Next generation escort cruiser?

[Valles]

Passage, Maoria Escort Cruiser laid down 1913 (Engine 1912)

Displacement:
   6,628 t light; 6,849 t standard; 8,329 t normal; 9,512 t full load

Dimensions: Length overall / water x beam x draught
   389.96 ft / 380.58 ft x 32.81 ft (Bulges 52.49 ft) x 24.61 ft (normal load)
   118.86 m / 116.00 m x 10.00 m (Bulges 16.00 m)  x 7.50 m

Armament:
      5 - 5.91" / 150 mm guns in single mounts, 102.98lbs / 46.71kg shells, 1913 Model
     Quick firing guns in deck mounts with hoists
     on centreline, evenly spread, 3 raised mounts
      8 - 2.95" / 75.0 mm guns in single mounts, 12.87lbs / 5.84kg shells, 1913 Model
     Quick firing guns in casemate mounts
     on side ends, evenly spread
   Weight of broadside 618 lbs / 280 kg
   Shells per gun, main battery: 150

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   7.87" / 200 mm   266.40 ft / 81.20 m   13.12 ft / 4.00 m
   Ends:   3.94" / 100 mm   114.14 ft / 34.79 m   13.12 ft / 4.00 m
   Upper:   1.97" / 50 mm   380.58 ft / 116.00 m   6.56 ft / 2.00 m
     Main Belt covers 108 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.98" / 25 mm   0.12" / 3 mm      0.12" / 3 mm
   2nd:   0.39" / 10 mm         -               -

   - Armour deck: 1.57" / 40 mm, Conning tower: 7.87" / 200 mm

Machinery:
   Oil fired boilers, steam turbines,
   Electric motors, 2 shafts, 43,163 shp / 32,200 Kw = 26.00 kts
   Range 10,000nm at 14.00 kts
   Bunker at max displacement = 2,663 tons

Complement:
   435 - 566

Cost:
   £0.587 million / $2.347 million

Distribution of weights at normal displacement:
   Armament: 77 tons, 0.9 %
   Armour: 1,872 tons, 22.5 %
      - Belts: 1,524 tons, 18.3 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 14 tons, 0.2 %
      - Armour Deck: 264 tons, 3.2 %
      - Conning Tower: 70 tons, 0.8 %
   Machinery: 1,721 tons, 20.7 %
   Hull, fittings & equipment: 2,208 tons, 26.5 %
   Fuel, ammunition & stores: 1,700 tons, 20.4 %
   Miscellaneous weights: 750 tons, 9.0 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     8,456 lbs / 3,836 Kg = 82.1 x 5.9 " / 150 mm shells or 1.5 torpedoes
   Stability (Unstable if below 1.00): 1.14
   Metacentric height 1.2 ft / 0.4 m
   Roll period: 20.2 seconds
   Steadiness   - As gun platform (Average = 50 %): 71 %
         - Recoil effect (Restricted arc if above 1.00): 0.28
   Seaboat quality  (Average = 1.00): 1.73

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.593
   Length to Beam Ratio: 7.25 : 1
   'Natural speed' for length: 19.51 kts
   Power going to wave formation at top speed: 65 %
   Trim (Max stability = 0, Max steadiness = 100): 41
   Bow angle (Positive = bow angles forward): 7.00 degrees
   Stern overhang: 6.56 ft / 2.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      22.97 ft / 7.00 m
      - Forecastle (15 %):   19.69 ft / 6.00 m
      - Mid (50 %):      19.69 ft / 6.00 m
      - Quarterdeck (15 %):   19.69 ft / 6.00 m
      - Stern:      19.69 ft / 6.00 m
      - Average freeboard:   19.88 ft / 6.06 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 84.7 %
      - Above water (accommodation/working, high = better): 78.2 %
   Waterplane Area: 9,073 Square feet or 843 Square metres
   Displacement factor (Displacement / loading): 125 %
   Structure weight / hull surface area: 77 lbs/sq ft or 375 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.84
      - Longitudinal: 5.22
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is adequate
   Room for accommodation and workspaces is cramped
   Ship has slow, easy roll, a good, steady gun platform
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

25 tons boat lifts
25 tons long-range wireless
100 tons spare parts and torpedo storage
6x 100 ton Torpedo Boats

Ships of the class are to have names like Quick Passage, Fortunate Passage, Dutiful Passage, etc.

As their designation implies, this class is mostly meant to swat - and be immune to - destroyers and torpedo boats. Details on those of the latter class carried will have to wait, but my mental sketch notes - the issued requirement, so to speak - for this type's spawn is to carry two torpedoes to at least 30 knots in up to sea state five. The 'tumblehome' hull plan is actually a reflection of the way the boats are carried - they're three to a side, with their keels about lined up with the ship's waterline.

[The Rock Doctor]

How big is a 100 t torpedo-boat?

