WesWorld

RA's lattest carrier has got me thinking about Nordmarks next offering in terms of Aircraft Carriers.
I'd like to get a ship with a truely armoured flight deck, but am at a loss how to sim it for a ship in the 17000t range and get a decent result.

Any suggestions.

How much deck armor are you thinking? And what's your definition of "decent"?

Well, in terms of Armour, I was thinking of somewhere above 3 inches, if possible 3.5.

In terms of Decent I still want a fair sized airgroup of 50+ planes in order to provide a reasonable offensive quality to the ship. Also I require the ship to be able to steam at 30+knots, though considering the number of 28knot cruisers I have, 28knots may be manageable.

Hmmmm. Shouldn't be too tough. If we look at my old 16,000 standard ton Peter Strasser design here and cut the airgroup from 60 to 50, we'll gain 1100 tons. Currently she has a 50mm deck, which weighs 1401 tons. Add all of that 1100 tons to it and you should be able to get at least 88-90mm of deck armor out of it. And that's on a 32.5 knot hull.....

The major problem I think is that to actually sim the deck armour as the flight deck you must have the freeboard at that level for the entire length of the armoured flight deck, so that the stability can be taken into account. This means that deck edge elevators are out.

After much playing about I've come up with this ship as a possible way of simming a carrier with an armoured flight deck.

Hök Class, Nordmark Carrier laid down 1934

Displacement:
16,932 t light; 17,445 t standard; 19,366 t normal; 20,904 t full load

Dimensions: Length overall / water x beam x draught
673.10 ft / 650.00 ft x 79.00 ft x 24.00 ft (normal load)
205.16 m / 198.12 m x 24.08 m x 7.32 m

Armament:
16 - 4.33" / 110 mm guns (8x2 guns), 40.61lbs / 18.42kg shells, 1934 Model
Dual purpose guns in deck mounts with hoists
on side ends, evenly spread, all raised mounts - superfiring
32 - 1.46" / 37.0 mm guns (8x4 guns), 1.55lbs / 0.70kg shells, 1934 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
32 - 0.79" / 20.0 mm guns (16x2 guns), 0.24lbs / 0.11kg shells, 1934 Model
Anti-aircraft guns in deck mounts
on side, evenly spread, all raised mounts
Weight of broadside 707 lbs / 321 kg
Shells per gun, main battery: 300

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 4.00" / 102 mm 480.00 ft / 146.30 m 11.00 ft / 3.35 m
Ends: Unarmoured
Upper: 1.50" / 38 mm 480.00 ft / 146.30 m 21.00 ft / 6.40 m
Main Belt covers 114 % of normal length

- Torpedo Bulkhead:
1.50" / 38 mm 480.00 ft / 146.30 m 21.00 ft / 6.40 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 2.00" / 51 mm 1.00" / 25 mm 1.00" / 25 mm
2nd: 1.00" / 25 mm - -
3rd: 1.00" / 25 mm - -

- Armour deck: 3.25" / 83 mm, Conning tower: 4.00" / 102 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 75,360 shp / 56,218 Kw = 29.00 kts
Range 11,000nm at 15.00 kts
Bunker at max displacement = 3,459 tons

Complement:
820 - 1,067

Cost:
£4.764 million / $19.055 million

Distribution of weights at normal displacement:
Armament: 88 tons, 0.5 %
Armour: 4,444 tons, 22.9 %
- Belts: 1,505 tons, 7.8 %
- Torpedo bulkhead: 559 tons, 2.9 %
- Armament: 74 tons, 0.4 %
- Armour Deck: 2,243 tons, 11.6 %
- Conning Tower: 62 tons, 0.3 %
Machinery: 2,168 tons, 11.2 %
Hull, fittings & equipment: 7,032 tons, 36.3 %
Fuel, ammunition & stores: 2,434 tons, 12.6 %
Miscellaneous weights: 3,200 tons, 16.5 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
48,563 lbs / 22,028 Kg = 1,195.8 x 4.3 " / 110 mm shells or 7.2 torpedoes
Stability (Unstable if below 1.00): 1.07
Metacentric height 4.0 ft / 1.2 m
Roll period: 16.6 seconds
Steadiness - As gun platform (Average = 50 %): 90 %
- Recoil effect (Restricted arc if above 1.00): 0.18
Seaboat quality (Average = 1.00): 2.00

