Going into 1939, the next tranche of Offshore Patrol Vessel is due.  This one will be bigger, as being able to do more escort work, and in the late 30s having subs that can run 22kts on the surface being a possibility......a faster and more capable escort needs to be put to use.  This type will also be much more useful for patrol work in the Pacific, and are better protected and more capable as well as testing the new 20mm rotary AA gun.

OPV-39, Aztec Offshore Patrol Vessel laid down 1939

Displacement:
   1,341 t light; 1,401 t standard; 1,581 t normal; 1,725 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (313.77 ft / 308.40 ft) x 33.14 ft x (10.83 / 11.56 ft)
   (95.64 m / 94.00 m) x 10.10 m  x (3.30 / 3.52 m)

Armament:
      4 - 3.54" / 90.0 mm 55.0 cal guns - 24.01lbs / 10.89kg shells, 400 per gun
     Dual purpose guns in deck mounts, 1939 Model
     2 x Twin mounts on centreline, forward evenly spread
      1 raised mount
      4 - 1.57" / 40.0 mm 50.0 cal guns - 2.07lbs / 0.94kg shells, 1,000 per gun
     Anti-air guns in deck and hoist mount, 1939 Model
     1 x 4 row quad mount on centreline, aft deck centre
      4 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 2,000 per gun
     Anti-air guns in deck and hoist mount, 1939 Model
     1 x 4 row quad mount on centreline, aft deck centre
      1 raised mount
      6 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 1,500 per gun
     Anti-air guns in deck mounts, 1939 Model
     6 x Single mounts on sides, forward evenly spread
      Weight of broadside 107 lbs / 49 kg

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.06" / 27 mm   1.06" / 27 mm            -
   2nd:   0.79" / 20 mm   0.79" / 20 mm      0.79" / 20 mm
   3rd:   0.79" / 20 mm   0.79" / 20 mm      0.79" / 20 mm

   - Box over machinery & magazines:
   1.06" / 27 mm

   - Conning towers: Forward 1.06" / 27 mm, Aft 0.00" / 0 mm

Machinery:
   Diesel Internal combustion motors,
   Geared drive, 2 shafts, 14,218 shp / 10,606 Kw = 26.00 kts
   Range 5,000nm at 14.00 kts
   Bunker at max displacement = 324 tons

Complement:
   124 - 162

Cost:
   £0.630 million / $2.519 million

Distribution of weights at normal displacement:
   Armament: 23 tons, 1.5 %
      - Guns: 23 tons, 1.5 %
   Armour: 192 tons, 12.2 %
      - Armament: 25 tons, 1.6 %
      - Armour Deck: 165 tons, 10.4 %
      - Conning Tower: 3 tons, 0.2 %
   Machinery: 385 tons, 24.3 %
   Hull, fittings & equipment: 424 tons, 26.8 %
   Fuel, ammunition & stores: 240 tons, 15.2 %
   Miscellaneous weights: 316 tons, 20.0 %
      - Hull below water: 160 tons
      - Hull above water: 10 tons
      - On freeboard deck: 93 tons
      - Above deck: 53 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     1,678 lbs / 761 Kg = 75.4 x 3.5 " / 90 mm shells or 0.7 torpedoes
   Stability (Unstable if below 1.00): 1.15
   Metacentric height 1.2 ft / 0.4 m
   Roll period: 12.5 seconds
   Steadiness   - As gun platform (Average = 50 %): 60 %
         - Recoil effect (Restricted arc if above 1.00): 0.16
   Seaboat quality  (Average = 1.00): 1.02

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and small transom stern
   Block coefficient (normal/deep): 0.500 / 0.511
   Length to Beam Ratio: 9.31 : 1
   'Natural speed' for length: 18.90 kts
   Power going to wave formation at top speed: 62 %
   Trim (Max stability = 0, Max steadiness = 100): 59
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  14.76 ft / 4.50 m,  13.12 ft / 4.00 m
      - Forward deck:   30.00 %,  13.12 ft / 4.00 m,  13.12 ft / 4.00 m
      - Aft deck:   35.00 %,  13.12 ft / 4.00 m,  9.84 ft / 3.00 m
      - Quarter deck:   15.00 %,  9.84 ft / 3.00 m,  9.84 ft / 3.00 m
      - Average freeboard:      12.19 ft / 3.72 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 97.0 %
      - Above water (accommodation/working, high = better): 131.1 %
   Waterplane Area: 6,972 Square feet or 648 Square metres
   Displacement factor (Displacement / loading): 117 %
   Structure weight / hull surface area: 38 lbs/sq ft or 184 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.70
      - Longitudinal: 1.42
      - Overall: 0.75
   Adequate machinery, storage, compartmentation space
   Excellent accommodation and workspace room

135t - Diesel Engines
15t - Enhanced Hydrophones
10t - Sonar

10t - Crew Comfort Improvements (Air Conditioning, recreation space)

25t - Minesweeping Equipment
2t - 2 x Y Throwers
30t - Depth Charges or Mines
12t - 1x3x21in HW TT
24t - 2 x 6t Motor Launches


3t - 1930 FC
25t - LR Radio
25t - NF Devices

Range:  10062nm @ 14kts

A few slight adjustments to the Gulf-class.  No it's not the most efficient design, yes I could cut protection down quite a bit and get her to 10,000t which would mean in 1939 she could be a .9 design.  But I don't really want to chop protection on what I consider a Frigate, which is a ship for independent cruising. 

Gulf-Class, Aztec Frigate laid down 1938

Displacement:
   10,923 t light; 11,598 t standard; 12,804 t normal; 13,768 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (628.44 ft / 620.08 ft) x 71.36 ft x (18.93 / 20.04 ft)
   (191.55 m / 189.00 m) x 21.75 m  x (5.77 / 6.11 m)

Armament:
      12 - 6.10" / 155 mm 55.0 cal guns - 147.20lbs / 66.77kg shells, 300 per gun
     Dual purpose guns in turret on barbette mounts, 1938 Model
     4 x 3-gun mounts on centreline ends, evenly spread
      2 raised mounts - superfiring
      12 - 3.54" / 90.0 mm 55.0 cal guns - 24.01lbs / 10.89kg shells, 400 per gun
     Dual purpose guns in deck mounts, 1938 Model
     6 x Twin mounts on sides, evenly spread
      16 - 1.57" / 40.0 mm 50.0 cal guns - 2.07lbs / 0.94kg shells, 3,000 per gun
     Anti-air guns in deck and hoist mounts, 1938 Model
     2 x 4 row quad mounts on sides, forward deck aft
      2 raised mounts
     2 x 4 row quad mounts on centreline ends, evenly spread
      2 double raised mounts
      20 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 2,000 per gun
     Anti-air guns in deck mounts, 1938 Model
     20 x Single mounts on sides, evenly spread
      Weight of broadside 2,093 lbs / 949 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   4.72" / 120 mm   421.65 ft / 128.52 m   13.12 ft / 4.00 m
   Ends:   1.77" / 45 mm   198.39 ft / 60.47 m   9.84 ft / 3.00 m
     Main Belt covers 105 % of normal length

