Logi's Design Studies

[KWorld]

Turret armor's probably a bit light in case you run into a rifled gun.

BC is VERY high.

A little more speed would be nice for going upriver.

[Logi]

It's slower than tankers today, which typically run 0.80 and above C_b. I don't think the C_b is much of a problem.
More speed might be nice, but I defer to the typical river-work monitors of the period.
Indeed, the turret work is light in the scenario you mention, but I don't think fighting a ship with a rifled gun is part of the mission description.

IMO, hypotheticals like that are dangerous in that they eventually double or triple a design's displacement.


In other news, a 1870 line battleship design.

Hull-08 Sch 1,  Battleship laid down 1870

Displacement:
   8,268 t light; 8,700 t standard; 9,500 t normal; 10,140 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (405.10 ft / 400.00 ft) x 51.50 ft x (27.00 / 28.52 ft)
   (123.47 m / 121.92 m) x 15.70 m  x (8.23 / 8.69 m)

Armament:
      4 - 14.00" / 356 mm 15.0 cal guns - 1,016.77lbs / 461.20kg shells, 80 per gun
     Muzzle loading guns in Coles/Ericsson turret mounts, 1870 Model
     2 x Twin mounts on centreline ends, evenly spread
      6 - 6.00" / 152 mm 30.0 cal guns - 83.29lbs / 37.78kg shells, 220 per gun
     Muzzle loading guns in deck mounts, 1870 Model
     6 x Single mounts on sides, evenly spread
      Weight of broadside 4,567 lbs / 2,071 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   24.0" / 610 mm   160.00 ft / 48.77 m   8.00 ft / 2.44 m
   Ends:   3.00" / 76 mm   240.00 ft / 73.15 m   8.00 ft / 2.44 m
     Main Belt covers 62 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   16.0" / 406 mm   3.00" / 76 mm            -
   2nd:   2.00" / 51 mm   1.00" / 25 mm            -

   - Armoured deck - single deck:
   For and Aft decks: 3.00" / 76 mm
   Forecastle: 3.00" / 76 mm  Quarter deck: 3.00" / 76 mm

   - Conning towers: Forward 16.00" / 406 mm, Aft 0.00" / 0 mm

Machinery:
   Coal fired boilers, simple reciprocating steam engines,
   Direct drive, 1 shaft, 5,048 ihp / 3,766 Kw = 14.00 kts
   Range 4,000nm at 8.00 kts
   Bunker at max displacement = 1,440 tons (100% coal)

Complement:
   480 - 625

Cost:
   £0.605 million / $2.419 million

Distribution of weights at normal displacement:
   Armament: 275 tons, 2.9 %
      - Guns: 275 tons, 2.9 %
   Armour: 3,165 tons, 33.3 %
      - Belts: 1,666 tons, 17.5 %
      - Armament: 522 tons, 5.5 %
      - Armour Deck: 823 tons, 8.7 %
      - Conning Tower: 155 tons, 1.6 %
   Machinery: 1,237 tons, 13.0 %
   Hull, fittings & equipment: 3,590 tons, 37.8 %
   Fuel, ammunition & stores: 1,232 tons, 13.0 %
   Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     8,281 lbs / 3,756 Kg = 8.6 x 14.0 " / 356 mm shells or 2.1 torpedoes
   Stability (Unstable if below 1.00): 1.10
   Metacentric height 2.2 ft / 0.7 m
   Roll period: 14.5 seconds
   Steadiness   - As gun platform (Average = 50 %): 50 %
         - Recoil effect (Restricted arc if above 1.00): 0.77
   Seaboat quality  (Average = 1.00): 1.01

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.598 / 0.604
   Length to Beam Ratio: 7.77 : 1
   'Natural speed' for length: 20.00 kts
   Power going to wave formation at top speed: 31 %
   Trim (Max stability = 0, Max steadiness = 100): 50
   Bow angle (Positive = bow angles forward): 20.00 degrees
   Stern overhang: -5.00 ft / -1.52 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  14.00 ft / 4.27 m,  9.00 ft / 2.74 m
      - Forward deck:   30.00 %,  9.00 ft / 2.74 m,  9.00 ft / 2.74 m
      - Aft deck:   35.00 %,  9.00 ft / 2.74 m,  9.00 ft / 2.74 m
      - Quarter deck:   15.00 %,  9.00 ft / 2.74 m,  11.00 ft / 3.35 m
      - Average freeboard:      9.55 ft / 2.91 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 58.5 %
      - Above water (accommodation/working, high = better): 52.5 %
   Waterplane Area: 14,702 Square feet or 1,366 Square metres
   Displacement factor (Displacement / loading): 136 %
   Structure weight / hull surface area: 156 lbs/sq ft or 762 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.94
      - Longitudinal: 1.69
      - Overall: 1.00
   Excellent machinery, storage, compartmentation space
   Cramped accommodation and workspace room

[KWorld]

Rifled guns were also used inland and on shore during the US Civil War, for example a 7.5" Blakely rifle was used by the Confederates against Union gunboats at Vicksburg, and the Union used 8" Parrott rifles both as siege weapons and as coast defense weapons.  The assumptions you make will potentially save you or cost you money or ships, depending on which way you bias the choice.


