Design Philosophies

[Kaiser Kirk]

The following posts will outline the design philosophies and reasons I have been and intend to follow in the construction of Italian vessels.
Much of it is based on stuff I've picked up over the years, and only mostly remember and so may be not entirely correct.
However, this is set 1890-1940 or so, and the folks back then didn't know either.

As time goes on, I may learn/recall new things, or people might comment in the mailbag, and so I may alter such things.

I do look at other's designs, and figure the longer ago the vessel was launched, the more I'd likely know, and so that may influence my speeds/armor/gun caliber,
but these are mostly the other things, and I hope to follow a sort of internal consistency in design.

[Kaiser Kirk]

Length
Usually, I look at historical vessels, and then try to gauge how much more/less I need for what I plan. For example, for a 3xT2 12/40 AQY, I'd look at the size of Brandenberg, and the 3xT2 240mm turrets, guess/figure out how much larger the T2x 12/40 would be, and use that.  Shoving ships up/down in length to match type 0/1/2/3/4/ breaks will be a standard occurrence.

L:B
It is the Med, so you will see DDs and CLs push towards 12:1 at times. For larger ships you'll see a lot of 7:1-10:1, which I know is ahistoric, but it's required in the speedfreak realm we have in Navalism.

Beam
I try to find some ship, somewhere, with similar main armament, and use that to set a minimum beam. The presence/absence of a TDS system must also be accounted for. Number of turrets and location relative to the end of the vessel, and the BC of the original vessel all factor into *guessing* what the beam on the Italian design needs to meet or exceed.

One bad habit I need to watch out for is picking a older, short high BC vessel with 2xT2 to establish a minimum beam, and then applying it to a long vessel with 4xT2 and a lower BC, as the beam abreast the end turrets will then be less.

I feel later US vessels, because of their unique and expensive use of STS steel, are bad guidelines, the long narrow bow distorts the BC, while the STS steel may mean they could use narrower beams overall, plus it is known that they sacrificed TDS depth at the ends near the turrets for hull form.

Likewise, vessels known for structural problems- like some Fisher battlecruisers or interwar Japanese vessels, are not good guidelines.

Block coefficents:
I like to use 0.4-0.45 for destroyers, 0.5-0.55 for cruisers and 0.55-0.65 for battleships. Italian battleships were historically pushing finer, longer hulls, higher freeboards, and so I will be inclined towards the lower end for Italian battleships.


Draft
I'm still trying to get a good feel for if there is a relationship in ship design between beam and associated draft, or if draft is governed more by docks and depths. It seems to be more docks and depth. Right now I'm leaning towards at least a 4:1 ratio or better, so a DD with a 12m beam would have a 3m draft, while a 20m beam needs at least 5m depth, but I may stop bothering with it.

Overall, I'm trying not to go beyond historic Italian drafts, which got deep fast, or 9.6m, as I have this unvalidated notion that's the depth of Suez at this time.

Deck heights :
Decks are typically expected to be 2.44m (8ft) or 2.5m (8.2ft) in height. Engine spaces at the lowest deck level may be assigned a 3.5-4m (11.5-13ft) height, with the understanding these Engines may in fact have open areas 2 deck heights, and so 4.88-6.44m (16-21ft), high.

Most Italian designs have the decks listed in the notes, with heights shown as above waterline (+ WL) or below (- WL). The first deck listed is normally expected to be the one the engines rest on, with the bilges and double hull below it. This is governed by the default result on the torpedo bulkhead tab.

Freeboard :
The freeboard of Italian vessels is typically governed by the deck heights assigned that vessel, though there may be a 1.5m rise towards the bow, and a 0.5m rise towards the stern. Higher rises towards the bow will start intercepting flat trajectory shells from my own guns, so I'll avoid that.

Where the ship has an amid-ships break, the mount in the "aft foreward" and the mount in the 'foreward aft; might both be non-superimposed, but the forward one can shoot over the aft one.

Carriers
I think the Springstyle notes on how to build a carrier do not work terribly well, particularly for smaller carriers.  I think things work out better when you include the hanger height as part of your freeboard. So that's what I will do. I may also provide separate miscellaneous weight for elevators as the number and size of those varied.

Deck length : I expect the carriers will be using about 1/3 of deck length for take off and about 1/2 for landing. I will use typical wingloading for period/tech level carrier planes as a guide to how much that should be. I'll tinker with the numbers as carriers come closer.
I'll also try to look up sortie rates a bit more, and look at old pictures of planes set for takeoff to figure deck needed. 

[Kaiser Kirk]

Armor Thicknesses
A quarter century ago, browsing in my college Library's federal archives floor, I read a piece about the thicknesses used on the Iowa class's 5" battery and that effects my splinter stopping ideas. Likewise some of the comments come from analysis I recollect about various armor thicknesses, such as Nathan Okun's comparisons of various battleship armor schemes. My recollections may be flawed...

