Draft Carrier Rules

[Kaiser Kirk]

This is a subject that we should all kick about and discuss before being adopted.

This started as a simple adaptation by Snip and I,  of Rocky's N3 take on Wesworld's take on the Springstyle note.txt take of how to do Carriers. USS Lexington and HMS Arc Royal were used as the trial ships and came out 'close'.

However, there was a desire to make it more comprehensive, and in particular add flight deck cruisers.
This unfortunately made this more complex than desired.

It should be usable, understandable, and give us some common rules cover most of the options players may want to explore.
I attempted to arrange it in a logical, step by step, format.

This is the draft result and is opened for Player comments on how it can be improved.
There's no rush on this, we want a result that is doable, consistent, and satisfies most of us (I doubt we could find something perfect for all).


Seaplane Carriers / Aircraft Carriers / flight deck cruiser
These are categorically warships. For Non-Aircraft Carriers, see next item

1. Sim your hull.
Set Length, beam, draft, BC normally.
Leave "Length (% of LWL) at defaults.
On the "Freeboard" tab, hit "Flush Deck"

2. Determine your Maximal Airgroup
On the Hull tab, Use the (waterplane area : square meters )/ 60 to determine the theoretical maximum number of aircraft embarked.

For Seaplane Carriers, multiply this by 50%.
For Single-hanger Carriers, multiply this by 70%.
For Dual-hanger Carriers, multiply this by 100%
For Flight Deck Cruisers, multiply this by (Aft Deck% ).

3. Sim your Freeboard.
This will depend on the type of vessel you wish to build.

For Seaplane Carriers
Hanger is assumed in-hull and a superstructure may be present.
Default or greater freeboard can be used.

For Single-hanger Carriers
Add at least 6m to the "Aft Deck" default.
Make the Foredeck the same height.
The flight deck is assumed to be at the top of this structure and carried foreward and aft.

For Dual-hanger Carriers
Add at least 12m to the "Aft Deck" default.
Make the Foredeck the same height.
The flight deck is assumed to be at the top of this structure and carried foreward and aft.

For Flight Deck Cruisers
This type of vessel was considered but not built in this period. As there are no historical examples to serve as 'proof of concept', they are subject to player & moderator evaluation for 'practicality' and if the proposed weapons can fit in the foredeck length provided.

Add at least 6m to the "Aft Deck" default.This represents the hanger.
The foredeck represents the space for the "Flight deck cruiser" armanent.
One can increase the hanger & flight deck area by changing the "Aft Deck" "Length % of LwL"
The flight deck is assumed to be at the top of the hanger and projecting over the stern, and their combined length will effect judgements on aircraft handling.

The remaining hull may be of any freeboard desired.
If the desire is a "Flight deck cruiser" armanent arranged "fore/aft", that should be specified in the notes.

Forecastle and Quarterdeck
These can be left at the default or altered.
Or these can be raised to the level of the Aft deck.
A flying off-deck can be fitted as described next.
The quarterdeck freeboard-aft can "round down" by a meter if desired.

Flying off deck
If a flying off deck is desired, then
'Forecastle freeboard-aft' should be -5m below the foredeck height.
'Forecastle freeboard-forward' should be +/- 1 meter of that.


4. Set aside Miscellaneous Weight "Hull-Above Water" for the Airgroup.

Aircraft Carrier : For single engine planes, N=25 tons is used.
Seaplane Carrier : For Single or Twin engine seaplanes, N=35 tons is used.

If the total number of aircraft is less than N, assign as miscellaneous weight Nt per aircraft.

If the total number of aircraft is N or higher, assign as miscellaneous weight the square of the number of aircraft (1600 t for 40 A/C, 3600t for 60 A/C, etc. ). 

Hangers vs. Deckparks. If you chose an airgroup greater than 70% of your theoretical maximum, you will require two hangars. Once you have 1932 tech, you may choose to have 1 hanger and a deckpark.  This will determine your freeboard later on.

If the carrier is a conversion started after the vessel is 33% complete multiply the required miscellaneous weight by 1.5 to represent inefficiencies of hull form, etc.

This figure includes all aspects of the aviation component - aircraft, fuel, ordnance, catapults, aircrew facilities.  Larger Carriers will have more stores / AC. Smaller carriers can choose to specify additional weight for stores.