As far as the ship goes, the 6" guns are too long for muzzleloaders, and long for blackpowder weapons in any case.  The main belt armor is very thick , but covers little of hulls length and leaves 5' exposed between the top of the belt and the top of the hull.  Armor on the 6" guns doesn't make sense for the period.  No sails, so you're limited to sailing where you can get coal.

[Logi]

I didn't look up the 6" gun's particulars, so I'll correct it to breech-loading. I'll remove the secondary armor. The secondary was based on that found on Jef's BB design.

The main belt is modeled off the Abercrombie-class monitor, which was thick at 24" (1870 armor is usually just iron plates), short (look at the US predreadnought armor heights for example), covers little of the hulls length. If you look at the data on US predreadnoughts and monitors, their main belts are only ~8 ft tall. Furthermore, if you look at the Indianna and Iowa cross-sections, they have 1 deck unarmored.

For example:
In Maine, the belt is 7' tall (3' above, 4' below) and 180' long on a 318' 3" long ship.
In Texas, the belt is 6.5' tall (2' above, 4.5' below) and 118' long on a 301' 4" long ship.
In New Jersey, the belt is 8' tall (3' above, 5' below) and 192' long on a 435' long ship.
In Louisiana, the belt is 9.3' tall and 200' long on a 450' long ship.


Well in any case, I messed with the design and found I can get more strength from a shorter hull length, so:

Hull-08 Sch 2,  Battleship laid down 1870

Displacement:
   7,001 t light; 7,316 t standard; 8,000 t normal; 8,548 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (300.00 ft / 300.00 ft) x 52.00 ft x (27.00 / 28.60 ft)
   (91.44 m / 91.44 m) x 15.85 m  x (8.23 / 8.72 m)

Armament:
      4 - 14.00" / 356 mm 15.0 cal guns - 1,016.77lbs / 461.20kg shells, 50 per gun
     Muzzle loading guns in Coles/Ericsson turret mounts, 1870 Model
     2 x Twin mounts on centreline ends, evenly spread
      6 - 6.00" / 152 mm 30.0 cal guns - 83.29lbs / 37.78kg shells, 150 per gun
     Breech loading guns in casemate mounts, 1870 Model
     6 x Single mounts on sides, evenly spread
      Weight of broadside 4,567 lbs / 2,071 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   24.0" / 610 mm   130.00 ft / 39.62 m   7.00 ft / 2.13 m
   Ends:   3.00" / 76 mm   170.00 ft / 51.82 m   7.00 ft / 2.13 m
   Upper:   4.00" / 102 mm   130.00 ft / 39.62 m   6.00 ft / 1.83 m
     Main Belt covers 67 % of normal length

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   16.0" / 406 mm   3.00" / 76 mm            -

   - Armoured deck - single deck:
   For and Aft decks: 3.00" / 76 mm
   Forecastle: 3.00" / 76 mm  Quarter deck: 3.00" / 76 mm

   - Conning towers: Forward 13.40" / 340 mm, Aft 0.00" / 0 mm

Machinery:
   Coal fired boilers, simple reciprocating steam engines,
   Direct drive, 1 shaft, 4,897 ihp / 3,653 Kw = 14.00 kts
   Range 4,000nm at 8.00 kts
   Bunker at max displacement = 1,232 tons (100% coal)

Complement:
   422 - 549

Cost:
   £0.555 million / $2.221 million

Distribution of weights at normal displacement:
   Armament: 277 tons, 3.5 %
      - Guns: 277 tons, 3.5 %
   Armour: 2,635 tons, 32.9 %
      - Belts: 1,379 tons, 17.2 %
      - Armament: 471 tons, 5.9 %
      - Armour Deck: 670 tons, 8.4 %
      - Conning Tower: 115 tons, 1.4 %
   Machinery: 1,200 tons, 15.0 %
   Hull, fittings & equipment: 2,888 tons, 36.1 %
   Fuel, ammunition & stores: 999 tons, 12.5 %
   Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     6,550 lbs / 2,971 Kg = 6.8 x 14.0 " / 356 mm shells or 1.7 torpedoes
   Stability (Unstable if below 1.00): 1.24
   Metacentric height 2.8 ft / 0.8 m
   Roll period: 13.2 seconds
   Steadiness   - As gun platform (Average = 50 %): 51 %
         - Recoil effect (Restricted arc if above 1.00): 0.76
   Seaboat quality  (Average = 1.00): 1.26