Hull form characteristics:
Hull has low quarterdeck
and transom stern
Block coefficient: 0.550
Length to Beam Ratio: 8.23 : 1
'Natural speed' for length: 29.38 kts
Power going to wave formation at top speed: 53 %
Trim (Max stability = 0, Max steadiness = 100): 45
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 10.00 ft / 3.05 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 36.00 ft / 10.97 m
- Forecastle (15 %): 34.00 ft / 10.36 m
- Mid (50 %): 34.00 ft / 10.36 m
- Quarterdeck (20 %): 27.00 ft / 8.23 m (34.00 ft / 10.36 m before break)
- Stern: 27.00 ft / 8.23 m
- Average freeboard: 32.72 ft / 9.97 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 79.3 %
- Above water (accommodation/working, high = better): 294.7 %
Waterplane Area: 37,309 Square feet or 3,466 Square metres
Displacement factor (Displacement / loading): 153 %
Structure weight / hull surface area: 109 lbs/sq ft or 531 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.88
- Longitudinal: 2.99
- Overall: 1.00
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

1 ship Built-Hök

Can carry 50 aircraft

Lets look at RN studies for armoured-deck carriers.

Design J is closest to 17500tons

J (with armoured flight deck)
600ft 84ft 22
17,000 tons std
20.000 deep
66,000 shp
3 shafts 28kts
Endurance 10000 nm at 12kts
2*twin 5.25in
4*8 barrel pom poms
24 TSR (hanger capacity)
660 by 84 flight deck
436*60*16 hanger
Lifts 45*22
40000 gallons of petrol
180*500lb bombs
150*250lb bombs
£3 million

Designs f and J had 2.5in NC steel flight deck covering full width of Flight deck and 400/480ft respectively in length (covering full hangers in both and then extending aft beyond). Both had 2in forward bulkhead. For an extra 600 tons design J could have a 3in flightdeck. All NC.
For F and J Belt 4.5in C armour covering Mags and machinery which ran from HD to 3.5 ft below waterline. Reducing this belt to 3in would save 220 tons and £45000.

Shes slower, less heavily armed and carries far fewer aircraft. Probably around 40 ac with a deckpark. Serious limitations with fuel and ordnance stowage.

You actually need flight deck armour plus armour lower in the ship, else you have very little defense against shellfire.

JA
3 in flight deck, 2in deck armour over machinery, displaced 17,800tons for 28.75kts boilers forced. For an extra £130000
JB
3in flighdeck extended just over the width of hanger only, with 4.5in CA carried all the way up to the hanger deck from mags to machinery and back to mags. Hangers covered by 3in NC with hanger deck covered in 1.75in NC over mags and machinery. Displaced 17,560 tons for an extra £110,000.
JC
3in flight deck covers full width of flight deck, 3in NC hanger deck over vitals and 1in hanger sides. Displaced 17,890 tons and had 2ft extra beam in compensation (+£170,000).
JD
As JC with 4.5in belt extended over entire hanger sides. The protected area of flighdeck was reduced from 480ft (JA JC) to 436ft. Displacement 18,370 tons, 80.000shp for 27.75 kts. (+£250.000)

Design M
LBP (ft) 600
LWL (ft) 625
LOA (ft) 650
BEXT (ft) 88
17,440 tons std
22.9ft draught 26.9 deep
Flight deck freeboard 41.8ft
Shp 102,000 shafts 3 for 29.75 kts
Feul 4000tons for 12,000nm at 14kts
1000 complement
25.000gallons of petrol
8 * 4.5 in guns arranged in twin BD mounts superfiring fore and aft of island
2 * 8 barral pompoms
Aircraft 18 hanger plus 6 deck park

Protection
4.5in side C
2.5in Bulkhead NC
1in D hanger bulkhead
Deck 3in
Flight deck 3in

Design N
LBP (ft) 650
LWL (ft) 675
LOA (ft) 700
BEXT (ft) 83
16,500 tons std
19.6ft draught 23.6 deep
Flight deck freeboard 43.9ft
Shp 100,000 shafts 4 for 30.5 kts
Feul 3500tons for 10,000nm at 14kts
1000 complement
28.000gallons of petrol
8 * 4.5 in guns arranged in twin BD mounts superfiring fore and aft of island
4 * 8 barral pompoms
Aircraft 20 hanger plus 6 deck park (note old type)

Protection
3.5in side C
1.5in Bulkhead NC
1in D hanger bulkhead
Deck 2in
Flight deck 2.5in
Stearing 2.5in
Underwater 750lb

Quoted

The major problem I think is that to actually sim the deck armour as the flight deck you must have the freeboard at that level for the entire length of the armoured flight deck, so that the stability can be taken into account.

Not quite. Use your engineering skills and do a few moment calculations

Seriously. What engineering skills, I only just passed the module dealing with Statics and Dynmanics.