   - Torpedo Bulkhead - Additional damage containing bulkheads:
      1.18" / 30 mm   421.65 ft / 128.52 m   17.13 ft / 5.22 m
   Beam between torpedo bulkheads 54.13 ft / 16.50 m

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   5.51" / 140 mm   2.99" / 76 mm      4.72" / 120 mm
   2nd:   2.76" / 70 mm   1.57" / 40 mm            -
   3rd:   0.79" / 20 mm   0.79" / 20 mm      0.79" / 20 mm
   4th:   0.59" / 15 mm         -               -

   - Armoured deck - single deck:
   For and Aft decks: 2.44" / 62 mm
   Forecastle: 1.18" / 30 mm  Quarter deck: 1.18" / 30 mm

   - Conning towers: Forward 3.15" / 80 mm, Aft 3.15" / 80 mm

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 77,639 shp / 57,919 Kw = 30.00 kts
   Range 10,000nm at 14.00 kts
   Bunker at max displacement = 2,170 tons

Complement:
   601 - 782

Cost:
   £4.918 million / $19.670 million

Distribution of weights at normal displacement:
   Armament: 621 tons, 4.8 %
      - Guns: 621 tons, 4.8 %
   Armour: 3,405 tons, 26.6 %
      - Belts: 1,210 tons, 9.5 %
      - Torpedo bulkhead: 316 tons, 2.5 %
      - Armament: 537 tons, 4.2 %
      - Armour Deck: 1,269 tons, 9.9 %
      - Conning Towers: 74 tons, 0.6 %
   Machinery: 2,126 tons, 16.6 %
   Hull, fittings & equipment: 4,534 tons, 35.4 %
   Fuel, ammunition & stores: 1,881 tons, 14.7 %
   Miscellaneous weights: 237 tons, 1.9 %
      - Hull above water: 31 tons
      - On freeboard deck: 100 tons
      - Above deck: 106 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     21,598 lbs / 9,797 Kg = 190.1 x 6.1 " / 155 mm shells or 3.7 torpedoes
   Stability (Unstable if below 1.00): 1.11
   Metacentric height 3.7 ft / 1.1 m
   Roll period: 15.6 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.34
   Seaboat quality  (Average = 1.00): 1.06

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.535 / 0.543
   Length to Beam Ratio: 8.69 : 1
   'Natural speed' for length: 24.90 kts
   Power going to wave formation at top speed: 54 %
   Trim (Max stability = 0, Max steadiness = 100): 66
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   18.00 %,  22.97 ft / 7.00 m,  21.33 ft / 6.50 m
      - Forward deck:   30.00 %,  21.33 ft / 6.50 m,  18.04 ft / 5.50 m
      - Aft deck:   38.00 %,  18.04 ft / 5.50 m,  18.04 ft / 5.50 m
      - Quarter deck:   14.00 %,  18.04 ft / 5.50 m,  18.04 ft / 5.50 m
      - Average freeboard:      19.25 ft / 5.87 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 93.7 %
      - Above water (accommodation/working, high = better): 181.1 %
   Waterplane Area: 30,450 Square feet or 2,829 Square metres
   Displacement factor (Displacement / loading): 132 %
   Structure weight / hull surface area: 113 lbs/sq ft or 550 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.99
      - Longitudinal: 1.06
      - Overall: 1.00
   Adequate machinery, storage, compartmentation space
   Excellent accommodation and workspace room
   Ship has slow, easy roll, a good, steady gun platform

40t - 2 x 5 x 21in HW TT on sides aft
60t - 2 x Catapult and 2 x Armed floatplane

25t - LR Wireless
50t - NF Devices x 2
62t - 1918 FC

Quote from: TacCovert4 on April 27, 2025, 04:10:13 PMYou have some points.  Definitely some issues with weights on stuff.  Hmm, I didn't review the difference on weights as much, probably should have developed the 155 with a twin and triple turret instead of a twin m&h.

I tend to put a TDS on stuff, it might not be strictly necessary, but then it's kind of become the norm.  I'll play around with them some more though.

The Gulf's TDS takes it from 2.8 torpedoes to 3.7.  I think that's actually enough to be the difference between a torpedo hit being 'pull out all the stops to save the ship' and 'we need to take her into port but she can finish the immediate fight'.  Or an air dropped torpedo being something that puts the ship immediately in drydock or something that can be partially repaired at an atoll by a salvage ship and pumped out.

On the guns, my 165mm is even heavier, but were managable as unpowered singles,  which is why the Pouseki class still had single mounts .  Another consideration is desired fighting range, Pensacola was expected to fight at long range, where a slow traverse or elevation, would still cover a large arc at range.  For a DP mount, you'd be wanting everything to be fast. Admittedly, RL 6" DP were still unsatisfactory. Parthia tried one, but I figured the 165 as DP was just unworkable. So the 130mm 39kg is my heaviest DP.

On the TDS, on cruisers they can have multiple functions and it would work for those.
Sprung seams from shell/bomb near misses - good. Mine damage- good.
Though honestly a 1m deep system with a flooding bulkhead works for that.

It's the depth of the system that really seems lacking - very shallow inside the hull.
Combine that with a 30mm bulkhead - fairly thin - and I doubt it will work out vs.
an Aerial torpedo. The increase in 'torpedoes' is if it holds.

So, it's certainly a viable choice, and has some merit, but is a very limited system.

All of which made me look at my Bahktiari III class again.
If I dropped it to 30 knots, I could fit in a similar bulkhead, but for me it only moves
it from 2.0 to 2.8 torpedoes, though at 10,000tons and 0.9 hull, it is more stressed to start.
Side effect of prioritizing firepower over toughness with that one.

Quote from: Kaiser Kirk on April 27, 2025, 07:40:12 PM

Quote from: TacCovert4 on April 27, 2025, 04:10:13 PMYou have some points.  Definitely some issues with weights on stuff.  Hmm, I didn't review the difference on weights as much, probably should have developed the 155 with a twin and triple turret instead of a twin m&h.

