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1

Thursday, February 16th 2012, 12:01am

Cruiser Ligero Antiaérea

Sometime in the next decade, Chile's four ex-Atlantean flak cruisers will run out of lifespan and require replacement. I'm pondering what sort of ship I'd build to replace them, and this design represents what I feel is my "minimalist" design. As these ships would likely be in company with much more heavily-armed consorts, they're armed and armoured appropriate to their role, rather than trying to take all comers.

Thoughts?

Quoted

[SIZE=3]CLAA-44, Chilean Cruiser Ligero Antiaérea laid down 1944[/SIZE]

Displacement:
4,684 t light; 5,051 t standard; 5,688 t normal; 6,197 t full load

Dimensions: Length overall / water x beam x draught
496.01 ft / 480.00 ft x 48.00 ft x 18.00 ft (normal load)
151.18 m / 146.30 m x 14.63 m x 5.49 m

Armament:
8 - 5.12" / 130 mm guns (4x2 guns), 67.03lbs / 30.41kg shells, 1944 Model
Automatic rapid fire guns in deck mounts with hoists
on centreline ends, evenly spread, 2 raised mounts - superfiring
16 - 1.57" / 40.0 mm guns (4x4 guns), 1.95lbs / 0.89kg shells, 1944 Model
Anti-aircraft guns in deck mounts with hoists
on side, all amidships, all raised mounts - superfiring
16 - 1.10" / 27.9 mm guns (4x4 guns), 0.67lbs / 0.30kg shells, 1944 Model
Anti-aircraft guns in deck mounts
on side, evenly spread, all raised mounts
Weight of broadside 578 lbs / 262 kg
Shells per gun, main battery: 750
12 - 21.0" / 533.4 mm above water torpedoes

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 1.57" / 40 mm 377.30 ft / 115.00 m 9.19 ft / 2.80 m
Ends: Unarmoured
Main Belt covers 121 % of normal length

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 1.18" / 30 mm 0.59" / 15 mm 0.59" / 15 mm
2nd: 0.59" / 15 mm 0.39" / 10 mm -
3rd: 0.59" / 15 mm 0.39" / 10 mm -

- Armour deck: 0.79" / 20 mm, Conning tower: 1.57" / 40 mm

Machinery:
Oil fired boilers, steam turbines plus diesel motors,
Geared drive, 2 shafts, 62,670 shp / 46,752 Kw = 33.00 kts
Range 5,500nm at 18.00 kts
Bunker at max displacement = 1,147 tons

Complement:
326 - 425

Cost:
£3.094 million / $12.377 million

Distribution of weights at normal displacement:
Armament: 86 tons, 1.5 %
Armour: 489 tons, 8.6 %
- Belts: 221 tons, 3.9 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 30 tons, 0.5 %
- Armour Deck: 228 tons, 4.0 %
- Conning Tower: 11 tons, 0.2 %
Machinery: 1,600 tons, 28.1 %
Hull, fittings & equipment: 2,258 tons, 39.7 %
Fuel, ammunition & stores: 1,004 tons, 17.7 %
Miscellaneous weights: 250 tons, 4.4 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
6,039 lbs / 2,739 Kg = 90.1 x 5.1 " / 130 mm shells or 1.0 torpedoes
Stability (Unstable if below 1.00): 1.15
Metacentric height 2.1 ft / 0.7 m
Roll period: 13.8 seconds
Steadiness - As gun platform (Average = 50 %): 62 %
- Recoil effect (Restricted arc if above 1.00): 0.38
Seaboat quality (Average = 1.00): 1.14

Hull form characteristics:
Hull has rise forward of midbreak
and transom stern
Block coefficient: 0.480
Length to Beam Ratio: 10.00 : 1
'Natural speed' for length: 25.06 kts
Power going to wave formation at top speed: 62 %
Trim (Max stability = 0, Max steadiness = 100): 54
Bow angle (Positive = bow angles forward): 30.00 degrees
Stern overhang: 1.00 ft / 0.30 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 26.00 ft / 7.92 m
- Forecastle (20 %): 24.00 ft / 7.32 m
- Mid (55 %): 22.00 ft / 6.71 m (14.00 ft / 4.27 m aft of break)
- Quarterdeck (15 %): 14.00 ft / 4.27 m
- Stern: 14.00 ft / 4.27 m
- Average freeboard: 19.31 ft / 5.89 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 111.6 %
- Above water (accommodation/working, high = better): 110.6 %
Waterplane Area: 15,673 Square feet or 1,456 Square metres
Displacement factor (Displacement / loading): 123 %
Structure weight / hull surface area: 79 lbs/sq ft or 387 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.90
- Longitudinal: 2.36
- Overall: 1.00
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is adequate

2

Thursday, February 16th 2012, 12:32am

Overall, I like the design. While somewhat on the small side, it is well armed and, given the miscellaneous weight in the design, can probably carry radar and fire control sufficient to engage two targets at a time with controlled fire. This is not bad on 4700 tons.

Given their AA role, the torpedo armament seems a tad excessive; it would make more sense for a flotilla cruiser - which the design could be readily adapted for. The only possible technical quibble would be the mount and hoist for the 40mm guns, versus a straight deck mount; and you may have reasons for that.

3

Thursday, February 16th 2012, 12:45am

Personally, I think a lot of folks, beyond you and I, have difficult choices to make between quantity and quality as we start replacing Cleito-era ships. This is one of those cases. Does Chile need dedicated AA cruisers, or is it better off investing in fewer, but larger and more rounded, light cruisers?

That being the case, I don't care for this design's protection. It seems sparse and ineffective. Either it needs to be more extensive, or it should go.

4

Thursday, February 16th 2012, 2:40pm

It fills a niche between a very low-end traditional CL and an oversized DDL.
It's affordable for sure and offers a decent package. The torpedoes give it a multi-role use, if it didn't have them then it would be rather weak with just 8x130mm and LAA.
I tend to agree with Rocky on the armour, its fine for splinter protection but if these run up against a surface fleet they won't last much longer than destroyers, yet given their role, are much less easy to replace. Protecting against bombs on a hull this small is impossible so there's not much point in beefing the decks too much. More armour is probably going to add another 800-900 tons. Like everything its a balacing act, but if Brock feels splinter protection is enough for these ships then it looks good.

Kaiser Kirk

Lightbringer and former European Imperialist

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5

Thursday, February 16th 2012, 4:37pm

I'd think that for a ship meant to shoot small fast moving targets out of the air, the best gun platform you can get in terms of seaworthiness would be desirable.

6

Thursday, February 16th 2012, 7:47pm

Parroting Kirk here, I think a purpose built AA cruiser needs to be an excellent sea boat and gun platform. That said, I really like this design, since she's more than a match for all but the ~10,000 light cruisers (my fault).

7

Friday, February 17th 2012, 4:22am

Thanks for the comments; much appreciated.

After giving this some thought, I think Rocky and Hood both made a key point: if you're going to spend tonnage on protection, make it effective or don't bother at all.