DD's

[Sachmle]

Question, is the 750t limit on Destroyer weight the normal or light hull weight?

[Borys]

Ahoj!
Light. We use light for all accounting.
Borys

[Desertfox]

However I would suggest not building to the limit, quantity counts more than quality for small ships.

[Ithekro]

Which some are finding out the hard way.

[P3D]

An 500t destroyer could take less damage than a 750t one, has about two/thirds the range, and half the armament. As UdSA does not have the luxury of oil-firing boilers, they are better off with large DDs, unless you are content with 2000@10kts range ans low speeds.

Switzerland has several 'economy' destroyer classes with 500t displacement but with speed limited to 27kts. For some reason they could not run away from cruisers (with similar nominal max speed) in heavy seas. Now you can debate whether it was worth it or not.

[Korpen]

An 500t destroyer could take less damage than a 750t one, has about two/thirds the range, and half the armament. As UdSA does not have the luxury of oil-firing boilers, they are better off with large DDs, unless you are content with 2000@10kts range ans low speeds.

Switzerland has several 'economy' destroyer classes with 500t displacement but with speed limited to 27kts. For some reason they could not run away from cruisers (with similar nominal max speed) in heavy seas. Now you can debate whether it was worth it or not.

Those are not the only disadvantages of small DDs. They also have significantly worse habitation, making them unsuited for long periods at sea. Also, never forget that seakeeping and seaboat rating are compared to ships of the same size, so a 50% increas in size will give better seakeeping by virtue of being larger.

As P3D said, a 750tonner can usally take about 50% more damage then a 500 tonner, without being a 50% larger target.

Finally we have the raised forecastle vs. flush decked issue. Generally, a DD with a high forecastle have much better ability to maintain speed in sea then a flushed decked one (with the same average freeboard). Flushed deck ones do have an advantage in that the hull is under less strain, so will most likely, so they are likely to have longer lifetimes as the hulls suffer less wear. 

[Sachmle]

I've been pounding my head into the wall trying to come up with something and this is the best I've come up with.  I can't seem to get the cross-section strenght above .47. Any help would be welcomed.

Enter ship name, USA Torpedoboat Destroyer laid down 1906 (Engine 1905)

Displacement:
   748 t light; 768 t standard; 880 t normal; 970 t full load

Dimensions: Length overall / water x beam x draught
   280.00 ft / 280.00 ft x 25.00 ft x 9.00 ft (normal load)
   85.34 m / 85.34 m x 7.62 m  x 2.74 m

Armament:
      1 - 4.00" / 102 mm guns in single mounts, 30.00lbs / 13.61kg shells, 1906 Model
     Quick firing gun in deck mount
     on centreline forward
      4 - 1.00" / 25.4 mm guns in single mounts, 0.50lbs / 0.23kg shells, 1906 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 32 lbs / 15 kg
   Shells per gun, main battery: 150
   2 - 19.0" / 482.6 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.00" / 25 mm         -               -

   - Conning tower: 1.00" / 25 mm

Machinery:
   Coal fired boilers, steam turbines,
   Direct drive, 4 shafts, 17,263 shp / 12,878 Kw = 29.00 kts
   Range 3,000nm at 10.00 kts
   Bunker at max displacement = 202 tons (100% coal)
     Caution: Delicate, lightweight machinery

Complement:
   80 - 105

Cost:
   £0.104 million / $0.417 million

Distribution of weights at normal displacement:
   Armament: 4 tons, 0.5 %
   Armour: 4 tons, 0.5 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 2 tons, 0.2 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 2 tons, 0.2 %
   Machinery: 533 tons, 60.6 %
   Hull, fittings & equipment: 186 tons, 21.1 %
   Fuel, ammunition & stores: 132 tons, 15.1 %
   Miscellaneous weights: 20 tons, 2.3 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     156 lbs / 71 Kg = 4.9 x 4.0 " / 102 mm shells or 0.2 torpedoes
   Stability (Unstable if below 1.00): 1.56
   Metacentric height 1.3 ft / 0.4 m
   Roll period: 9.1 seconds
   Steadiness   - As gun platform (Average = 50 %): 60 %
         - Recoil effect (Restricted arc if above 1.00): 0.04
   Seaboat quality  (Average = 1.00): 1.10

Hull form characteristics:
   Hull has raised forecastle
   Block coefficient: 0.489
   Length to Beam Ratio: 11.20 : 1
   'Natural speed' for length: 16.73 kts
   Power going to wave formation at top speed: 67 %
   Trim (Max stability = 0, Max steadiness = 100): 55
   Bow angle (Positive = bow angles forward): 0.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      20.00 ft / 6.10 m
      - Forecastle (30 %):   20.00 ft / 6.10 m (8.00 ft / 2.44 m aft of break)
      - Mid (50 %):      8.00 ft / 2.44 m
      - Quarterdeck (15 %):   8.00 ft / 2.44 m
      - Stern:      8.00 ft / 2.44 m
      - Average freeboard:   11.60 ft / 3.54 m

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 201.5 %
      - Above water (accommodation/working, high = better): 73.8 %
   Waterplane Area: 4,617 Square feet or 429 Square metres
   Displacement factor (Displacement / loading): 30 %
   Structure weight / hull surface area: 20 lbs/sq ft or 95 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.47
      - Longitudinal: 1.43
      - Overall: 0.52
   Hull space for machinery, storage, compartmentation is extremely poor
   Room for accommodation and workspaces is cramped

[Korpen]

I've been pounding my head into the wall trying to come up with something and this is the best I've come up with.  I can't seem to get the cross-section strenght above .47. Any help would be welcomed.