Anyhow, I'll see what i can do with this design and post again latter

RA, have you done serious calculations for your CVs? If so I´d like to learn more about it as I have no idea how to run such calculations.... :o/

Do you have a spreadsheet or something?

Ditto, by copying your calculation for the stability loss for deck armour, and using your methods of working out the misc weights required I've come up with this design, which is quite balanced. Am unsure how the armour simmed as misc weight affects the survivability though.

Hök Class, Nordmark Carrier laid down 1934

Displacement:
17,112 t light; 17,601 t standard; 19,517 t normal; 21,050 t full load

Dimensions: Length overall / water x beam x draught
621.10 ft / 600.00 ft x 90.00 ft x 23.00 ft (normal load)
189.31 m / 182.88 m x 27.43 m x 7.01 m

Armament:
12 - 4.33" / 110 mm guns (6x2 guns), 40.61lbs / 18.42kg shells, 1934 Model
Dual purpose guns in deck mounts with hoists
on side ends, evenly spread, all raised mounts - superfiring
32 - 1.46" / 37.0 mm guns (8x4 guns), 1.55lbs / 0.70kg shells, 1934 Model
Anti-aircraft guns in deck mounts
on side, all amidships, all raised mounts - superfiring
32 - 0.79" / 20.0 mm guns (16x2 guns), 0.24lbs / 0.11kg shells, 1934 Model
Anti-aircraft guns in deck mounts
on side, evenly spread, all raised mounts
Weight of broadside 545 lbs / 247 kg
Shells per gun, main battery: 300

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 4.00" / 102 mm 480.00 ft / 146.30 m 11.00 ft / 3.35 m
Ends: Unarmoured
Upper: 1.50" / 38 mm 480.00 ft / 146.30 m 21.00 ft / 6.40 m
Main Belt covers 123 % of normal length

- Torpedo Bulkhead:
1.50" / 38 mm 480.00 ft / 146.30 m 21.00 ft / 6.40 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 2.00" / 51 mm 1.00" / 25 mm 1.00" / 25 mm
2nd: 1.00" / 25 mm - -
3rd: 1.00" / 25 mm - -

- Armour deck: 1.50" / 38 mm, Conning tower: 4.00" / 102 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 83,938 shp / 62,618 Kw = 29.50 kts
Range 11,000nm at 15.00 kts
Bunker at max displacement = 3,450 tons

Complement:
825 - 1,073

Cost:
£4.881 million / $19.522 million

Distribution of weights at normal displacement:
Armament: 68 tons, 0.3 %
Armour: 3,270 tons, 16.8 %
- Belts: 1,503 tons, 7.7 %
- Torpedo bulkhead: 559 tons, 2.9 %
- Armament: 57 tons, 0.3 %
- Armour Deck: 1,089 tons, 5.6 %
- Conning Tower: 62 tons, 0.3 %
Machinery: 2,415 tons, 12.4 %
Hull, fittings & equipment: 6,159 tons, 31.6 %
Fuel, ammunition & stores: 2,405 tons, 12.3 %
Miscellaneous weights: 5,200 tons, 26.6 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
35,140 lbs / 15,939 Kg = 865.3 x 4.3 " / 110 mm shells or 5.6 torpedoes
Stability (Unstable if below 1.00): 1.16
Metacentric height 5.6 ft / 1.7 m
Roll period: 15.9 seconds
Steadiness - As gun platform (Average = 50 %): 57 %
- Recoil effect (Restricted arc if above 1.00): 0.05
Seaboat quality (Average = 1.00): 1.27

Hull form characteristics:
Hull has raised forecastle
and transom stern
Block coefficient: 0.550
Length to Beam Ratio: 6.67 : 1
'Natural speed' for length: 28.75 kts
Power going to wave formation at top speed: 58 %
Trim (Max stability = 0, Max steadiness = 100): 45
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 8.00 ft / 2.44 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 36.00 ft / 10.97 m
- Forecastle (10 %): 34.00 ft / 10.36 m (25.00 ft / 7.62 m aft of break)
- Mid (50 %): 25.00 ft / 7.62 m
- Quarterdeck (20 %): 25.00 ft / 7.62 m
- Stern: 25.00 ft / 7.62 m
- Average freeboard: 25.98 ft / 7.92 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 93.7 %
- Above water (accommodation/working, high = better): 226.5 %
Waterplane Area: 39,235 Square feet or 3,645 Square metres
Displacement factor (Displacement / loading): 141 %
Structure weight / hull surface area: 112 lbs/sq ft or 545 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.94
- Longitudinal: 1.76
- Overall: 1.00
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
Good seaboat, rides out heavy weather easily

1 ship Built-Hök

Misc weight of 5200tons is

3000tons-50 Aircraft
2200tons is 3inch flight deck armour, over an area of 450ft by 65ft

Stability with 3inch flight deck armour 450ft by 65ft = stabilty -0.08 therefore true stability is 1.08.

