictions. It's much the same reason they used twin and triple turrets instead of two and three-gun turrets those years. So many design practices were adopted to save weight, and that's a restriction I don't have to play with too much.

And, I have to deal with a hefty pricetag - the Rio Grande's are $11,500,000 per ship ($147M in 2012 dollars).

_________________
Redhorse

Current Projects:
Republic of Texas Navy
FD Scale F-14s

OK, now we're getting somewhere. You did the right thing, using a TE powerplant as a guide, but it also caused a big problem. The WV's powerplant is designed to provide 28,900-shp (it actually provided something over 30,000-shp on trials). This is only one-third to one-quarter the amount of power a cruiser will, unless you're designing a very slow cruiser.
Springsharp only gives data for turbine plants in general. Neither Rick (writer of the original program) nor Ian (who writes the current versions) have programmed weight or volume data for turbo-electric plants. That's why I put up the US CV preliminary designs - you have to figure the volume, and possibly the weight, yourself.

Take the preliminary designs that I posted earlier (I think that designs #1 or #2 will work best), reduce it to SB scale - waterline length and beam are given. Then remove boilers until you have a plant that generates the amount of power you require (approximately 10k shp per boiler). Rearrange boilers as necessary and determine powerplant length. My gut tells me that this ship will have to be the length of a Japanese CA (about 650 ft or more) in order to fit a turbo-electric plant of 80,000 to 120,000-shp.
Actually, you've already done that, you just haven't realized it yet . Friedman noted in British Cruisers that all cruiser machinery spaces are 3 decks in height - approximately 24 feet - The overhead for the machinery spaces is the armor deck. The double bottom is generally 3 feet in depth. This 27 foot depth from the armor deck to the keel is a feature of both USN and RN cruiser designs. That's not in his exact words, but that's the gist of it.

All post-WW I armored ship designs placed the top of the armor belt at the armor deck. In your design, the deck illustrated by the yellow line will be the armor deck - it is approximately 27 feet above the keel. What you need to do is get that deck several feet above the waterline (and by extension get the top of the armor belt several feet above the waterline) so that you have some armored freeboard that is vital to a ship's survival. Note: you will need at least 5 feet of the belt below the normal waterline to protect the hull against shells that fall just short of the ship and to protect areas of the ship that are exposed by wave formation (more accurately, wave troughs) at high speed.

Normally, you would get the increased armored freeboard through one of three ways: increased hull depth, decreased draft or reduction in the heights of the two upper decks. However, you can't increase hull depth in this design, it's already spot on if I estimate it correctly - I'm guessing about 42 to 43 feet. All USN flush-deck cruiser designs from the Brooklyn to the Des Moines classes had hull depths from 41 to 43 feet - raised forecastle types have hull depths between 34 and 36.5 feet. Reducing upper deck heights (and thereby reducing the sheer of the AD) will only raise the armor deck a small amount, perhaps a foot or so. That leaves reduced draft - I'd recommend 20 to 21 feet - with increases in length, beam and block coefficient to keep your desired displacment.

In case you haven't noticed, once you decided on a cruiser, the depth from armor deck to keel is largely fixed. The decision of hull type, flush-deck or raised forecastle, then determines hull depth amidships. Hull sheer then determines freeboard fore and aft. It all falls into place relatively easily - and I didn't even have to draw it. Then its just a matter of finding ideal length, beam and BC.



The reason that I've taken this time to point out what I consider to be errors in this design (and the earlier CL by extension) is because I've enjoyed following your AU. One of the things that you've done better than many others is to keep things real. That said, a TE powered cruiser doesn't seem particularly realistic. The USN never consider one, and I think that this is because they knew that a cruiser, with less reserve bouyancy than a battleship or carrier, would never survive the flooding of a generator room. But cruisers, with their narrow beam, could never be fitted with a torpedo defense system to prevent that from happening. Hence my attempt to keep your AU from jumping the shark, as it were.

Some very informative information in this thread. I've always been interested in turbo electric drive as I've always seen the system as being perfect for large capital ships that need performance and cruise efficiency. Prewar experience with the New Mexico seems to have indicated that had tonnage restrictions not been in place. The USN would have been in favour of adopting TE drive for the 'standards'.

A final note on the design itself, do you plan on depicting the evolution of the design during its years of service or do you just have planned to complete it "as-commissioned" ?

_________________
"The first rule is not to lose; The second rule is not to forget the first rule"

After looking at design #1, my TG rooms are only 10 feet shorter and 1 foot narrower. Ten square feet of deck area should not make that much difference - that's smaller than my closet. I have eight boilers, which according to your estimate, provides 80K for a 68K shp powerplant.
I've got the armored deck set at the green line, just under the main deck. From there, it won't be too difficult to extend the belt an additional 3 feet below the waterline.
I wouldn't use those ships for comparison - the Brooklyns' design can be traced back to 1930, four years after this design, and had to conform to treaty restrictions. The Des Moines is almost 20 years later. Using ships designed after 1926 would be the equivalent of reading the first and last chapters of a novel. I deliberately avoid looking at later designs to keep them from inappropriately influencing my current ones. The influences I take from the USN are usually limited to gunnery, fire control, and upper deck structures.

Using TE powerplants in a cruiser is going to cause disagreement, only because there's a lack of available data for how it might be done. I've done my best to produce correlative assumptions based on what is out there and your powerplant data for carriers from the early 1920s was helpful. There were several innovative and creative solutions proposed and implemented in these years to solve treaty restriction problems...perhaps there could have been a solution just as innovative and creative for a TE powered cruiser. I took a calculated risk knowing the more educated and experienced SB members might voice criticism.
There may be a lesson learned here. Not all designs, for any Navy, are perfect. Some have very real (and at the time, unknown or unsassessed) flaws. The USN may have also decided against TE propulsion in a cruiser because of the weight. Geared turbine plants are much lighter, allowing the saved weight to be used elsewhere.

I don't think one or two designs will "jump the shark". It's a navy with a manpower cap of 10,000 men. Once these three ships are built, I have to replace eight destroyers and four submarines. After that, I'll only continue building up to my 10K man limit, and the preponderance of those ships will be smaller combatatants because I can get more of them to sea. I won't have to replace any other capital ships until 1936, if I decide they can't keep pace with requirements.

_________________
Redhorse

Current Projects:
Republic of Texas Navy
FD Scale F-14s