Vilnius Union Ships, 1920+: Electric Drive Boogaloo

[The Rock Doctor]

Scaling up to 3,000 t is certainly an option, and I've done that previously with that escort cruiser a few pages back.  Something that focused more on (any) protection might be easier than that one, which was dictated by speed.

[The Rock Doctor]

It just isn't cool when bad people use airplanes to blow up your ships.  And while the obvious answer is to just shoot down the airplanes, sometimes you want other options.

Like putting out balloons that the airplanes have to avoid flying into, because that isn't good for the airplanes and voids their warranties.

So you get something like this, which is a ship designed to deploy a modest balloon barrage in support of an anchorage or amphibious landing or what have you.  There's a hydrogen facility below water.  Above decks are two holds for deflated balloons, which I've assumed require about half the length/width/height of an inflated balloon, and a hold between those for buoys. 

The general notion is that the buoy is moved by hoist/lift to an exterior working platform.  Then the balloon is lifted out of the hold, inflated, and attached to the buoy.  The completed contraption is then loaded onto one of the two smaller buoy tenders (the small craft shown aft) and taken out to deploy while the mother ship stays safe at anchor behind her torpedo nets.  The buoy tender sets the buoy in the water, unreel its anchor so it stays put, then adjust the winch to let the balloon float at the desired height.

Barrage Tender, laid down 1924

Displacement:
   5,601 t light; 5,752 t standard; 6,152 t normal; 6,471 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (448.72 ft / 438.65 ft) x 62.34 ft x (13.12 / 13.68 ft)
   (136.77 m / 133.70 m) x 19.00 m  x (4.00 / 4.17 m)

Armament:
      2 - 5.12" / 130 mm 45.0 cal guns - 67.61lbs / 30.67kg shells, 250 per gun
     Quick firing guns in deck and hoist mount, 1924 Model
     1 x 2-gun mount on centreline, aft deck aft
      2 - 3.94" / 100.0 mm 45.0 cal guns - 30.77lbs / 13.96kg shells, 250 per gun
     Anti-air guns in deck mounts, 1924 Model
     2 x Single mounts on centreline, evenly spread
      2 raised mounts
      4 - 0.59" / 15.0 mm 90.0 cal guns - 0.12lbs / 0.05kg shells, 4,000 per gun
     Machine guns in deck mounts, 1924 Model
     4 x Single mounts on sides amidships
      4 raised mounts
      Weight of broadside 197 lbs / 89 kg

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.97" / 50 mm   1.18" / 30 mm      1.97" / 50 mm
   2nd:   0.79" / 20 mm   0.79" / 20 mm            -

Machinery:
   Diesel Internal combustion generators,
   Electric motors, 2 shafts, 13,405 shp / 10,000 Kw = 20.48 kts
   Range 9,000nm at 10.00 kts
   Bunker at max displacement = 718 tons

Complement:
   346 - 451

Cost:
   £0.847 million / $3.386 million

Distribution of weights at normal displacement:
   Armament: 48 tons, 0.8 %
   Armour: 20 tons, 0.3 %
      - Armament: 20 tons, 0.3 %
   Machinery: 442 tons, 7.2 %
   Hull, fittings & equipment: 2,879 tons, 46.8 %
   Fuel, ammunition & stores: 550 tons, 8.9 %
   Miscellaneous weights: 2,213 tons, 36.0 %
      - Hull below water: 1,243 tons
      - Hull above water: 570 tons
      - On freeboard deck: 200 tons
      - Above deck: 200 tons

