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Development of Ericsson design for monitor
Development of Ericsson design for Requirement 5 - sea service ironclad


Ericsson's initial impulse when attempting to fulfil US Ordnance department requirements for ironclads was to produce his beloved turret vessels. His original design aimed to fulfil his initial appreciation, which was that any two-turret ship was manifestly inferior to a one-turret ship capable of a far more powerful and better protected turret on the same displacement; as such his initial monitor design for the Calvinist did not fulfil requirements and was also considered dangerously lacking stability.

USS Calvinist, United States of America Monitor laid down 1864

Displacement:
5,586 t light; 5,837 t standard; 6,448 t normal; 6,936 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(340.00 ft / 340.00 ft) x 50.00 ft x (25.00 / 26.52 ft)
(103.63 m / 103.63 m) x 15.24 m x (7.62 / 8.08 m)

Armament:
2 - 20.00" / 508 mm 13.0 cal guns - 2,754.66lbs / 1,249.49kg shells, 40 per gun
Muzzle loading guns in Coles/Ericsson turret mount, 1864 Model
1 x Single mount on centreline amidships (forward deck)
Weight of broadside 5,509 lbs / 2,499 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 8.00" / 203 mm 221.00 ft / 67.36 m 6.00 ft / 1.83 m
Ends: 8.00" / 203 mm 118.98 ft / 36.27 m 6.00 ft / 1.83 m
Main Belt covers 100 % of normal length

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 10.0" / 254 mm 10.0" / 254 mm -

- Armoured deck - multiple decks: 2.00" / 51 mm For and Aft decks
Forecastle: 2.00" / 51 mm Quarter deck: 2.00" / 51 mm

- Conning towers: Forward 12.00" / 305 mm, Aft 0.00" / 0 mm

Machinery:
Coal fired boilers, simple reciprocating steam engines,
Direct drive, 1 shaft, 4,268 ihp / 3,184 Kw = 14.00 kts
Range 3,000nm at 8.00 kts
Bunker at max displacement = 1,099 tons (100% coal)

Complement:
359 - 467

Cost:
£0.513 million / $2.052 million

Distribution of weights at normal displacement:
Armament: 280 tons, 4.3 %
Armour: 1,581 tons, 24.5 %
- Belts: 666 tons, 10.3 %
- Armament: 405 tons, 6.3 %
- Armour Deck: 420 tons, 6.5 %
- Conning Tower: 90 tons, 1.4 %
Machinery: 1,210 tons, 18.8 %
Hull, fittings & equipment: 2,516 tons, 39.0 %
Fuel, ammunition & stores: 862 tons, 13.4 %
Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
2,002 lbs / 908 Kg = 0.8 x 20.0 " / 508 mm shells or 0.7 torpedoes
Stability (Unstable if below 1.00): 1.00
Metacentric height 1.8 ft / 0.5 m
Roll period: 15.8 seconds
Steadiness - As gun platform (Average = 50 %): 26 %
- Recoil effect (Restricted arc if above 1.00): 0.39
Seaboat quality (Average = 1.00): 0.18

Hull form characteristics:
Hull has a flush deck,
a normal bow and a cruiser stern
Block coefficient (normal/deep): 0.531 / 0.539
Length to Beam Ratio: 6.80 : 1
'Natural speed' for length: 18.44 kts
Power going to wave formation at top speed: 34 %
Trim (Max stability = 0, Max steadiness = 100): 74
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 %, 3.00 ft / 0.91 m, 3.00 ft / 0.91 m
- Forward deck: 30.00 %, 3.00 ft / 0.91 m, 3.00 ft / 0.91 m
- Aft deck: 35.00 %, 3.00 ft / 0.91 m, 3.00 ft / 0.91 m
- Quarter deck: 15.00 %, 3.00 ft / 0.91 m, 3.00 ft / 0.91 m
- Average freeboard: 3.00 ft / 0.91 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 82.7 %
- Above water (accommodation/working, high = better): 17.9 %
Waterplane Area: 11,266 Square feet or 1,047 Square metres
Displacement factor (Displacement / loading): 119 %
Structure weight / hull surface area: 159 lbs/sq ft or 779 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.69
- Longitudinal: 1.20
- Overall: 0.73
Caution: Hull subject to strain in open-sea
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is extremely poor
Ship has quick, lively roll, not a steady gun platform
Caution: Lacks seaworthiness - very limited seakeeping ability



After it was pointed out that this did not fulfil the requirement for the ship to have a four-gun broadside, Ericsson went away in bad temper and redid his design. This second model (Calvinist design 2) possessed the requisite four-gun broadside but was clearly the most minor alteration he felt possible to get away with.



