Irish Frigate 1920

[snip]

This is the current proposal for a home designed and built multipurpose warship. It may not be the best at any of the roles it can fill, but for a small navy, it should work out for the better.

Garrison Ahern Class, Irish Frigate laid down 1920 (Engine 1912)

Displacement:
   602 t light; 633 t standard; 750 t normal; 844 t full load

Dimensions: Length overall / water x beam x draught
   228.14 ft / 225.00 ft x 20.00 ft x 10.00 ft (normal load)
   69.54 m / 68.58 m x 6.10 m  x 3.05 m

Armament:
      4 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1920 Model
     Quick firing guns in deck mounts
     on centreline ends, evenly spread, 1 raised mount aft
      10 - 0.98" / 25.0 mm guns (5x2 guns), 0.48lbs / 0.22kg shells, 1920 Model
     Machine guns in deck mounts
     on centreline, evenly spread
      10 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1920 Model
     Machine guns in deck mounts
     on side, evenly spread
   Weight of broadside 133 lbs / 61 kg
   Shells per gun, main battery: 200
   2 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   0.75" / 19 mm   225.00 ft / 68.58 m   5.37 ft / 1.64 m
   Ends:   Unarmoured
     Main Belt covers 154 % of normal length
     Main belt does not fully cover magazines and engineering spaces

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.00" / 25 mm         -               -
   2nd:   0.50" / 13 mm         -               -

   - Conning tower: 1.00" / 25 mm

Machinery:
   Diesel Internal combustion motors,
   Direct drive, 2 shafts, 11,670 shp / 8,706 Kw = 26.00 kts
   Range 7,200nm at 10.00 kts
   Bunker at max displacement = 211 tons

Complement:
   71 - 93

Cost:
   £0.187 million / $0.750 million

Distribution of weights at normal displacement:
   Armament: 17 tons, 2.2 %
   Armour: 45 tons, 6.0 %
      - Belts: 34 tons, 4.5 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 9 tons, 1.2 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 2 tons, 0.2 %
   Machinery: 316 tons, 42.1 %
   Hull, fittings & equipment: 150 tons, 20.1 %
   Fuel, ammunition & stores: 148 tons, 19.7 %
   Miscellaneous weights: 75 tons, 10.0 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     189 lbs / 86 Kg = 5.9 x 4.0 " / 102 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.17
   Metacentric height 0.6 ft / 0.2 m
   Roll period: 10.9 seconds
   Steadiness   - As gun platform (Average = 50 %): 43 %
         - Recoil effect (Restricted arc if above 1.00): 0.49
   Seaboat quality  (Average = 1.00): 0.73

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.583
   Length to Beam Ratio: 11.25 : 1
   'Natural speed' for length: 15.00 kts
   Power going to wave formation at top speed: 70 %
   Trim (Max stability = 0, Max steadiness = 100): 50
   Bow angle (Positive = bow angles forward): 15.25 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      11.50 ft / 3.51 m
      - Forecastle (10 %):   11.50 ft / 3.51 m
      - Mid (30 %):      11.50 ft / 3.51 m (9.00 ft / 2.74 m aft of break)
      - Quarterdeck (15 %):   9.00 ft / 2.74 m
      - Stern:      9.00 ft / 2.74 m
      - Average freeboard:   9.75 ft / 2.97 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 164.4 %
      - Above water (accommodation/working, high = better): 58.3 %
   Waterplane Area: 3,240 Square feet or 301 Square metres
   Displacement factor (Displacement / loading): 63 %
   Structure weight / hull surface area: 21 lbs/sq ft or 102 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 1.97
      - Overall: 0.58
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is cramped
   Poor seaboat, wet and uncomfortable, reduced performance in heavy weather

25 tons Firecontrole
25 tons long range wireless
10 tons for mines
10 tons unasined (most likely depth changes once I have the tech)
5 ton construction reserve

Comments?

[ciders]

A poor seabot in the Irish Sea, it's not a good thing I think. Your frigate would be sunk at the first tempest. Furthermore, ship tends to be wet forward.

