Small Gun Boat

[miketr]

This is in response to Rocky suggestion that I need some more patrol craft... Which I do as I have none and use TB's right now.

At 300 tons compared to 2200 tons for the four big patrol gun boats I could build....  14 of these smaller ones in place of 2 of the larger ones.

Michael

GB-1916-A, Iberia Gun Boat laid down 1916 (Engine 1912)

Displacement:
   299 t light; 312 t standard; 510 t normal; 668 t full load

Dimensions: Length overall / water x beam x draught
   166.07 ft / 164.04 ft x 24.61 ft x 9.02 ft (normal load)
   50.62 m / 50.00 m x 7.50 m  x 2.75 m

Armament:
      1 - 2.95" / 75.0 mm guns in single mounts, 12.87lbs / 5.84kg shells, 1916 Model
     Breech loading gun in deck mount
     on centreline forward, 1 raised gun
      2 - 1.97" / 50.0 mm guns in single mounts, 3.81lbs / 1.73kg shells, 1916 Model
     Breech loading guns in deck mounts
     on side, all amidships, 1 raised mount
      4 - 0.49" / 12.5 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1916 Model
     Breech loading guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 21 lbs / 9 kg
   Shells per gun, main battery: 200
   3 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.98" / 25 mm         -               -
   2nd:   0.98" / 25 mm         -               -
   3rd:   0.39" / 10 mm         -               -

   - Conning tower: 1.97" / 50 mm

Machinery:
   Coal fired boilers, steam turbines,
   Direct drive, 2 shafts, 1,000 shp / 746 Kw = 14.58 kts
   Range 11,100nm at 10.00 kts
   Bunker at max displacement = 357 tons (100% coal)

Complement:
   53 - 69

Cost:
   £0.031 million / $0.123 million

Distribution of weights at normal displacement:
   Armament: 3 tons, 0.5 %
   Armour: 6 tons, 1.2 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 4 tons, 0.7 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 3 tons, 0.5 %
   Machinery: 44 tons, 8.6 %
   Hull, fittings & equipment: 146 tons, 28.6 %
   Fuel, ammunition & stores: 211 tons, 41.4 %
   Miscellaneous weights: 100 tons, 19.6 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     1,138 lbs / 516 Kg = 88.4 x 3.0 " / 75 mm shells or 0.9 torpedoes
   Stability (Unstable if below 1.00): 1.20
   Metacentric height 0.9 ft / 0.3 m
   Roll period: 11.2 seconds
   Steadiness   - As gun platform (Average = 50 %): 75 %
         - Recoil effect (Restricted arc if above 1.00): 0.06
   Seaboat quality  (Average = 1.00): 1.87

Hull form characteristics:
   Hull has raised forecastle
   Block coefficient: 0.490
   Length to Beam Ratio: 6.67 : 1
   'Natural speed' for length: 12.81 kts
   Power going to wave formation at top speed: 52 %
   Trim (Max stability = 0, Max steadiness = 100): 40
   Bow angle (Positive = bow angles forward): 10.00 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 %):   11.48 ft / 3.50 m (8.20 ft / 2.50 m aft of break)
      - Mid (50 %):      8.20 ft / 2.50 m
      - Quarterdeck (15 %):   8.20 ft / 2.50 m
      - Stern:      8.20 ft / 2.50 m
      - Average freeboard:   8.86 ft / 2.70 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 54.5 %
      - Above water (accommodation/working, high = better): 38.3 %
   Waterplane Area: 2,665 Square feet or 248 Square metres
   Displacement factor (Displacement / loading): 237 %
   Structure weight / hull surface area: 32 lbs/sq ft or 155 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.88
      - Longitudinal: 3.12
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is extremely poor
   Ship has slow, easy roll, a good, steady gun platform
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

[ledeper]

A little lighter,more heavily armed :D

Enter ship name, Enter country Gunboat laid down 1916 (Engine 1912)

