Cost Patrol Cruiser - or how to increase seakeeping?

[P3D]

As it would have more than 80t military weight (560t misc) definitely not civilian.

[miketr]

Why do you need the high speed for a patrol ship?  My big patrol cruiser came out at 2,200 tons light displacement with a speed of 22.5 knots.

[Guinness]

The rule on mercantile construction as it is today:

Mercantile Standards/Auxiliaries

A ship in government service may be built to mercantile standards if armament and armor take up no more than 2% of the ship's weight at normal displacement.  Such ships could include colliers, transports, survey ships, and others.

Tenders, as described below, can not be built to mercantile standards

In this case, the cash and BP cost of construction is quartered.  This also pertains to upkeep, future repair, refit, and scrapping of the vessel.  The time required to build, refit, repair, or scrap the ship remains unchanged, however.

Moderators have may require a ship to be built to normal military standards if they believe that the intent of a design is to produce a cheap warship.

I've been sort of sitting on the sidelines on this one to wait to see what develops, but: To me this ship as it is now would fall under that last clause; it looks like the design is meant to produce a cheap warship.

Very few civilian ships, even liners, ever made 29 knots. Those that ever did approach that speed were much larger liners. I think building a ship of these capabilities would require full military construction techniques.

[maddox]

I agree with Guinness.  This ain't buildable with civilian building practises.  
The only civilian ships with such an amount of engine are tugs and icebreakers.

Tugs don't race around at 29 kts.
And icebreakers arguably, are build to military standard with 2-5" of  hull plating.

Oh well, if France would be "military cash deficient" and in need for a coastal defence cruiser, a small merchant would be converted.

This is the result.
The draught and freeboard are not as what the merchant vessel would see as usable. But for military use, the plimsol marks are just placed differently.
In her full merchant outfit she's a bog standard 4000 long ton vessel (SS is still lousy in simming merchants) .

Soldes, French CC CL laid down 1919 (Engine 1916)

Displacement:
   2.736 t light; 2.856 t standard; 3.406 t normal; 3.846 t full load

Dimensions: Length overall / water x beam x draught
   393,70 ft / 390,42 ft x 52,49 ft x 9,84 ft (normal load)
   120,00 m / 119,00 m x 16,00 m  x 3,00 m

Armament:
      5 - 5,51" / 140 mm guns in single mounts, 92,59lbs / 42,00kg shells, 1919 Model
     Quick firing guns in deck mounts with hoists
     on centreline, evenly spread, 2 raised mounts
      4 - 1,46" / 37,0 mm guns in single mounts, 1,55lbs / 0,70kg shells, 1919 Model
     Anti-aircraft guns in deck mounts
     on side, all amidships
   Weight of broadside 469 lbs / 213 kg
   Shells per gun, main battery: 200

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0,75" / 19 mm   0,50" / 13 mm            -
   2nd:   0,50" / 13 mm   0,50" / 13 mm            -

Machinery:
   Coal fired boilers, complex reciprocating steam engines,
   Direct drive, 2 shafts, 4.847 ihp / 3.616 Kw = 17,00 kts
   Range 6.000nm at 12,00 kts
   Bunker at max displacement = 990 tons (100% coal)

Complement:
   222 - 289

Cost:
   £0,403 million / $1,612 million

Distribution of weights at normal displacement:
   Armament: 53 tons, 1,6%
   Armour: 15 tons, 0,4%
      - Belts: 0 tons, 0,0%
      - Torpedo bulkhead: 0 tons, 0,0%
      - Armament: 15 tons, 0,4%
      - Armour Deck: 0 tons, 0,0%
      - Conning Tower: 0 tons, 0,0%
   Machinery: 317 tons, 9,3%
   Hull, fittings & equipment: 1.351 tons, 39,7%
   Fuel, ammunition & stores: 671 tons, 19,7%
   Miscellaneous weights: 1.000 tons, 29,4%