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.665 / 0.671
   Length to Beam Ratio: 5.77 : 1
   'Natural speed' for length: 17.32 kts
   Power going to wave formation at top speed: 44 %
   Trim (Max stability = 0, Max steadiness = 100): 40
   Bow angle (Positive = bow angles forward): 0.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  9.00 ft / 2.74 m,  9.50 ft / 2.90 m
      - Forward deck:   30.00 %,  9.50 ft / 2.90 m,  9.50 ft / 2.90 m
      - Aft deck:   35.00 %,  9.50 ft / 2.90 m,  9.50 ft / 2.90 m
      - Quarter deck:   15.00 %,  9.50 ft / 2.90 m,  9.00 ft / 2.74 m
      - Average freeboard:      9.42 ft / 2.87 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 66.5 %
      - Above water (accommodation/working, high = better): 51.3 %
   Waterplane Area: 11,970 Square feet or 1,112 Square metres
   Displacement factor (Displacement / loading): 125 %
   Structure weight / hull surface area: 161 lbs/sq ft or 785 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.88
      - Longitudinal: 2.86
      - Overall: 1.00
   Excellent machinery, storage, compartmentation space
   Cramped accommodation and workspace room
   Good seaboat, rides out heavy weather easily

[KWorld]

Not sure what a WWI monitor design has to do with an 1870 ship design.

I don't think a Cole/Ericcson turret is going to work with that much discrepancy in weight between the front and the sides  At best, it will be similar to the early USN turrets of the New Navy, where the turrets were unbalanced  and training the guns resulted in the ship heeling.

[Logi]

Er, sorry. I had the two ships opened next to each other and seem to have gotten the names wrong. How embarrassing. I mean to say the Colossus-class battleship (1882).

I'm not as privy to the details of the Cole/Ericsson construction, so what is the recommended ratio?

In any case, I'm a bit confused on a point. The balance of a turret is determined by it's center of gravity which is a function of it's front/back weight ratio and it's left/right side weight ratio. Why should it matter if the sides are lighter as long as it's balanced? The center of gravity does not change if the front/back is heavier than the sides.

[Delta Force]

The rule of thumb for black powder cannons is to never have a barrel longer than 20 times the projectile's diameter. Black powder gives a sharp jolt instead of a smooth combustion. Exceeding 20 caliber actually reduces muzzle velocity, range, and accuracy. Brown powder and smokeless powder burn slower and provide a smoother and more sustained acceleration, allowing for longer barrels.

[KWorld]

An Ericsson turret literally turns on a spindle, so having a turret that's substantially unbalanced (like having a 16" face and 3" sides, rear, and top) would not work well.  Pictures of both the Coles and Ericsson plans are here: http://www.cityofart.net/bship/turretships.html.  Judging by HMS Monarch, I would suggest keeping the front and sides/rear of the turret within a few inches of one another, up to perhaps as many as 5".


<nod>   Yeah, and the improved prismatic powder with a more consistent burning speed won't be available for few years yet.

[Nobody]

*nods to the short black powder cannons*
Also the bigger the caliber the shorter the barrel (measured in calibers).

I have found a few exceptions though: Krupp produced a few very big (like 45 cm or so) guns, which were breech loaders and between 40 and 50 calibers long in the mid 19^th century. Unfortunately, I can't find the right link anymore. This page mentions such a gun, but not when it was written, while this was written in 1887 and might refer to a different gun because I remember them being around and discussed for the Italia (laid down 1876).
I also found a few pictures (but no relevant data) about a giant Krupp breech loader which won a prize on the 1867 world exhibition.

[KWorld]

*nods to the short black powder cannons*
Also the bigger the caliber the shorter the barrel (measured in calibers).

I have found a few exceptions though: Krupp produced a few very big (like 45 cm or so) guns, which were breech loaders and between 40 and 50 calibers long in the mid 19^th century. Unfortunately, I can't find the right link anymore. This page mentions such a gun, but not when it was written, while this was written in 1887 and might refer to a different gun because I remember them being around and discussed for the Italia (laid down 1876).
I also found a few pictures (but no relevant data) about a giant Krupp breech loader which won a prize on the 1867 world exhibition.

The article on The New Krupp Guns from Scientific American is from 1887.  Those L/40 guns are using brown powder, NOT black powder.