I tend to put a TDS on stuff, it might not be strictly necessary, but then it's kind of become the norm.  I'll play around with them some more though.

The Gulf's TDS takes it from 2.8 torpedoes to 3.7.  I think that's actually enough to be the difference between a torpedo hit being 'pull out all the stops to save the ship' and 'we need to take her into port but she can finish the immediate fight'.  Or an air dropped torpedo being something that puts the ship immediately in drydock or something that can be partially repaired at an atoll by a salvage ship and pumped out.

On the guns, my 165mm is even heavier, but were managable as unpowered singles,  which is why the Pouseki class still had single mounts .  Another consideration is desired fighting range, Pensacola was expected to fight at long range, where a slow traverse or elevation, would still cover a large arc at range.  For a DP mount, you'd be wanting everything to be fast. Admittedly, RL 6" DP were still unsatisfactory. Parthia tried one, but I figured the 165 as DP was just unworkable. So the 130mm 39kg is my heaviest DP.

On the TDS, on cruisers they can have multiple functions and it would work for those.
Sprung seams from shell/bomb near misses - good. Mine damage- good.
Though honestly a 1m deep system with a flooding bulkhead works for that.

It's the depth of the system that really seems lacking - very shallow inside the hull.
Combine that with a 30mm bulkhead - fairly thin - and I doubt it will work out vs.
an Aerial torpedo. The increase in 'torpedoes' is if it holds.

So, it's certainly a viable choice, and has some merit, but is a very limited system.

All of which made me look at my Bahktiari III class again.
If I dropped it to 30 knots, I could fit in a similar bulkhead, but for me it only moves
it from 2.0 to 2.8 torpedoes, though at 10,000tons and 0.9 hull, it is more stressed to start.
Side effect of prioritizing firepower over toughness with that one.

Fiddling with the Mountain class.  So the 155s are DP, but on this ship they're accepted as being more of an anti-TB DP gun, with the full up turrets and single mounts being more of the rapid fire DP (though everyone will be unsatisfied with a 6in DP gun when the 4.7in DP gun is far better.

Removed the TDS, it did reduce by a bit but not drastic.  Instead, I was able to do a box over the machinery and magazines for splinter-catching that will back up the belt and deck better than just a slightly thicker belt and deck (as shells in the class that this ship is fighting will likely detonate before reaching the inner protection.  Sped it up a little bit as well, and went up to four 2 gun mounts for the 155s.

Mountain, Aztec Corvette laid down 1939

Displacement:
   5,974 t light; 6,426 t standard; 7,113 t normal; 7,663 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (509.73 ft / 501.97 ft) x 52.82 ft x (17.72 / 18.75 ft)
   (155.37 m / 153.00 m) x 16.10 m  x (5.40 / 5.72 m)

Armament:
      8 - 6.10" / 155 mm 55.0 cal guns - 147.16lbs / 66.75kg shells, 300 per gun
     Dual purpose guns in deck and hoist mounts, 1939 Model
     4 x 2-gun mounts on centreline ends, evenly spread
      2 raised mounts - superfiring
      8 - 3.54" / 90.0 mm 55.0 cal guns - 24.01lbs / 10.89kg shells, 500 per gun
     Dual purpose guns in deck mounts, 1939 Model
     4 x Twin mounts on sides, evenly spread
      12 - 1.57" / 40.0 mm 50.0 cal guns - 2.07lbs / 0.94kg shells, 4,000 per gun
     Anti-air guns in deck and hoist mounts, 1939 Model
     2 x 4 row quad mounts on sides amidships
     1 x 4 row quad mount on centreline, aft deck centre
      1 raised mount
      16 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 2,000 per gun
     Anti-air guns in deck mounts, 1939 Model
     16 x Single mounts on sides, evenly spread
      Weight of broadside 1,398 lbs / 634 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   3.94" / 100 mm   411.61 ft / 125.46 m   12.30 ft / 3.75 m
   Ends:   Unarmoured
     Main Belt covers 126 % of normal length
     Main Belt inclined -10.00 degrees (positive = in)

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   2.36" / 60 mm   1.18" / 30 mm      2.36" / 60 mm
   2nd:   1.06" / 27 mm   1.06" / 27 mm            -
   3rd:   0.79" / 20 mm   0.79" / 20 mm      0.79" / 20 mm

   - Box over machinery & magazines:
   1.97" / 50 mm

   - Conning towers: Forward 3.15" / 80 mm, Aft 3.15" / 80 mm

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 60,771 shp / 45,335 Kw = 31.00 kts
   Range 8,000nm at 14.00 kts
   Bunker at max displacement = 1,237 tons

Complement:
   386 - 503

Cost:
   £3.306 million / $13.222 million

Distribution of weights at normal displacement:
   Armament: 389 tons, 5.5 %
      - Guns: 389 tons, 5.5 %
   Armour: 1,608 tons, 22.6 %
      - Belts: 794 tons, 11.2 %
      - Armament: 91 tons, 1.3 %
      - Armour Deck: 672 tons, 9.4 %
      - Conning Towers: 50 tons, 0.7 %
   Machinery: 1,644 tons, 23.1 %
   Hull, fittings & equipment: 1,857 tons, 26.1 %
   Fuel, ammunition & stores: 1,139 tons, 16.0 %
   Miscellaneous weights: 476 tons, 6.7 %
      - Hull above water: 342 tons
      - On freeboard deck: 40 tons
      - Above deck: 94 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     6,607 lbs / 2,997 Kg = 58.2 x 6.1 " / 155 mm shells or 1.2 torpedoes
   Stability (Unstable if below 1.00): 1.09
   Metacentric height 2.3 ft / 0.7 m
   Roll period: 14.7 seconds
   Steadiness   - As gun platform (Average = 50 %): 60 %
         - Recoil effect (Restricted arc if above 1.00): 0.62
   Seaboat quality  (Average = 1.00): 1.05