Fittings:
-500 t:  Ballast (BW)
-500 t:  Hydrogen production plant and stores (BW)
-243 t:  That sweet turbo-electic drive (BW)
-320 t:  Balloon storage (AW)
-16 t:  Balloons themselves (AW)
-100 t:  16 buoys, storage, workbench, and lift (AW)
-134 t:  Anti-torpedo nets (AW)
-80 t:  2 x 20 t buoy tenders and davits (FD)
-50 t:  Two big cranes (FD)
-70 t:  Weight reserve (FD)
-120 t:  Inflation/work platform (AD)
-25 t:  L/R wireless (AD)
-25 t:  Meteorology office (AD)
-5 t:  Model 1918 fire control (AD)
-25 t:  More Weight reserve (AD)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     20,174 lbs / 9,151 Kg = 301.0 x 5.1 " / 130 mm shells or 2.9 torpedoes
   Stability (Unstable if below 1.00): 1.27
   Metacentric height 3.8 ft / 1.2 m
   Roll period: 13.5 seconds
   Steadiness   - As gun platform (Average = 50 %): 90 %
         - Recoil effect (Restricted arc if above 1.00): 0.07
   Seaboat quality  (Average = 1.00): 2.00

Hull form characteristics:
   Hull has low quarterdeck ,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.600 / 0.605
   Length to Beam Ratio: 7.04 : 1
   'Natural speed' for length: 20.94 kts
   Power going to wave formation at top speed: 45 %
   Trim (Max stability = 0, Max steadiness = 100): 45
   Bow angle (Positive = bow angles forward): 10.00 degrees
   Stern overhang: 4.92 ft / 1.50 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   10.00 %,  29.20 ft / 8.90 m,  26.25 ft / 8.00 m
      - Forward deck:   30.00 %,  26.25 ft / 8.00 m,  26.25 ft / 8.00 m
      - Aft deck:   35.00 %,  26.25 ft / 8.00 m,  26.25 ft / 8.00 m
      - Quarter deck:   25.00 %,  18.37 ft / 5.60 m,  18.37 ft / 5.60 m
      - Average freeboard:      24.40 ft / 7.44 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 59.0 %
      - Above water (accommodation/working, high = better): 289.0 %
   Waterplane Area: 19,999 Square feet or 1,858 Square metres
   Displacement factor (Displacement / loading): 188 %
   Structure weight / hull surface area: 91 lbs/sq ft or 446 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 1.04
      - Longitudinal: 3.62
      - Overall: 1.18
   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
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

[The Rock Doctor]

And the buoy tender in more detail...

Enter ship name, Enter country Enter ship type laid down 1924

Displacement:
   20 t light; 21 t standard; 22 t normal; 22 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (52.63 ft / 49.21 ft) x 13.12 ft x (1.80 / 1.82 ft)
   (16.04 m / 15.00 m) x 4.00 m  x (0.55 / 0.56 m)

Armament:
      2 - 0.59" / 15.0 mm 45.0 cal guns - 0.10lbs / 0.05kg shells, 4,000 per gun
     Breech loading guns in deck mounts, 1924 Model
     2 x Single mounts on sides, forward deck centre
      Weight of broadside 0 lbs / 0 kg

Machinery:
   Diesel Internal combustion generators,
   Electric motors, 2 shafts, 67 shp / 50 Kw = 10.05 kts
   Range 200nm at 8.00 kts
   Bunker at max displacement = 1 tons

Complement:
   4 - 6

Cost:
   £0.003 million / $0.013 million

Distribution of weights at normal displacement:
   Armament: 0 tons, 0.5 %
   Machinery: 2 tons, 10.2 %
   Hull, fittings & equipment: 11 tons, 51.2 %
   Fuel, ammunition & stores: 1 tons, 5.7 %
   Miscellaneous weights: 7 tons, 32.3 %
      - Hull below water: 1 tons
      - Above deck: 6 tons

Fittings:
-1 t:  Smallest diesel-electric drive in the Union (BW)
-6 t:  Crane and cradle for one balloon buoy (AD to reflect topweight/weathervaning of balloon)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     139 lbs / 63 Kg = 1,349.8 x 0.6 " / 15 mm shells or 0.5 torpedoes
   Stability (Unstable if below 1.00): 1.22
   Metacentric height 0.3 ft / 0.1 m
   Roll period: 9.4 seconds
   Steadiness   - As gun platform (Average = 50 %): 69 %
         - Recoil effect (Restricted arc if above 1.00): 0.01
   Seaboat quality  (Average = 1.00): 1.43

