WesWorld

Messing around with gunboats for my fleet I came up with an idea, why not build an agile gunboat with a casemate gun with heavy armour. She could tackle lighter coastal guns and in rivers could be useful. Is the idea sound?
First up is a small gunboat under the small boats rule (ie under 199tons and armed with an updated French 75mm with rapid fire. The engine is an MTB petrol.

El Plata Replacement 1, Argentina Gunboat laid down 1932

Displacement:
122 t light; 137 t standard; 139 t normal; 140 t full load

Dimensions: Length overall / water x beam x draught
131.23 ft / 131.23 ft x 14.76 ft x 3.61 ft (normal load)
40.00 m / 40.00 m x 4.50 m x 1.10 m

Armament:
1 - 2.95" / 75.0 mm guns in single mounts, 12.66lbs / 5.74kg shells, 1932 Model
Breech loading gun in casemate mount
on centreline forward
2 - 3.19" / 81.0 mm guns in single mounts, 16.22lbs / 7.36kg shells, 1932 Model
Muzzle loading guns in deck mounts
on side, all aft
2 - 1.46" / 37.0 mm guns (1x2 guns), 1.55lbs / 0.70kg shells, 1932 Model
Anti-aircraft guns in deck mount
on centreline aft
2 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1932 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
Weight of broadside 49 lbs / 22 kg
Shells per gun, main battery: 350

Armour:
- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 3.54" / 90 mm - -
2nd: 0.39" / 10 mm - -
4th: 0.98" / 25 mm - -

- Conning tower: 2.76" / 70 mm

Machinery:
Petrol Internal combustion motors,
Direct drive, 1 shaft, 750 shp / 560 Kw = 15.90 kts
Range 1,000nm at 5.00 kts
Bunker at max displacement = 3 tons

Complement:
19 - 26

Cost:
£0.057 million / $0.228 million

Distribution of weights at normal displacement:
Armament: 6 tons, 4.4 %
Armour: 8 tons, 6.1 %
- Belts: 0 tons, 0.0 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 7 tons, 4.9 %
- Armour Deck: 0 tons, 0.0 %
- Conning Tower: 2 tons, 1.1 %
Machinery: 22 tons, 16.0 %
Hull, fittings & equipment: 71 tons, 51.0 %
Fuel, ammunition & stores: 16 tons, 11.7 %
Miscellaneous weights: 15 tons, 10.8 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
225 lbs / 102 Kg = 17.5 x 3.0 " / 75 mm shells or 0.3 torpedoes
Stability (Unstable if below 1.00): 1.04
Metacentric height 0.3 ft / 0.1 m
Roll period: 11.2 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.79
Seaboat quality (Average = 1.00): 1.70

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.694
Length to Beam Ratio: 8.89 : 1
'Natural speed' for length: 11.46 kts
Power going to wave formation at top speed: 61 %
Trim (Max stability = 0, Max steadiness = 100): 41
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: 11.48 ft / 3.50 m
- Forecastle (20 %): 9.51 ft / 2.90 m
- Mid (50 %): 7.22 ft / 2.20 m
- Quarterdeck (15 %): 7.22 ft / 2.20 m
- Stern: 7.22 ft / 2.20 m
- Average freeboard: 8.18 ft / 2.49 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 103.8 %
- Above water (accommodation/working, high = better): 119.1 %
Waterplane Area: 1,533 Square feet or 142 Square metres
Displacement factor (Displacement / loading): 119 %
Structure weight / hull surface area: 22 lbs/sq ft or 107 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.80
- Longitudinal: 6.90
- Overall: 0.99
Caution: Hull subject to strain in open-sea
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is adequate
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather


Next is a Type 0 slip type with belt and deck armour and a 130mm gun. The engines are two MTB engines driving a gearbox that powers one screw.