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and small transom stern
   Block coefficient (normal/deep): 0.530 / 0.539
   Length to Beam Ratio: 9.50 : 1
   'Natural speed' for length: 24.05 kts
   Power going to wave formation at top speed: 60 %
   Trim (Max stability = 0, Max steadiness = 100): 57
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   12.00 %,  21.33 ft / 6.50 m,  19.69 ft / 6.00 m
      - Forward deck:   30.00 %,  19.69 ft / 6.00 m,  18.86 ft / 5.75 m
      - Aft deck:   52.00 %,  18.86 ft / 5.75 m,  17.06 ft / 5.20 m
      - Quarter deck:   6.00 %,  17.06 ft / 5.20 m,  17.06 ft / 5.20 m
      - Average freeboard:      18.59 ft / 5.67 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 100.3 %
      - Above water (accommodation/working, high = better): 169.3 %
   Waterplane Area: 18,604 Square feet or 1,728 Square metres
   Displacement factor (Displacement / loading): 108 %
   Structure weight / hull surface area: 69 lbs/sq ft or 339 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.71
      - Longitudinal: 1.28
      - Overall: 0.75
   Caution: Hull subject to strain in open-sea
   Adequate machinery, storage, compartmentation space
   Excellent accommodation and workspace room

39t - 1930 FC
50t - NF Devices x 2
25t - LR Radio

40t - 2 x 5 x 21in HW TT Aft

322t - 27mm Splinter Box over Magazines and Machinery

And as I have time to work on them.  The Aztec Carrier fleet is up to a number that can comfortably put hulls and air groups over fleets.  Shifting from building for quantity, the Sultanate will be moving towards quality, with a mind towards a mid-40s fast light carrier type, and a strike carrier type built in a low rate production like the Sultanate's battleships.

Ursus, Aztec Strike Carrier laid down 1940

Displacement:
   34,766 t light; 35,815 t standard; 38,218 t normal; 40,141 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (810.13 ft / 787.40 ft) x 104.99 ft x (29.53 / 30.67 ft)
   (246.93 m / 240.00 m) x 32.00 m  x (9.00 / 9.35 m)

Armament:
      16 - 4.72" / 120 mm 55.0 cal guns - 56.91lbs / 25.81kg shells, 400 per gun
     Dual purpose guns in deck and hoist mounts, 1940 Model
     8 x Twin mounts on sides, evenly spread
      32 - 1.57" / 40.0 mm 50.0 cal guns - 2.07lbs / 0.94kg shells, 2,000 per gun
     Anti-air guns in deck and hoist mounts, 1940 Model
     8 x 4 row quad mounts on sides, evenly spread
      28 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 1,500 per gun
     Anti-air guns in deck mounts, 1940 Model
     28 x Single mounts on sides, evenly spread
      8 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 3,000 per gun
     Anti-air guns in deck and hoist mounts, 1940 Model
     2 x 4 row quad mounts on sides, aft deck forward
      2 double raised mounts
      Weight of broadside 986 lbs / 447 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   3.94" / 100 mm   511.81 ft / 156.00 m   16.40 ft / 5.00 m
   Ends:   1.97" / 50 mm   275.56 ft / 83.99 m   16.40 ft / 5.00 m
   Upper:   3.15" / 80 mm   511.81 ft / 156.00 m   8.01 ft / 2.44 m
     Main Belt covers 100 % of normal length

   - Torpedo Bulkhead - Additional damage containing bulkheads:
      1.57" / 40 mm   511.81 ft / 156.00 m   27.07 ft / 8.25 m
   Beam between torpedo bulkheads 78.74 ft / 24.00 m

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.57" / 40 mm   1.57" / 40 mm      1.57" / 40 mm
   2nd:   0.79" / 20 mm   0.79" / 20 mm      0.79" / 20 mm
   4th:   0.79" / 20 mm   0.79" / 20 mm      0.79" / 20 mm

   - Armoured deck - multiple decks:
   For and Aft decks: 5.91" / 150 mm
   Forecastle: 1.77" / 45 mm  Quarter deck: 1.77" / 45 mm

   - Conning towers: Forward 1.97" / 50 mm, Aft 0.00" / 0 mm

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 158,813 shp / 118,475 Kw = 31.50 kts
   Range 10,000nm at 14.00 kts
   Bunker at max displacement = 4,325 tons

Complement:
   1,366 - 1,776

Cost:
   £11.572 million / $46.288 million

Distribution of weights at normal displacement:
   Armament: 288 tons, 0.8 %
      - Guns: 288 tons, 0.8 %
   Armour: 8,940 tons, 23.4 %
      - Belts: 2,288 tons, 6.0 %
      - Torpedo bulkhead: 807 tons, 2.1 %
      - Armament: 145 tons, 0.4 %
      - Armour Deck: 5,652 tons, 14.8 %
      - Conning Tower: 48 tons, 0.1 %
   Machinery: 4,246 tons, 11.1 %
   Hull, fittings & equipment: 12,932 tons, 33.8 %
   Fuel, ammunition & stores: 3,453 tons, 9.0 %
   Miscellaneous weights: 8,359 tons, 21.9 %
      - Hull below water: 4,000 tons
      - Hull above water: 4,000 tons
      - On freeboard deck: 120 tons
      - Above deck: 239 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     97,720 lbs / 44,325 Kg = 1,853.4 x 4.7 " / 120 mm shells or 13.1 torpedoes
   Stability (Unstable if below 1.00): 1.40
   Metacentric height 9.6 ft / 2.9 m
   Roll period: 14.2 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.05
   Seaboat quality  (Average = 1.00): 2.00

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and small transom stern
   Block coefficient (normal/deep): 0.548 / 0.554
   Length to Beam Ratio: 7.50 : 1
   'Natural speed' for length: 30.42 kts
   Power going to wave formation at top speed: 54 %
   Trim (Max stability = 0, Max steadiness = 100): 35
   Bow angle (Positive = bow angles forward): 30.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  39.37 ft / 12.00 m,  39.37 ft / 12.00 m
      - Forward deck:   30.00 %,  39.37 ft / 12.00 m,  39.37 ft / 12.00 m
      - Aft deck:   35.00 %,  39.37 ft / 12.00 m,  39.37 ft / 12.00 m
      - Quarter deck:   15.00 %,  39.37 ft / 12.00 m,  39.37 ft / 12.00 m
      - Average freeboard:      39.37 ft / 12.00 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 84.2 %
      - Above water (accommodation/working, high = better): 323.9 %
   Waterplane Area: 59,002 Square feet or 5,482 Square metres
   Displacement factor (Displacement / loading): 142 %
   Structure weight / hull surface area: 137 lbs/sq ft or 670 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.90
      - Longitudinal: 2.46
      - Overall: 1.00
   Adequate machinery, storage, compartmentation space
   Excellent accommodation and workspace room
   Ship has slow, easy roll, a good, steady gun platform
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

29t - 1930 FC
75t - NF Devices x 3 (Space for Radar)
25t - LR Radio
10t - Additional SR Radio
100t - Flag Facilities

20t - 4 x Catapult on Deck
100t - Additional Firefighting Equipment

100t - Firefighting Equipment in Hangar
100t - Flag Quarters
3325t - Aircraft (70 Total)
475t (Reserve Aircraft Space)

100t - Additional Damage Control Equipment
100t - Aviation Repair Shop
3325 - Aircraft Support (70 Total)
475t (Reserve Aircraft Space)

Deck:  80mm Flight Deck, 45mm Hangar Floor, 25mm Splinter Deck

Air Group:  4 x COD, 6 x ASC, 24 x TB, 36 x F/DB (Expansion Space for 4 x ASC, 6 F/DB)

Ah going the armored carrier route. You can improve on Parthian errors in the Barcusk class, which is why I took one to Veracruz :)
Though I expect by 1940 I may have a new armored carrier to lay down as well.