5. The Miscellaneous Weight will note the effective Airgroup carried.

The actual Airgroup size will vary by the nations current Aircraft Technology. 
This can be determined as needed by events in-SIM.
Historically, it reflects the increasing size and needs of planes over time, and trend for carriers to field  smaller airgroups than originally designed for.   

For example : Lexington's airgroup by #2 is 93.75, or 94.  In 1922 aircraft she can carry 117.5 vs a historic 118. In 1938 Aircraft, what she had on the eve of WW2,  she can carry 84 vs the historical 83.
Likewise, Arc Royal was designed for 60, but entered the war with 54, which is the same here. 

1902: Up to Historical 1906 aircraft and countermeasures [1.50]
1906: Up to Historical 1910 aircraft and countermeasures [1.45]
1910: Up to Historical 1914 aircraft and countermeasures [1.40]
1914: Up to Historical 1916 aircraft and countermeasures [1.35]
1918: Up to Historical 1919 aircraft and countermeasures [1.30]
1922: Up to Historical 1924 aircraft and countermeasures [1.25]
1926: Up to Historical 1929 aircraft and countermeasures [1.20]
1930: Up to Historical 1933 aircraft and countermeasures [1.10]
1934: Up to Historical 1937 aircraft and countermeasures [1.00]
1938: Up to Historical 1940 aircraft and countermeasures [0.90]
1942: Up to Historical 1944 aircraft and countermeasures [0.80]
1946: Up to Historical 1948 aircraft and countermeasures[0.70]

Plane Operability and Sorties.
Historically, during WW2, torpedo bombers could not operate effectively on shorter flight decks, and escort carriers often had to catapult launch heavier aircraft, but were otherwise effective platforms.

Be advised the tonnage dedicated to aircraft fuel and munitions on interwar carriers, and such the wieght model here,  was frequently only sufficient for 6-8 fully armed sorties. Fleet Train ships, or onboard "Extra" Misc. weight specified for Av-Gas or munitions can expand this.

Armanent
Single-hanger and Dual-hanger carriers should not have centerline-mounted weapons.
Flight deck cruisers may, but they are restricted to the forecastle.
Flight deck cruisers which wish fore/aft weaponry should specify in the notes that arrangement.

6. Armored Box Carriers.
For armored box carriers, the freeboard represents the height of the armored flight deck.
Bear in mind that this will be atop one or two hangars and a typical cruiser-like freeboard.

The thickness of the armor deck should be 150% of your intended average flight deck thickness (i.e., 4.5" if you want 3").  The extra 50% represents the weight of the armored hangar floor with the same thickness.

Use upper belt armor to represent armored hangar sides. 
Length will correspond to hangar length (65% hull length) and height to your hangar height as above.

Make a note directly under the SS report's "Armour deck" line that the ship is an armored box carrier, and note the actual average thickness of the flight deck and hangar floor.
Note also the number of hangars.


7. Non-Aircraft Carriers
For vessels embarking Six or fewer reconnaissance  Floatplane Aircraft. :
Set aside 20 tons per reconnaissance  Floatplane "On Deck".  Add 5 tons per catapult if desired. As lightweight reconnaissance  assets, These are effectively unarmed. 

If  armed float planes / single use catapult fighters : 25 tons per aircraft. Add 5 tons per catapult desired. These are considered "armanent".

8. For Seaplane Tenders  :
Seaplane tenders do not have dedicated aircraft. Rather they serve in a sheltered anchorage as a maritime basing and support for a "Air Point" and "deployment point" representing Flying Boats and or Maritime reconnaissance  Bombers, along with associated Floatplane fighters.

Assign as miscellaneous weight 6400t.  This covers crew quarters, spare parts, spare engines, weapons and fuel.

[The Rock Doctor]

So on flight deck cruisers:  There are, arguably, cases to be made for designs with the flight deck forward and the main battery aft.  I did this in Wesworld on the Urumi class.  It seemed more suitable to a defensive main battery configuration.   I'd propose that wording for flight deck cruisers allow for either fore deck or aft deck as the flight deck and the other deck to be available for the main battery.

I've seen some sketches where there's a main battery at each end and a flight deck in the middle but that doesn't seem like it'll work well with what's proposed here. 