Displacement:
   288 t light; 304 t standard; 501 t normal; 659 t full load

Dimensions: Length overall / water x beam x draught
   166,27 ft / 164,04 ft x 26,25 ft x 8,20 ft (normal load)
   50,68 m / 50,00 m x 8,00 m  x 2,50 m

Armament:
      2 - 3,94" / 100 mm guns in one mount, 30,51lbs / 13,84kg shells, 1916 Model
     Quick firing guns in deck mount
     on centreline forward, 1 raised gun
      4 - 1,57" / 40,0 mm guns in single mounts, 1,95lbs / 0,89kg shells, 1916 Model
     Quick firing guns in deck mounts
     on side, all amidships
   Weight of broadside 69 lbs / 31 kg
   Shells per gun, main battery: 150
   4 - 20,9" / 530 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0,98" / 25 mm         -               -
   2nd:   0,39" / 10 mm         -               -

Machinery:
   Coal fired boilers, steam turbines,
   Direct drive, 1 shaft, 1.874 shp / 1.398 Kw = 17,00 kts
   Range 11.100nm at 10,00 kts
   Bunker at max displacement = 355 tons (100% coal)

Complement:
   52 - 68

Cost:
   £0,047 million / $0,189 million

Distribution of weights at normal displacement:
   Armament: 9 tons, 1,7 %
   Armour: 5 tons, 0,9 %
      - Belts: 0 tons, 0,0 %
      - Torpedo bulkhead: 0 tons, 0,0 %
      - Armament: 5 tons, 0,9 %
      - Armour Deck: 0 tons, 0,0 %
      - Conning Tower: 0 tons, 0,0 %
   Machinery: 82 tons, 16,4 %
   Hull, fittings & equipment: 93 tons, 18,5 %
   Fuel, ammunition & stores: 213 tons, 42,6 %
   Miscellaneous weights: 100 tons, 19,9 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     437 lbs / 198 Kg = 14,3 x 3,9 " / 100 mm shells or 0,5 torpedoes
   Stability (Unstable if below 1.00): 1,26
   Metacentric height 1,0 ft / 0,3 m
   Roll period: 10,9 seconds
   Steadiness   - As gun platform (Average = 50 %): 69 %
         - Recoil effect (Restricted arc if above 1.00): 0,14
   Seaboat quality  (Average = 1.00): 1,38

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0,497
   Length to Beam Ratio: 6,25 : 1
   'Natural speed' for length: 12,81 kts
   Power going to wave formation at top speed: 61 %
   Trim (Max stability = 0, Max steadiness = 100): 50
   Bow angle (Positive = bow angles forward): 9,00 degrees
   Stern overhang: 0,00 ft / 0,00 m
   Freeboard (% = measuring location as a percentage of overall length):
      - Stem:      14,07 ft / 4,29 m
      - Forecastle (20 %):   8,96 ft / 2,73 m
      - Mid (50 %):      8,96 ft / 2,73 m
      - Quarterdeck (15 %):   8,96 ft / 2,73 m
      - Stern:      8,96 ft / 2,73 m
      - Average freeboard:   9,37 ft / 2,85 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 88,6 %
      - Above water (accommodation/working, high = better): 33,2 %
   Waterplane Area: 2.749 Square feet or 255 Square metres
   Displacement factor (Displacement / loading): 148 %
   Structure weight / hull surface area: 20 lbs/sq ft or 97 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0,50
      - Longitudinal: 1,90
      - Overall: 0,57
   Caution: Hull subject to strain in open-sea
   Hull space for machinery, storage, compartmentation is adequate
   Room for accommodation and workspaces is extremely poor
   Good seaboat, rides out heavy weather easily

[Guinness]

woo! that's a lot of coal for such a little boat. I'm not sure I'd want to be on-board for the entire 46.5 days (at cruising speed) it would take to burn it all, but I imagine that's what it takes to get from Iberia to the Pacific.

Otherwise, she's broadly similar to the CSA's Sloops and spin off Minesweepers. Have you considered using diesels instead in a slightly smaller boat?

