Armored Carrier Cleanup

[Kaiser Kirk]

1. Background
Having actually started designing Armored carriers, I was running into difficulties with the current rule, specifically the

-Use (actual thickness * 1.5) for Armored Box Carrier decks

For a design with a 75mm flight deck and 35mm hanger floor, that requires a 110*1.5 = 165mm deck.
Which is extremely weighty and makes simming historical designs hard.

The solution is to add tonnage via wider bulges and greater depth, but the LIGHT tonnage winds up far in excess of historical, and the STANDARD even worse.

We could just stick with what is written. I would still likely make at least One Armored Carrier.

2. The Current Rule :

6.  Armored Box Carrier:

-Use (actual thickness * 1.5) for Armored Box Carrier decks

-Use upper belts (65% of hull length, 5.5m height per hangar deck) for hangar sides

-Make notes accordingly.
 
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.

3. The Source
Searching for the source of the 'Armored Box Carrier' rule, I think that was adopted from Foxy's.
There is a very important line that looks to have been dropped. I have colored that line blue.

https://www.navalism.org/index.php/topic,7631.30.html#quickreply_anchor

4. Armored Box Carriers. [/b]
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.

Armored hangars will require a +3m freeboard over a normal ship

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.

4. Thoughts
4A.  The The extra 50% represents the weight of the armored hangar floor with the same thickness. should be added to our Current Aviation Ship Rules to clarify that is what is meant.

4B. I am unsure why we do not allow simple specification of how the carrier armor decks are divvied up.
If the player wants a Flight Deck of 100mm, a Hanger Deck Floor of 35mm, and a splinter 35mm armored box around magazines, why not allow them to specify that?
Oddly usually Fox was the one fighting for more flexibility, so there may be some reason that escapes me right now.

Player commentary on 4A & 4B ?

[Kaiser Kirk]

the results of this will of course effect my Armored Carrier designs, so my HY1, 1933 will come after this is all worked out :)

[The Rock Doctor]

I've had trouble with it myself, so have not been seriously pursuing the concept.  The 1.5x really distorts things.

I'd be inclined to say "Take the true thickness of the flight deck + hanger deck, apply it all at the true flight deck height."  Allocate whatever the hanger deck armor is, as part of the comments, or just assume it's got a half-inch of basic splinter protection separate to the actual "armor deck".   

[Kaiser Kirk]

I've had trouble with it myself, so have not been seriously pursuing the concept.  The 1.5x really distorts things.

I'd be inclined to say "Take the true thickness of the flight deck + hanger deck, apply it all at the true flight deck height."  Allocate whatever the hanger deck armor is, as part of the comments, or just assume it's got a half-inch of basic splinter protection separate to the actual "armor deck".   

That's basically 4B above. - Armored Deck, Multiple layers, specify in notes.

Honestly we have no mechanism to allocate at the flight deck level, but we can't get around that.

My preferred solution as well.
I'd like to have a 65-75mm flight deck, 25-35mm hanger deck floor, and maybe even a 25-35mm protective deck under it all.

[The Rock Doctor]

I suppose one could sim the cost of the hanger-deck level armor and then assign that as miscellaneous weight "above water" to see what it does.

That's assuming the flight deck armor is basically "freeboard".

[Kaiser Kirk]

Test of three different approaches – deck armor, On Deck misc, and Above Deck misc.
There is some minor changes to stability, dropping from 1.53 to 1.35, but
the results are not near any instability in the vessel.  Increasing the ship to a 15m double hanger freeboard, adding the +5.5 upper belt, and decreasing the draft 1m for displacement..dropped stability of the Above Deck version to 1.25.

Granted, on narrower ships it could show up, as this was a tubby example.
But there's only so much modeling I want to do :)

Overall, it does not seem like SS thinks these vessels are on the cusp of instability.

As such, I would prefer either (4A) – our current rule with Fox's missing line.
Or (4B) – specify Armoured deck - multiple decks  with a note in the SS text for Flight / Hanger Floor / any other deck thicknesses under the Armor deck listing .