[Logi]

Laid down in 1880, the Kaze-class uses it's high endurance, speed, and steady gun platform to raid enemy commerce.

Kaze, Japan Commerce Raider laid down 1880

Displacement:
   6,000 t light; 6,250 t standard; 7,220 t normal; 7,996 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (505.36 ft / 500.00 ft) x 44.00 ft x (22.50 / 24.41 ft)
   (154.03 m / 152.40 m) x 13.41 m  x (6.86 / 7.44 m)

Armament:
      4 - 8.00" / 203 mm 45.0 cal guns - 238.03lbs / 107.97kg shells, 200 per gun
     Breech loading guns in deck mounts, 1880 Model
     4 x Single mounts on centreline, evenly spread
      Weight of broadside 952 lbs / 432 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   1.50" / 38 mm   500.00 ft / 152.40 m   8.00 ft / 2.44 m
     Main Belt covers 154 % of normal length

   - Protected deck - single deck:
   For and Aft decks: 0.50" / 13 mm
   Forecastle: 0.50" / 13 mm  Quarter deck: 0.50" / 13 mm

   - Conning towers: Forward 1.00" / 25 mm, Aft 0.00" / 0 mm

Machinery:
   Coal fired boilers, simple reciprocating steam engines,
   Direct drive, 1 shaft, 15,845 ihp / 11,821 Kw = 21.00 kts
   Range 10,000nm at 7.00 kts
   Bunker at max displacement = 1,746 tons (100% coal)

Complement:
   391 - 509

Cost:
   £0.713 million / $2.852 million

Distribution of weights at normal displacement:
   Armament: 138 tons, 1.9 %
      - Guns: 138 tons, 1.9 %
   Armour: 363 tons, 5.0 %
      - Belts: 222 tons, 3.1 %
      - Armour Deck: 133 tons, 1.8 %
      - Conning Tower: 8 tons, 0.1 %
   Machinery: 3,274 tons, 45.3 %
   Hull, fittings & equipment: 2,225 tons, 30.8 %
   Fuel, ammunition & stores: 1,220 tons, 16.9 %
   Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     2,663 lbs / 1,208 Kg = 12.2 x 8.0 " / 203 mm shells or 0.6 torpedoes
   Stability (Unstable if below 1.00): 1.36
   Metacentric height 2.5 ft / 0.8 m
   Roll period: 11.7 seconds
   Steadiness   - As gun platform (Average = 50 %): 100 %
         - Recoil effect (Restricted arc if above 1.00): 0.27
   Seaboat quality  (Average = 1.00): 1.51

Hull form characteristics:
   Hull has a flush deck,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.511 / 0.521
   Length to Beam Ratio: 11.36 : 1
   'Natural speed' for length: 22.36 kts
   Power going to wave formation at top speed: 37 %
   Trim (Max stability = 0, Max steadiness = 100): 66
   Bow angle (Positive = bow angles forward): 15.00 degrees
   Stern overhang: 0.00 ft / 0.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  20.00 ft / 6.10 m,  15.00 ft / 4.57 m
      - Forward deck:   30.00 %,  15.00 ft / 4.57 m,  13.00 ft / 3.96 m
      - Aft deck:   35.00 %,  13.00 ft / 3.96 m,  13.00 ft / 3.96 m
      - Quarter deck:   15.00 %,  13.00 ft / 3.96 m,  14.00 ft / 4.27 m
      - Average freeboard:      14.18 ft / 4.32 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 153.4 %
      - Above water (accommodation/working, high = better): 93.5 %
   Waterplane Area: 14,253 Square feet or 1,324 Square metres
   Displacement factor (Displacement / loading): 98 %
   Structure weight / hull surface area: 88 lbs/sq ft or 430 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.98
      - Longitudinal: 1.16
      - Overall: 1.00
   Cramped machinery, storage, compartmentation space
   Adequate accommodation and workspace room
   Ship has slow, easy roll, a good, steady gun platform
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

[Walter]

L:B ratio might be a bit of an issue here. I assume the armor is only to protect from hand guns that would be carried by the crews of target ships.

[Logi]

You would be correct with regard to the armor.
I'll attempt to work some magic on the hull form.

[KWorld]

45 caliber guns also make no sense in 1880, they're too long for brown powder to use efficiently and given the technology of the day would probably suffer badly from droop.


For a commerce raider, 4 8" guns are also an odd choice: too big to fire rapidly, too small to punch through armor, and bigger than necessary to attack unarmed vessels.

[Walter]

For a commerce raider, 4 8" guns are also an odd choice: too big to fire rapidly, too small to punch through armor, and bigger than necessary to attack unarmed vessels.

It's probably going to be faster than anything that can hurt it so probably better to go for the smaller guns you think?