6-8mm : Typical thickness for cruiser or larger hull plates. Structural steel.
7-10mm :  thickness used to make for bullet proof.
25mm : proof against light & medium caliber shell splinters.
20mm : Deck thickness proof out to 7500m against small-intermediate caliber shells.
30mm : Deck thickness proof out to 10000m against small-intermediate caliber shells
40mm : Deck thickness proof out to 10000m against all caliber shells
40-50mm : proof against intermediate caliber shell splinters and proof against HE shells.
65mm: proof against all shell splinters
90-120mm : proof against Semi-Armor piecing shells.
150mm : Maximum current pre1905tech shells can penetrate intact. Over this thickness, pre1905tech solid shot must be used.
220mm : Rough maximum early AP shells can reliably penetrate intact. Over this, tend to break up or detonate prior to penetration. 
230mm+ : These thicknesses are sufficient to defeat all but solid shot. Solid shot can be defeated based on the kinetic energy and angle of attack of the incoming round.

Of course, as time goes on and new guns, AP shells, and fire control change the range and penetration my vessels have to contend with, values will change...well increase. But values for splinters, HE and SAP rounds should stay the same.

Multiple layers of armor :
Typically the Italians figure the thinner layer of armor adds 50% of its thickness to the heavier layer, not a straight additive process. This may be foresight, as I believe folks in that era simply added thicknesses.

Deck types
all deck thicknesses are in armor steels assumed to be laminated to 6mm deck plating, while historically reported deck thicknesses also included the mild steel deck plates, incorrectly representing the defensive properties

Springsharp interpretation : My interpretation of the "% Hull Space" shown is this is the volume of hull, minus some for corridors, available between the bulkheads at the end of the belt armor (located at bow & stern breaks on freeboard tab) and below the waterline. When this % exceeds 100%, then in order to fit all critical systems between the bulkheads, they will extend above the waterline. For my purposes, this governs if I can fit protected decks versus armored decks.



Protected Decks :
Shown as 'Protected Deck',  are crowned a short distance above the waterline, with the slopes extending below the waterline and the rest of the hull left unprotected.

The disadvantage of protective decks is the majority of the hull is vulnerable to shell fire and can be wrecked & set ablaze.

The low set protective deck results in a low reserve of buoyancy, and listing or loss of floatation rapidly results in flooding over the protective deck, at which point water can flood in hatches/vents/funnels. 
Last, protective decks can only be fitted (my opinion) when % hullspace is less than 100%, or critical systems must be placed above this area and be made vulnerable to shell fire.   

Protected Decks with thickened slopes:
Represented as 'Protected Deck' with a 2.44m (or 3.66m) tall main belt, this deck has the belt thickness added to the slopes of the deck.

Turtleback decks :
Shown as 'Protected Deck',  but with a conventional main belt. This reflects a deck which crowns a short distance above the waterline, but with the slopes extending below the waterline to the bottom of the main belt. The slopes are not necessarily thicker than the crown, as they are behind the main belt.

The turtleback deck has the same disadvantages and volume restrictions as a Protected Deck.
However the addition of the main belt in front of the slopes turns the function of the slopes into  basically splinter plates. These slopes then can stop shell or belt fragments, confine a successful explosion between the belt and deck, or in the case of a penetrating solid shot, deflect it up into the hull. based on Okun's analysis of the Bismarck's belt, this is actually very effective.

Where the multiple protected deck setting is used, deck armor is split between a turtleback deck set low, and an armored deck capping the upper belt.

Armor deck :
In Italian service, Armor Decks typically are fitted in two locations, extending across the hull to the top of the main or upper belts.

Frequently, an armored turtleback deck is fitted, with a second armor deck fitted to the top of the upper belt armor. In these cases the two decks generally are rated against different threats, with the upper belt & upper deck making a citadel for the casement weapons that is proof to light and medium shell fire, while the turtleback deck is meant to defeat all calibers.

Armor decks are located several meters above waterline, providing much greater reserve buoyancy, and so far greater protection to flooding over the deck.  Also, the higher position in hull allows more than 100% of the hull to be used. However, to extend from the armor deck to below the waterline requires a much taller belt. Further, the splinter armor effect of a turtledeck behind the belt is lost, and so a thicker belt may also be required. The resulting taller, thicker belt adds considerable weight to the design.

Frequently the armor decks over the bow and stern are set at a protected deck level.

Belt armor
Belt armor thickness varies based on the threat it is meant to defeat. A belt meant to stop QF HE shells may only be 40-50mm thick. A belt meant to stop splinters from light guns may only be 25mm thick.

Belt armor has bulkheads extending the width of the ship at the ends of the belt. The default tab will make the belt extend from the "bow" break to the "stern" break.

Protected Decks with thickened slopes:
Represented as 'Protected Deck' with a 2.44m (or 3.66m) tall main belt, this deck has the belt thickness added to the slopes of the deck.