USS Calvinist, United States of America Monitor laid down 1864
Central citadel ship

Displacement:
5,578 t light; 5,837 t standard; 6,448 t normal; 6,936 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(340.00 ft / 340.00 ft) x 50.00 ft x (25.00 / 26.52 ft)
(103.63 m / 103.63 m) x 15.24 m x (7.62 / 8.08 m)

Armament:
2 - 20.00" / 508 mm 13.0 cal guns - 2,754.66lbs / 1,249.49kg shells, 40 per gun
Muzzle loading guns in Coles/Ericsson turret mount, 1864 Model
1 x Single mount on centreline, forward deck centre
2 - 8.00" / 203 mm 20.0 cal guns - 179.24lbs / 81.30kg shells, 40 per gun
Muzzle loading guns in Coles/Ericsson turret mount, 1864 Model
1 x Single mount on centreline, aft deck centre
Weight of broadside 5,868 lbs / 2,662 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 8.00" / 203 mm 221.00 ft / 67.36 m 6.00 ft / 1.83 m
Ends: 8.00" / 203 mm 118.98 ft / 36.27 m 6.00 ft / 1.83 m
Main Belt covers 100 % of normal length

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 10.0" / 254 mm 10.0" / 254 mm -
2nd: 5.00" / 127 mm 5.00" / 127 mm -

- Armoured deck - multiple decks: 2.00" / 51 mm For and Aft decks
Forecastle: 2.00" / 51 mm Quarter deck: 2.00" / 51 mm

- Conning towers: Forward 12.00" / 305 mm, Aft 0.00" / 0 mm

Machinery:
Coal fired boilers, simple reciprocating steam engines,
Direct drive, 1 shaft, 4,268 ihp / 3,184 Kw = 14.00 kts
Range 3,000nm at 8.00 kts
Bunker at max displacement = 1,099 tons (100% coal)

Complement:
359 - 467

Cost:
£0.528 million / $2.111 million

Distribution of weights at normal displacement:
Armament: 324 tons, 5.0 %
Armour: 1,624 tons, 25.2 %
- Belts: 666 tons, 10.3 %
- Armament: 448 tons, 7.0 %
- Armour Deck: 420 tons, 6.5 %
- Conning Tower: 90 tons, 1.4 %
Machinery: 1,210 tons, 18.8 %
Hull, fittings & equipment: 2,421 tons, 37.5 %
Fuel, ammunition & stores: 870 tons, 13.5 %
Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,843 lbs / 836 Kg = 0.8 x 20.0 " / 508 mm shells or 0.6 torpedoes
Stability (Unstable if below 1.00): 1.00
Metacentric height 1.8 ft / 0.5 m
Roll period: 15.8 seconds
Steadiness - As gun platform (Average = 50 %): 25 %
- Recoil effect (Restricted arc if above 1.00): 0.41
Seaboat quality (Average = 1.00): 0.18

Hull form characteristics:
Hull has a flush deck,
a normal bow and a cruiser stern
Block coefficient (normal/deep): 0.531 / 0.539
Length to Beam Ratio: 6.80 : 1
'Natural speed' for length: 18.44 kts
Power going to wave formation at top speed: 34 %
Trim (Max stability = 0, Max steadiness = 100): 71
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 %, 3.00 ft / 0.91 m, 3.00 ft / 0.91 m
- Forward deck: 30.00 %, 3.00 ft / 0.91 m, 3.00 ft / 0.91 m
- Aft deck: 35.00 %, 3.00 ft / 0.91 m, 3.00 ft / 0.91 m
- Quarter deck: 15.00 %, 3.00 ft / 0.91 m, 3.00 ft / 0.91 m
- Average freeboard: 3.00 ft / 0.91 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 84.7 %
- Above water (accommodation/working, high = better): 17.9 %
Waterplane Area: 11,266 Square feet or 1,047 Square metres
Displacement factor (Displacement / loading): 115 %
Structure weight / hull surface area: 155 lbs/sq ft or 758 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.65
- Longitudinal: 1.18
- Overall: 0.69
Caution: Hull subject to strain in open-sea
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is extremely poor
Ship has quick, lively roll, not a steady gun platform
Caution: Lacks seaworthiness - very limited seakeeping ability

At this point Dahlgren remonstrated with Ericsson, and (after some memos flew back and forth) it was decided to waive the requirement for a four-gun broadside for Ericsson's design provided that the vessel be manifestly capable of actual sea travel (including resisting the effect of waves on the ship)

Ericsson's third design included a somewhat higher freeboard, reducing the impact of the waves of the open sea on the ship, though the extra belt to be armoured and height out of the water caused Ericsson to consider it a betrayal of his "true" Monitor design with a low freeboard.
It also resulted in something very nearly as big as HMS Warrior, and still slower (as the third design reduced engine displacement to allow the hull strengthening required).