Either way, there should be a note added that "Hanger armor is assumed to replace hull sheathing, and the 5.5m per hanger covers from main belt to freeboard"

#1 is 150mm Armored deck simmed as deck armor, weighing 4,759 tons. Miscellaneous weights are those for the speculative carrier

- Armoured deck - multiple decks:
    For and Aft decks: 5.91" / 150

 - Armour Deck: 4,759 tons, 12.7 %
    Miscellaneous weights: 6,999 tons, 18.7 %
      - Hull below water: 266 tons
      - Bulge void weights: 160 tons
      - Hull above water: 3,170 tons
      - On freeboard deck: 3,223 tons
      - Above deck: 180 tons

Overall survivability and seakeeping ability:
    Stability (Unstable if below 1.00): 1.53
    Metacentric height 10.0 ft / 3.1 m
    Roll period: 14.8 seconds
    Steadiness    - As gun platform (Average = 50 %): 50 %
            - Recoil effect (Restricted arc if above 1.00): 0.07
    Seaboat quality  (Average = 1.00): 1.97

#2 is 150mm Armored deck simmed as On Deck miscellaneous weight weighing 4,759 tons.
This adds to the prior 3223 for 7982

- Armoured deck - multiple decks:
No Deck listed due to lack of deck armor

    Armour: 3,143 tons, 8.4 %
      - Belts: 1,662 tons, 4.4 %
      - Torpedo bulkhead: 1,060 tons, 2.8 %
      - Bulges: 125 tons, 0.3 %
      - Armament: 153 tons, 0.4 %
No Deck listed due to lack of deck armor
      - Conning Tower: 142 tons, 0.4 %
   
    Miscellaneous weights: 11,758 tons, 31.4 %
      - Hull below water: 266 tons
      - Bulge void weights: 160 tons
      - Hull above water: 3,170 tons
      - On freeboard deck: 7,982 tons
      - Above deck: 180 tons
Overall survivability and seakeeping ability:
    Stability (Unstable if below 1.00): 1.41
    Metacentric height 8.9 ft / 2.7 m
    Roll period: 15.7 seconds
    Steadiness    - As gun platform (Average = 50 %): 49 %
            - Recoil effect (Restricted arc if above 1.00): 0.08
    Seaboat quality  (Average = 1.00): 1.91

#3 is 150mm Armored deck simmed as Above Deck miscellaneous weight weighing 4,759 tons.
This adds to the prior 180 for 4939.  Trim was moved from 25 to 26 to boost steadiness back to 50

- Armoured deck - multiple decks:
No Deck listed due to lack of deck armor

    Armour: 3,143 tons, 8.4 %
      - Belts: 1,662 tons, 4.4 %
      - Torpedo bulkhead: 1,060 tons, 2.8 %
      - Bulges: 125 tons, 0.3 %
No Deck listed due to lack of deck armor
      - Armament: 153 tons, 0.4 %
      - Conning Tower: 142 tons, 0.4 %

Miscellaneous weights: 11,758 tons, 31.4 %
      - Hull below water: 266 tons
      - Bulge void weights: 160 tons
      - Hull above water: 3,170 tons
      - On freeboard deck: 3,223 tons
      - Above deck: 4,939 tons


Overall survivability and seakeeping ability:
    Stability (Unstable if below 1.00): 1.35
    Metacentric height 8.3 ft / 2.5 m
    Roll period: 16.2 seconds
    Steadiness    - As gun platform (Average = 50 %): 50 %
            - Recoil effect (Restricted arc if above 1.00): 0.08
    Seaboat quality  (Average = 1.00): 1.94

[Jefgte]

Putting 150mm of armoured deck on a CV, as much as on a BB, seems excessive to me for 1933-35.

[Kaiser Kirk]

Putting 150mm of armoured deck on a CV, as much as on a BB, seems excessive to me for 1933-35.

It is, but the current rule is that you have to provide 1.5* the actual deck thickness.
So if I want a 75mm deck + 25mm hanger floor = 100mm, I have to budget 150mm.

The problem is the original idea had "The extra 50% represents the weight of the armored hangar floor with the same thickness. " but we failed to copy that part.

So we need to either

• Leave the rules broken and armored carriers extremely penalized, or
• Add the missing line that to the current rules, or
• come up with a different way of doing armored carriers.

[The Rock Doctor]

I'm reasonably sure the Brits and Japanese didn't put an equal amount of armor on the hanger floors as they did on the flight deck.