Quote from: Kaiser Kirk on April 28, 2025, 10:28:05 PMAh going the armored carrier route. You can improve on Parthian errors in the Barcusk class, which is why I took one to Veracruz :)
Though I expect by 1940 I may have a new armored carrier to lay down as well.

The need for a larger hull to hold 70+ aircraft, combined with the expense of said hull, is a driver.  The Parthian armored carrier showing that you can make something far more survivable, a ship that will likely take a bomb hit or two before being rendered inoperable, is also a driver.  The Aztecs also understand that it's more efficient to build a single iterative type of capital ship at a steady rate than surge produce two, followed by years without production.  That and the escort carrier type has grown in size to practically be even with the Martinique type....I'd expect the next 'escort carrier' will be a light carrier with a 3 squadron flight group and around 18,000t with full carrier speeds.

Re-looking at the Mountain-class.  Chopping the guns back to singles which will preserve their speed, and putting more effort into sheer range (reason will be obvious soon), the ship is now more in line with being an escort for fast convoys. 

Mountain, Aztec Corvette laid down 1939

Displacement:
   5,800 t light; 6,228 t standard; 8,263 t normal; 9,891 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (515.69 ft / 508.53 ft) x 55.77 ft x (19.69 / 68.91 ft)
   (157.18 m / 155.00 m) x 17.00 m  x (6.00 / 21.00 m)

Armament:
      5 - 6.10" / 155 mm 55.0 cal guns - 147.16lbs / 66.75kg shells, 300 per gun
     Dual purpose guns in deck and hoist mounts, 1939 Model
     5 x Single mounts on centreline ends, majority forward
      2 raised mounts - superfiring
      12 - 3.54" / 90.0 mm 55.0 cal guns - 24.01lbs / 10.89kg shells, 500 per gun
     Dual purpose guns in deck mounts, 1939 Model
     6 x Twin mounts on sides, evenly spread
      2 raised mounts
      12 - 1.57" / 40.0 mm 50.0 cal guns - 2.07lbs / 0.94kg shells, 4,000 per gun
     Anti-air guns in deck and hoist mounts, 1939 Model
     2 x 4 row quad mounts on sides amidships
     1 x 4 row quad mount on centreline, aft deck centre
      1 double raised mount
      16 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 2,000 per gun
     Anti-air guns in deck mounts, 1939 Model
     16 x Single mounts on sides, evenly spread
      Weight of broadside 1,053 lbs / 478 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   3.94" / 100 mm   411.61 ft / 125.46 m   12.30 ft / 3.75 m
   Ends:   Unarmoured
     Main Belt covers 125 % of normal length
     Main Belt inclined -10.00 degrees (positive = in)

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   4.33" / 110 mm   2.17" / 55 mm      4.33" / 110 mm
   2nd:   1.06" / 27 mm   1.06" / 27 mm            -
   3rd:   0.79" / 20 mm   0.79" / 20 mm      0.79" / 20 mm

   - Box over machinery & magazines:
   1.85" / 47 mm

   - Conning towers: Forward 3.15" / 80 mm, Aft 3.15" / 80 mm

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 57,879 shp / 43,178 Kw = 30.00 kts
   Range 12,500nm at 18.00 kts
   Bunker at max displacement = 3,663 tons

Complement:
   433 - 563

Cost:
   £2.993 million / $11.971 million

Distribution of weights at normal displacement:
   Armament: 281 tons, 3.4 %
      - Guns: 281 tons, 3.4 %
   Armour: 1,553 tons, 18.8 %
      - Belts: 798 tons, 9.7 %
      - Armament: 150 tons, 1.8 %
      - Armour Deck: 549 tons, 6.6 %
      - Conning Towers: 55 tons, 0.7 %
   Machinery: 1,566 tons, 19.0 %
   Hull, fittings & equipment: 1,906 tons, 23.1 %
   Fuel, ammunition & stores: 2,463 tons, 29.8 %
   Miscellaneous weights: 495 tons, 6.0 %
      - Hull above water: 336 tons
      - On freeboard deck: 70 tons
      - Above deck: 89 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     9,165 lbs / 4,157 Kg = 80.7 x 6.1 " / 155 mm shells or 1.7 torpedoes
   Stability (Unstable if below 1.00): 1.15
   Metacentric height 2.7 ft / 0.8 m
   Roll period: 14.2 seconds
   Steadiness   - As gun platform (Average = 50 %): 68 %
         - Recoil effect (Restricted arc if above 1.00): 0.34
   Seaboat quality  (Average = 1.00): 1.05

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and small transom stern
   Block coefficient (normal/deep): 0.518 / 0.177
   Length to Beam Ratio: 9.12 : 1
   'Natural speed' for length: 24.27 kts
   Power going to wave formation at top speed: 59 %
   Trim (Max stability = 0, Max steadiness = 100): 65
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   12.00 %,  19.69 ft / 6.00 m,  18.04 ft / 5.50 m
      - Forward deck:   30.00 %,  18.04 ft / 5.50 m,  18.04 ft / 5.50 m
      - Aft deck:   52.00 %,  18.04 ft / 5.50 m,  16.40 ft / 5.00 m
      - Quarter deck:   6.00 %,  16.40 ft / 5.00 m,  16.40 ft / 5.00 m
      - Average freeboard:      17.60 ft / 5.36 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 79.4 %
      - Above water (accommodation/working, high = better): 151.7 %
   Waterplane Area: 19,677 Square feet or 1,828 Square metres
   Displacement factor (Displacement / loading): 136 %
   Structure weight / hull surface area: 67 lbs/sq ft or 328 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.72
      - Longitudinal: 1.09
      - Overall: 0.75
   Caution: Hull subject to strain in open-sea
   Excellent machinery, storage, compartmentation space
   Excellent accommodation and workspace room

28t - 1930 FC
50t - NF Devices x 2
25t - LR Radio

30t - 1 x Armed Floatplane w/ Catapults
40t - 2 x 5 x 21in HW TT Aft

322t - 27mm Splinter Box over Magazines and Machinery

Range is 14,375nm @ 18kts

And for the reason why I might look at an extremely long-ranged escort cruiser.  As part of a trio of escort cruiser, fast OPV, and Fast Troop Transport.  All with a Veracruz-Parthia unrefueled range at 18kts with a thousand or so nautical miles at over 20kts as a speed run.  The concept being to bring a brigade of troops and a basic load of equipment all the way to Parthia in a crisis situation at maximum speed through potentially contested waters.