El Plata Replacement 2, Argentina Gunboat laid down 1932

Displacement:
535 t light; 573 t standard; 580 t normal; 586 t full load

Dimensions: Length overall / water x beam x draught
229.66 ft / 229.66 ft x 27.89 ft x 6.40 ft (normal load)
70.00 m / 70.00 m x 8.50 m x 1.95 m

Armament:
1 - 5.12" / 130 mm guns in single mounts, 66.14lbs / 30.00kg shells, 1932 Model
Breech loading gun in casemate mount
on centreline forward
4 - 3.19" / 81.0 mm guns in single mounts, 16.22lbs / 7.36kg shells, 1932 Model
Muzzle loading guns in deck mounts
on side, all aft
2 - 1.46" / 37.0 mm guns (1x2 guns), 1.55lbs / 0.70kg shells, 1932 Model
Anti-aircraft guns in deck mount
on centreline aft
2 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1932 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
Weight of broadside 135 lbs / 61 kg
Shells per gun, main battery: 300

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 1.97" / 50 mm 82.02 ft / 25.00 m 7.55 ft / 2.30 m
Ends: Unarmoured
Main Belt covers 55 % of normal length

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 6.10" / 155 mm - 1.97" / 50 mm
2nd: 0.39" / 10 mm - -
4th: 0.98" / 25 mm - -

- Armour deck: 1.97" / 50 mm, Conning tower: 2.76" / 70 mm

Machinery:
Petrol Internal combustion motors,
Geared drive, 1 shaft, 1,500 shp / 1,119 Kw = 16.32 kts
Range 2,000nm at 5.00 kts
Bunker at max displacement = 13 tons

Complement:
58 - 76

Cost:
£0.178 million / $0.712 million

Distribution of weights at normal displacement:
Armament: 17 tons, 2.9 %
Armour: 232 tons, 40.1 %
- Belts: 59 tons, 10.1 %
- Torpedo bulkhead: 0 tons, 0.0 %
- Armament: 21 tons, 3.6 %
- Armour Deck: 149 tons, 25.6 %
- Conning Tower: 4 tons, 0.7 %
Machinery: 44 tons, 7.6 %
Hull, fittings & equipment: 227 tons, 39.1 %
Fuel, ammunition & stores: 45 tons, 7.7 %
Miscellaneous weights: 15 tons, 2.6 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
1,600 lbs / 726 Kg = 23.9 x 5.1 " / 130 mm shells or 1.1 torpedoes
Stability (Unstable if below 1.00): 1.35
Metacentric height 1.3 ft / 0.4 m
Roll period: 10.4 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.16
Seaboat quality (Average = 1.00): 1.46

Hull form characteristics:
Hull has a flush deck
Block coefficient: 0.495
Length to Beam Ratio: 8.24 : 1
'Natural speed' for length: 15.15 kts
Power going to wave formation at top speed: 45 %
Trim (Max stability = 0, Max steadiness = 100): 48
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: 11.48 ft / 3.50 m
- Forecastle (20 %): 9.51 ft / 2.90 m
- Mid (50 %): 7.22 ft / 2.20 m
- Quarterdeck (15 %): 7.22 ft / 2.20 m
- Stern: 7.22 ft / 2.20 m
- Average freeboard: 8.18 ft / 2.49 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 53.9 %
- Above water (accommodation/working, high = better): 103.9 %
Waterplane Area: 4,081 Square feet or 379 Square metres
Displacement factor (Displacement / loading): 123 %
Structure weight / hull surface area: 38 lbs/sq ft or 183 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.98
- Longitudinal: 1.30
- Overall: 1.00
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is adequate
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily

A good idea or just too much time on my hands on a bank holiday weekend?

Just for the case you didn´t notice: it was a joke when you were told to leave your sanity at the door!

A 137ts boat with a 75mm gun in a casemat and two 81mm MZZLE loading guns? C´mon....

Well, it IS different after all. :o)

Sorry I forgot to mention the 81mm are standard army mortars bolted to the deck on both designs, the armour is the bulwark on the sides to offer protection from splinters etc.

What sanity!!! :0) I warned you I was bored...

Me like ^_^

Its a good idea with the mortars.

At first I was thinking you intended a modern version of the US Navy's Cairo-class gunboats from the US Civil War but with casemented guns instead of broadside. 512 tons, 14 guns ! hey, it would work for #2.

http://upload.wikimedia.org/wikipedia/co…airo_h61568.jpg

(I have no idea if that worked)

I like the mortars. I don't care for the bow mounted gun with basically an armored pivot shield. For one thing, in a river, I would hazard you'd like to point with or against the flow for navigation while engaging shore targets with your battery. With the current design, if your gun is facing the target, you're steaming into the bank ?