Calculations - I've just realised that I've gone wrong and should have allowed for metacentric height as well. At least this means that the ship has more stability. I'll post a walk-through of calculations later when I'm finished adjusting.

Quoted

Am unsure how the armour simmed as misc weight affects the survivability though.

I assumed that it didn't. Its not in a position to do anything. misc weight takes up volume which is what affects the survivability calcs. The deck armour is essentially a lamina and should have no effect apart from on stability.

Quoted

Seriously. What engineering skills, I only just passed the module dealing with Statics and Dynmanics.

and here's me hoping that you'd be able to step in when I went on to talk about bending moments.

Well, I've sort of forgotten everything so that I can revise for the module I failed. I eargly await the walk through, it is gonna quite useful.

Introduction to Stability in Ships

A not so brief introduction to stability in ships that is a good starting point.

I'll just give you the simple calculations that I did rather than go into more complicated loading diagrams.

I´m looking forward for more. Hopefully your calculations take care fo the fact that you have a non solid hull - at least in the last part of your ship. Non-solid meaning that you have a waterplane area aft with two skegs instead of a center hull.

Please explain how this affects your calculations (center of gravity, center of buoyancy) that finally lead to your modified SS sheet. Thanks.

I don't think I have the detail calculations that you want but here goes in trying to determine flight decks affect on stability.

Open up SS with your carrier design. Set an arbitary value as the misc weight, say 5000tons. Look at the difference in stability between 0tons misc weight and 1000tons. Say this difference is 0.10. Now we calculate the moment arm of that misc weight.

misc weight x (freeboard (box 9) - metacentric height) as metacentric height is essentially the centre of buoyancy.

so 5000 x 8m = 40,000 ton m which corresponds to a drop in stability of 0.10 or 0.01 per 4,000ton m

Now say we want to armour our flight deck. Work out how much it weighs first, area*thickness*7.84. Say a figure of 3000tons

This is really where you need a drawing so you can see where your flight deck is located. e.g. 15m

do the same calculation again

armour deck weight x (flight deck height - GM)

3000 x 15m = 45,000 ton m

as we worked out above, the ship loses 0.01 for every 4000ton m so with the 3000ton armour deck 15m up the ship will lose 0.11 points of stability.

Its really not that hard to do.

For survivability ratings I'm assuming the flight deck armour has no effect as it has negligible volume. So misc weight - armour deck weight and look at the shellfire and torpedoes to sink.

I've just had an idea with regards to stability of the skegs. Use them to store fuel oil. It gives them more protection as the blast from a torpedo is dissapated more and when flooded the ship's attitude won't change much as specific gravity of oil is around 0.90 - 0.95 compared to 1.00 of water

Thanks for that, turns out my guesswork was roughly correct.

Unfortunately, I can't see an armoured deck design with its reduced airgroup and speed, while being heavier than previous designs, realistically getting past the Naval Planning commitee in Karlskrona.

The Naval Planning Committee would have to be convinced that the threat that it faces will be more from dive bombers than from other sources. Once they're convinced of that, then the armored-deck carriers start to make sense (though the issue can become "how big a bomb are they dropping, and can we protect against that").

Aye, and the commitee hasn't seen any serious incedences of dive bombing, and carrier vs carrier operation

Exactly the case. Germany's carrier, if and when we get around to building one, will probably not have an armored flight deck, for exactly the same reasons.

Quoted

The Naval Planning Committee would have to be convinced that the threat that it faces will be more from dive bombers than from other sources.

Well Italy has some experience in level bombing with D'Annunzio's raids on AH warships with Caproni bombers. These were moderately succesful and show promise for the future. Reports of dive bombing from Germany and Russia indicate that it is significantly more accurate but isn't as powerful a means of weapons delivery. Skip bombing seems better to RA pilots as a means of delivery as it gives a more normal parabolic flight path and allows the use of AP shells as a baseline.

I don't see why an armoured flight deck isn't useful against level bombers. If they make a run at 4000m or so then you're not going to be able to intercept them with fighters. An continuous CAP would place too much strain on the pilots and planes. Radar and higher performance planes make level bombing attacks less likely to succeed.