[Korpen]

woo! that's a lot of coal for such a little boat. I'm not sure I'd want to be on-board for the entire 46.5 days (at cruising speed) it would take to burn it all, but I imagine that's what it takes to get from Iberia to the Pacific.

I think it is even more usefull for cruising around in the Philippines, or along the Brazilian coast, large fuel hold means they can be away from base longer, while staying in small fishing villages or small towns, maintaining a presence dispersed throughout the territory

[ledeper]

Using Diesel will reduce OA weight by 25 t and reduce bunkerage weight by130t

[miketr]

leaper: Ship is too slow to use the TB tech so I can't push the hull strength that low.

Guinness:  I could fit a pair of 500 hp marine diesels I guess I have the 1905 IC engine tech...  I went with coal because thats something I have in particular in the Philippines.

Korpen: Thats roughly the idea.

[The Rock Doctor]

Mike, I like.  Depending on your miscellaneous weight allocation, she might even qualify for "merchantile standard" construction.

[miketr]

I doubt torps, FC and depth charges would work.  Its a warship and nothing but.

Michael

[Jefgte]

IMO, your gun boats are unable to engage any warship with 17kts.
Peru don't use small gun boats.
We prefer 200t TB - 27kts
more useful with the speed.
You could perhaps made the same thing (or 300t) & add a fleet tender for the patrol range.


;)

[Guinness]

IMO, your gun boats are unable to engage any warship with 17kts.
Peru don't use small gun boats.
We prefer 200t TB - 27kts
more useful with the speed.
You could perhaps made the same thing (or 300t) & add a fleet tender for the patrol range.


;)

Well, there's a lot of utility in a ship that can get around, show the flag, fend off the occasional evildoer, etc. A 200t TB, even if a lot faster, will not be nearly as inhabitable and will have much worse seakeeping qualities.

Now, it may be true that a gunboat armed with bigger guns (say in the 150mm range) might be able to give a bigger scare to a real warship, but I imagine if Iberia is fighting any real warships, these boats probably aren't going to be on the front lines anyway. My guess is you could still get a boat with this range with a pair of 150mm guns for about 300 or 325 tons, and it would still fit in a type 0 dock.

But obviously, your approach has merit too (at least merit to the CSA which has adopted just such an idea), but for a nation that has to cover vast distances, this may be better. Iberia has lots of TBs and DDs, some of which might be forward deployed to be the cavalry for these little guys.

[miketr]

As guinness pointed out Iberia has a good number of TB's.  The Philippines have two divisions of 300 ton TB's already and another of two of 500 ton TB's.  Thats twenty TB's in the Philippines already.  The mission of this things is to show the flag and act in war time as patrol and maybe a escort (more vs. subs and DD's) than a real warship.  I am going to redesign with diesels and see what that does.  Odds are more range but will see.

Michael

[P3D]

The ship can be actually classified as an armed collier. It might be problem that the ship has a draught of ~3.7m at full load but like 1.2m light - too fine BC.

Military standard is justified. I realized that my civilian standard patrol boat (the 1000t ones) can take on like 10t of mines/depth charges/minesweeping equipment or go over weight limit (and I might have to ditch some armament for that).

The ship is too slow for anti-sub work, the ones Iberia have can do 14kts on surface - and 10kts submerged.
What is the reason for the 50mm guns? IMO two 75mm guns and MGs would be just as fine. About torpedoes, the ship won't use them against anything naval (all faster and better armed)- you might have two old torpedoes to sunk whatever merchants ships that needs to be sunk.

Direct drive turbines for 15kts is a bit uneconomical. Either get reciprocating engines, electric drive, geared drive or diesels.

[Jefgte]

You have powerful neighbours & the reinforcement of the battleline with light TBs could be useful.
(...They could also scout the battleline or made raids...)


;)

[Korpen]

Direct drive turbines for 15kts is a bit uneconomical. Either get reciprocating engines, electric drive, geared drive or diesels.