Otherwise this looks like a good, detailed start.

[snip]

So on flight deck cruisers:  There are, arguably, cases to be made for designs with the flight deck forward and the main battery aft.

I didn't think of that before when arguing aggressively promoting inclusion. But as you say, a simple reword to say ether For or Aft deck should suffice.

I've seen some sketches where there's a main battery at each end and a flight deck in the middle but that doesn't seem like it'll work well with what's proposed here. 

There is something to account for this.

If the desire is a "Flight deck cruiser" armanent arranged "fore/aft", that should be specified in the notes.

We just cant use the typical Springsharp distribution because of the Freeboard.

[Kaiser Kirk]

I don't see why it can't be either Aft deck or fore deck that sets that benchmark.
I'm looking for a specific section of the Springsharp report we can look to to figure the air ops part out, but it doesn't really matter which one.

As for the either end, this was supposed to allow that : "If the desire is a "Flight deck cruiser" armanent arranged "fore/aft", that should be specified in the notes."

[The Rock Doctor]

First cut at Bearn

Note:

-Conversion appears to have started at less than 33% complete.
-Conversion appears to have retained original 1914 machinery.
-Maximal airgroup by size:  60
-Designed airgroup:  32, low energy.

So, I mean, it works, but you'd think from the SS that the design was quite an under-achiever.  Not that Bearn was known as an overachiever.

Enter ship name, Enter country Enter ship type laid down 1914

Displacement:
   25,050 t light; 25,735 t standard; 26,774 t normal; 27,606 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
   (598.48 ft / 574.15 ft) x 88.58 ft x (28.35 / 29.09 ft)
   (182.42 m / 175.00 m) x 27.00 m  x (8.64 / 8.87 m)

Armament:
      8 - 6.10" / 155 mm 45.0 cal guns - 114.59lbs / 51.98kg shells, 250 per gun
     Breech loading guns in casemate mounts, 1914 Model
     8 x Single mounts on side ends, evenly spread
      8 hull mounts in casemates- Limited use in heavy seas
      6 - 2.95" / 75.0 mm 45.0 cal guns - 12.98lbs / 5.89kg shells, 450 per gun
     Anti-air guns in deck mounts, 1914 Model
     6 x Single mounts on sides, evenly spread
      8 - 1.46" / 37.0 mm 45.0 cal guns - 1.56lbs / 0.71kg shells, 375 per gun
     Anti-air guns in deck mounts, 1914 Model
     8 x Single mounts on sides, evenly spread
      Weight of broadside 1,007 lbs / 457 kg

Armour:
   - Belts:      Width (max)   Length (avg)      Height (avg)
   Main:   3.27" / 83 mm   373.20 ft / 113.75 m   17.95 ft / 5.47 m
   Ends:   Unarmoured
     Main Belt covers 100 % of normal length

   - Torpedo Bulkhead - Additional damage containing bulkheads:
      0.79" / 20 mm   373.20 ft / 113.75 m   27.23 ft / 8.30 m
   Beam between torpedo bulkheads 82.02 ft / 25.00 m

   - Gun armour:   Face (max)   Other gunhouse (avg)   Barbette/hoist (max)
   Main:   1.97" / 50 mm   1.97" / 50 mm            -
   2nd:   0.79" / 20 mm   0.79" / 20 mm            -
   3rd:   0.79" / 20 mm         -               -

   - Armoured deck - multiple decks:
   For and Aft decks: 1.77" / 45 mm
   Forecastle: 1.77" / 45 mm  Quarter deck: 1.77" / 45 mm

Machinery:
   Oil fired boilers, reciprocating cruising steam engines and steam turbines
   Direct drive, 4 shafts, 36,400 ihp / 27,154 Kw = 21.50 kts
   Range 6,500nm at 10.00 kts
   Bunker at max displacement = 1,871 tons

