Requests of Indochinese Navy

[ciders]

Indochinese Navy open a first competition for the supply of 12 Light Torpedo Boats.

Minimum requirements :

- 200 to 400 t light displacement
- 30-32 kts
- 1500-2000 nm range at 15 kts
- good seakeeping

Weapons available : 12,7 to 75 mm guns

Torpedoes : 533 mm

[Sachmle]

Indochinese Navy open a first competition for the supply of 12 Light Torpedo Boats.

Minimum requirements :

- 200 to 400 t light displacement
- 30-32 kts
- 1500-2000 nm range at 15 kts
- good seakeeping

Weapons available : 12,7 to 75 mm guns

Torpedoes : 533 mm

1) Define "Good Seakeeping". Do you want the SS value for good seakeeping, or do you want the "Guinness Adjusted Value" for good seakeeping?

2) Weapons available : 12,7 to 75 mm guns? Do you mean you have all sizes between 12.7mm and 75mm, or that those 2 are available?

3) Do you want and ASW capability?

[Guinness]

Speaking of the GASR (Guinness Adjusted Seakeeping Rating), the Ottomans would offer this design, already entering service with the Ottoman Navy:

http://www.navalism.org/index.php?topic=5092.msg61945#msg61945

Bolting on an Indochinese standard 75mm gun should be no problem, nor should Indochinese standard torpedos. Likewise, if provision to lay mines is undesired, a pair of 75mm guns could be fitted. If the Indochinese would prefer more freeboard, this should be possible at the expense of slightly higher displacement.

[TexanCowboy]

La Romania will come up with a design tomarrow.

[The Rock Doctor]

Theoretically, an Ustupo type torpedo-boat could be bumped up to about 30.5 knots with 1920 engine tech. 

[snip]

Ireland might try to come up with something...

[maddox]

France has a design perfectly fitting in the parameters. The 202 ton Minime.

[Carthaginian]

The Confederacy too shall offer a vessel (probably tonight if real world conditions allow).

[Kaiser Kirk]

Minimum requirements :

- 30-32 kts

Trial speed I presume?
If so I may attempt to modify this design for more range.
http://www.navalism.org/index.php?topic=5062.msg61240#msg61240

[ciders]

1) Define "Good Seakeeping". Do you want the SS value for good seakeeping, or do you want the "Guinness Adjusted Value" for good seakeeping?

2) Weapons available : 12,7 to 75 mm guns? Do you mean you have all sizes between 12.7mm and 75mm, or that those 2 are available?

3) Do you want and ASW capability?

1. In fact, I don't know, I never had MTB in my fleet, in Egypt or Indochina. Is 1.10 a good number ?

2. All the sizes between 12.7 and 75 mm.

3. No. Only naval strike capability. Indeed, there isn't a lot of submarines in the area.

Bolting on an Indochinese standard 75mm gun should be no problem, nor should Indochinese standard torpedos. Likewise, if provision to lay mines is undesired, a pair of 75mm guns could be fitted. If the Indochinese would prefer more freeboard, this should be possible at the expense of slightly higher displacement.

No mines too. Only torpedoes and some guns (maybe one 75 mm gun, one 40 mm AA gun and 2 12,7 mm machine guns ?).

Trial speed I presume?

Is it possible to have a 30kts speed in service ?

[Guinness]

Seakeeping: 1.1 would be exceptional (in my humble opinion) for a ship of this sort. See elsewhere, but I've done a lot of research on this based on real world ships. For a TB, the emphasis should be on speed and low silhouette, followed by concerns of range, offensive firepower, and finally habitability (which is really what seakeeping is about).

One thing about Springsharp is that seakeeping is represented as an absolute value, when in fact it is not. A really big ship, like a battlecruiser with a seakeeping value of 1.0 is not necessarily a worse "seaboat", meaning is not necessarily less comfortable to crew and operate at sea than a 300 ton sloop with a seakeeping rating of 1.8. By far the greatest factor in "seakeeping" is really just size.

Another factor of seakeeping is a boats ability to steam at full speed in heavier seas. A boat with less freeboard would necessarily be less capable in this regard, but again here size matters much more. A very large ship will be able to hold speed in heavier speeds much more easily than a very small ship, no matter what.

There are other factors like wavelengths, etc. which I'm only now becoming conversant in, so I'll set those aside for now.

