WesWorld

Well, I'm curious to see what the reaction is to this beastie. Stats follow the picture.

This is proposed to be India's first purpose-built CV, and should therefore reflect early 1920's doctrine on carriers (since the design work is starting in 1922). Thus, you get a cruiser-sized ship with a modest airgroup and a substantial anti-surface armament.

The island is offset to port for no particular reason, as my aircraft use inline engines and shouldn't (I don't think) have excessive problems pulling to one direction or another. If it's a problem, I only need to "mirror image" the plan view and cut out the island sponson from the profile.

Thoughts? Odd layout aside, does she look like a '20s product?



Urumi, laid down 1925

Length, 675 ft x Beam, 74.0 ft x Depth, 20.0 ft
14557 tons normal displacement (12959 tons standard)

Main battery: 9 x 5.9-inch (3 x 3; 1 superfiring)
Secondary battery: 8 x 4.1-inch
AA battery: 8 x 1.4-inch

Weight of broadside: 1211 lbs

4 TT, 19.7" (submerged)

Main belt, 4.0 inches; ends unarmored
Armor deck, average 2.0 inches
C.T., 4.0 inches

Battery armor:
Main, 4.0" / secondary, 2.0" shields
AA, 1.0" shields

Maximum speed for 95026 shp = 31.33 knots
Approximate cruising radius, 15000 nm / 12 kts

Typical complement: 663-861


Estimated cost, $13.077 million (£3.269 million)

Remarks:

Main turrets are grouped together.

Relative extent of belt armor, 95 percent of 'typical' coverage.

Good seaboat; rides out heavy weather easily.

Ship is roomy, with superior accommodation and working space.


Distribution of weights:
Percent
normal
displacement:

Armament ......................... 151 tons = 1 pct
Armor, total ..................... 2287 tons = 16 pct

Belt 712 tons = 5 pct
Deck 1177 tons = 8 pct
C.T. 51 tons = 0 pct
Armament 346 tons = 2 pct

Machinery ........................ 3085 tons = 21 pct
Hull and fittings; equipment ..... 5344 tons = 37 pct
Fuel, ammunition, stores ......... 1990 tons = 14 pct
Miscellaneous weights ............ 1700 tons = 12 pct
-----
14557 tons = 100 pct

Estimated metacentric height, 4.6 ft

Displacement summary:

Light ship: 12567 tons
Standard displacement: 12959 tons
Normal service: 14557 tons
Full load: 15777 tons

Loading submergence 909 tons/foot

+++++++++++++++++++++++++


Estimated overall survivability and seakeeping ability:

Relative margin of stability: 1.22

Shellfire needed to sink: 20023 lbs = 195.0 x 5.9-inch shells
(Approximates weight of penetrating
shell hits needed to sink ship,
not counting critical hits)

Torpedoes needed to sink: 2.1
(Approximates number of 'typical'
torpedo hits needed to sink ship)

Relative steadiness as gun platform, 61 percent
(50 percent is 'average')

Relative rocking effect from firing to beam, 0.14

Relative quality as a seaboat: 1.22

+++++++++++++++++++++++++


Hull form characteristics:

Block coefficient: 0.51
Sharpness coefficient: 0.34
Hull speed coefficient 'M' = 8.46
'Natural speed' for length = 26.0 knots
Power going to wave formation
at top speed: 53 percent


Estimated hull characteristics and strength:

Relative underwater volume absorbed by
magazines and engineering spaces: 93 percent

Relative accommodation and working space: 192 percent


Displacement factor: 129 percent
(Displacement relative to loading factors)


Relative cross-sectional hull strength: 1.00
(Structure weight per square
foot of hull surface: 110 lbs)

Relative longitudinal hull strength: 1.09
(for 21.0 ft average freeboard;
freeboard adjustment +4.7 ft)

Relative composite hull strength: 1.01

+++++++++++++++++++++++++


[Machine-readable parameters: Spring Style v. 1.2.1]

675.00 x 74.00 x 20.00; 21.00 -- Dimensions
0.51 -- Block coefficient
1925 -- Year laid down
31.33 / 15000 / 12.00; Oil-fired turbine or equivalent -- Speed / radius / cruise
1700 tons -- Miscellaneous weights
++++++++++
9 x 5.90; 3; 1 -- Main battery; turrets; superfiring
Central positioning of guns
:
8 x 4.10; 0 -- Secondary battery; turrets
Gun-shields
:
8 x 1.40 -- Tertiary (QF/AA) battery
Gun-shields
:
0 -- No fourth (light) battery
4 / 4 / 19.70 -- TT / submerged / size
++++++++++
4.00 / 0.00 / 0.00 / 0.00; 95 -- Belt armor; relative extent
2.00 / 4.00 -- Deck / CT
4.00 / 2.00 / 1.00 / 0.00 -- Battery armor


