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Shigure
Post subject: US Light Cruiser PhiladelphiaPosted: June 19th, 2016, 10:49 am
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Philadelphia class light cruiser - as constructed in 1924
[ img ]

Ships in class:
  • Philadelphia
  • Scranton
  • Clarion
  • Wilkes-Barre
  • Reading
  • Flemington
  • Wayne
  • Hanover
  • Perkasie
  • Easton
  • Harrisburg - Converted into subclass
  • Wildwood - Converted into subclass
SpringSharp report, made by Keisser
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USS Philadelphia, USA cruiser laid down 1924

Displacement:
5 976 t light; 6 159 t standard; 6 693 t normal; 7 120 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(500,06 ft / 492,00 ft) x 52,00 ft x (21,00 / 21,93 ft)
(152,42 m / 149,96 m) x 15,85 m x (6,40 / 6,68 m)

Armament:
8 - 6,00" / 152 mm 45,0 cal guns - 108,92lbs / 49,41kg shells, 100 per gun
Dual purpose guns in turret on barbette mounts, 1924 Model
2 x Twin mounts on centreline, forward deck forward
1 raised mount - superfiring
2 x Twin mounts on centreline, aft deck aft
1 raised mount aft - superfiring
6 - 1,10" / 27,9 mm 40,0 cal guns - 0,64lbs / 0,29kg shells, 500 per gun
Anti-air guns in deck mounts, 1924 Model
6 x Single mounts on side ends, majority aft
2 raised mounts - superfiring
Weight of broadside 875 lbs / 397 kg
Main Torpedoes
8 - 21,0" / 533 mm, 30,00 ft / 9,14 m torpedoes - 1,910 t each, 15,283 t total
In 2 sets of deck mounted side rotating tubes

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 2,99" / 76 mm 328,08 ft / 100,00 m 6,56 ft / 2,00 m
Ends: Unarmoured
Main Belt covers 103% of normal length
Main belt does not fully cover magazines and engineering spaces

- Torpedo Bulkhead - Strengthened structural bulkheads:
2,01" / 51 mm 328,08 ft / 100,00 m 6,56 ft / 2,00 m
Beam between torpedo bulkheads 45,93 ft / 14,00 m

- Hull void:
2,99" / 76 mm 175,52 ft / 53,50 m 11,48 ft / 3,50 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 3,98" / 101 mm 4,00" / 102 mm 3,00" / 76 mm

- Armoured deck - multiple decks:
For and Aft decks: 1,42" / 36 mm
Forecastle: 1,42" / 36 mm Quarter deck: 1,42" / 36 mm

- Conning towers: Forward 10,00" / 254 mm, Aft 10,00" / 254 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 61 223 shp / 45 672 Kw = 31,00 kts
Range 8 000nm at 12,00 kts
Bunker at max displacement = 960 tons

Complement:
369 - 480

Cost:
£1,774 million / $7,098 million

Distribution of weights at normal displacement:
Armament: 243 tons, 3,6%
- Guns: 213 tons, 3,2%
- Weapons: 31 tons, 0,5%
Armour: 1 423 tons, 21,3%
- Belts: 264 tons, 3,9%
- Torpedo bulkhead: 160 tons, 2,4%
- Void: 223 tons, 2,8%
- Armament: 197 tons, 2,9%
- Armour Deck: 427 tons, 6,4%
- Conning Towers: 153 tons, 2,3%
Machinery: 2 017 tons, 30,1%
Hull, fittings & equipment: 2 293 tons, 34,3%
Fuel, ammunition & stores: 717 tons, 10,7%
Miscellaneous weights: 0 tons, 0,0%

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
5 630 lbs / 2 554 Kg = 52,1 x 6,0 " / 152 mm shells or 0,8 torpedoes
Stability (Unstable if below 1.00): 1,00
Metacentric height 1,9 ft / 0,6 m
Roll period: 15,9 seconds
Steadiness - As gun platform (Average = 50 %): 55 %
- Recoil effect (Restricted arc if above 1.00): 0,47
Seaboat quality (Average = 1.00): 0,87

