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Personal Design - Derry-class CA
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Author:  matedow [ November 3rd, 2017, 1:05 pm ]
Post subject:  Personal Design - Derry-class CA
[ img ]

Post-WW1 Scouting Cruiser designed for a US fleet



Derry, Heavy Cruiser laid down 1917

Displacement:
8,350 t light; 8,672 t standard; 10,434 t normal; 11,844 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(620.50 ft / 609.00 ft) x 65.00 ft x (16.30 / 18.06 ft)
(189.13 m / 185.62 m) x 19.81 m x (4.97 / 5.50 m)

Armament:
5 - 7.00" / 178 mm 45.0 cal guns - 164.99lbs / 74.84kg shells, 220 per gun
Breech loading guns in deck mounts, 1900 Model
4 x Single mounts on centreline ends, evenly spread
2 raised mounts - superfiring
1 x Single mount on centreline, aft deck centre
1 double raised mount aft
4 - 3.00" / 76.2 mm 50.0 cal guns - 13.01lbs / 5.90kg shells, 450 per gun
Anti-air guns in deck mounts, 1915 Model
4 x Single mounts on sides, forward deck aft
Weight of broadside 877 lbs / 398 kg
Main Torpedoes
8 - 21.0" / 533 mm, 22.56 ft / 6.88 m torpedoes - 1.442 t each, 11.538 t total
In 2 sets of deck mounted side rotating tubes

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 3.50" / 89 mm 400.00 ft / 121.92 m 10.00 ft / 3.05 m
Ends: 1.00" / 25 mm 70.00 ft / 21.34 m 10.00 ft / 3.05 m
139.00 ft / 42.37 m Unarmoured ends
Main Belt covers 101 % of normal length

- Armoured deck - single deck:
Fore and Aft decks: 1.50" / 38 mm
Forecastle: 0.25" / 6 mm Quarter deck: 0.50" / 13 mm

- Conning towers: Forward 4.00" / 102 mm, Aft 0.00" / 0 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 2 shafts, 79,286 shp / 59,147 Kw = 31.00 kts
Range 12,500nm at 14.00 kts
Bunker at max displacement = 3,172 tons

Complement:
516 - 671

Cost:
£1.351 million / $5.404 million

Distribution of weights at normal displacement:
Armament: 162 tons, 1.6 %
- Guns: 139 tons, 1.3 %
- Weapons: 23 tons, 0.2 %
Armour: 1,321 tons, 12.7 %
- Belts: 604 tons, 5.8 %
- Armour Deck: 676 tons, 6.5 %
- Conning Tower: 41 tons, 0.4 %
Machinery: 2,906 tons, 27.9 %
Hull, fittings & equipment: 3,830 tons, 36.7 %
Fuel, ammunition & stores: 2,085 tons, 20.0 %
Miscellaneous weights: 130 tons, 1.2 %
- Hull below water: 40 tons
- Hull above water: 20 tons
- On freeboard deck: 30 tons
- Above deck: 40 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
16,961 lbs / 7,693 Kg = 98.9 x 7.0 " / 178 mm shells or 1.7 torpedoes
Stability (Unstable if below 1.00): 1.32
Metacentric height 4.3 ft / 1.3 m
Roll period: 13.1 seconds
Steadiness - As gun platform (Average = 50 %): 80 %
- Recoil effect (Restricted arc if above 1.00): 0.12
Seaboat quality (Average = 1.00): 1.37

Hull form characteristics:
Hull has a flush deck,
a straight bulbous bow and a cruiser stern
Block coefficient (normal/deep): 0.566 / 0.580
Length to Beam Ratio: 9.37 : 1
'Natural speed' for length: 24.68 kts
Power going to wave formation at top speed: 55 %
Trim (Max stability = 0, Max steadiness = 100): 58
Bow angle (Positive = bow angles forward): 15.00 degrees
Stern overhang: 4.00 ft / 1.22 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 28.00 ft / 8.53 m, 25.00 ft / 7.62 m
- Forward deck: 40.00 %, 25.00 ft / 7.62 m, 22.00 ft / 6.71 m
- Aft deck: 25.00 %, 22.00 ft / 6.71 m, 20.00 ft / 6.10 m
- Quarter deck: 15.00 %, 20.00 ft / 6.10 m, 21.00 ft / 6.40 m
- Average freeboard: 22.97 ft / 7.00 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 96.2 %
- Above water (accommodation/working, high = better): 228.7 %
Waterplane Area: 28,044 Square feet or 2,605 Square metres
Displacement factor (Displacement / loading): 136 %
Structure weight / hull surface area: 90 lbs/sq ft or 442 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.96
- Longitudinal: 1.41
- Overall: 1.00
Adequate machinery, storage, compartmentation space
Excellent accommodation and workspace room
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily
Author:  Kannevets [ November 3rd, 2017, 2:34 pm ]
Post subject:  Re: Personal Design - Derry-class CA
Very good overall, but there should be at least some sort of protection for the gun crews. Otherwise this is better than my first design!
Author:  sebu [ November 4th, 2017, 6:58 am ]
Post subject:  Re: Personal Design - Derry-class CA
Welcome to SB matedow! A very good start indeed. I don't know much of ships of this era, but you've good approach to SB style. Much better design than my first :)
Author:  matedow [ November 4th, 2017, 11:27 am ]
Post subject:  Re: Personal Design - Derry-class CA
Kannevets wrote: *November 3rd, 2017, 2:34 pm
Very good overall, but there should be at least some sort of protection for the gun crews.
I looked at putting a shield on the guns, but it doesn't appear to fit with US practice for the period. If you look at the deck mounted secondaries on the battleships or Lexington-class battlecruisers, the US didn't put shields for protection of the crews, instead preferring the "handiness" of the weapon.