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.650 / 0.651
   Length to Beam Ratio: 3.75 : 1
   'Natural speed' for length: 7.02 kts
   Power going to wave formation at top speed: 68 %
   Trim (Max stability = 0, Max steadiness = 100): 48
   Bow angle (Positive = bow angles forward): 10.00 degrees
   Stern overhang: 1.97 ft / 0.60 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  8.20 ft / 2.50 m,  6.23 ft / 1.90 m
      - Forward deck:   30.00 %,  6.23 ft / 1.90 m,  6.23 ft / 1.90 m
      - Aft deck:   35.00 %,  6.23 ft / 1.90 m,  6.23 ft / 1.90 m
      - Quarter deck:   15.00 %,  6.23 ft / 1.90 m,  6.23 ft / 1.90 m
      - Average freeboard:      6.39 ft / 1.95 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 43.5 %
      - Above water (accommodation/working, high = better): 146.9 %
   Waterplane Area: 495 Square feet or 46 Square metres
   Displacement factor (Displacement / loading): 183 %
   Structure weight / hull surface area: 13 lbs/sq ft or 61 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.71
      - Longitudinal: 22.41
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is excellent
   Good seaboat, rides out heavy weather easily

[The Rock Doctor]

How about a hospital ship.

Enter ship name, Enter country Enter ship type laid down 1924

Displacement:
   7,308 t light; 7,465 t standard; 7,870 t normal; 8,194 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (405.30 ft / 393.70 ft) x 65.62 ft x (16.40 / 16.98 ft)
   (123.53 m / 120.00 m) x 20.00 m  x (5.00 / 5.17 m)

Machinery:
   Diesel Internal combustion generators,
   Electric motors, 2 shafts, 12,065 shp / 9,000 Kw = 18.90 kts
   Range 8,000nm at 10.00 kts
   Bunker at max displacement = 729 tons

Complement:
   417 - 543

Cost:
   £0.963 million / $3.850 million

Distribution of weights at normal displacement:
   Armament: 0 tons, 0.0 %
   Machinery: 397 tons, 5.0 %
   Hull, fittings & equipment: 2,277 tons, 28.9 %
   Fuel, ammunition & stores: 563 tons, 7.1 %
   Miscellaneous weights: 4,633 tons, 58.9 %
      - Hull below water: 818 tons
      - Hull above water: 2,400 tons
      - On freeboard deck: 400 tons
      - Above deck: 1,015 tons

Fittings:
-218 t:  D-E machinery (BW)
-600 t:  Stores (BW)
-2,400 t:  Wards for 800 patients (AW)
-100 t:  Boats and cranes (FD)
-300 t:  Triage area, general hospital facilities, and five operating theatres (FD)
-800 t:  Accommodation for 400 staff (AD)
-150 t:  Staff and patient amenities (AD)
-25 t:  L/R wireless (AD)
-40 t:  Weight reserve (AD)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     18,569 lbs / 8,423 Kg = 171.9 x 6 " / 152 mm shells or 2.8 torpedoes
   Stability (Unstable if below 1.00): 1.18
   Metacentric height 3.6 ft / 1.1 m
   Roll period: 14.5 seconds
   Steadiness   - As gun platform (Average = 50 %): 90 %
         - Recoil effect (Restricted arc if above 1.00): 0.00
   Seaboat quality  (Average = 1.00): 2.00