Hull form characteristics:
Hull has raised forecastle, rise aft of midbreak, low quarterdeck ,
a normal bow and a cruiser stern
Block coefficient (normal/deep): 0,436 / 0,444
Length to Beam Ratio: 9,46 : 1
'Natural speed' for length: 22,18 kts
Power going to wave formation at top speed: 58 %
Trim (Max stability = 0, Max steadiness = 100): 63
Bow angle (Positive = bow angles forward): 21,00 degrees
Stern overhang: 0,00 ft / 0,00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 33,00%, 21,00 ft / 6,40 m, 14,50 ft / 4,42 m
- Forward deck: 0,00%, 0,00 ft / 0,00 m, 0,00 ft / 0,00 m
- Aft deck: 67,00%, 14,50 ft / 4,42 m, 14,50 ft / 4,42 m
- Quarter deck: 0,00%, 0,00 ft / 0,00 m, 0,00 ft / 0,00 m
- Average freeboard: 15,36 ft / 4,68 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 123,5%
- Above water (accommodation/working, high = better): 114,1%
Waterplane Area: 16 139 Square feet or 1 499 Square metres
Displacement factor (Displacement / loading): 107%
Structure weight / hull surface area: 96 lbs/sq ft or 468 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0,96
- Longitudinal: 1,46
- Overall: 1,00
Cramped machinery, storage, compartmentation space
Adequate accommodation and workspace room
Poor seaboat, wet and uncomfortable, reduced performance in heavy weather

1941

[ img ]

1942

[ img ]

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Last edited by Shigure on July 6th, 2016, 9:46 am, edited 9 times in total.

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Thiel
Post subject: Re: US Light Cruiser PhiladelphiaPosted: June 19th, 2016, 1:12 pm
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I doubt that's a workable idea with the technology available at the time. Heck, it's not easy to do today with weapons that has a significantly smaller impact

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Shigure
Post subject: Re: US Light Cruiser PhiladelphiaPosted: June 20th, 2016, 2:00 pm
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I've made the ship longer

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apdsmith
Post subject: Re: US Light Cruiser PhiladelphiaPosted: June 20th, 2016, 3:33 pm
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As I understand it, the problem is that the "light cruiser" role is basically a single role. By 1930 there's wasn't (yet) an AA gunboat role, nobody in 1930 - not even the IJN, as I recall - knew how devastating aircraft could be, so the main difference I'm aware of would be fitting with ASDIC or not - and it's important to note that light cruisers would make comparatively poor anti-submarine boats as they're less manoeuvrable than destroyers, plus anti-submarine weaponry isn't really a like-for-like change when measured against CL 155mm guns. What differences in role do you see there being?

Edit: To expand, I don't think that this would be able to "step up" to the CA role particularly well as it's, well, missing the "A" ("CA" is "Cruiser, armoured") - anything armoured to CL standards is going to suffer in a duel with a CA if things are even slightly equal. Stepping down to some sort of destroyer leader is possible, but I'm not sure how economical it would be to, I don't know, ship quad 5"/38 turrets instead of a CL's usual triple 155? Is there some other thing that you're thinking of that I've missed?

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Shigure
Post subject: Re: US Light Cruiser PhiladelphiaPosted: June 20th, 2016, 4:04 pm
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apdsmith wrote:
As I understand it, the problem is that the "light cruiser" role is basically a single role. By 1930 there's wasn't (yet) an AA gunboat role, nobody in 1930 - not even the IJN, as I recall - knew how devastating aircraft could be, so the main difference I'm aware of would be fitting with ASDIC or not - and it's important to note that light cruisers would make comparatively poor anti-submarine boats as they're less manoeuvrable than destroyers, plus anti-submarine weaponry isn't really a like-for-like change when measured against CL 155mm guns. What differences in role do you see there being?

Edit: To expand, I don't think that this would be able to "step up" to the CA role particularly well as it's, well, missing the "A" ("CA" is "Cruiser, armoured") - anything armoured to CL standards is going to suffer in a duel with a CA if things are even slightly equal. Stepping down to some sort of destroyer leader is possible, but I'm not sure how economical it would be to, I don't know, ship quad 5"/38 turrets instead of a CL's usual triple 155? Is there some other thing that you're thinking of that I've missed?

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The ship's original role was that of a light cruiser, but during WW2 it will be refitted for 2 or 3 different roles.

