Shipbucket

You must have an enemy! no matter how weak or unlikely other wise the treasury will win...
In this case the RN is fine (it worked in part for USN in 20s/30s) I would suggest dusting off risk fleet ideas .
Then set a RN fleet you might face? Say a fast fleet of Hood,R&R and Tiger or anything you get to set doctrine its not really an issue as many navy's had complete S*** in OTL WWI HSF and WWII IJN to name only two.

It just should be over exact and have scientific ratios and numbers so none experts cant really debate it. I think you are misunderstanding,
WNT gives a limit of 27,000t per ship for CVs, but you (well IJN/USN) are allowed two conversions at 33,000t.
You will also have a total tonnage limit and the 12,000t old CV will count to that but you can scrap her (or just remove flight deck and call her a support ship) at any time due to experimental clause.
They where broke and didn't have the cash to build anything anyway, they had already stopped building programs so lost nothing by signing, you have 3 ships big building so are very much not the same. They also did not build any CVs apart from Béarn in 1927. (and she is really not a first line CV with 21Kn)
Not really cost will make the tiger much cheaper to run due to lower crew numbers and realistically in a single battle she would win as she can hold the range and kill with much more powerful weapons. The only advantage of the Indefatigable is being in two places at once for trade protection but even then at 26Kn she is to slow to hunt down 1920s CAs/Cls so is less of a threat than Tiger and some Cls with radios.

This part on CAs is post WNT planning but, The thing is everybody (in treaty) went to 8" and 10,000t (or close + or -) in OTL in 1920s, I think you will follow them.
A balanced 175mm design will be in trouble v an 8" unbalanced ship, I just don't think you can provide protection from 8" shells on 10,000t (with speed etc).

I think cruiser wise the choice is 6" with or without hand loading working or 8" without. (note RN 7.5" failed and I would start to copy 1930 USSR navy with 7.1")
You will have 6" CLs from WWI for fleet work and 6" AMCs can be built in war time so I think you will like OTL powers build 8" CAs as effectively second class battleships and trade protection flagships.

Since you opponent is the RN you need to plan fighting a force of 8x8" 'Counties' a 140mm-155mm will not cut it...
The 1908 ships are going to be replaced by 1928 (inside WNT building holiday time frame! The ships will need laying down in 1925) so you need to plan it now at the WNT conference!
'block obsolescent' was the result for everybody....
Thinking in 1921 WNT was a building scheduled from 1931-42 for all the power setting out replacements for all the ships they had.(this later got changed at LNT)
I still think your very weak with only two really good gun ships (one might be in dock at any time) combine this with no 'post Jutland ships' and I think you can realistically ask to early replace the 1908 BC with two of the building ships with 380mm guns. I think any 1921 navy will go for this over very unproven aircraft.
How did you get 9x15" and 31Kn and battleship protection on them in 1918, on 32000t? (in late 30s with much better engines RN couldn't get that speed on 35,000t)

And finally, I would suggest its more to "keep people from doing any gunboat politics on them" and protect inter island trade than an invasion that's very unlikely? In that case I don't think you need the TB (save cash) just a fleet in being that looks strong, ie massively top heavy with just a few BCs/BBs is OK as it shows the flag well and makes you look like a proper rich developed civilised power to the White Europeans. (remember this is 1920s its not really about fighting more prestige)

Hope you don't mind me adding my contrary thought its quite fun and good luck drawing.

Ok here I have to agree.

RN works as the enemy, and most likely would be.
But combating them with battleships is a losing proposition. They have 13 381mm capships. 5 QE, 5 R-class BB and 3 BC. on top of that they have 4 Iron Dukes and 2 BC all with 343mm guns. So at the time they have a total of 21 capital ships.
And they also just got permission to build 2 new BB with 406mm guns.
So even if the entire Royal Navy can sortie only in a surge,

In WNT my country gave up 4 280mm battleships the axe. so a force of 10 Battleships 4 280mm 4 320mm and 2 280mm and 4 battlecruisers 2 280mm and 2 320mm, turned in a force of 6 BB 4 320mm and 2 380, and 4 BC 2 280mm and 2 320mm

33000 for conversion yes but the hull to convert is not big enough anyway.
The Battlecruisers are not that big 9 320mm on 32000t and 29kt. The other idea was to build them with 6 380mm guns.
That idea was disregarded as it would not make a balanced design. on 32000t and 320mm they are balanced.