These ships can go from Veracruz, through the upper outer gates, around the Horn, and into the Persian Gulf to Parthia in 32 days nonstop.

Albatross, Aztec High Speed Troopship laid down 1939

Displacement:
   13,979 t light; 14,320 t standard; 16,069 t normal; 17,469 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (626.83 ft / 623.36 ft) x 72.18 ft x (20.83 / 22.29 ft)
   (191.06 m / 190.00 m) x 22.00 m  x (6.35 / 6.79 m)

Armament:
      6 - 3.54" / 90.0 mm 55.0 cal guns - 24.01lbs / 10.89kg shells, 150 per gun
     Dual purpose guns in deck mounts, 1939 Model
     6 x Single mounts on side ends, majority forward
      8 - 1.57" / 40.0 mm 50.0 cal guns - 2.07lbs / 0.94kg shells, 500 per gun
     Anti-air guns in deck mounts, 1939 Model
     4 x Twin mounts on centreline ends, evenly spread
      16 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 1,000 per gun
     Anti-air guns in deck mounts, 1939 Model
     16 x Single mounts on sides, evenly spread
      Weight of broadside 165 lbs / 75 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Ends:   Unarmoured

   - Torpedo Bulkhead - Additional damage containing bulkheads:
      0.39" / 10 mm   405.18 ft / 123.50 m   18.57 ft / 5.66 m
   Beam between torpedo bulkheads 52.49 ft / 16.00 m

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.06" / 27 mm         -               -

   - Box over magazines:
   0.47" / 12 mm

   - Conning towers: Forward 0.47" / 12 mm, Aft 0.00" / 0 mm

Machinery:
   Diesel Internal combustion motors,
   Geared drive, 3 shafts, 36,444 shp / 27,187 Kw = 24.00 kts
   Range 7,000nm at 18.00 kts
   Bunker at max displacement = 3,149 tons

Complement:
   713 - 927

Cost:
   £3.711 million / $14.842 million

Distribution of weights at normal displacement:
   Armament: 40 tons, 0.2 %
      - Guns: 40 tons, 0.2 %
   Armour: 141 tons, 0.9 %
      - Torpedo bulkhead: 110 tons, 0.7 %
      - Armament: 14 tons, 0.1 %
      - Armour Deck: 11 tons, 0.1 %
      - Conning Tower: 6 tons, 0.0 %
   Machinery: 986 tons, 6.1 %
   Hull, fittings & equipment: 5,553 tons, 34.6 %
   Fuel, ammunition & stores: 2,090 tons, 13.0 %
   Miscellaneous weights: 7,259 tons, 45.2 %
      - Hull below water: 3,050 tons
      - Hull above water: 2,650 tons
      - On freeboard deck: 1,530 tons
      - Above deck: 29 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     24,477 lbs / 11,102 Kg = 1,100.4 x 3.5 " / 90 mm shells or 4.2 torpedoes
   Stability (Unstable if below 1.00): 1.33
   Metacentric height 5.1 ft / 1.5 m
   Roll period: 13.5 seconds
   Steadiness   - As gun platform (Average = 50 %): 60 %
         - Recoil effect (Restricted arc if above 1.00): 0.00
   Seaboat quality  (Average = 1.00): 1.14

Hull form characteristics:
   Hull has raised forecastle, raised quarterdeck ,
     a normal bow and small transom stern
   Block coefficient (normal/deep): 0.600 / 0.610
   Length to Beam Ratio: 8.64 : 1
   'Natural speed' for length: 26.80 kts
   Power going to wave formation at top speed: 44 %
   Trim (Max stability = 0, Max steadiness = 100): 53
   Bow angle (Positive = bow angles forward): 10.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  19.69 ft / 6.00 m,  19.69 ft / 6.00 m
      - Forward deck:   30.00 %,  9.84 ft / 3.00 m,  9.84 ft / 3.00 m
      - Aft deck:   35.00 %,  9.84 ft / 3.00 m,  9.84 ft / 3.00 m
      - Quarter deck:   15.00 %,  16.40 ft / 5.00 m,  16.40 ft / 5.00 m
      - Average freeboard:      12.80 ft / 3.90 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 82.6 %
      - Above water (accommodation/working, high = better): 88.7 %
   Waterplane Area: 33,741 Square feet or 3,135 Square metres
   Displacement factor (Displacement / loading): 170 %
   Structure weight / hull surface area: 127 lbs/sq ft or 618 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 1.57
      - Longitudinal: 0.86
      - Overall: 1.00
   Excellent machinery, storage, compartmentation space
   Cramped accommodation and workspace room

4t - 1930 FC
25t - LR Radio

30t - 1 x Armed Floatplane and Catapult
80t - 4 x 10t Landing Barge
120t - 3 x 20t Crane
1300t - Deck Cargo

346t - Diesel Engines
54t - Additional DC Equipment

3600t - Space for 1800 Soldiers/PAX

1000t - Dry Storage Cargo
200t - Refrigerated Storage Cargo
320t - Ammunition Storage
120t - 12mm Splinter Protection over Ammunition Storage

Range is 14,500nm @ 18kts

The third in the 'Parthia Route Trio', an OPV designed for the purpose of high speed escort work.  Cutting the extra tonnage to get DD speeds, but armed with what could be considered a DD's firepower, she's designed to perform unrefueled escort for extended distances.  With slower vessels her range gets even more extreme.

At a more sedate 12 knots......she can travel over 40,000nm without refueling.  With her extra spaces full of food and stores, it would be theoretically possible for this 1000t ship to circumnavigate the globe from Veracruz to Acapulco with fuel left over for operations when she gets there.