+++++++++++++++++++++++++++++++++++++++++++++++++++++++

She looks a bit like a german design circa1940 for what they refered to as the "Atlantikflugzeugkreuzer", but they mounted their turrets on the bow. And if memory serves, they dropped the idea because if a carrier gets to within gun range, it has lost it's primary advantage - Range of attack - and it cannot stand up to anything carrying gins of similiar size, better to use the weight for more aircraft!

Quoted

The island is offset to port for no particular reason, as my aircraft use inline engines and shouldn't (I don't think) have excessive problems pulling to one direction or another

unless the planes use counter-rotative blades, there WILL be a yaw effect created by the engine torque, either to the left or to the right depending wether the propeller is rotating clockwise or counterclockwise.

Inline engines don't change a thing, they produce as much torque as a radial engine may do.

Quoted

Originally posted by Commodore Green
She looks a bit like a german design circa1940 for what they refered to as the "Atlantikflugzeugkreuzer", but they mounted their turrets on the bow. And if memory serves, they dropped the idea because if a carrier gets to within gun range, it has lost it's primary advantage - Range of attack - and it cannot stand up to anything carrying gins of similiar size, better to use the weight for more aircraft!

true enouhg - but: the 20s were the timne when they experimented with the carrier doctrine - thet Germany did so in the 30s is just an example of VT-induced time-lag ...

cheers

Bernhard

BTW not to be nit-picking, but the image shows three turrets, 2 superfiring, but the springstyle report says 3 turrets: 1 superfiring.


on a more in-depth explanation on the reasons of aircraft yaw because engine torque, I may have to explain that a propeller creates a spiral-shape turbulence, turning on the same direction as the propeller itself. When this turbulence hits the vertical surfaces of the aircraft (may be the tail surfaces, but also the same fuselage acts as such), it produces a "sail" effect, pulling the tail on that direction i.e. creating yaw towards that direction. This effect is much more pronounced at low speeds and must be rectified by the use of rudder pedals.

If you have a contra-rotating propeller (or you have two engines with propellers rotating in inverse direction ,as the P38 had), each propeller creates it's own turbulence and as both are turning at the same speed the yaw effect is almost negated.


the problem with torque and engines comes when you change power drastically. When you increase (or decrease) the power output of the engine in a fast way (for instance, in a landing where no wire is catched), the principles of newton and Galileo apply fully. Inertia. As the propeller is pulling with more force to one side, the plane tends to roll to the opposite direction. You must compensate then with aileron input to rectify.

Then there's the gyroscopic effect of the propeller accelerating (or deccelerating) suddenly, and the increased or decreased power of the engine itself. The plane tends to yaw to the left or right, depending on the direction of rotation of the propeller, so you also have to compensate with rudder to rectify the immediate yaw produced.


again, with counter-rotating propellers this effect is negligible because one prop counters the effect of the other.


if you're in a landing, and you suddenly have to increase power for a failed approach, you have to deal and fight against torque-induced yaw and roll, and also against an increased stream of air hitting against your plane's rudder and fuselage, stream which creates more yaw which adds to the torque-induced yaw.

Given that most of the single-engined fighters and planes of WWII had clockwise turning propellers, that means that if you are approaching a carrier at a low powersetting and have to increase power to 100% in a hurry, you'll find your plane yawing and rolling HUGHELY to the left.

This effect can be controlled but not without problems. At low speeds aileron and rudder response is sluggish, and many times it's simply not enough to compensate for the sudden increase of power (both in landings or takeoffs).

That is the reason why if a plane increased engine power suddenly, smashing into a port-side island was a very real possibility while if it had the island to starboard the main problem was putting the plane into the air in controlled flight before falling off the deck.

Quoted

Given that most of the single-engined fighters and planes of WWII had clockwise turning propellers, that means that if you are approaching a carrier at a low powersetting and have to increase power to 100% in a hurry, you'll find your plane yawing and rolling HUGHELY to the left.