Complement:
   1,046 - 1,360

Cost:
   £1.481 million / $5.924 million

Distribution of weights at normal displacement:
   Armament: 155 tons, 0.6 %
      - Guns: 155 tons, 0.6 %
   Armour: 2,635 tons, 9.8 %
      - Belts: 960 tons, 3.6 %
      - Torpedo bulkhead: 296 tons, 1.1 %
      - Armament: 91 tons, 0.3 %
      - Armour Deck: 1,287 tons, 4.8 %
   Machinery: 1,706 tons, 6.4 %
   Hull, fittings & equipment: 19,180 tons, 71.6 %
   Fuel, ammunition & stores: 1,724 tons, 6.4 %
   Miscellaneous weights: 1,374 tons, 5.1 %
      - Hull below water: 200 tons
      - Hull above water: 1,024 tons
      - On freeboard deck: 100 tons
      - Above deck: 50 tons

Overall survivability and seakeeping ability:
   Survivability (Non-critical penetrating hits needed to sink ship):
     158,894 lbs / 72,073 Kg = 1,398.4 x 6.1 " / 155 mm shells or 28.7 torpedoes
   Stability (Unstable if below 1.00): 1.09
   Metacentric height 5.0 ft / 1.5 m
   Roll period: 16.7 seconds
   Steadiness   - As gun platform (Average = 50 %): 50 %
         - Recoil effect (Restricted arc if above 1.00): 0.07
   Seaboat quality  (Average = 1.00): 2.00

Hull form characteristics:
   Hull has low forecastle,
     a normal bow and a cruiser stern
   Block coefficient (normal/deep): 0.650 / 0.653
   Length to Beam Ratio: 6.48 : 1
   'Natural speed' for length: 23.96 kts
   Power going to wave formation at top speed: 47 %
   Trim (Max stability = 0, Max steadiness = 100): 25
   Bow angle (Positive = bow angles forward): 10.00 degrees
   Stern overhang: 19.69 ft / 6.00 m
   Freeboard (% = length of deck as a percentage of waterline length):
            Fore end,    Aft end
      - Forecastle:   20.00 %,  26.35 ft / 8.03 m,  21.56 ft / 6.57 m
      - Forward deck:   30.00 %,  56.10 ft / 17.10 m,  56.10 ft / 17.10 m
      - Aft deck:   35.00 %,  56.10 ft / 17.10 m,  56.10 ft / 17.10 m
      - Quarter deck:   15.00 %,  56.10 ft / 17.10 m,  52.82 ft / 16.10 m
      - Average freeboard:      49.33 ft / 15.04 m
   Ship tends to be wet forward

Ship space, strength and comments:
   Space   - Hull below water (magazines/engines, low = better): 31.7 %
      - Above water (accommodation/working, high = better): 398.0 %
   Waterplane Area: 38,961 Square feet or 3,620 Square metres
   Displacement factor (Displacement / loading): 340 %
   Structure weight / hull surface area: 222 lbs/sq ft or 1,085 Kg/sq metre
   Hull strength (Relative):
      - Cross-sectional: 1.50
      - Longitudinal: 22.78
      - Overall: 1.96
   Excellent machinery, storage, compartmentation space
   Excellent accommodation and workspace room
   Excellent seaboat, comfortable, can fire her guns in the heaviest weather

[Desertfox]

Well that's complicated... I will give Hosho a try when I get home. Some thoughts:

Armanent
Single-hanger and Dual-hanger carriers should not have centerline-mounted weapon

How about changing this to centerline turret or heavy weapons? I believe single 5" size mounts where actually quite common among escort carriers.

7. Non-Aircraft Carriers
For vessels embarking Six or fewer reconnaissance  Floatplane Aircraft. :
Set aside 20 tons per reconnaissance  Floatplane "On Deck".  Add 5 tons per catapult if desired. As lightweight reconnaissance  assets, These are effectively unarmed.

If  armed float planes / single use catapult fighters : 25 tons per aircraft. Add 5 tons per catapult desired. These are considered "armanent".

8. For Seaplane Tenders  :
Seaplane tenders do not have dedicated aircraft. Rather they serve in a sheltered anchorage as a maritime basing and support for a "Air Point" and "deployment point" representing Flying Boats and or Maritime reconnaissance  Bombers, along with associated Floatplane fighters.

Assign as miscellaneous weight 6400t.  This covers crew quarters, spare parts, spare engines, weapons and fuel.

I get that the tender is supposed to support an entire "Air Point" but I would like some flexibility for smaller ones. How about adding a tender category to 7.

