Torpedobooten for the Rift

[Sachmle]

A small torpedobooten for use in the Ost Afrika/Rift Sea area. Intent is to deliver torpedoes, not get in gun fights, therefore the 88mm guns and the 6 50cm TTs.

A-1, Brandenburg Torpedobooten laid down 1916

Displacement:
   610 t light; 629 t standard; 690 t normal; 739 t full load

Dimensions: Length overall / water x beam x draught
   242.78 ft / 234.58 ft x 24.93 ft x 9.84 ft (normal load)
   74.00 m / 71.50 m x 7.60 m  x 3.00 m

Armament:
      2 - 3.46" / 88.0 mm guns in single mounts, 22.05lbs / 10.00kg shells, 1908 Model
     Quick firing guns in deck mounts
     on centreline ends, evenly spread, 1 raised mount
      4 - 0.30" / 7.7 mm guns in single mounts, 0.01lbs / 0.01kg shells, 1916 Model
     Machine guns in deck mounts
     on side ends, evenly spread
   Weight of broadside 44 lbs / 20 kg
   Shells per gun, main battery: 200
   6 - 19.7" / 500 mm above water torpedoes

Machinery:
   Oil fired boilers, steam turbines,
   Direct drive, 2 shafts, 17,749 shp / 13,241 Kw = 29.60 kts
   Range 3,000nm at 12.00 kts
   Bunker at max displacement = 110 tons

Complement:
   66 - 87

Cost:
   £0.125 million / $0.502 million

Distribution of weights at normal displacement:
   Armament: 5 tons, 0.8 %
   Machinery: 364 tons, 52.7 %
   Hull, fittings & equipment: 225 tons, 32.6 %
   Fuel, ammunition & stores: 80 tons, 11.6 %
   Miscellaneous weights: 16 tons, 2.3 %
        -10t Small Markoni Installation
        -6t Torpedoes

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     205 lbs / 93 Kg = 9.9 x 3.5 " / 88 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.11
   Metacentric height 0.8 ft / 0.2 m
   Roll period: 12.0 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.15
   Seaboat quality  (Average = 1.00): 1.10

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.419
   Length to Beam Ratio: 9.41 : 1
   'Natural speed' for length: 15.32 kts
   Power going to wave formation at top speed: 72 %
   Trim (Max stability = 0, Max steadiness = 100): 63
   Bow angle (Positive = bow angles forward): 16.70 degrees
   Stern overhang: 3.28 ft / 1.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      16.40 ft / 5.00 m
      - Forecastle (20 %):   16.01 ft / 4.88 m
      - Mid (30 %):      16.01 ft / 4.88 m (12.01 ft / 3.66 m aft of break)
      - Quarterdeck (15 %):   12.01 ft / 3.66 m
      - Stern:      12.01 ft / 3.66 m
      - Average freeboard:   13.24 ft / 4.04 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 178.8 %
      - Above water (accommodation/working, high = better): 50.3 %
   Waterplane Area: 3,645 Square feet or 339 Square metres
   Displacement factor (Displacement / loading): 50 %
   Structure weight / hull surface area: 25 lbs/sq ft or 123 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 4.80
      - Overall: 0.62
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is cramped
   Ship has slow, easy roll, a good, steady gun platform

[The Rock Doctor]

Bear in mind that you don't need to leave room for short-range wireless any more. 

If you reduced the width until you get a 10:1 L:W ratio - would you lose much performance?

[Desertfox]

The question is, do you need a torpedo heavy DD in the Rift? What is to be her role?

[Sachmle]

Bear in mind that you don't need to leave room for short-range wireless any more. 

If you reduced the width until you get a 10:1 L:W ratio - would you lose much performance?

Same weight, better seakeeping (1.13 v 1.10) but less steadiness (63 v 70) w/ same stability 1.10

The question is, do you need a torpedo heavy DD in the Rift? What is to be her role?

To make Orange Juice?