Not so convinced that is true. Turbines are after all most economical at close to max output, so if the ship will be running at full power or close to it most of the time, I would not be surprised if even direct drive turbines might be more economical then VTEs running max power.

[miketr]

Made some changes and a slight increase in displacement is the result.

Switched to Diesel, would be four 500 HP motors; two on each shaft.  A slight increase in speed to 17.25 knots.  Switched to a pair of 75's instead of the mixed setup. 

As to the number of tubes...  A triple mount is the "standard" for new construction so they get a triple.  I would be stunned if a warship in anything other a very weird situation would be killed by something like this but merchantmen are another matter and some type of weird ambush in the Philippines with all those islands is always possible.

Michael

GB-1916-b, Iberia Gun Boat laid down 1916 (Engine 1912)

Displacement:
   333 t light; 346 t standard; 510 t normal; 641 t full load

Dimensions: Length overall / water x beam x draught
   166.07 ft / 164.04 ft x 24.61 ft x 9.02 ft (normal load)
   50.62 m / 50.00 m x 7.50 m  x 2.75 m

Armament:
      2 - 2.95" / 75.0 mm guns in one mount, 12.87lbs / 5.84kg shells, 1916 Model
     Breech loading guns in deck mount
     on centreline forward, 1 raised gun
      4 - 0.49" / 12.5 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1916 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 26 lbs / 12 kg
   Shells per gun, main battery: 200
   3 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.98" / 25 mm         -               -
   3rd:   0.39" / 10 mm         -               -

   - Conning tower: 1.97" / 50 mm

Machinery:
   Diesel Internal combustion motors,
   Direct drive, 2 shafts, 2,000 shp / 1,492 Kw = 17.29 kts
   Range 12,800nm at 10.00 kts
   Bunker at max displacement = 295 tons

Complement:
   53 - 69

Cost:
   £0.042 million / $0.167 million

Distribution of weights at normal displacement:
   Armament: 3 tons, 0.6 %
   Armour: 5 tons, 1.0 %
      - Belts: 0 tons, 0.0 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 3 tons, 0.5 %
      - Armour Deck: 0 tons, 0.0 %
      - Conning Tower: 3 tons, 0.5 %
   Machinery: 80 tons, 15.6 %
   Hull, fittings & equipment: 149 tons, 29.2 %
   Fuel, ammunition & stores: 177 tons, 34.7 %
   Miscellaneous weights: 96 tons, 18.8 %

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     798 lbs / 362 Kg = 62.0 x 3.0 " / 75 mm shells or 0.6 torpedoes
   Stability (Unstable if below 1.00): 1.18
   Metacentric height 0.8 ft / 0.3 m
   Roll period: 11.3 seconds
   Steadiness   - As gun platform (Average = 50 %): 52 %
         - Recoil effect (Restricted arc if above 1.00): 0.06
   Seaboat quality  (Average = 1.00): 1.23

Hull form characteristics:
   Hull has raised forecastle
   Block coefficient: 0.490
   Length to Beam Ratio: 6.67 : 1
   'Natural speed' for length: 12.81 kts
   Power going to wave formation at top speed: 61 %
   Trim (Max stability = 0, Max steadiness = 100): 42
   Bow angle (Positive = bow angles forward): 10.00 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 %):   11.48 ft / 3.50 m (8.20 ft / 2.50 m aft of break)
      - Mid (50 %):      8.20 ft / 2.50 m
      - Quarterdeck (15 %):   8.20 ft / 2.50 m
      - Stern:      8.20 ft / 2.50 m
      - Average freeboard:   8.86 ft / 2.70 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 77.0 %
      - Above water (accommodation/working, high = better): 38.3 %
   Waterplane Area: 2,665 Square feet or 248 Square metres
   Displacement factor (Displacement / loading): 178 %
   Structure weight / hull surface area: 32 lbs/sq ft or 158 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.88
      - Longitudinal: 3.18
      - Overall: 1.00
   Hull space for machinery, storage, compartmentation is excellent
   Room for accommodation and workspaces is extremely poor
   Good seaboat, rides out heavy weather easily