Hull form characteristics:
   Hull has low quarterdeck ,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.650 / 0.654
   Length to Beam Ratio: 6.00 : 1
   'Natural speed' for length: 19.84 kts
   Power going to wave formation at top speed: 49 %
   Trim (Max stability = 0, Max steadiness = 100): 45
   Bow angle (Positive = bow angles forward): 10.00 degrees
   Stern overhang: 6.56 ft / 2.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  28.54 ft / 8.70 m,  23.62 ft / 7.20 m
      - Forward deck:   30.00 %,  23.62 ft / 7.20 m,  23.62 ft / 7.20 m
      - Aft deck:   25.00 %,  23.62 ft / 7.20 m,  23.62 ft / 7.20 m
      - Quarter deck:   25.00 %,  15.75 ft / 4.80 m,  15.75 ft / 4.80 m
      - Average freeboard:      22.05 ft / 6.72 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 61.7 %
      - Above water (accommodation/working, high = better): 213.5 %
   Waterplane Area: 19,790 Square feet or 1,839 Square metres
   Displacement factor (Displacement / loading): 145 %
   Structure weight / hull surface area: 78 lbs/sq ft or 383 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.90
      - Longitudinal: 2.37
      - 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
   Excellent seaboat, comfortable, rides out heavy weather easily

[The Rock Doctor]

1924 is going to see a fair bit of minor refitting amongst the fleet.

The 20 H- and 20 I- class torpedo-boats are coastal swarm assets in the North Sea.  They don't have a lot of life left (laid down 1902-07), and very little in the way of available weight.

Option 1:  ~$0.2 and ~0.2 BP for the entire group (~5 t of work each)

-Replace the 10mm machine guns with 15mm machine guns
-Use up the remaining misc. weight (up to 2 t) on depth charges; not that there's any hydrophones, but it provides a basic blind ASW ability.

Option 2:  ~20 t of work each, I haven't simmed it so this is a guess.  Up to $0.8 and 0.8 BP for the whole 40.

-In addition to the above, remove existing 50mm QF
-Install one 50mm AA
-Install basic hydrophones
-Update to 1918 fire control
-Maybe have a few extra tonnes for more depth charges.

The I class has a second 100mm gun, so they certainly benefit more from the more extensive refit.  Plus they'll be around a little longer.  I don't think there would be weight for heavier torpedoes, but we'll see.

[The Rock Doctor]

Also likely to refit the three remaining Bug and four Pawtomeck class protected cruisers.  Laid down 1908-1912, the easy issues are:

-They're two generations behind on fire control
-Swap out the various 50mm QF guns for a couple of 100mm AA
-Swap out 10mm for 15mm machine guns
-See if heavier torpedoes can be added.

If I bump up to a refurbishment, I could switch to all oil-firing bunkerage at no BP cost.

The Bugs have an all-100mm battery and I don't think I would mess with that.

The Pawtowecks have a mixed battery of 2x130 (DM, not M&H)/10x100mm.  While I could refurb to 6x130mm M&H, the alternative might be to replace the 130mm with 2-gun 100mm.  That would mean they don't have much of a punch against armored targets, but 14 x 100mm guns, with nine on the broadside, would be fairly effective in an anti-TB role perhaps.

[Jefgte]

Option 2:  ~20 t of work each, I haven't simmed it so this is a guess.  Up to $0.8 and 0.8 BP for the whole 40.

-In addition to the above, remove existing 50mm QF
-Install one 50mm AA
-Install basic hydrophones
-Update to 1918 fire control
-Maybe have a few extra tonnes for more depth charges.

After a look on H & I class, , option 2 is better & economical, I think.

[The Rock Doctor]

You can tell I was rusty when I designed those torpedo-boats; I've got mount and hoist for the 100mm and 50mm guns.  Not only does that add unnecessary weight, it also means that changing those guns requires a more expensive refurbishment.

[The Rock Doctor]

Refurbing an H class, including a change of bunkerage (2500 --> 3300 nm with 100% oil) would cost $0.20 and 0.045 BP per unit, or $4.00 and 0.9 BP for the class of 20.  That otherwise follows what's described above, with enough miscellaneous weight to swap in 3 21" torpedoes and several tonnes of ASW hardware.