Also, you can probably save some weight by dropping the deck armor <2" on #2. Unless your rivers have high bluffs you expect the opposition to hold, that much plunging fire seems unlikely.

Like a Pre-Dreadnought armoured gunboat that I can't find any pictures of at the moment.

1 single mount as part of the superstructure with limited train +-90°.

Mortars should be simmed using misc. weight as SS assumes a muzzle-loading gun of about 50-cal, not a lightweight mortar.

Coal/wood fired boilers are a must. Simply go on shore to get more fuel.

Gunboatlaid down 1932
Armoured gunboat

Displacement:
141 t light; 145 t standard; 145 t normal; 145 t full load
Loading submergence 95 tons/feet

Dimensions:
131.23 ft x 29.53 ft x 1.64 ft (normal load)
40.00 m x 9.00 m x 0.50 m

Armament:
1 - 2.95" / 75 mm guns
Caution: Main guns limited to end-on fire
Weight of broadside 13 lbs / 6 kg

Armour:
Main gun shields 0.79" / 20 mm
Conning tower 0.79" / 20 mm

Machinery:
Coal fired boilers, complex reciprocating steam engines,
Geared drive, 1 shaft, 200 ihp / 149 Kw = 10.15 kts
Range 5nm at 10.15 kts

Complement:
20 - 27

Cost:
£0.037 million / $0.146 million

Distribution of weights at normal displacement:
Armament: 2 tons, 1.1 %
Armour: 3 tons, 2.0 %
Belts: 0 tons, 0.0 %, Armament: 2 tons, 1.7 %, Armour Deck: 0 tons, 0.0 %
Conning Tower: 0 tons, 0.3 %, Torpedo bulkhead: 0 tons, 0.0 %
Machinery: 12 tons, 8.6 %
Hull, fittings & equipment: 109 tons, 75.3 %
Fuel, ammunition & stores: 4 tons, 2.7 %
Miscellaneous weights: 15 tons, 10.3 %

Metacentric height 1.2

Remarks:
Hull space for machinery, storage & compartmentation is excellent
Room for accommodation & workspaces is excellent

Estimated overall survivability and seakeeping ability:
Relative margin of stability: 1.26
Shellfire needed to sink: 997 lbs / 452 Kg = 77.5 x 3.0 " / 75 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 1.0
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 51 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.02
Relative quality as seaboat: 1.02

Hull form characteristics:
Block coefficient: 0.800
Sharpness coefficient: 0.55
Hull speed coefficient 'M': 7.62
'Natural speed' for length: 11.46 kts
Power going to wave formation at top speed: 34 %
Trim: 50
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)

Estimated hull characteristics & strength:
Underwater volume absorbed by magazines and engineering spaces: 48.8 %
Relative accommodation and working space: 239.8 %
(Average = 100%)
Displacement factor: 261 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 0.91
(Structure weight / hull surface area: 28 lbs / square foot or 136 Kg / square metre)
Relative longitudinal hull strength: 3.05
(for 7.55 ft / 2.30 m average freeboard, freeboard adjustment 1.05 ft)
Relative composite hull strength: 1.02

RA, I think it may have been in the Greek navy, a small gunboat with a massive rounded casemate forward with no traverse on the gun. It was in 1919 Jane's, I'll have a look tonight. Wood/coal seems the best solution but I wanted a degree of coastal capability too. So Design 2 may be better.

I was right, the boat I thought of was Greek. The Aktion and Ambrakia built Blackwall 1891 and rebuilt 1910. 433tons, 128 (p.p.)/25/9.5ft, one 10.2in in casemate and Aktion had 2 14pdrs. Speed was 11kts on 380hp. 70 crew and no mention of armour. I have no scanner so can't post a pic but it's on P294 in 'Jane's Fighting Ships of World War I' reprint by Studio. RRP £25 or $40 but I picked up mine for a few quid in a cheap bookshop:0)

I have the book and I have the page...
Looks rather ugly...
Got my edition cheap as well. :-)