For the armament, I think you can reduce the number of machine guns. 20 machine guns, it seems a WW2 destroyer in 1943-1944. Why not two 25 mm guns and two 12,7 mm guns ?

Range... 13 000 km ? Did you have some conquests in the future ?  I think you can reduce too. And increase the number of torpedoes.  ;)

[Jefgte]

... & increase seaboat quality.

[mentat]

  Pretty handy firepower for the size

Agree with the comment on sea-keeping - esp. for a multi-purpose ship - ability to handle rough seas a big advantage - maybe 15' at the bow will help - the quaterdeck looks OK

Is there reason for long very thin and narrow Belt - runs whole length- alternative would be 7/8' - a whole deck - and maybe 30mm to cover Mags + Machry if poss

- or as alternative -  if Policing actions are important - some splinter armour for Bridge,  CT and Lt Gun positions ..

[maddox]

It looks like a small sloop or a corvette, not a frigate.

Armament looks "funny", with the 20 machineguns.
Also, with 4 main guns, and the fact the main and secundary guns can't use the full capacity of the FC  I would use the 25 tons spend on FC somewere else. (DC and/or hydrophones)
2 torpedo tubes can't give a useable spread to fire on alert targets. The least I would suggest is a tripple mount amidships.

Range and homewaters.  If the ship is ment to stay close to Ireland, the range is excessive. If the ship is ment for convoying (she's scary to subs, and cheap enough) the bad seakeeping, and cramped habitability will cause very unhappy crews.

On speed. She can't run with the fast destroyers, she can't run with the fast cruisers, and she's to small and allround to be in a larger fleet.
Or you should go full DD, and then a speed of 30 kts is "low".
Or you could sacrifice speed (22kts sounds a nice figure) in exchange for better seakeeping habitability and maybe some scraps of armor ,as indicated by others. Splinter/weathershields for the guns, a tad of armor on the CT.

[TexanCowboy]

There isn't a reason for any belt armour. The minimum size I would put any on, (varying for CD ships and the like) is 4,000 tons.

Remove that, and use the extra weight for speed.

Also, diesel isn't the best choice on a ship meant to go fast like this ship. SS doesn't represent this accurately, but a diesel engine at the size you have it compared to the size of the ship is about the same weight as a reciprocating engine.

[snip]

Ok made a few revisions.

Garrison Ahern Class, Irish Frigate laid down 1920 (Engine 1912)

Displacement:
   639 t light; 669 t standard; 750 t normal; 815 t full load

Dimensions: Length overall / water x beam x draught
   229.09 ft / 225.00 ft x 20.00 ft x 10.00 ft (normal load)
   69.83 m / 68.58 m x 6.10 m  x 3.05 m

Armament:
      4 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1920 Model
     Quick firing guns in deck mounts
     on centreline ends, evenly spread, 1 raised mount aft
      4 - 0.98" / 25.0 mm guns (2x2 guns), 0.48lbs / 0.22kg shells, 1920 Model
     Machine guns in deck mounts
     on centreline, evenly spread
      4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1920 Model
     Machine guns in deck mounts
     on side, evenly spread
   Weight of broadside 130 lbs / 59 kg
   Shells per gun, main battery: 200

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   1.00" / 25 mm   168.75 ft / 51.44 m   5.37 ft / 1.64 m
   Ends:   Unarmoured
   Upper:   0.50" / 13 mm   168.75 ft / 51.44 m   8.00 ft / 2.44 m
     Main Belt covers 115 % of normal length
     Main belt does not fully cover magazines and engineering spaces

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.00" / 25 mm   1.00" / 25 mm            -
   2nd:   0.50" / 13 mm         -               -

   - Armour deck: 0.50" / 13 mm, Conning tower: 2.00" / 51 mm

Machinery:
   Coal fired boilers, steam turbines,
   Direct drive, 2 shafts, 9,850 shp / 7,348 Kw = 25.00 kts
   Range 3,500nm at 10.00 kts
   Bunker at max displacement = 145 tons (100% coal)