Yes two ships are more expensive to keep that one larger one.

You asked for scientific ratios. two hull together carrying 16 280mm guns will have a throw weight of 280mm has a 280kg shell (circa) so two ships send 4480 kg at the enemy each salvo. If we add higher rate if fire of 280mm over 381mm.
My two ships will deliver 13440kg each minute.
From memory RN 15''/42 mark I fired a 880kg shell, and had a RoF of 2 shots a minute.
So if the Hood would to happen upon my two ships.
my ships will lob 13440kg at it in 48 rounds
Hood will fire 14080kg in 16 rounds. that is quite close in throw weight alone.
And if we take that 1 in 10 shells hit we my ships hit the Hood 4 times in a minute being hit once.
If we go with more realistic one in one hundred.
Then the hood will score its first hit in the seventh minute.
My ships will score their first in the third minute, by the time Hood hits my two old ships once it would be hit 3 times already.
Those two old BC together can take on any single BC in existence.
I could joke if every body jumped of the bridge would you follow?
I have not yet chose the caliber for the large threat cruisers. I'm thinking of using 188mm round.

I'm using a very rudimentary method of figuring out the shell weight.
I just cube the calibre of the barrel. So a 203mm round 8.3 million heavy and a 188mm is 6.6 million heavy.
Again we are looking at lower per tube throw weight but my ships will have more tubes.
A six gun Exeter will fire in a salvo 49.8 my ships will fire 52.8 Again my ship sends more rounds down range.
While true,that my ships would be one upped by later Kent class 8x8, They would fire 66.4
I too will add more tubes.Building 10 gun heavy cruisers will be firing 66. The diffrence is one decimal point so my ships are still competitive.
Well I do have to say that the Navy is run by a cook of Jackie Fisher level.
The queen.
Its a young person that grown up with her grandfather the last King jumping up and down an telling everybody that the torpedo is the weapon that can kill any battleship. They experimented extensively air dropped torpedo since the inception of the idea. At first it was with land based torpedo bombers, then with float planes and flying boats. Then when the Royal Navy put the Sopwith Cuckoo in service. They more or less had an epiphany.
The is the way to deliver a torpedo.
We put a torpedo on a airplane we put a plane on a ship.
It is one thing to evade or destroy a motor torpedo boat going at 30-35 kt.
It is quite another to evade a plane moving at 90-100 kt. Even in a 30kt wind going at the wind the battle cruiser would be The plane is closing with 30kt speed advantage.

The one more incentive for converting all 3 BC under construction is that Royal Navy already has 3 large fast carriers that can support the fleet in large actions. We can not close the gap in BC. But we can close it in carriers.

The plane and the carrier that carriers them is in the mind of the planers like having a motor torpedo boat flotilla with you even in the middle of pacific were no small craft would have endurance to follow the battleline.

But going back to the point of the two older BC needing replacments in by 1928.
I guess it could be negotiated to swap 2 BC and one older BB for 2 new fast battleships.
To be honest at the moment I have no idea how those ship would look like. Or if they get build instead of a class of 4 heavy cruisers.
No, you misunderstood me, or I was not clear enough. If the later sorry.

The class of 3 battle-cruisers being build are armed with 320mm guns.
Putting 380mm guns on them was disregarded as it would make the ship very big and expensive.
Or if smaller more manageable size was chose they would either be under gunned or under armoured or to slow to act as BCs.
The Battleship is a 1916 design based on what was known of US 'standards'.
Those have all or nothing armour scheme ships.
32000t armed with 380mm, and with speed of 23-24kt. Those ships were build to be as well armed as fast and better protected that the Queen Elizabeth class.
You do have a point that prestige is more important at the time that actual fighting capability.
So you need large ships that are nice thing to show visiting dignitaries.
But even with just that, it is better to have a battle line of 10 big gun ships and 3 flat tops at a fleet review.
Then a fleet of one off BC 2 more BCs 2 BB 2 Carriers.
As for the older ship, they can be put behind the larger ones so they will still look impressive from a distance.

But disregarding the large Torpedo Bout fleet would mean massive cuts in naval spending.
Those torpedo boats need a lot of bases. So every island chain has one of or two of those.
If we stop building those we are looking at closing naval bases one after another.
What else can those base be used for?
Submarines, the number of those is limited by the treaty. Destroyers will not need that many bases as they are far longer legged and can go further between pits stops.
The population would also not like if we start closing down bases.
A torpedo boat flotilla requires more personal that a refuelling station of the few destroyers that will replace them.
If we start building destroyer tenders then entire communities find themselves without the sailors that bought their food drank their beer and married their daughters.