I have a shielded 7" mount that I plan on using when I do a WW2 era refit of these ships.
Kannevets wrote:
Otherwise this is better than my first design!
Thank you for the feedback.
sebu wrote: *November 4th, 2017, 6:58 am
Welcome to SB matedow! A very good start indeed. I don't know much of ships of this era, but you've good approach to SB style. Much better design than my first :)
Thank you for the feedback and the welcome.
Author:  Rodondo [ November 5th, 2017, 12:13 am ]
Post subject:  Re: Personal Design - Derry-class CA
Welcome aboard! :)

Nice long range foreign station cruiser, design wise is all very agreeable, styling your'e almost there, the hull seems to lack some shading (especially the stern) also you need to cut out the double black lines which give it a heavy appearance.

Aside for that a very strong start
Author:  Novice [ November 5th, 2017, 7:46 pm ]
Post subject:  Re: Personal Design - Derry-class CA
Welcome to SB Matedow.
This is a very well executed first drawing, but it has some issues IMHO.
SB style wise first: the credits appear to be not in Arial, or to be slightly larger than they should Ship's name and class usually go on the first line,and artist's name in parentheses like so (Matedow). If you used some other artist's work his name goes first (Karle 94, Matedow). You don't need to specify which part you took on the drawing itself (most artists here will recognize their work). Here as far as the credits I think you don't need to add Karle94's name if you used only the mast. Most parts are free to use by all other artists without crediting, with credits only for complete hull, or entire superstructure for instance.
Now for some design issues. The first is the armor belt which doesn't extends to the ship's ends, thus leaving the magazines of both end guns exposed and unprotected.
Author:  JSB [ November 5th, 2017, 10:56 pm ]
Post subject:  Re: Personal Design - Derry-class CA
Novice wrote: *November 5th, 2017, 7:46 pm
...
Now for some design issues. The first is the armor belt which doesn't extends to the ship's ends, thus leaving the magazines of both end guns exposed and unprotected.
Does that matter when the guns are single hand loaded mounts as the hoists are not going to be directly under them but could be behind them in the superstructure?
Author:  matedow [ November 6th, 2017, 11:13 am ]
Post subject:  Re: Personal Design - Derry-class CA
[ img ]

Second version:
Removed doubled up black lines on the steam release lines on the forward side of the stacks

Changed black lines on the foundations for the stacks to shaded gray

Eliminated doubling up on rigging and main deck
Author:  matedow [ November 6th, 2017, 11:17 am ]
Post subject:  Re: Personal Design - Derry-class CA
Rodondo wrote: *November 5th, 2017, 12:13 am
Welcome aboard! :)

Nice long range foreign station cruiser, design wise is all very agreeable, styling your'e almost there, the hull seems to lack some shading (especially the stern) also you need to cut out the double black lines which give it a heavy appearance.
Made the changes to the stacks for the doubled up black lines. The only remaining ones that I could find were the doublers at the base of the bits.

I couldn't find an example of shading for the stern on existing designs. I assume you are referring to highlighting on the upper side?
Quote:
Aside for that a very strong start
Thank you
Author:  matedow [ November 6th, 2017, 12:45 pm ]
Post subject:  Re: Personal Design - Derry-class CA
Novice wrote: *November 5th, 2017, 7:46 pm
Welcome to SB Matedow.
This is a very well executed first drawing, but it has some issues IMHO.
SB style wise first: the credits appear to be not in Arial, or to be slightly larger than they should Ship's name and class usually go on the first line,and artist's name in parentheses like so (Matedow). If you used some other artist's work his name goes first (Karle 94, Matedow). You don't need to specify which part you took on the drawing itself (most artists here will recognize their work). Here as far as the credits I think you don't need to add Karle94's name if you used only the mast. Most parts are free to use by all other artists without crediting, with credits only for complete hull, or entire superstructure for instance.
The font was Ariel Narrow 14pt.

I also fixed the leading parentheses on the credit. I have Karle94's credit for the moment because I do feel that I stole it whole cloth from the Tillman drawing, and left the foremast reference because of drawing attention to it. I will probably remove that part in a future version. I have also changed the font to a regular Ariel in a 12 pt. Hopefully the size and the font look more correct now.
Quote:
Now for some design issues. The first is the armor belt which doesn't extends to the ship's ends, thus leaving the magazines of both end guns exposed and unprotected.
The hoists for the forwardmost and aftermost 7" guns would be in the superstructure, and would put the magazines in an area protected by the main belt. If you look at a drawing of the Northampton-class you will see that the main belt only appears to cover the engine rooms. This tends to make me comfortable with the choice, but thank you for taking the time to give feedback, I really appreciate it.
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