Peruvian Studies

[Jefgte]

Here is a Squadron Gun Boat or a Protrector for the BBs.
Just 120m -27kts to turn around the BBs & intercept DDs attack.
with 27kts, she could work with the 1st generation of Peruvian cruisers.


3000T , Peru Squadron Gunboat laid down 1918 (Engine 1916)

Displacement:
   3 000 t light; 3 150 t standard; 3 521 t normal; 3 818 t full load

Dimensions: Length overall / water x beam x draught
   393.70 ft / 393.70 ft x 43.73 ft x 14.31 ft (normal load)
   120.00 m / 120.00 m x 13.33 m  x 4.36 m

Armament:
     4 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1918 Model
     Breech loading guns in casemate mounts
     on centreline, evenly spread, 2 raised mounts
     Aft Main mounts separated by engine room
     4 - 6.00" / 152 mm guns in single mounts, 108.00lbs / 48.99kg shells, 1918 Model
     Breech loading guns in casemate mounts
     on side, evenly spread
     4 - 1.57" / 40.0 mm guns (2x2 guns), 1.95lbs / 0.88kg shells, 1918 Model
     Anti-aircraft guns in deck mounts
     on side, evenly spread, all raised mounts
     4 - 0.50" / 12.7 mm guns in single mounts, 0.06lbs / 0.03kg shells, 1918 Model
     Machine guns in deck mounts
     on side, evenly spread, all raised mounts
   Weight of broadside 872 lbs / 396 kg
   Shells per gun, main battery: 150
   12 - 21.0" / 533.4 mm above water torpedoes

Armour:
  - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   1.57" / 40 mm   321.52 ft / 98.00 m   8.01 ft / 2.44 m
   Ends:   1.57" / 40 mm     65.62 ft / 20.00 m   8.01 ft / 2.44 m
     6.56 ft / 2.00 m Unarmoured ends
     Main Belt covers 126 % of normal length

  - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   0.79" / 20 mm         -               -
   2nd:   0.79" / 20 mm         -               -
   3rd:   0.79" / 20 mm         -               -
   4th:   0.50" / 13 mm         -               -

  - Armour deck: 0.79" / 20 mm

Machinery:
   Oil fired boilers, steam turbines,
   Geared drive, 2 shafts, 28 000 shp / 20 888 Kw = 27.29 kts
   Range 7 000nm at 12.00 kts
   Bunker at max displacement = 668 tons

Complement:
   228 - 297

Cost:
   £0.685 million / $2.741 million

Distribution of weights at normal displacement:
   Armament: 109 tons, 3.1 %
   Armour: 385 tons, 10.9 %
      - Belts: 195 tons, 5.5 %
      - Torpedo bulkhead: 0 tons, 0.0 %
      - Armament: 23 tons, 0.7 %
      - Armour Deck: 167 tons, 4.7 %
      - Conning Tower: 0 tons, 0.0 %
   Machinery: 1 043 tons, 29.6 %
   Hull, fittings & equipment: 1 308 tons, 37.1 %
   Fuel, ammunition & stores: 521 tons, 14.8 %
   Miscellaneous weights: 155 tons, 4.4 %
100t - high fire control
10t - long range wireless
10t - crew confort
5t - ammunition climat control
5t - damages control extra pump& generators
10t - Marconi


Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     3 015 lbs / 1 368 Kg = 27.9 x 6.0 " / 152 mm shells or 0.7 torpedoes
   Stability (Unstable if below 1.00): 1.23
   Metacentric height 2.1 ft / 0.6 m
   Roll period: 12.7 seconds
   Steadiness   - As gun platform (Average = 50 %): 71 %
         - Recoil effect (Restricted arc if above 1.00): 0.34
   Seaboat quality  (Average = 1.00): 1.19

Hull form characteristics:
   Hull has a flush deck
   Block coefficient: 0.500
   Length to Beam Ratio: 9.00 : 1
   'Natural speed' for length: 19.84 kts
   Power going to wave formation at top speed: 59 %
   Trim (Max stability = 0, Max steadiness = 100): 60
   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:      21.00 ft / 6.40 m
      - Forecastle (21 %):   17.72 ft / 5.40 m
      - Mid (50 %):      14.44 ft / 4.40 m
      - Quarterdeck (19 %):   14.44 ft / 4.40 m
      - Stern:      14.44 ft / 4.40 m
      - Average freeboard:   15.88 ft / 4.84 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 124.8 %
      - Above water (accommodation/working, high = better): 75.8 %
   Waterplane Area: 11 472 Square feet or 1 066 Square metres
   Displacement factor (Displacement / loading): 101 %
   Structure weight / hull surface area: 68 lbs/sq ft or 331 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 0.93
      - Longitudinal: 1.89
      - Overall: 1.00
   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

[eltf177]

A most interesting design, but then again your designs usually are (Erwhon keeps an eye on its neighbor!).

I note your use of bow and stern casemates rather than turrets, and the drawing shows them as having almost as large a field-of-fire as a regular turret would probably have.

But what are the advantages and disadvantages of using a casemate instead of a turret? One thing I would guess is the casemate gives you less elevation, hence less range. Or do the rules cover things like this?

Inquiring minds want to know!

[Guinness]

I seriously doubt that a casemate would be good for more than about 180 degrees of field of fire. Beyond that, the shield would have to be constrictively large (I think).

I've been wracking my brain for an OTL analogue with casemates with a field that big, but can't find one yet.