The Hawker Typhoon/tempest had so much power that you couldn't just ram the throttle foreward when on the ground, else the aeroplane cartwheeled.

Now contra-rotating props aren't really practical for the 1920's.. if any one wants any pictures look at the Tupolev "Bear"; the fastest propeller engined aircraft ever.

Thanks for the detailed explanation of torque issues. Perhaps I'll end up sticking the island to starboard after all.

I've been finding that Springstyle won't acknowledge having two of the three turrets superfiring when it spits out the report, even if that's what I input. I think that the hull strength, being 1.01, is probably sufficient to account for the difference. At least, I hope so.

Although I wouldn't want to match her up against a CA, I'd contend that she could hold her own against any CL that started chasing her - not that such a situation is desirable, but at the time, it was considered quite possible.

Quoted

I've been finding that Springstyle won't acknowledge having two of the three turrets superfiring when it spits out the report, even if that's what I input. I think that the hull strength, being 1.01, is probably sufficient to account for the difference. At least, I hope so.

Spring Sharp also whines about the fact that no more than half the turrets can be superfiring, but still puts it in the report. I gave it a shot myself and the 1.01 is not enough but if you lower the freeboard by 0.1, you're there.

In the end you'll end up with this:

Urumi, India Carrier laid down 1925

Displacement:
12,567 t light; 12,960 t standard; 14,557 t normal; 15,776 t full load
Loading submergence 909 tons/feet

Dimensions:
675.00 ft x 74.00 ft x 20.00 ft (normal load)
205.74 m x 22.56 m x 6.10 m

Armament:
9 - 5.91" / 150 mm guns (3 Main turrets x 3 guns, 2 superfiring turrets)
Main turrets are grouped together
8 - 4.13" / 105 mm guns
8 - 1.46" / 37 mm AA guns
Weight of broadside 1,222 lbs / 554 kg
4 - 19.7" / 500.38 mm submerged torpedo tubes
Planes 40

Armour:
Belt 4.00" / 102 mm, ends unarmoured
Belts cover 94 % of normal area
Main turrets 4.00" / 102 mm, 2nd gun shields 2.00" / 51 mm
AA gun shields 1.00" / 25 mm
Armour deck 2.00" / 51 mm, Conning tower 4.00" / 102 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 3 shafts, 95,026 shp / 70,890 Kw = 31.33 kts
Range 15,000nm at 12.00 kts

Complement:
662 - 861

Cost:
£3.273 million / $13.092 million

Distribution of weights at normal displacement:
Armament: 153 tons, 1.0 %
Armour: 2,301 tons, 15.8 %
Belts: 701 tons, 4.8 %, Armament: 371 tons, 2.6 %, Armour Deck: 1,177 tons, 8.1 %
Conning Tower: 51 tons, 0.4 %, Torpedo bulkhead: 0 tons, 0.0 %
Machinery: 3,085 tons, 21.2 %
Hull, fittings & equipment: 5,328 tons, 36.6 %
Fuel, ammunition & stores: 1,990 tons, 13.7 %
Miscellaneous weights: 1,700 tons, 11.7 %

Metacentric height 4.1

Remarks:
Hull space for machinery, storage & compartmentation is adequate
Room for accommodation & workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily

Estimated overall survivability and seakeeping ability:
Relative margin of stability: 1.14
Shellfire needed to sink: 19,196 lbs / 8,707 Kg = 186.4 x 5.9 " / 150 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 2.1
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 70 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.17
Relative quality as seaboat: 1.21

Hull form characteristics:
Block coefficient: 0.510
Sharpness coefficient: 0.34
Hull speed coefficient 'M': 8.46
'Natural speed' for length: 25.98 kts
Power going to wave formation at top speed: 53 %
Trim: 58
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)

Estimated hull characteristics & strength:
Underwater volume absorbed by magazines and engineering spaces: 93.0 %
Relative accommodation and working space: 191.3 %
(Average = 100%)
Displacement factor: 128 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 0.99
(Structure weight / hull surface area: 110 lbs / square foot or 537 Kg / square metre)
Relative longitudinal hull strength: 1.07
(for 20.90 ft / 6.37 m average freeboard, freeboard adjustment 4.58 ft)
Relative composite hull strength: 1.00

Walter

At least Sharp lets you do it. I'll have to upgrade one day.

Dropping the freeboard by 0.1 feet is fine with me; I doubt anybody would notice the difference on board.

Thanks, Walter.

J