[Kaiser Kirk]

One unresolved issue on refitting ships with the destroyer architecture is the weight calculation for 50% machinery is a bit wacky.
Even if the engines aren't touched...So just a spot to double check.
It's one of those "we should come up with a rule to fix that' ....

[The Rock Doctor]

Yeah, I hadn't thought about it that way but will have to check.

My gut instinct is a simple, cheap refit of the H clase and the more intensive refurbishment for the I class.

And then maybe I need to consider a big run of new 500 to 1,000 t boats for the swarm function.

[Jefgte]

...
And then maybe I need to consider a big run of new 500 to 1,000 t boats for the swarm function.

The Byzantine TGBs were built for this function.
However, you can downgrade old Destroyers and Torpedo Boats and only build Fleet Destroyers.

[Kaiser Kirk]

...

The Byzantine TGBs were built for this function.
However, you can downgrade old Destroyers and Torpedo Boats and only build Fleet Destroyers.

Currently, if you 'downgrade' old DDs and TBs under the 50% machinery, they then need to meet cruiser rules.

Obviously that does not easily allow for the real life WW2 Destroyer Escorts,
but fixing that is a subject for future rule changes.

A BIG part of the problem is ... take my Tiger II class - 1864 tons normal and 933 tons of engines : 50.1%
So rip out half the engines, save 466 tons, stick in 466 tons of other stuff !!

Except the reason we're using the modified comp hull for DDs is the Engines really are not taking up 933 tons,
SS overestimates engine tonnage as it's based on battlewagons.
So in reality, there's far less weight to be saved. 

So figuring out how to fix that is on the 'to do list' for rule updates
...which may have been what we did if we didn't have the Mayan war.
but we did, and now everyone's busy again.

[The Rock Doctor]

The refurbishment of the I class would leave the engines alone.  The top speed of 24 knots is pretty crappy for 1924, but enough to overtake submarines or most merchies and to at least make enemy capital ships put in some effort to avoid them.  Happily, the ship continues to have 54%+ of its normal weight assigned to machinery, Kirk's comments and concerns notwithstanding.

As generally noted above:

-Chop out the old 50mm M&H and 10mm machine guns; replace them with a single 50mm AA and four 15mm machine guns
-Switch to all-oil-fired machinery, which increases the range from 2500 to 3100 nm @ 10 knots.
-Increase miscellaneous weight to 39 t, all of it new, even the radio.
-Basic refurb cost.

I cost this at $0.199 and 0.041 BP per unit, no drydock required.  As a North Sea/Baltic patroller/pest, it's probably adequate until new replacements come along in a few years.

I-class refurb, laid down 1905, refurbished 1924

Displacement:
   539 t light; 560 t standard; 614 t normal; 658 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (229.66 ft / 226.38 ft) x 22.97 ft x (9.84 / 10.31 ft)
   (70.00 m / 69.00 m) x 7.00 m  x (3.00 / 3.14 m)

Armament:
      2 - 3.94" / 100.0 mm 45.0 cal guns - 30.77lbs / 13.96kg shells, 200 per gun
     Quick firing guns in deck and hoist mounts, 1905 Model
     2 x Single mounts on centreline, evenly spread
      2 raised mounts
      1 - 1.97" / 50.0 mm 45.0 cal gun - 3.85lbs / 1.74kg shells, 200 per gun
     Anti-air gun in deck mount, 1905 Model
     1 x Single mount on centreline, aft deck forward
      1 raised mount
      4 - 0.59" / 15.0 mm 90.0 cal guns - 0.12lbs / 0.05kg shells, 4,000 per gun
     Machine guns in deck mounts, 1905 Model
     4 x Single mounts on sides amidships
      4 raised mounts
      Weight of broadside 66 lbs / 30 kg

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm   0.20" / 5 mm            -
   2nd:   0.79" / 20 mm   0.12" / 3 mm            -