I think I'd like to see a sketch of the concept, please.

[Valles]

About 30m long by 5m beam by 1.5m draft; I figured it was better to guess 'large' than run out of room.

And I'm working on it now. ^_^

[The Rock Doctor]

I'll look forward to it.

[Valles]

An in-progress sketch. The 'working deck' is about halfway up the hull from the waterline.

[Jefgte]

Are you sure that the place for the 100t torpedo boats is the best ?

Imagine the cruiser in a heavy sea or a storm ...

Your 100t torpedo boats are going to be damage or ...lost.  :(

Better place is probably in the stern... Remember the design of the aviso Saranda class


Just a remark... you made what you want...


Jef  ;)

[Borys]

Maybe we could assign some weight for cranes and/or strenghtening of ship to carry such unusual cargo?
Borys

[Valles]

Better place is probably in the stern... Remember the design of the aviso Saranda class

I do, and I agree, but I figured that I'd save myself the shrieking fit when the purists saw a well deck or quasi-transom this early.

Maybe we could assign some weight for cranes and/or strenghtening of ship to carry such unusual cargo?

I'm more concerned with upping the performance of the boats than shaving weight off of their motherships. About how much would you consider reasonable?

[Borys]

Ahoj!
I'll pluck a figure from thin air :)
How about a 4:1 ratio - i.e. every 10 tonnes of carried attack boats generates 2,5 tonnes of structure reinforcement/ unusaul add-ons.
This is pure speculation, mind you.

Borys 

[P3D]

Better place is probably in the stern... Remember the design of the aviso Saranda class

I do, and I agree, but I figured that I'd save myself the shrieking fit when the purists saw a well deck or quasi-transom this early.

Actually, Orange has a 'TB carrier' with an almost well deck - a 'slip' in the stern that allows boats to be lowered in the water, TBs that are pretty similar to what you have.
SS2 assumes that you have internal armor with the bulges. Simming with full 16m beam (without bulges) would be more accurate, if the armor is external.

http://www.navalism.org/index.php?topic=337.0

[The Rock Doctor]

I'd be thinking at least a 1:1 ratio between crane and boat.  Suspending that much weight from above is going require a very sturdy structure.

I'd also want to see accommodations set aside for the boat crews.

I agree with Jef on the problems of wave action with the suspended craft - the bow wave may also be a problem for the foremost units.

I'd be curious to know how you'd operate the vessel(s):  do you intend for the TBs to launch and recover underway, or at rest?

On the whole, I don't see what this can do that a 4,000 t cruiser and three mid-sized destroyers can't.

[Valles]

These TBs would be deliberately and utterly expendable - I figure, five to eight crewmen, total. Coxswain, commander, an engineer or two, and a crew for a small gun or something. No damage control, no long-term accommodations. Any pretense of long-range ability they might make would be an artifact of a cultural heritage of crossing oceans in glorified canoes, like a sail and a steppable aluminum mast.

I think that a cruiser-sized vessel can manage to spare thirty men or so.

The original design spec would call for underway, certainly. At rest might have to be settled for.

In terms of actual abilities, there's no real advantage, at least assuming that I can't yet build forty to fifty knot planing boats. But building thirty-knot destroyers with the handling characteristics I consider prerequisite for the seas to Maoria's south is, at the least and pardon my language, a stone cold bitch. Not worth the headaches on my part and not worth the man-hours and development time that the Maori would have to put into designing and building them.

Also, in a situation where they end up getting expended - which, for an unarmored fighting vessel, is inevitable - I'm down thirty crewmen and six hundred tons of material rather than three hundred and three thousand.

Regardless, now that I know there won't be screaming tantrums over a fantail design, I'm going to go back to the drawing board and go with that. Stay tuned!

[P3D]

100t TBs require more than 8 crew members. 8-9 in enough for a MTB (MAS) but not a steam turbine powered boat.

WWII:A 60t S-boot needed a crew of 12. A 100t one needed ~25 - that's with diesel engines.
The 1885 TB (similar size) 16-20.

[maddox]

These TBs would be deliberately and utterly expendable - I figure, five to eight crewmen, total. Coxswain, commander, an engineer or two, and a crew for a small gun or something. No damage control, no long-term accommodations. Any pretense of long-range ability they might make would be an artifact of a cultural heritage of crossing oceans in glorified canoes, like a sail and a steppable aluminum mast.

Make that a wooden mast- like the MK barges have. Aluminium is still hidiously expensive compared to any other useable material, and the lack of good alloys, nor corrosion protection. But that's only "story line info".

I'd be thinking at least a 1:1 ratio between crane and boat.  Suspending that much weight from above is going require a very sturdy structure.

And then you're very generous Rocky.  

[Borys]

The German 150 tonne boats for Flanders had crews of 28. With VTE though.
Borys