Yes the last point has little to do with actual usefulness of a destroyers versus torpedo flotilla. But those are the little spices that make designing fantasy fleets more interesting.

The problem is that at WNT I think CVs are generally regarded as big expensive fleet scouts not capital ships?

They are going to scout to find the enemy battle line as primary task for the gun ships to then fight. With strikes against harbours and to try to slow down fleets at sea by crippling a straggler as a secondary task. You are talking about having 2 or 3 very expensive CVs to be great scouts without the fire power to really benefit from it without more 380mm ships.
I think you need to set yourself a WNT ratio?

I think a ratio of RN that you might need to fight? Something between RN/USN @100% (500,000ish 15 ships) IJN @60% (9 ships 300,000ish) and Fr/It @35% (10/10 221,170t/182,800t going to 5 ships 175,000t after new ships)

My best guess would be something like,
4 320mm (23,500 ?) and 2 380mm (32000t?), and 4 BC 2 280mm (18,000?) and 2 320mm (26,000?) so 246,000t and 10 ships.
Its significantly over Fr and Italy and weaker than Japan, since you are also not broke you have a good position to ask for more than Fr/It.

As to your ratio going forward look in terms of 35,000t ships,
I would pick one of 5 is 175,000 6= 210 7=245 8= 280 9=315,000t

I would say you have about 6 ships worth at the moment (2 (380mm)+ 1/2 of the 8 rest)

In CV terms they got USN/RN 135,000 t IJN 81,000t Fr/It 60,000t (basically 5,3,2 27,000t CVs)
This means that 2 conversions might well eat you entire tonnage allowance. 3 is massively more in %ratio and would put you over USN/IJN in CVs!

Basically I think your weak in guns and too heavy in CVs with the conversions? I think with no post Jutland/16" ships you cant really claim to be in the big league, I would advise completing the BC/Fast BBs to 6x380mm as that at least gives you 4 ships that can fight modern capital ships. I cant see anybody complaining (and less than they would for 3 CVs) so you end up as a fleet of,

4x380mm (2BB+2BC) and 4x320mm (4BB or 2BB+2BC) that then will go down to 6x 16"/35,000t treaty ships from 1932 (until LNT steps in).

A ratio for 6 ships at WNT would be 40% and that gives you 54,000t.
Like Fr/It it will be bumped up to say one 33,000t conversion and one 27,000t and your 12,000t CVL gives you 72,000t and sits nicely in the middle.(you might agree to 70,000t if the conversion is going to be lighter)

But balance against yourself doesn't really matter its balance v your opponents that matter (and is harder to calculate but gun size gives an idea) 12.6" is just to small to hurt the majority of ships of major powers RN/USN/IJN kept post WNT. at least a 6x380mm ship has a chance or it can add its fire to a ship engaged with one of your BBs.
NO!
The problem with this is Hood hits at much longer range 15" shells have longer range and are more accurate at that range as they slow down less as weight is cubed and air resistance is only squared, the 15" doesn't get stopped by your old light belt/deck and its 1v1 time then 1v0....
I could add that once you are over 8" rate of fire is just about mechanical loading and newer ships generally fire faster even if they are bigger.
To give an example,
28 cm/45 (11") SK L/45 v 15-inch Mark I
Shell 302 kg-869.5 kg
RoF 3-2
max range @20deg elevation 18,900 m - (@19.1)22,860 m and later 1918 ship would have 30 for 29,720 m
Penetration, @12,000 m of 200 mm - @13,582 m of 305 mm and @21,702 m of 229 mm
Basically the 15" is going to get 10,000m of free shooting and any hits are going to not be stopped.
Sending sailors in 1908 ships to fight a 1918 is basically a death sentence.....
Everybody sensible got 6" or 8" for a reason. The problem is penetration and explosive charge are also cubed so the lighter guns are much easier to survive hits from. Pre war everybody thought 8" wins every time, basically 6" only makes sense if you hand load or are limited by LNT later.
And 8x8" are earlier than 6x8" Exeter (a cheaper version that's not worth it only saves £200,000 for 25% less fire power)
This is not going to make you friends in other navy's they treaties are a method of control by RN/USN to make everybody have useless balanced fleets rather than more useful Uboat or raiders and US/GB hold the power at WNT as they could simply out build you and the SD and G3s instantly render your ships into costly scrap metal as soon as they are in service... (both in prestige terms and in fighting power)
I think they are to small for new late WWI builds you just get pummelled to bits by 14"/15"/16" (and the coming 18" pre WNT)