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     6.755 lbs / 3.064 Kg = 80,7 x 5,5 " / 140 mm shells or 1,6 torpedoes
   Stability (Unstable if below 1.00): 1,20
   Metacentric height 2,7 ft / 0,8 m
   Roll period: 13,5 seconds
   Steadiness   - As gun platform (Average = 50 %): 75 %
         - Recoil effect (Restricted arc if above 1.00): 0,21
   Seaboat quality  (Average = 1.00): 1,49

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0,591
   Length to Beam Ratio: 7,44 : 1
   'Natural speed' for length: 19,76 kts
   Power going to wave formation at top speed: 37 %
   Trim (Max stability = 0, Max steadiness = 100): 50
   Bow angle (Positive = bow angles forward): -5,00 degrees
   Stern overhang: 3,28 ft / 1,00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      21,72 ft / 6,62 m
      - Forecastle (20%):   13,85 ft / 4,22 m
      - Mid (50%):      13,85 ft / 4,22 m
      - Quarterdeck (15%):   13,85 ft / 4,22 m
      - Stern:      13,85 ft / 4,22 m
      - Average freeboard:   14,48 ft / 4,41 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 75,3%
      - Above water (accommodation/working, high = better): 176,6%
   Waterplane Area: 14.864 Square feet or 1.381 Square metres
   Displacement factor (Displacement / loading): 164%
   Structure weight / hull surface area: 68 lbs/sq ft or 330 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0,98
      - Longitudinal: 1,26
      - Overall: 1,00
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is excellent
   Ship has slow, easy roll, a good, steady gun platform
   Good seaboat, rides out heavy weather easily

Weathershielded gun mounts

ERADe equipment
Long range marconi
50 tons undesignated.

900 tons left over on misc weight is the "left over" from the humble merchant design
The holds can be filled with about anything, but the French sailors have comfort in mind.

[Nobody]

Well that's not completely unexpected, but allow me a question: What kind of ship is the coast guard/water police/customs supposed to have that's capable of "catching" a ocean liner like the Mauretania/Lusitania or this, those, these or that?
It's not so easy to design a fast small ship with 1.0 composite strength and good seakeeping that can still carry a least a gun and bit of equipment - that's why I started with a big one.


How is this?
Smaller, less armament, fewer ammo, lower speed and range. Also older engine to represent it's civilian origin.

Coast Patrol Cruiser 3, Orange Sloop laid down 1920 (Engine 1916)

Displacement:
   2.400 t light; 2.473 t standard; 2.599 t normal; 2.701 t full load

Dimensions: Length overall / water x beam x draught
   367,45 ft / 367,45 ft x 45,93 ft x 11,02 ft (normal load)
   112,00 m / 112,00 m x 14,00 m  x 3,36 m

Armament:
      2 - 6,00" / 152 mm guns in single mounts, 105,82lbs / 48,00kg shells, 1920 Model
     Breech loading guns in deck mounts with hoists
     on centreline ends, evenly spread
      2 - 3,46" / 88,0 mm guns in single mounts, 20,79lbs / 9,43kg shells, 1920 Model
     Quick firing guns in deck mounts
     on centreline ends, evenly spread, all raised mounts
      2 - 1,00" / 25,4 mm guns in single mounts, 0,50lbs / 0,23kg shells, 1920 Model
     Anti-aircraft guns in deck mounts
     on side, all aft
      2 - 0,50" / 12,7 mm guns in single mounts, 0,06lbs / 0,03kg shells, 1920 Model
     Machine guns in deck mounts
     on side, all forward
   Weight of broadside 254 lbs / 115 kg
   Shells per gun, main battery: 140

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0,79" / 20 mm   0,39" / 10 mm      0,79" / 20 mm
   2nd:   0,39" / 10 mm         -               -

   - Conning tower: 1,18" / 30 mm

Machinery:
   Oil fired boilers, steam turbines,
   Electric motors, 2 shafts, 20.002 shp / 14.921 Kw = 26,00 kts
   Range 560nm at 22,00 kts
       340 nm @ 26 kn
       560 nm @ 22 kn
       980 nm @ 18 kn
      1570 nm @ 15 kn
      2670 nm @ 12 kn
   Bunker at max displacement = 228 tons