USS Calvinist, United States of America Monitor laid down 1864
Central citadel ship

Displacement:
7,383 t light; 7,673 t standard; 8,379 t normal; 8,943 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(340.00 ft / 340.00 ft) x 50.00 ft x (25.00 / 26.47 ft)
(103.63 m / 103.63 m) x 15.24 m x (7.62 / 8.07 m)

Armament:
2 - 20.00" / 508 mm 13.0 cal guns - 2,754.66lbs / 1,249.49kg shells, 40 per gun
Muzzle loading guns in Coles/Ericsson turret mount, 1864 Model
1 x Single mount on centreline, forward deck centre
Weight of broadside 5,509 lbs / 2,499 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 8.00" / 203 mm 221.00 ft / 67.36 m 12.00 ft / 3.66 m
Ends: 8.00" / 203 mm 118.98 ft / 36.27 m 12.00 ft / 3.66 m
Main Belt covers 100 % of normal length

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 10.0" / 254 mm 10.0" / 254 mm -

- Armoured deck - multiple decks: 2.00" / 51 mm For and Aft decks
Forecastle: 2.00" / 51 mm Quarter deck: 2.00" / 51 mm

- Conning towers: Forward 12.00" / 305 mm, Aft 0.00" / 0 mm

Machinery:
Coal fired boilers, simple reciprocating steam engines,
Direct drive, 1 shaft, 2,942 ihp / 2,194 Kw = 12.00 kts
Range 3,000nm at 8.00 kts
Bunker at max displacement = 1,269 tons (100% coal)

Complement:
437 - 569

Cost:
£0.523 million / $2.094 million

Distribution of weights at normal displacement:
Armament: 280 tons, 3.3 %
Armour: 2,361 tons, 28.2 %
- Belts: 1,350 tons, 16.1 %
- Armament: 405 tons, 4.8 %
- Armour Deck: 500 tons, 6.0 %
- Conning Tower: 107 tons, 1.3 %
Machinery: 834 tons, 10.0 %
Hull, fittings & equipment: 3,909 tons, 46.6 %
Fuel, ammunition & stores: 995 tons, 11.9 %
Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
7,359 lbs / 3,338 Kg = 3.0 x 20.0 " / 508 mm shells or 1.4 torpedoes
Stability (Unstable if below 1.00): 1.11
Metacentric height 2.2 ft / 0.7 m
Roll period: 14.3 seconds
Steadiness - As gun platform (Average = 50 %): 52 %
- Recoil effect (Restricted arc if above 1.00): 1.00
Seaboat quality (Average = 1.00): 0.89

Hull form characteristics:
Hull has a flush deck,
a normal bow and a cruiser stern
Block coefficient (normal/deep): 0.690 / 0.695
Length to Beam Ratio: 6.80 : 1
'Natural speed' for length: 18.44 kts
Power going to wave formation at top speed: 31 %
Trim (Max stability = 0, Max steadiness = 100): 58
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 %, 8.00 ft / 2.44 m, 8.00 ft / 2.44 m
- Forward deck: 30.00 %, 8.00 ft / 2.44 m, 8.00 ft / 2.44 m
- Aft deck: 35.00 %, 8.00 ft / 2.44 m, 8.00 ft / 2.44 m
- Quarter deck: 15.00 %, 8.00 ft / 2.44 m, 8.00 ft / 2.44 m
- Average freeboard: 8.00 ft / 2.44 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 49.8 %
- Above water (accommodation/working, high = better): 46.7 %
Waterplane Area: 13,395 Square feet or 1,244 Square metres
Displacement factor (Displacement / loading): 154 %
Structure weight / hull surface area: 200 lbs/sq ft or 975 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.92
- Longitudinal: 2.03
- Overall: 1.00
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is extremely poor
Poor seaboat, wet and uncomfortable, reduced performance in heavy weather


At this point, Ericsson gave up and switched to trying to fulfil the other requirements, declaring that the Monitor was not a ship type for the open sea. His anger upon discovering that Delano had designed a two-turret vessel to fulfil the ocean going ironclad requirement was considerable.
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