Just tinkering...

[The Rock Doctor]

I was playing with this.  I envision it as a gunship to patrol against pirates and armed merchantmen functioning as raiders.  Decent firepower and survivability, but half the cost of a protected cruiser on account of the reduced speed. 

I could use older protected cruisers for the role in a coastal role - on account of the shorter range and lower freeboard - but they wouldn't be suitable for the role on an open-ocean setting.

Enter ship name, Enter country Enter ship type laid down 1916

Displacement:
   2,487 t light; 2,585 t standard; 2,951 t normal; 3,244 t full load

Dimensions: Length overall / water x beam x draught
   390.78 ft / 387.14 ft x 42.98 ft x 14.11 ft (normal load)
   119.11 m / 118.00 m x 13.10 m  x 4.30 m

Armament:
      4 - 5.51" / 140 mm guns in single mounts, 83.72lbs / 37.98kg shells, 1916 Model
     Breech loading guns in deck mounts with hoists
     on centreline ends, evenly spread, 2 raised mounts - superfiring
      1 - 2.56" / 65.0 mm guns in single mounts, 8.38lbs / 3.80kg shells, 1916 Model
     Breech loading anti-airship gun in deck mount
     on side amidships, 1 raised gun
      4 - 0.31" / 8.0 mm guns in single mounts, 0.02lbs / 0.01kg shells, 1916 Model
     Machine guns in deck mounts
     on side, evenly spread
   Weight of broadside 343 lbs / 156 kg
   Shells per gun, main battery: 200
   6 - 21.0" / 533 mm above water torpedoes

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   2.95" / 75 mm   229.66 ft / 70.00 m   11.48 ft / 3.50 m
   Ends:   0.98" / 25 mm   157.48 ft / 48.00 m   11.48 ft / 3.50 m
     Main Belt covers 91 % of normal length

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

   - Armour deck: 0.98" / 25 mm, Conning tower: 2.95" / 75 mm

Machinery:
   Coal and oil fired boilers, steam turbines,
   Direct drive, 2 shafts, 14,000 shp / 10,444 Kw = 23.73 kts
   Range 10,000nm at 10.00 kts (Bunkerage = 659 tons)

Complement:
   199 - 260

Cost:
   £0.326 million / $1.304 million

Distribution of weights at normal displacement:
   Armament: 43 tons, 1.5 %
   Armour: 616 tons, 20.9 %
      - Belts: 397 tons, 13.5 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 15 tons, 0.5 %
      - Armour Deck: 192 tons, 6.5 %
      - Conning Tower: 13 tons, 0.4 %
   Machinery: 544 tons, 18.4 %
   Hull, fittings & equipment: 1,113 tons, 37.7 %
   Fuel, ammunition & stores: 464 tons, 15.7 %
   Miscellaneous weights: 171 tons, 5.8 %
-100 t:  Fire Control
-25 t:  LR Wireless
-25 t:  Flag facilities
-21 t:  What-nots and thingamajiggers.

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     4,890 lbs / 2,218 Kg = 58.4 x 5.5 " / 140 mm shells or 1.3 torpedoes
   Stability (Unstable if below 1.00): 1.21
   Metacentric height 2.0 ft / 0.6 m
   Roll period: 12.8 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.27
   Seaboat quality  (Average = 1.00): 1.42

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.440
   Length to Beam Ratio: 9.01 : 1
   'Natural speed' for length: 19.68 kts
   Power going to wave formation at top speed: 50 %
   Trim (Max stability = 0, Max steadiness = 100): 49
   Bow angle (Positive = bow angles forward): 10.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      20.67 ft / 6.30 m
      - Forecastle (20 %):   17.72 ft / 5.40 m
      - Mid (50 %):      17.72 ft / 5.40 m (9.84 ft / 3.00 m aft of break)
      - Quarterdeck (15 %):   9.84 ft / 3.00 m
      - Stern:      9.84 ft / 3.00 m
      - Average freeboard:   14.02 ft / 4.27 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 78.4 %
      - Above water (accommodation/working, high = better): 102.1 %
   Waterplane Area: 10,529 Square feet or 978 Square metres
   Displacement factor (Displacement / loading): 133 %
   Structure weight / hull surface area: 66 lbs/sq ft or 320 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.95
      - Longitudinal: 1.53
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is adequate
   Ship has slow, easy roll, a good, steady gun platform
   Good seaboat, rides out heavy weather easily

[Guinness]

So it's basically an Aviso then?

[The Rock Doctor]

More or less.

[Guinness]

Interesting. It would be hard for me to resist just building a cruiser. I can see the need if you want to be many places at once. It's still fast enough to run down the reasonably large numbers of obsolete Confederate cruisers and frigates you might expect to see chewing on your shipping too.

If it were me, I'd consider shipping a few mines too. This ship might be just as useful as a raider (especially prepositioned somewhere in your Pacific island holdings). A string of mines laid one night off certain enemy ports might just sink a couple of ships, and tie up the enemy's resources. A torpedo or two might not be a bad idea either, just in case you have to try to deter a surprise opponent that gets too close, or dispatch a big prize in a hurry.

The thing about open ocean raiders (and their antidotes) is that they can be force multipliers. A few can cause the enemy to spend resources trying to find them and kill them, or it forces him to convoy his merchant traffic, etc. One can spend the money on making their raiders impervious to interception, or just put enough of them afloat that it can be afforded to lose a few. You really only need to make them strong enough and fast enough that your enemy has to spend his first-line cruiser resources to combat them.

So, for instance, build 6 of these at the cost of 3 light cruisers, and you'll force me (just for instance) to tie up probably 12 of my first line cruisers to try to catch them. That's a pretty good deal.

Of course, I could do the same thing...

[The Rock Doctor]

The temptation to build a cruiser would be hard to resist.  I'm leery of building cheap warships that can't do that job of a more expensive one well.

I had thought about mines; there's a bit of room left over, or I could just bump the tonnage up a bit to add another 50 t of miscellaneous weight.

Truth be told, though, I view this more as a defensive platform than an offensive one, but it'd be amusing for us to have a war in which our battlefleets are stuck at home for lack of suitable screening units.

[Guinness]

It does make me understand the seemingly ludicrous number of cruisers the USN said it needed at the end of WW1.

[The Rock Doctor]

They and me both...