Yes looking forward to your fleet

Looking at the math of threaty allocations I am inclined to agree.
I have to many ships.
I do need to scale it down a bit.
2x380mm (BB) and 4x320 (2 BB 2 BC) two 320mm BB will be put in reserve. 280mm BC will be scrapped.
And negotate 2 fast Battleship 380mm. Well fast for 1920's my head math guestimate give a 35000t battleship with a 1925 engine and 8-9 380mm guns at around 25-26kt.

There will be only 2 carrier conversions. Two 27000t ships.

YES!
A 15/42 Mark I does not have any any meaning full advantage in aerodynamics over a 280mm shell.
The distinction between shell size and its performence in the air disappear as a meaningful consideration around 50kg shell.
A 155mm howitzar round has supperior aerodynamics performance over a 122mm shell.
But a 203mm round has no real advantage over a 155mm round. At the sizes were are talking about 280mm or 11'' and above the aerodynamic consideration.

So a 280mm shell at around 20 degrees elevation has the same exact range as the 380mm shell.
Bofors 283mm Model 12 had a range of 24000m at 20deg
German 28 SK L/50 had range of 21,700m at 22,5 deg
15/42 mark I had 21.702m at 20 deg.
Hood can out run out gun but it will not out range my ship.
As for penetration.
Yes a bigger shell will have better penetration.
Still the volume of fire from 16 tubes versus 8 on Hood.
Hood would be burning bow to stern before it will sink any of my ships.
No critical hits still sink ships.
If Hood is afire, hit 3 times for every hit it dishes out Hood dies, or retreats or is scuffled.
The immunity zone is one theory.
But the the 1894 battle of Yalu showed that two Chinese battleship were shelled in to submission by Japanese cruiser force. The battleship armour protection was never penetrated yet both were forced to retreat without causing much damage to the Japanese fleet.

Still I am not under the illusion that two 1908 battle cruiser are in any way superior to a single 1918 battle cruiser.
But they are still a credible threat. Also Hood is the out liner. It is the only battlecruiser in existence with a 305mm belt.
None other ship has belt thicker that 203mm. So my 280mm shell will penetrated any other ship protection.

Yes their usefulness end is not the horizon, but the thing that will make the useless is not any one Battlecruiser or Battleship. It will be a squadron of 8'' armed cruisers. Those ships would put my ships under the volume of fire that will burn them bow to stern.
No one said I have to be sensible.
As you may noticed I'm a strong proponent of volume of fire concept.
If I did not put historic consideration in this little fleet idea. I would build 10000t cruisers and arm them with 12-15 152mm guns.
But this idea even with hindsight is hard to defend.
A 188mm shell will make just about as much damage as 203mm shell would, but my ship will have 2 more tubes.
Hmm.
I have to agree.
Only 2 CV would be build, yes still the converted BC hull. Third uncompleted hull will be scrapped.
Its armour will be used for gunnery testing.

Small or not that is what I chose as it makes sense with the limitations I put on my countries shipbuilding.
The ordered two 380mm armed battleships during the war. The Queen Elizabeth class was just that powerful of a ship that it made them build counters even with out getting the chance to evaluate the combat experience of the fighting powers.
Post war first thing they did was order 3 BC. Not that big but fast enough for the changing situation.
The next class would most likely be Hood sized. But the WNT put that idea to rest.
Thanks

That reminds me.
I found out that computer RPG games are evil incarnate.
They eat your free time like crazy. Yesterday I didn't even open MS Paint
Last time I spend so much time in front of a computer playing video games was in 1990's playing the original Sid Mayer's Civilisation.

I need to get back to drawing the parts sheets.
I didn't even begun to drawing the hulls, let alone completed ships.
I did draw the 1908 280mm battlecruiser. Problem was both versions looked like a carbon copy of Von der Tann and the second looked like HMS Hood shrunk.

That is the reason I started drawing part sheets. If I use original, well not that original but just different enough from what everybody else is using. My ships will have just enough of a fell to look new and different.
Yes that is just cosmetics but it is fun to make something new.