These sorts of boats really wouldn't be at sea for very long, given their range and size (and limited on-board facilities for their crews). They also wouldn't be much use in very large seas or very bad weather just by virtue of how small they are, no matter how much freeboard they have.

So for me, I've abandoned SS's seakeeping value for ships I design under the TB/DD rules entirely, and instead think in terms of deck heights and structural strength. If adding freeboard increases strength somewhat, that it might be worth it, for instance. Likewise, 1.5 meter deck heights wouldn't be much use. For larger boats, eventually "wetness" becomes a factor to be considered, but it's impossible to design a passable 200 ton boat which isn't "wet" forward.

As for the Ottoman design, here it is with 2x75mm and 1x40mm AA. I don't personally believe the 40mm would be much use on a boat this size, however.:

200t Coastal Torpedo Boat - Export, Ottoman Empire Torpedo Boat laid down 1919 (Engine 1916)

Displacement:
   200 t light; 206 t standard; 240 t normal; 267 t full load

Dimensions: Length overall / water x beam x draught
   181.26 ft / 177.49 ft x 16.90 ft x 6.56 ft (normal load)
   55.25 m / 54.10 m x 5.15 m  x 2.00 m

Armament:
      2 - 2.95" / 75.0 mm guns in single mounts, 10.80lbs / 4.90kg shells, 1919 Model
     Quick firing guns in deck mounts
     on centreline ends, evenly spread
      2 - 0.51" / 13.0 mm guns in single mounts, 0.07lbs / 0.03kg shells, 1919 Model
     Machine guns in deck mounts
     on side, all amidships, all raised mounts - superfiring
      1 - 1.57" / 40.0 mm guns in single mounts, 1.95lbs / 0.89kg shells, 1919 Model
     Anti-aircraft gun in deck mount
     on centreline amidships, 1 raised gun
   Weight of broadside 24 lbs / 11 kg
   Shells per gun, main battery: 122
   2 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.59" / 15 mm         -               -

Machinery:
   Oil fired boilers, steam turbines,
   Direct drive, 1 shaft, 9,100 shp / 6,788 Kw = 28.57 kts
   Range 1,729nm at 15.00 kts
   Bunker at max displacement = 61 tons
     Caution: Delicate, lightweight machinery

Complement:
   29 - 39

Cost:
   £0.061 million / $0.246 million

Distribution of weights at normal displacement:
   Armament: 3 tons, 1.4 %
   Armour: 2 tons, 0.7 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 2 tons, 0.7 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 130 tons, 54.2 %
   Hull, fittings & equipment: 59 tons, 24.8 %
   Fuel, ammunition & stores: 40 tons, 16.8 %
   Miscellaneous weights: 5 tons, 2.1 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     44 lbs / 20 Kg = 3.5 x 3.0 " / 75 mm shells or 0.1 torpedoes
   Stability (Unstable if below 1.00): 1.08
   Metacentric height 0.4 ft / 0.1 m
   Roll period: 11.1 seconds
   Steadiness   - As gun platform (Average = 50 %): 36 %
         - Recoil effect (Restricted arc if above 1.00): 0.13
   Seaboat quality  (Average = 1.00): 0.30

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.427
   Length to Beam Ratio: 10.50 : 1
   'Natural speed' for length: 13.32 kts
   Power going to wave formation at top speed: 74 %
   Trim (Max stability = 0, Max steadiness = 100): 86
   Bow angle (Positive = bow angles forward): 10.70 degrees
   Stern overhang: 1.97 ft / 0.60 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      9.51 ft / 2.90 m
      - Forecastle (14 %):   9.19 ft / 2.80 m
      - Mid (33 %):      9.02 ft / 2.75 m (5.09 ft / 1.55 m aft of break)
      - Quarterdeck (10 %):   5.09 ft / 1.55 m
      - Stern:      5.09 ft / 1.55 m
      - Average freeboard:   6.44 ft / 1.96 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 188.0 %
      - Above water (accommodation/working, high = better): 38.7 %
   Waterplane Area: 1,784 Square feet or 166 Square metres
   Displacement factor (Displacement / loading): 34 %
   Structure weight / hull surface area: 17 lbs/sq ft or 85 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 1.29
      - Overall: 0.55
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is extremely poor
   Caution: Lacks seaworthiness - very limited seakeeping ability

Misc Weight:
4t: 2x21" Torpedoes
1t: Reserve

Range at max speed: 230nm, or 8 hours
Trial Speed: 34 knots

[ciders]

Seakeeping: 1.1 would be exceptional (in my humble opinion) for a ship of this sort. See elsewhere, but I've done a lot of research on this based on real world ships. For a TB, the emphasis should be on speed and low silhouette, followed by concerns of range, offensive firepower, and finally habitability (which is really what seakeeping is about).