So I'm all for the "find a better way" approach.

[TacCovert4]

Within the constraints of springsharp, maybe we add a smaller percentage than 50%? 

If you want a 100mm flight deck and a 25mm hangar deck, then do 125mm armored deck.  And 20% (or something) of the deck tonnage for the actual flight deck (so 100mm) added as AW misc weight to account for larger and more numerous girders and other structure?

Alternatively, go with an upper belt that's a bit taller and that accounts for the full hangar height and the tonnage?  Maybe have a required minimum thickness equal to the flight deck?

[Kaiser Kirk]

I'm reasonably sure the Brits and Japanese didn't put an equal amount of armor on the hanger floors as they did on the flight deck.

So I'm all for the "find a better way" approach.

Well crud, looks like I lost my pre-go to bed reply.
Shame because it was a detailed one.

You are correct, Illustrious was 3" on the deck, and 1.5" on the hanger floor.

Foxy's 150% actually works for that.
His quote doesn't indicate that.

It probably should be "2/3 the thickness is the Flight Deck, 1/3 the lower hanger floor". Then we'd need a line "Hanger Wall thickness carries from main belt to freeboard, supplanting hull plating."

Within the constraints of springsharp, maybe we add a smaller percentage than 50%? 

If you want a 100mm flight deck and a 25mm hangar deck, then do 125mm armored deck.  And 20% (or something) of the deck tonnage for the actual flight deck (so 100mm) added as AW misc weight to account for larger and more numerous girders and other structure?

Alternatively, go with an upper belt that's a bit taller and that accounts for the full hangar height and the tonnage?  Maybe have a required minimum thickness equal to the flight deck?

So we can do anything at this point.
Revamping the rules for Armored Carriers is an option.

The problem is that real armored carriers were rather complicated and may be hard to do in SS.

Then there's the "How do we keep the ruleset simple and equal for all?"
That part is why we have set freeboards and hanger heights.

A non-Armored carrier has a 9m freeboard "paid for" but really 12m,
while an Armored carrier pays for that extra structural steel with a 12m freeboard.

Actual British hanger heights varied by hanger, and all were less than 5.5m we require, which led to problems with fitting later aircraft. They also used 1/2 hangers, and the hanger floor could be below the waterline. I beleive the freeboard was kept lower as well. Then add in that in this period the Brits were replacing some hull/deck plating with homogenous armor, welding could reduce structural weights ~10%, and using better $$$ alloys like STS could allow reduction of those structural members- or turn hull plating into light armor. One reason the USN ships cost so much / ton was the lavish use of STS steels.
....but all of which makes SSing the designs hard.


A good online resource is :   https://www.armouredcarriers.com

and I have some books on carriers, but I think making an accurate SS of the various classes and reverse engineering that to come up with a ruleset very complex.
Other folks are welcome to volunteer for that.

[Kaiser Kirk]

My opinion :
4B is the best - Have the player sim the total amount of deck armor, but must specify in notes where it's allocated, otherwise 2/3rds Flight deck, 1/3 hanger floor. Clarify that the hanger side armor covers from top of main belt to freeboard*. Leave the rest of the rules as is.





*Earlier I posted armored carrier designs I posted that people correctly observed did not follow these rules. That made me wonder what the armored rules were...and then made me aware I did not recognize them.
In my "gee how to do an armored carrier" I was paying for the entire side coverage, from top of main belt to freeboard.

Meanwhile I found a pic of Illustrious with a scale, looks like 12-13m freeboard. So we're actually good there.

[The Rock Doctor]

Agree with you on the approach to deck armor, it's a simple process to deal with it.

I'd assume the hanger walls would be 5.5metres high, as an upper belt, but I don't know whether the Brits armored from top of the main belt all the way up to the flight deck. 

[Kaiser Kirk]

I'd assume the hanger walls would be 5.5metres high, as an upper belt, but I don't know whether the Brits armored from top of the main belt all the way up to the flight deck. 

Yep that is already in the current version

-Use upper belts (65% of hull length, 5.5m height per hangar deck) for hangar sides

[Kaiser Kirk]

If there's not further discussion, or an alternate proposal put forth,
I'll go ahead and modify the Aviation Ship rules this coming weekend with the clarifying statements