OPV-39, Aztec Offshore Patrol Vessel laid down 1939

Displacement:
   1,088 t light; 1,165 t standard; 1,652 t normal; 2,042 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (300.89 ft / 295.28 ft) x 32.81 ft x (10.89 / 12.86 ft)
   (91.71 m / 90.00 m) x 10.00 m  x (3.32 / 3.92 m)

Armament:
      6 - 3.54" / 90.0 mm 55.0 cal guns - 24.01lbs / 10.89kg shells, 400 per gun
     Dual purpose guns in deck mounts, 1939 Model
     3 x Twin mounts on centreline ends, majority forward
      1 raised mount - superfiring
      8 - 1.57" / 40.0 mm 50.0 cal guns - 2.07lbs / 0.94kg shells, 1,000 per gun
     Anti-air guns in deck mounts, 1939 Model
     4 x Twin mounts on sides, forward deck aft
      10 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 2,000 per gun
     Anti-air guns in deck mounts, 1939 Model
     10 x Single mounts on side ends, majority forward
      Weight of broadside 163 lbs / 74 kg

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.06" / 27 mm   0.79" / 20 mm            -

   - Conning towers: Forward 0.79" / 20 mm, Aft 0.00" / 0 mm

Machinery:
   Diesel Internal combustion motors,
   Geared drive, 2 shafts, 13,085 shp / 9,762 Kw = 25.00 kts
   Range 7,000nm at 18.00 kts
   Bunker at max displacement = 877 tons

Complement:
   129 - 168

Cost:
   £0.569 million / $2.277 million

Distribution of weights at normal displacement:
   Armament: 33 tons, 2.0 %
      - Guns: 33 tons, 2.0 %
   Armour: 17 tons, 1.0 %
      - Armament: 14 tons, 0.9 %
      - Conning Tower: 2 tons, 0.1 %
   Machinery: 354 tons, 21.4 %
   Hull, fittings & equipment: 391 tons, 23.7 %
   Fuel, ammunition & stores: 564 tons, 34.1 %
   Miscellaneous weights: 293 tons, 17.7 %
      - Hull below water: 149 tons
      - Hull above water: 10 tons
      - On freeboard deck: 80 tons
      - Above deck: 54 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     1,884 lbs / 855 Kg = 84.7 x 3.5 " / 90 mm shells or 0.8 torpedoes
   Stability (Unstable if below 1.00): 1.25
   Metacentric height 1.4 ft / 0.4 m
   Roll period: 11.6 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.16
   Seaboat quality  (Average = 1.00): 1.04

Hull form characteristics:
   Hull has rise forward of midbreak,
     a normal bow and small transom stern
   Block coefficient (normal/deep): 0.548 / 0.573
   Length to Beam Ratio: 9.00 : 1
   'Natural speed' for length: 18.47 kts
   Power going to wave formation at top speed: 63 %
   Trim (Max stability = 0, Max steadiness = 100): 67
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  15.42 ft / 4.70 m,  15.42 ft / 4.70 m
      - Forward deck:   30.00 %,  15.42 ft / 4.70 m,  15.42 ft / 4.70 m
      - Aft deck:   35.00 %,  8.86 ft / 2.70 m,  8.86 ft / 2.70 m
      - Quarter deck:   15.00 %,  8.86 ft / 2.70 m,  8.86 ft / 2.70 m
      - Average freeboard:      12.14 ft / 3.70 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 88.6 %
      - Above water (accommodation/working, high = better): 121.4 %
   Waterplane Area: 6,914 Square feet or 642 Square metres
   Displacement factor (Displacement / loading): 148 %
   Structure weight / hull surface area: 36 lbs/sq ft or 176 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.69
      - Longitudinal: 1.44
      - Overall: 0.75
   Adequate machinery, storage, compartmentation space
   Excellent accommodation and workspace room
   Ship has slow, easy roll, a good, steady gun platform

124t - Diesel Engines
15t - Enhanced Hydrophones
10t - Sonar

10t - Crew Comfort Improvements (Air Conditioning, recreation space)

24t - Minesweeping Equipment
4t - 4 x Y Throwers
36t - Depth Charges or Mines
16t - 1x4x21in HW TT



4t - 1930 FC
25t - LR Radio
25t - NF Devices

Interesting.

Rather nice little escort destroyer at heart.
I have a 900 ton aux sloop that seeks to do the same role, but it is limited by the aux rules.
-bow - you could have a little .5-1.5m rise at the bow. *might* address that wet forward.
-MSW , usually we go with 25t, not 24t. Trivial.

Of course tankers exist, and I suppose there's no reason they can not be armed..

But considering the RN's desire for Light cruisers, and the USN desire for range,
and the way fuel doesn't count against treaty limits, it's fair to wonder
why they didn't push ships to 34.1% fuel faction.

My guess is it has to do with stability as you use the fuel in the tanks.
backflooding with seawater works, but apparently has some negatives as it will mix with some of the fuel.

I recall long, so long, ago, trying some modeling of USN hulls. I don't think I had BC numbers,
so used LxBxD + range @ speed and then slid BC up and down to get the standard disp.
So...considering how fuzzy standard disp were, that's not going to give a firm number.
But I did wind up with 19% as what IMHO seemed the maximum actually used.

old consideration on range surfaced ... Stores.
Ships don't have infinite food/water/common spare parts/fabrication material.
I have typically figured 1-2 weeks for DDs/ 3 or maybe 4 for Cruisers/ 4 for battleships.

I know my 4 "raider" ships had extra tonnage for extra stores as their range/cruise speed worked
out to 6 weeks of cruise distance.

This all did make me check my Xiyon class as I think it's my longest range - 20.8% fuel, so pushing over my own normal upper limit. I expect I had it at 19% at some point, and then found I had tonnage to shove in more fuel and trim the Light disp down, but did not check back.  It cruises at 22knots fo 6070nm, or 11.5 days. At 12knots that works out to 25,565nm and 89days, which they are not provisioned for.

Quote from: Kaiser Kirk on May 09, 2025, 05:24:43 PMInteresting.

Rather nice little escort destroyer at heart.
I have a 900 ton aux sloop that seeks to do the same role, but it is limited by the aux rules.
-bow - you could have a little .5-1.5m rise at the bow. *might* address that wet forward.
-MSW , usually we go with 25t, not 24t. Trivial.

Of course tankers exist, and I suppose there's no reason they can not be armed..

But considering the RN's desire for Light cruisers, and the USN desire for range,
and the way fuel doesn't count against treaty limits, it's fair to wonder
why they didn't push ships to 34.1% fuel faction.