Machinery:
   Oil fired boilers, complex reciprocating steam engines,
   Direct drive, 2 shafts, 6,970 ihp / 5,200 Kw = 24.13 kts
   Range 3,100nm at 10.00 kts
   Bunker at max displacement = 98 tons
     Caution: Delicate, lightweight machinery

Complement:
   61 - 80

Cost:
   £0.072 million / $0.288 million

Distribution of weights at normal displacement:
   Armament: 18 tons, 3.0 %
   Armour: 4 tons, 0.7 %
      - Armament: 4 tons, 0.7 %
   Machinery: 335 tons, 54.5 %
   Hull, fittings & equipment: 143 tons, 23.2 %
   Fuel, ammunition & stores: 75 tons, 12.2 %
   Miscellaneous weights: 39 tons, 6.4 %
      - Hull below water: 5 tons
      - On freeboard deck: 17 tons
      - Above deck: 17 tons

Fittings: 
-2 t:  1918 Fire control (AD)
-10 t:  S/R wireless (AD)
-5 t:  Nightfighting doodads (AD)
-12 t:  1x3 heavyweight 21" torpedo carriage (FD)
-5 t:  ASW stuff (FD)
-5 t:  Basic hydrophone package (BW)

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     118 lbs / 53 Kg = 3.9 x 3.9 " / 100 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.18
   Metacentric height 0.7 ft / 0.2 m
   Roll period: 11.2 seconds
   Steadiness   - As gun platform (Average = 50 %): 52 %
         - Recoil effect (Restricted arc if above 1.00): 0.51
   Seaboat quality  (Average = 1.00): 1.09

Hull form characteristics:
   Hull has raised forecastle,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.420 / 0.429
   Length to Beam Ratio: 9.86 : 1
   'Natural speed' for length: 15.05 kts
   Power going to wave formation at top speed: 62 %
   Trim (Max stability = 0, Max steadiness = 100): 48
   Bow angle (Positive = bow angles forward): 0.00 degrees
   Stern overhang: 3.28 ft / 1.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  15.75 ft / 4.80 m,  17.72 ft / 5.40 m
      - Forward deck:   20.00 %,  7.87 ft / 2.40 m,  7.87 ft / 2.40 m
      - Aft deck:   45.00 %,  7.87 ft / 2.40 m,  7.87 ft / 2.40 m
      - Quarter deck:   15.00 %,  7.87 ft / 2.40 m,  7.87 ft / 2.40 m
      - Average freeboard:      9.69 ft / 2.95 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 186.8 %
      - Above water (accommodation/working, high = better): 79.7 %
   Waterplane Area: 3,241 Square feet or 301 Square metres
   Displacement factor (Displacement / loading): 32 %
   Structure weight / hull surface area: 23 lbs/sq ft or 114 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 1.70
      - Overall: 0.56
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is cramped

Warning: Date too early for anti-air gun - 2nd battery oh no it isn't

[The Rock Doctor]

...

The Byzantine TGBs were built for this function.
However, you can downgrade old Destroyers and Torpedo Boats and only build Fleet Destroyers.

Currently, if you 'downgrade' old DDs and TBs under the 50% machinery, they then need to meet cruiser rules.

Obviously that does not easily allow for the real life WW2 Destroyer Escorts,
but fixing that is a subject for future rule changes.

A BIG part of the problem is ... take my Tiger II class - 1864 tons normal and 933 tons of engines : 50.1%
So rip out half the engines, save 466 tons, stick in 466 tons of other stuff !!

Except the reason we're using the modified comp hull for DDs is the Engines really are not taking up 933 tons,
SS overestimates engine tonnage as it's based on battlewagons.
So in reality, there's far less weight to be saved. 

So figuring out how to fix that is on the 'to do list' for rule updates
...which may have been what we did if we didn't have the Mayan war.
but we did, and now everyone's busy again.

I agree it's a rule thing to consider.

I interpreted Jef's comment to mean "Change the role of old destroyers/torpedo boats" rather than "Rip out the old engines and put in newer, more efficient engines".