Complement:
   71 - 93

Cost:
   £0.184 million / $0.736 million

Distribution of weights at normal displacement:
   Armament: 16 tons, 2.2 %
   Armour: 110 tons, 14.7 %
      - Belts: 64 tons, 8.5 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 13 tons, 1.7 %
      - Armour Deck: 30 tons, 4.0 %
      - Conning Tower: 4 tons, 0.5 %
   Machinery: 298 tons, 39.8 %
   Hull, fittings & equipment: 160 tons, 21.3 %
   Fuel, ammunition & stores: 111 tons, 14.7 %
   Miscellaneous weights: 55 tons, 7.3 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     228 lbs / 103 Kg = 7.1 x 4.0 " / 102 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.15
   Metacentric height 0.6 ft / 0.2 m
   Roll period: 11.0 seconds
   Steadiness   - As gun platform (Average = 50 %): 56 %
         - Recoil effect (Restricted arc if above 1.00): 0.57
   Seaboat quality  (Average = 1.00): 1.11

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.583
   Length to Beam Ratio: 11.25 : 1
   'Natural speed' for length: 15.00 kts
   Power going to wave formation at top speed: 68 %
   Trim (Max stability = 0, Max steadiness = 100): 50
   Bow angle (Positive = bow angles forward): 15.25 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      15.00 ft / 4.57 m
      - Forecastle (10 %):   14.00 ft / 4.27 m
      - Mid (30 %):      14.00 ft / 4.27 m (9.00 ft / 2.74 m aft of break)
      - Quarterdeck (15 %):   9.00 ft / 2.74 m
      - Stern:      9.00 ft / 2.74 m
      - Average freeboard:   10.54 ft / 3.21 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 153.7 %
      - Above water (accommodation/working, high = better): 89.8 %
   Waterplane Area: 3,240 Square feet or 301 Square metres
   Displacement factor (Displacement / loading): 65 %
   Structure weight / hull surface area: 21 lbs/sq ft or 102 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 2.52
      - Overall: 0.59
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is cramped

25 tons long range wireless
10 tons for mines (or depth charges once I have the tech)
15 tons unasigned (DC's maybe as well)
5 tons construction reserve

[maddox]

Where did the torps go?

[snip]

I could not fit more than two tubes on so figuered leave them off. Im also planing some PT-like MTBs so those could fill the role.

[Guinness]

25 knots and armored feels like a violation of the spirit of the DD/TB tech rule to me...

[snip]

@ Guinness so your saying no armor?
I will play with this a bit more tonight, heading to work soon. Any other comments are welcome

[Guinness]

I'm not sure yet. I'm mulling and will likely need to conspire with the other mods.

You could certainly have the same ship on the same (or less) displacement with less speed and be perfectly within the rules, and I'd have no concerns.

Some have in the past had issues with the building of cheap light cruisers using the DD rules. The 0.50 cross sectional strength rule is really there to allow the simming of high shp/ton powerplants and the ships that carry them. The 25 knot minimum was quite reasonable to that end in about 1906, but in 1920 it's way too slow, I'm afraid.

[TexanCowboy]

I doubt armour should even be on this kind of ship.....never was OTL, and it just slows down the ship while providing barely any protection.

[maddox]

Why spend 110 tons of belt armor to do what?
Keep a French submarines 70mm L45 out?  Stop a 105mm UNK secundary? Even a pirates old muzzle loader could do a number on this patrol corvette. Even with the 1" of small armor belt.

Other point to take in account. Why a long range Marconi set for a ship that's obviously a corvette?

It seems you have only the twin torpedo tube tech. But that doesn't stop you putting 2 sets on the ship.

And yes, I concur, Guinness. 25 kts seems very slow for the minimum on DD tech these modern days.

[Kaiser Kirk]

I doubt armour should even be on this kind of ship.....never was OTL, and it just slows down the ship while providing barely any protection.

Actually the Dutch Gruno class gunboats were 540t, 4x105mm, 14kts, and had 55mm belt and 17mm decks.

The Ahern's 25mm is a little light for a belt though, there isn't a reasonable expectation that it will stop common 4" counds. Plus it should cover the full engineering spaces. Perhaps drop the upperbelt and thicken & extend the main. I'll leave the speed/comp hull issue to others.