Might i suggest something close to the Dutch F-Class?
http://www.navalism.org/index.php?topic=690.msg6349#msg6349

It is 1,4 kts slower then you ship however.

[P3D]

1905 engines are too heavy for 29kts. Go with 27kts. 533t of 750 is machinery.
Misc weight should not be larger than 14-15t (10t for W/T + torps + other) with the current armament.

An Orange design for comparison.
http://www.navalism.org/index.php?topic=138.0

[Desertfox]

Your ship is too big, that's the problem. For comparision a 500ton, 29kt TB with 1905 engines:

Fisher class (ex-TR-96), New Switzerland (ex-CSA) Destroyer laid down 1896 (Engine 1905)

Displacement:
   499 t light; 518 t standard; 576 t normal; 622 t full load

Dimensions: Length overall / water x beam x draught
   251.31 ft / 250.00 ft x 21.00 ft x 9.50 ft (normal load)
   76.60 m / 76.20 m x 6.40 m  x 2.90 m

Armament:
      2 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1905 Model
     Quick firing guns in deck mounts
     on centreline ends, evenly spread
      1 - 1.57" / 40.0 mm guns in single mounts, 1.95lbs / 0.88kg shells, 1896 Model
     Quick firing gun in deck mount
     on centreline aft
      4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1896 Model
     Machine guns in deck mounts
     on side, evenly spread
   Weight of broadside 66 lbs / 30 kg
   Shells per gun, main battery: 200
   4 - 19.7" / 500.38 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.50" / 13 mm         -               -

Machinery:
   Coal and oil fired boilers, steam turbines,
   Direct drive, 2 shafts, 13,251 shp / 9,885 Kw = 29.00 kts
   Range 2,000nm at 10.00 kts
   Bunker at max displacement = 103 tons (90% coal)
     Caution: Delicate, lightweight machinery

Complement:
   58 - 76

Cost:
   £0.070 million / $0.282 million

Distribution of weights at normal displacement:
   Armament: 8 tons, 1.4 %
   Armour: 2 tons, 0.4 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 2 tons, 0.4 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 328 tons, 57.0 %
   Hull, fittings & equipment: 156 tons, 27.2 %
   Fuel, ammunition & stores: 77 tons, 13.3 %
   Miscellaneous weights: 4 tons, 0.7 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     114 lbs / 52 Kg = 3.6 x 4.0 " / 102 mm shells or 0.1 torpedoes
   Stability (Unstable if below 1.00): 1.22
   Metacentric height 0.7 ft / 0.2 m
   Roll period: 10.6 seconds
   Steadiness   - As gun platform (Average = 50 %): 70 %
         - Recoil effect (Restricted arc if above 1.00): 0.23
   Seaboat quality  (Average = 1.00): 1.02

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.404
   Length to Beam Ratio: 11.90 : 1
   'Natural speed' for length: 15.81 kts
   Power going to wave formation at top speed: 65 %
   Trim (Max stability = 0, Max steadiness = 100): 69
   Bow angle (Positive = bow angles forward): 5.00 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 (20 %):   12.00 ft / 3.66 m
      - Mid (50 %):      8.00 ft / 2.44 m
      - Quarterdeck (15 %):   8.00 ft / 2.44 m
      - Stern:      8.00 ft / 2.44 m
      - Average freeboard:   9.64 ft / 2.94 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 196.0 %
      - Above water (accommodation/working, high = better): 51.1 %
   Waterplane Area: 3,239 Square feet or 301 Square metres
   Displacement factor (Displacement / loading): 25 %
   Structure weight / hull surface area: 22 lbs/sq ft or 107 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.50
      - Longitudinal: 1.84
      - Overall: 0.57
   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

[P3D]

A DD without W/T, 66% the range of the 750t one, draught limiting littoral capabilities, so abysmal seakeeping that the ship can do 29kts only in sea state 1 or 2, and could not fit lvl 0 docks. Did I miss anything?

[Desertfox]

Switzerland has several 'economy' destroyer classes with 500t displacement but with speed limited to 27kts. For some reason they could not run away from cruisers (with similar nominal max speed) in heavy seas. Now you can debate whether it was worth it or not.

Ah yes a brand new 28kt cruiser with untrained crew, managed to chase down not one but 4, 29kt DDs with good crews, all going separate direction. Exceptional performance I would say, since not even with bad weather would the cruiser have more than 1kt of speed advantage.

A DD without W/T, 66% the range of the 750t one, draught limiting littoral capabilities, so abysmal seakeeping that the ship can do 29kts only in sea state 1 or 2, and could not fit lvl 0 docks. Did I miss anything?