My guess is it has to do with stability as you use the fuel in the tanks.
backflooding with seawater works, but apparently has some negatives as it will mix with some of the fuel.

I recall long, so long, ago, trying some modeling of USN hulls. I don't think I had BC numbers,
so used LxBxD + range @ speed and then slid BC up and down to get the standard disp.
So...considering how fuzzy standard disp were, that's not going to give a firm number.
But I did wind up with 19% as what IMHO seemed the maximum actually used.

Good points.  The troop transport obviously has the capacity for extra provision in its holds. The OPV has that 10 tons reserved to additional comfort spaces,  I'd view that like on a submarine, those spaces being packed to the bulkhead with stores if a long voyage was indicated.  I do need to adjust on the cruiser though.  The design sets it up for possibly a high speed minelayer and I need to adjust to make it better as a cruiser.

Looking back at my mine warfare equipment, the last time I built a fast minelayer was the GTB-class vessels that are now 20 years old or more.  So I present the Stingray class of fast minelayer, with enough capability to function as a 2nd line escort cruiser when not acting as minelayer.

Stingray, Aztec Fast Minelayer laid down 1939

Displacement:
   5,747 t light; 6,121 t standard; 6,789 t normal; 7,324 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (499.29 ft / 492.13 ft) x 53.61 ft x (17.39 / 18.41 ft)
   (152.18 m / 150.00 m) x 16.34 m  x (5.30 / 5.61 m)

Armament:
      4 - 6.10" / 155 mm 55.0 cal guns - 147.16lbs / 66.75kg shells, 300 per gun
     Dual purpose guns in deck and hoist mounts, 1939 Model
     4 x Single mounts on centreline ends, evenly spread
      2 raised mounts - superfiring
      12 - 3.54" / 90.0 mm 55.0 cal guns - 24.01lbs / 10.89kg shells, 500 per gun
     Dual purpose guns in deck mounts, 1939 Model
     6 x Twin mounts on sides, evenly spread
      2 raised mounts
      12 - 1.57" / 40.0 mm 50.0 cal guns - 2.07lbs / 0.94kg shells, 4,000 per gun
     Anti-air guns in deck and hoist mounts, 1939 Model
     2 x 4 row quad mounts on sides amidships
     1 x 4 row quad mount on centreline, aft deck centre
      1 double raised mount
      16 - 0.79" / 20.0 mm 55.0 cal guns - 0.26lbs / 0.12kg shells, 2,000 per gun
     Anti-air guns in deck mounts, 1939 Model
     16 x Single mounts on sides, evenly spread
      Weight of broadside 906 lbs / 411 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   4.33" / 110 mm   411.61 ft / 125.46 m   12.30 ft / 3.75 m
   Ends:   Unarmoured
     Main Belt covers 129 % of normal length
     Main Belt inclined -10.00 degrees (positive = in)

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   4.33" / 110 mm   2.17" / 55 mm      4.33" / 110 mm
   2nd:   1.06" / 27 mm   1.06" / 27 mm            -
   3rd:   0.79" / 20 mm   0.79" / 20 mm      0.79" / 20 mm

   - Armoured deck - single deck:
   For and Aft decks: 1.57" / 40 mm

   - Conning towers: Forward 3.15" / 80 mm, Aft 3.15" / 80 mm

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 4 shafts, 51,983 shp / 38,779 Kw = 30.00 kts
   Range 8,000nm at 14.00 kts
   Bunker at max displacement = 1,203 tons

Complement:
   373 - 486

Cost:
   £2.770 million / $11.079 million

Distribution of weights at normal displacement:
   Armament: 239 tons, 3.5 %
      - Guns: 239 tons, 3.5 %
   Armour: 1,552 tons, 22.9 %
      - Belts: 872 tons, 12.8 %
      - Armament: 130 tons, 1.9 %
      - Armour Deck: 500 tons, 7.4 %
      - Conning Towers: 49 tons, 0.7 %
   Machinery: 1,406 tons, 20.7 %
   Hull, fittings & equipment: 1,712 tons, 25.2 %
   Fuel, ammunition & stores: 1,042 tons, 15.4 %
   Miscellaneous weights: 839 tons, 12.4 %
      - Hull below water: 308 tons
      - Hull above water: 12 tons
      - On freeboard deck: 432 tons
      - Above deck: 87 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     7,358 lbs / 3,338 Kg = 64.8 x 6.1 " / 155 mm shells or 1.5 torpedoes
   Stability (Unstable if below 1.00): 1.12
   Metacentric height 2.4 ft / 0.7 m
   Roll period: 14.4 seconds
   Steadiness   - As gun platform (Average = 50 %): 60 %
         - Recoil effect (Restricted arc if above 1.00): 0.35
   Seaboat quality  (Average = 1.00): 1.04

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and small transom stern
   Block coefficient (normal/deep): 0.518 / 0.528
   Length to Beam Ratio: 9.18 : 1
   'Natural speed' for length: 23.86 kts
   Power going to wave formation at top speed: 59 %
   Trim (Max stability = 0, Max steadiness = 100): 58
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   12.00 %,  19.69 ft / 6.00 m,  18.04 ft / 5.50 m
      - Forward deck:   30.00 %,  18.04 ft / 5.50 m,  18.04 ft / 5.50 m
      - Aft deck:   52.00 %,  18.04 ft / 5.50 m,  16.40 ft / 5.00 m
      - Quarter deck:   6.00 %,  16.40 ft / 5.00 m,  16.40 ft / 5.00 m
      - Average freeboard:      17.60 ft / 5.36 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 86.3 %
      - Above water (accommodation/working, high = better): 163.8 %
   Waterplane Area: 18,303 Square feet or 1,700 Square metres
   Displacement factor (Displacement / loading): 114 %
   Structure weight / hull surface area: 65 lbs/sq ft or 318 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.72
      - Longitudinal: 1.11
      - Overall: 0.75
   Caution: Hull subject to strain in open-sea
   Adequate machinery, storage, compartmentation space
   Excellent accommodation and workspace room

24t - 1930 FC
50t - NF Devices x 2
25t - LR Radio

400t - 400 x Mines
32t - 2 x 4 x 21in HW TT on sides

308t - 27mm Box over Magazines and Machinery Spaces

That is more like a minelaying light cruiser. Which is something I had at the beginning, but moved away from in favor of a handful of dedicated mine layers. I haven't built one in 2 years, perhaps I should consider a light cruiser ML design as well. This is about the size of the Boran patrol frigates, maybe use that as a base...