For vessels tendering Six or fewer flying boat or maritime reconnaissance aircraft:
Set aside 50 tons per aircraft "supported".  Add 10 tons per crane if desired.

[Kaiser Kirk]

In general I don't want to be responding to each post, as I want a group discussion,
Plus Weds is 'Mods day off'.

So, I mean, it works, but you'd think from the SS that the design was quite an under-achiever.  Not that Bearn was known as an overachiever.

Bearn's a big ship for such a tiny airgroup.
It may be that we need a different set point for the Conversion bit. That's part of this larger conversation.
looking here : https://www.naval-encyclopedia.com/ww2/France/aircraft-carrier-bearn she was 8-10% complete with 25% of machinery installed.

The 'problem' area would seem that she kept at 21knots, while ditching the battleship armor.
On any ship that would wind up a ton of internal room.
That does put her design capacity at 40 aircraft, with a double hanger, but also indicates she was meant to be experimental and testing.

From that page, she could at least fit more planes, as in 1940 she was loaded with 106 planes for delivery (not operations).

Anyhow, that's why this is out for discussion - kick holes in it !
...and then suggest "fixes"

I get that the tender is supposed to support an entire "Air Point" but I would like some flexibility for smaller ones. How about adding a tender category to 7.

Snip's KISS tried to eliminate tracking of small elements, so  Land points and Air points are not subdividable.
By carving out a non-carrier section with allowance for up to 6 planes I hoped to cover those needs.
Feel free to suggest options.

[The Rock Doctor]

I think the conversion point is reasonable; if it goes lower, nobody would bother with conversions.

It seems more like the French were very conservative in their effort (retaining the same slow machinery, using the outboard VTEs, etc).

I do wonder if 6m is excessive for hangar height, especially in the early going.  That said, I don't know how much space there actually is between the roof of the hangar and the top of the flight deck above it. 

[Kaiser Kirk]

The 6m is actually an attempt at future proofing, so that there will not come a later time where we have to check hanger heights to see if they can operate the most recent planes.
That wound up being a real life issue for the Brits, so by mandating a "tall enough" hanger from the start, I wanted to avoid that.

[Kaiser Kirk]

Follow up thought on Bearn - the linked page noted that even with 3 elevators, Bearn was very slow to cycle her airgroup.

Reports were not flattering on their performance, in particular one of 1937 which underlined Béarn could make land fifteen planes in one hour eight minutes, thirty-two aircraft for the Glorious in  forty-two minutes and on the Saratoga forty in just eleven minutes.

If you can only handle landing 15 planes in 68 minutes, landing 32 would take 2 hrs 25minutes. 
With that performance, and the experimental nature of the ship, they may have felt larger groups just not workable.

[snip]

This made me recall that the other day a picture of Bearn's elevators came up in a discussion. They are strange.

[Kaiser Kirk]

Ok,
I found a problem with my work.
Sadly it's one I found before, and thought I had fixed, but but didn't make it into this draft.

the Sim of Ark Royal works well with a 6m whole length hanger.
Unfortunately, she was a two hanger ship,
and does not work with Fore/Aft decks at +12.

Which I had realized and wrote up a fix for.
Which does not appear in the draft.

I had realized that, and figured the solution was accepting these hanger / flight deck structures
were not as heavily built as the rest of the hull - they do have weight, they should be "free" but
lesser.

What "Works" is treating the twin hangers as +7m, which would make the single +3.5.
The presumption being each represents a lightweight structure 5.5-6m tall.

Anyhow, sorry about that mixup.
But, the reason it's a draft is it's not perfect
and so if y'all have better ways, present !


Foxy : I saw your centerline comment, I'm leaving it for group discussion.

[Desertfox]

Perhaps getting rid of the freeboard requirements (Section 3) for carriers without armored boxes? And instead add a seakeeping (at least 1.0) requirement?

[snip]

I like the freeboard requirement as it is a nice, easy to check, bright line. Most designs will have over 1.0 Seakeeping anyway, so its not a real requirement but instead a check for basic fails.

[Desertfox]

Eh, if it doesn't really add anything, its one less thing I would rather not look at, especially since its in metric and all my designs are in imperial units.

Also I keep re-reading Section 4 and I am still very much confused as to what "N" is.