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apdsmith
Post subject: Re: US Light Cruiser PhiladelphiaPosted: June 20th, 2016, 4:28 pm
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OK, but which different roles? Rebuilding it into an Atlanta would require major, major work (you'd basically be building a new ship). One rebuild that is a possibility is a light carrier, but I get the impression that this is not what you're discussing...

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bezobrazov
Post subject: Re: US Light Cruiser PhiladelphiaPosted: June 20th, 2016, 4:46 pm
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TristanAlting: your premise won't work. Your hull is too small for any such "flexible" purpose, besides not looking very "American"; i.e. your stem is too straight, you have a continuous upper-deck deckhouse structure, your bilgekeels are way too high up on the underwater hull. Also, whereas the USN opted for a quadruple shaft system you've got only two. Since you've evidently abandoned the unit machinery system (which was done in the New Orleans-class with detrimental results, and the early Brooklyns) you won't have the option of installing a machinery that could compensate for that design choice; your machinery/boiler room area will simply be too cramped, too small.
The hull you've got right now will not support the 8" gunhouses or, for that matter, the later gun-turrets. You have to consider your length/beam ratio, which, with your design choices by necessity must be quite large (9.5-11.5!) in order to create rather fine forward hull lines to assist in achieving any respectable speed.
Your bridge looks VERY odd! It's like it's 1 1/2 stories high! Decidedly un-American! Did you consider the right deck height before drawing that? Furthermore it lacks any notion of a conning tower, which US cruisers had till the USS Wichita of 1939 vintage. Also your forward tripod stops right in the air - almost literally. It will not be of any good use whatsoever in its present configuration! Your fighting/spotting top above it looks very basic, and not at all as per USN requirements. And, in 1930 (as you've dated the drawing!) there were no, I repeat no radars! Over-the-horizon spotting would be carried out by a couple of reconnaissance planes, for which you don't seem to have planned...

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My Avatar:Петр Алексеевич Безобразов (Petr Alekseevich Bezobrazov), Вице-адмирал , царская ВМФ России(1845-1906) - I sign my drawings as Ari Saarinen


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Karle94
Post subject: Re: US Light Cruiser PhiladelphiaPosted: June 20th, 2016, 5:33 pm
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Here's a couple of us cruisers you can look at, namely the Northampton CA and Pensacola class CL

https://dl.dropboxusercontent.com/u/939 ... on1930.png
https://dl.dropboxusercontent.com/u/939 ... la1928.png


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bezobrazov
Post subject: Re: US Light Cruiser PhiladelphiaPosted: June 20th, 2016, 5:58 pm
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Except my friend Karle94, your's is NOT the CA-26 Northampton! I leave it to you tofigure that one out...(I know you will!)

Instead for an ACCURATE look at the Northampton-class CAs, I will provide this: It's the USS Augusta as of 1933, i. e. near as original as you can get:[ img ]
Now, study this one, since it's the result of careful observations of both builder's plans, photos and drawings, as well, as reading the textual context of the ship.

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My Avatar:Петр Алексеевич Безобразов (Petr Alekseevich Bezobrazov), Вице-адмирал , царская ВМФ России(1845-1906) - I sign my drawings as Ari Saarinen


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Colosseum
Post subject: Re: US Light Cruiser PhiladelphiaPosted: June 20th, 2016, 6:29 pm
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The odd sweep of the stem and the tall, boxy pilot house reminds me of some the earlier Jap CLs, but the fact that you have a defined 01 level of the superstructure on top of a flush deck hull just doesn't make sense to me.

As usual the underwater hull aft of the bilge keel has been copy/pasted from the Atlanta and the funnels have been copy/pasted from the Brooklyn. I hope you understand that these parts are not necessarily interchangeable between ships and really should be drawn from scratch instead of cheaply lifted from drawing to drawing.

As for the concept of "modularity", well that concept just didn't exist back then. I think you should attempt to draw a reasonably accurate Treaty era light cruiser like the Omaha (or the never-built Phoenix from World of Warships) and then draw a few iterations of it as it would have been refitted during the war. I think a cool thing might be to show the fictional "Philadelphia" in, say, 1925, then again in the mid 1930s (maybe it's stationed in the Philippines as part of the Asiatic Fleet), and maybe around December 7th, 1941, painted in Cavite Blue, and then finally a 1943 or 1944 Mare Island or PHNY refit with a cut down superstructure, modern AA fit, and a few radars.

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