[Sachmle]

I fiddled w/ it a little:

A-1, Brandenburg Torpedobooten laid down 1916

Displacement:
   580 t light; 598 t standard; 656 t normal; 702 t full load

Dimensions: Length overall / water x beam x draught
   242.78 ft / 234.58 ft x 23.46 ft x 9.84 ft (normal load)
   74.00 m / 71.50 m x 7.15 m  x 3.00 m

Armament:
      2 - 3.46" / 88.0 mm guns in single mounts, 22.05lbs / 10.00kg shells, 1908 Model
     Quick firing guns in deck mounts
     on centreline ends, evenly spread, 1 raised mount
      4 - 0.30" / 7.7 mm guns in single mounts, 0.01lbs / 0.00kg shells, 1916 Model
     Machine guns in deck mounts
     on side ends, evenly spread
   Weight of broadside 44 lbs / 20 kg
   Shells per gun, main battery: 200
   6 - 19.7" / 500 mm above water torpedoes

Machinery:
   Oil fired boilers, steam turbines,
   Direct drive, 2 shafts, 17,050 shp / 12,719 Kw = 29.60 kts
   Range 2,900nm at 12.00 kts
   Bunker at max displacement = 104 tons

Complement:
   64 - 84

Cost:
   £0.120 million / $0.479 million

Distribution of weights at normal displacement:
   Armament: 5 tons, 0.8 %
   Machinery: 346 tons, 52.8 %
   Hull, fittings & equipment: 223 tons, 33.9 %
   Fuel, ammunition & stores: 76 tons, 11.6 %
   Miscellaneous weights: 6 tons, 0.9 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     198 lbs / 90 Kg = 9.5 x 3.5 " / 88 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.10
   Metacentric height 0.7 ft / 0.2 m
   Roll period: 11.9 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.19
   Seaboat quality  (Average = 1.00): 1.20

Hull form characteristics:
   Hull has rise forward of midbreak
   Block coefficient: 0.424
   Length to Beam Ratio: 10.00 : 1
   'Natural speed' for length: 15.32 kts
   Power going to wave formation at top speed: 71 %
   Trim (Max stability = 0, Max steadiness = 100): 58
   Bow angle (Positive = bow angles forward): 16.70 degrees
   Stern overhang: 3.28 ft / 1.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      16.40 ft / 5.00 m
      - Forecastle (20 %):   16.01 ft / 4.88 m
      - Mid (30 %):      16.01 ft / 4.88 m (12.01 ft / 3.66 m aft of break)
      - Quarterdeck (15 %):   12.01 ft / 3.66 m
      - Stern:      12.01 ft / 3.66 m
      - Average freeboard:   13.24 ft / 4.04 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 177.9 %
      - Above water (accommodation/working, high = better): 43.9 %
   Waterplane Area: 3,440 Square feet or 320 Square metres
   Displacement factor (Displacement / loading): 50 %
   Structure weight / hull surface area: 25 lbs/sq ft or 120 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 5.43
      - Overall: 0.63
   Hull space for machinery, storage, compartmentation is cramped
   Room for accommodation and workspaces is extremely poor
   Ship has slow, easy roll, a good, steady gun platform
   Good seaboat, rides out heavy weather easily

[Korpen]

I fiddled w/ it a little:

A-1, Brandenburg Torpedobooten laid down 1916

Displacement:
   580 t light; 598 t standard; 656 t normal; 702 t full load

I think you give up far too much performance to get the seakeeping number. You can get 30kts and marginally better range on a 300ton ship if you are willing to accept a seakeeping below 0,8. It should not be a problem considering the mission profile I think.

I would also reduce the number of torpedoes to 3-4, if the ship does not hit with the first attack, it is unlikely it will be able to get into a position for a 2nd in any case.

[The Rock Doctor]

I agree with the first point.  I'd assume you're just going to fire off all six fish in one go, however.

[Sachmle]

I agree with the first point.  I'd assume you're just going to fire off all six fish in one go, however.

Two fixed tubes over the bow fired on the way in, two twin sets amidships to fire as she turns.