Complement:
   181 - 236

Cost:
   £0,509 million / $2,037 million

Distribution of weights at normal displacement:
   Armament: 32 tons, 1,2%
   Armour: 12 tons, 0,5%
      - Belts: 0 tons, 0,0%
      - Torpedo bulkhead: 0 tons, 0,0%
      - Armament: 7 tons, 0,3%
      - Armour Deck: 0 tons, 0,0%
      - Conning Tower: 5 tons, 0,2%
   Machinery: 745 tons, 28,7%
   Hull, fittings & equipment: 1.141 tons, 43,9%
   Fuel, ammunition & stores: 200 tons, 7,7%
   Miscellaneous weights: 470 tons, 18,1%
       25 t Radar
       25 t night equipment
       50 t FC
       25 t long range radio
       20 t medical facility
        5 t customs office
       20 t command facility
      300 t reinforced structure and bulkheads

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     2.730 lbs / 1.238 Kg = 25,3 x 6,0 " / 152 mm shells or 0,7 torpedoes
   Stability (Unstable if below 1.00): 1,14
   Metacentric height 2,0 ft / 0,6 m
   Roll period: 13,7 seconds
   Steadiness   - As gun platform (Average = 50 %): 62 %
         - Recoil effect (Restricted arc if above 1.00): 0,17
   Seaboat quality  (Average = 1.00): 1,25

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0,489
   Length to Beam Ratio: 8,00 : 1
   'Natural speed' for length: 19,17 kts
   Power going to wave formation at top speed: 58 %
   Trim (Max stability = 0, Max steadiness = 100): 50
   Bow angle (Positive = bow angles forward): 0,00 degrees
   Stern overhang: 0,00 ft / 0,00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      22,31 ft / 6,80 m
      - Forecastle (20%):   20,67 ft / 6,30 m
      - Mid (42%):      20,34 ft / 6,20 m (13,12 ft / 4,00 m aft of break)
      - Quarterdeck (15%):   13,78 ft / 4,20 m
      - Stern:      15,75 ft / 4,80 m
      - Average freeboard:   16,77 ft / 5,11 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 122,2%
      - Above water (accommodation/working, high = better): 185,6%
   Waterplane Area: 11.134 Square feet or 1.034 Square metres
   Displacement factor (Displacement / loading): 117%
   Structure weight / hull surface area: 64 lbs/sq ft or 314 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0,91
      - Longitudinal: 2,31
      - Overall: 1,00
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is excellent
   Good seaboat, rides out heavy weather easily

[ctwaterman]

To Catch one of these those or this...

You use a real Protected Cruiser maybe even more then one.   Or an Armored Cruiser.

If none of your PC or AC can go 25 knots well then its time to design one that can.

Charles

[Borys]

Well that's not completely unexpected, but allow me a question: What kind of ship is the coast guard/water police/customs supposed to have that's capable of "catching" a ocean liner like the Mauretania/Lusitania or this, those, these or that?

I believe that it is not the job of the Coast Guard to catch such ships, as:
- such fast passanger ships are not so numerous, and very rarely up to no-good;
- 99% of ships which the CG will be chasing will be VTE engined freighters or fishing vessels (the fast ones making 12 knots, 8-9 being the norm)
- if some fast odd-ball is heading toowards the horizon at a higher speed than the CG vessel, then they call in the Navy;

Borys

[maddox]

If such a fast large, expensive  liner doesn't "yield" to official demands,  it's time to open a can of Whoopass.

In other words, when a liner doesn't slow down to official demands, get the fleet out and the coast guard out of the way as there is something a lot larger going on.

[Sachmle]

As an example here is the Brandenburg Coast Guard:

4 of these
30 some odd of these
and 12 of these

[TexanCowboy]

Whoopass? You didn't dare just make post this...http://uncyclopedia.wikia.com/wiki/List_of_weapons_that_don%27t_exist%2C_but_should#55_Gallon_Drum_of_Whoop-Ass