Like if 1905 DDs had W/T. Gotta give something up in this case range. Abysmal seakeeping? Heck no warning on a 29kt DD, I would call that Good Seakeeping. Can't fit in L0 Docks? Neither can the USA one, and this one has twice the firepower.

[P3D]

[quote author=Desertfox link=topic=1491.msg15088#msg15088 Ah yes a brand new 28kt cruiser with untrained crew, managed to chase down not one but 4, 29kt DDs with good crews, all going separate direction. Exceptional performance I would say, since not even with bad weather would the cruiser have more than 1kt of speed advantage.

Abysmal seakeeping? Heck no warning on a 29kt DD, I would call that Good Seakeeping. Can't fit in L0 Docks? Neither can the USA one, and this one has twice the firepower.
[/quote]

No need to lie, Desertfox. That specific battle was in a sea state of 6, where the engine SHP hardly matters determining max speed. The DKB speed advantage was rather like 5-6kts in that sea, as . The DDs could not do more than 21-22kts. After that, the DKB crew just would not miss some live target practice, inexperienced crew or not.

Just there's no point in building 500t 29kts ships with average (for his class, i.e. abysmal) seakeeping, if 30% the time the weather won't allow you go faster than 24kts.

[Ithekro]

11 foot draft might help, or just stick to the lighter 12 pounder as your main anti-torpedo boat gun.  It won't be able to do anything to a cruiser, but if it is designed to take on torpedo boats, destroyers, and unarmored cruisers with the guns and larger ships with the torpedoes, you could build a relatively cheap destroyer.

This is a roughly historical Chilean destroyer...post-1909 refit.
A destroyer like this was common until about 1912 when the larger 1,200 ton destroyers started to be built.  Note that this was the best I could do with the specification listed in Janes' Fighting Ships.


Capitan O'Brien

Chilean Destroyer laid down 1902 (Engine 1909)

Displacement:
266 t light; 275 t standard; 311 t normal; 339 t full load

Dimensions: Length overall / water x beam x draught
215.17 ft / 213.00 ft x 21.50 ft x 8.50 ft (normal load)
65.58 m / 64.92 m x 6.55 m x 2.59 m

Armament:
1 - 2.88" / 73.3 mm guns in single mounts, 12.00lbs / 5.44kg shells, 1902 Model
Quick firing gun in deck mount
on centreline forward
5 - 2.29" / 58.2 mm guns in single mounts, 6.00lbs / 2.72kg shells, 1902 Model
Quick firing guns in deck mounts
on side, evenly spread
Weight of broadside 42 lbs / 19 kg
Shells per gun, main battery: 100
3 - 18.0" / 457.2 mm above water torpedoes

Machinery:
Coal fired boilers, complex reciprocating steam engines,
Direct drive, 2 shafts, 4,986 ihp / 3,719 Kw = 25.00 kts
Range 900nm at 15.00 kts (Bunkerage = 66 tons)

Complement:
36 - 48

Cost:
£0.037 million / $0.147 million

Distribution of weights at normal displacement:
Armament: 5 tons, 1.7 %
Machinery: 165 tons, 52.9 %
Hull, fittings & equipment: 91 tons, 29.1 %
Fuel, ammunition & stores: 46 tons, 14.7 %
Miscellaneous weights: 5 tons, 1.6 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
83 lbs / 38 Kg = 6.9 x 2.9 " / 73 mm shells or 0.1 torpedoes
Stability (Unstable if below 1.00): 1.25
Metacentric height 0.7 ft / 0.2 m
Steadiness - As gun platform (Average = 50 %): 100 %
- Recoil effect (Restricted arc if above 1.00): 0.17
Seaboat quality (Average = 1.00): 1.18

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.280
Length to Beam Ratio: 9.91 : 1
'Natural speed' for length: 14.59 kts
Power going to wave formation at top speed: 57 %
Trim (Max stability = 0, Max steadiness = 100): 85
Bow angle (Positive = bow angles forward): 4.30 degrees
Stern overhang: 1.00 ft / 0.30 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 15.50 ft / 4.72 m
- Forecastle (20 %): 9.50 ft / 2.90 m
- Mid (50 %): 6.00 ft / 1.83 m
- Quarterdeck (15 %): 6.00 ft / 1.83 m
- Stern: 6.00 ft / 1.83 m
- Average freeboard: 7.71 ft / 2.35 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 185.1 %
- Above water (accommodation/working, high = better): 74.9 %
Waterplane Area: 3,112 Square feet or 289 Square metres
Displacement factor (Displacement / loading): 38 %
Structure weight / hull surface area: 18 lbs/sq ft or 90 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.50
- Longitudinal: 1.50
- Overall: 0.55
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

[Ithekro]

I might note that in some navies, some new ship's crews tend to have good gunnery skills because they are fresh from live fire training.  They do not however have very good skills in other areas because it is harder to practice live damage control, and live battle manuevers that it is to fire live shells at a target.

However that does not help a destroyer much.  A common speed for this era was 25 knots, at least in South America.