[eltf177]

I seriously doubt that a casemate would be good for more than about 180 degrees of field of fire. Beyond that, the shield would have to be constrictively large (I think).

I've been wracking my brain for an OTL analogue with casemates with a field that big, but can't find one yet.

I can't think of any ship with bow or stern casemates, with the sole execption of the "Omaha"-class CL's which ended up getting twin gunhouses fore and aft to increase the broadside.

[Jefgte]

When I SS & draw the ship, I think about bow & stern casemate concept...

A large circular room , (diam 4m) to receive all gun installation & gunners. A rotation platform for the gun.
The circular room is open by small windows on rails for the guns (-5°+30° elevation).

I could probably made a study drawing of the system.


The advantages of this mount are, lighter mount than turrets & the complet protection of the gunners from the bad sea.


;)

[TexanCowboy]

Speaking of casemates, I just had a wierd ship Idea with like 20 14'' guns, but all in casemates.

[eltf177]

I noticed that the casemates have very little armor, any shell gets inside and they become a deathtrap. And a MG or light cannon can quickly decimate the crew if it can get into firing range...

Another problem is the large opening for the gun barrel. I started looking at this from an engineering standpoint. To allow the gun to traverse there can't be any supports from top to bottom (although a plate can be bolted around the entire opening both inside and out to stiffen it somewhat). thus the opening can only be so large before structural integrity is affected. If the opening is large enough to allow good elevation and depression it would need to be narrlow, allowing limited traverse. And if wide enough for good traverse then it can't be very tall, thus poor elevation, I just can't see the opening being large enough to allow both good training _and_ good elevation without being so large as to compromise the casemate's integrity (and being a huge target for light weapons). Also, I think 270 degrees of training is probably somewhat over-optomistic.

I think a referee would need to review this idea, but it is still a most interesting idea!

[maddox]

Technicaly there is no reason why such a setup won't be buildable.
Concerning the large opening, ,that is simple to solve, and it's a trick easely done with a circular construction.  On the outside there is a armorplate that runs in bronze rails, and that plate is moving together with the barrel.

In effect, when this setup is used, it's more like a Coles/Ericsson turret with a solid mounted roof. In other words, more limited in all respects than a Mount and Hoist, and heavier to boot.

[eltf177]

Technicaly there is no reason why such a setup won't be buildable.
Concerning the large opening, ,that is simple to solve, and it's a trick easely done with a circular construction.  On the outside there is a armorplate that runs in bronze rails, and that plate is moving together with the barrel.

In effect, when this setup is used, it's more like a Coles/Ericsson turret with a solid mounted roof. In other words, more limited in all respects than a Mount and Hoist, and heavier to boot.

That should work, and the armor can probably be designed to give support to the opening.

So heavier than mount and hoist (and slower training/firing to boot), but lighter than a standard turret.

[maddox]

If the casemates would be of the standard kind, with armoring as the belt, it would deliver limited firearc, for a weigth advantage.

[Jefgte]

A large circular room , (diam 4m) to receive all gun installation & gunners. A rotation platform for the gun.
The circular room is open by small windows on rails for the guns (-5°+30° elevation).

I have made quickly a study drawing .
1- diam 4m for the gun & gunners activity is correct
2- No rotation platform for the gun but a mount on 2 rails - diam 3m & 2m to have a good stability
3- The movement of the gun could be made by motorised rack-railway ("crémaillère" in french)
4- the windows to pass the gun are fixed on small rails. I have tested 7x45°) windows with total rotation (360°)

Globaly, my impression is that the mount is good & 270° fire arc, not a problem.
This mount need more armor protection - 40mm (min) for splinters.
The 7 rotation windows are probably fragile & are really the weak side.

Finaly...
Remove the bow & stern casemates & instal T2
:D  :D  :D


Jef  ;)

[Guinness]

The closest OTL analogue we've thought of so far is the 6" casemates on the Omahas:

http://hnsa.org/doc/guncat/cat-0468.htm

The working circle on that schematic is shown as 170", which is a smidge over 4 meters. That means the *radius* of casemate would really need to be 4 meters to allow the gun to be worked over a full 270 degrees of train, or a diameter if 8 meters or so.

That's going to be a pretty big casemate. Also, we've just touched on what should be a major issue: what's holding the roof of that casemate up? A roughly 8 meter circular cupola, which is what that amounts to, supported only somewhere in the back 90 degrees strikes me as a structural challenge.

So yeah, I think you're right that a 6" twin at A and Y is probably a better choice.

[maddox]

Not a structural challenge, just heavy. And the roof can be supported in the middle, just a bracing with a bearing that stands over the gun, at the center pivot.

But that too is a heavy solution.

[ctwaterman]

Evil Chuckle-

Hey Ericsons Turret on the USS Monitor is a Mount and Hoist.

I admit the Hoist is a chain connected to a pulley but it did hoist the Shot up out of the bottom of the boat.

It sounds like its a difficult build for a Barbette but the problem I see is how does SS see the Barbette here when built into the side of a ship it doesnt require very much armor to cover the  Barbette.  How this works I just dont have a clue.

Charles

[Tanthalas]

Actualy the secondary guns on even the Iowas are what we in the nverse would refer to as mount and hoist (you can tell if you look at the armor on them it actualy matches what we restrict mount and hoist to).  its how I was convinced that mount and hoist was acceptable for secondaries.