As for the Ottoman design, here it is with 2x75mm and 1x40mm AA. I don't personally believe the 40mm would be much use on a boat this size, however.:

I think you're right for your classification (but I think offensive firepower should be before range). If we remove this 40 mm gun, that will make more space in the ship.

[Guinness]

I think you're right for your classification (but I think offensive firepower should be before range). If we remove this 40 mm gun, that will make more space in the ship.

I think you are quite correct here. With the 2nd 75mm and the 40mm, the area aft will be getting pretty crowded. A better solution may be another pair of 13mm mgs, or maybe some dismountable ~8mm mgs.

[ciders]

So, one 75 mm gun on the front of the ship, and four 12,7 mm machine guns for the self-protection of the ship ? I think it's a good choice. :)

Indochina will study all the propositions which will be made for her.

[maddox]

Displacement:
   208 t light; 216 t standard; 234 t normal; 249 t full load

Dimensions: Length overall / water x beam x draught
   170,55 ft / 169,09 ft x 13,78 ft x 5,25 ft (normal load)
   51,98 m / 51,54 m x 4,20 m  x 1,60 m

Armament:
      2 - 2,76" / 70,0 mm guns in single mounts, 12,13lbs / 5,50kg shells, 1918 Model
     Quick firing guns in deck mounts
     on centreline ends, evenly spread
      2 - 0,98" / 25,0 mm guns in single mounts, 0,48lbs / 0,22kg shells, 1918 Model
     Machine guns in deck mounts
     on centreline ends, evenly spread, all raised mounts
   Weight of broadside 25 lbs / 11 kg
   Shells per gun, main battery: 200
   2 - 21,0" / 533,4 mm above water torpedoes

Machinery:
   Oil fired boilers, steam turbines,
   Direct drive, 1 shaft, 5.768 shp / 4.303 Kw = 25,00 kts
   Range 2.500nm at 10,00 kts
   Bunker at max displacement = 33 tons

Complement:
   29 - 38

Cost:
   £0,052 million / $0,209 million

Distribution of weights at normal displacement:
   Armament: 3 tons, 1,2%
   Machinery: 118 tons, 50,5%
   Hull, fittings & equipment: 77 tons, 33,0%
   Fuel, ammunition & stores: 26 tons, 11,0%
   Miscellaneous weights: 10 tons, 4,3%

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     74 lbs / 33 Kg = 7,1 x 2,8 " / 70 mm shells or 0,1 torpedoes
   Stability (Unstable if below 1.00): 1,06
   Metacentric height 0,3 ft / 0,1 m
   Roll period: 10,8 seconds
   Steadiness   - As gun platform (Average = 50 %): 51 %
         - Recoil effect (Restricted arc if above 1.00): 0,44
   Seaboat quality  (Average = 1.00): 1,03

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0,670
   Length to Beam Ratio: 12,27 : 1
   'Natural speed' for length: 13,00 kts
   Power going to wave formation at top speed: 74 %
   Trim (Max stability = 0, Max steadiness = 100): 50
   Bow angle (Positive = bow angles forward): 7,00 degrees
   Stern overhang: 0,00 ft / 0,00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      11,84 ft / 3,61 m
      - Forecastle (20%):   9,19 ft / 2,80 m
      - Mid (60%):      9,19 ft / 2,80 m
      - Quarterdeck (15%):   9,19 ft / 2,80 m
      - Stern:      9,19 ft / 2,80 m
      - Average freeboard:   9,40 ft / 2,86 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 177,1%
      - Above water (accommodation/working, high = better): 44,3%
   Waterplane Area: 1.798 Square feet or 167 Square metres
   Displacement factor (Displacement / loading): 51%
   Structure weight / hull surface area: 15 lbs/sq ft or 74 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0,50
      - Longitudinal: 5,88
      - Overall: 0,64
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is extremely poor

4 tons torpedo's 2 tubes fixed forward.
6 ton Depth Charges in 2 stern racks, 9 charges a rack.

Trial speed 30 kts.