Main Belts:
Main armor belts are designed to extend from below the waterline to the armored deck or protected deck crown level, generally at the top of the first deck above WL. This then extends to below the waterline. Earlier designs simply extended the belt to the first deck below waterline, but more recent designs have standardized on 1.5-1.6m below waterline. This is intended to ensure that wave motion does not expose unprotected hull to incoming rounds, and to catch "short" rounds near the hull.

Historically in this period many belts did not extend below the waterline, or were only a couple feet beneath the waterline, so making any allowance for wave period is a little foresight. Due to the flat trajectories, diving shells would have to enter the water a considerable distance from the hull to get below the 1.6m belt, and would tumble and loose velocity/direction long before impact. As combat distances rise, shells will enter the water at a steeper angle and have a shorter route, making extending the belt down to 2.5m wise. 

Likewise it was found prudent to raise the top of the main belt above the first deck level to ensure a diving shell did not skim the top of the main belt armor and impact the angled portion of the armor deck. While the shell would have to pass through the upper belt, which would likely damage and deflect it, and probably set off any fuse, this was still seen as an undue risk. Initial evaluations used a diving shell of 12degrees, based on their  12"L40 and 13.5"L30 around 10,000yards.   With the turtleback deck being a slope extending 2.44m inboard at 45degrees, the amount of additional belt elevation to ensure a shell can not dive over the belt and strike the slope is 2.44xtan(12) = 0.52m.  Later, considerations of diving at 15, and then 20+ degrees will lead to higher belts.

Upper belt :
Upper belt armor is designed to protect casements and hull spaces. Typically this means a height of one deck level, or 2.44m.  In cases of double stacked casements, two deck levels are used, or 4.88m. Where the upper belt is carrying to freeboard and hull has a break fore/aft,  the upper belt is usually prorated between the two and so figures such as 3.66m may appear, indicating 1 deck level aft and 2 deck levels forward.

End belts
End belts are meant to protect floatation at the ends of the vessel. Loss of floatation at the bow is a particular concern as the bow may dig in, hull plates peel back, and progressive flooding occur unless the vessel slows down – which would then force the squadron mates to slow down, as well as cost the Italians any speed advantage they may have had.

End belts are typically thick enough to stop splinters, and may be thick enough to stop lighter shells. The Italians realize that a 65mm armor plate may let a 150mm or 200mm SAP shell enter, but serve fuse it and cause it to detonate inside the vessel.  However it is felt the small 150mm entrance hull will be easier for damage control parties to address than dozens of small splinter exit holes would be, especially as the 150mm hole will likely be above the waterline, while the splinter exit holes would be both above and below the waterline. Further, that 65mm plate will be proof against HE rounds.

[Kaiser Kirk]

Torpedo Nets
The Italian fleet deploys torpedo nets weighing ~ 1t/m length hull. With the advent of net-cutter torpedoes in the early 1900s, net thicknesses  (and weights) were increased 50%-100%.

Anti-Mine Blisters :
Moored sea mines are a technology developed elsewhere but of concern to the Italians due to the number of seas suited to them in the potential area of operations.

Initially it was believed that deploying the Torpedo nets would enable a vessel to double as minesweeper, though at significant cost to the nets. However it was noted that the blast effects could burst hull seams.  This lead to an anti-mine blister.

The first efforts to address this were by adding a double hull, which turned into the 'Anti-mine blister' of 1-1.5m on each side and divided into subcompartments. These were left void to both decouple the explosive force from the main hull, restrict any leakage to the blister, and to provide an area for counterflooding. Bulges typically extend from the bottom of the main belt to the ship's bottom and are made of 6-8mm of simple hull plating, the weight of which is "paid for" with armor shown in the bulges tab. 

Torpedo Defense Systems
The Italian approach to torpedo defense will evolve with the technology.
Italian TDS bulkheads may either extend to the bottom of an inclined main belt, or will likely extend to the armor deck level, and so may extend 'above' the waterline. Where the main belt is interior to the hull, typically the first bulkhead will rise to meet the belt, while the armored holding bulkhead is expected to also serve as a splinter plate behind the main belt and so rises to the armor deck. Math may be done to ensure sufficient material is allocated for the bulkheads, or I may just use deck heights to figure out how tall to make the TDS.

Step 1) The anti-mine blister will be first expanded to 1.5m on each side to provide the 'decoupling' effect (which doesn't really work except vs. shallow torpedoes where the explosion breaches the surface). When void spaces, they also allow for counterflooding.
Depth of system : (8mm) 1.5m (hull)

Step 2) Wing passages 1.5m wide will be added to allow damage control access to leaking or breached portions of the hull. An 8mm bulkhead of hull plating will be fitted inside these passages. This will be very useful for near misses, short rounds, etc., but not so much for torpedoes. The improved damage control access and compartmentation will be a boon.  This approach will also be far superior to the centerline bulkhead approach, which simply led to off-center flooding.
Depth of system : (8mm) 1.5m (hull) 1.5m. (8mm)

Step 3) The 8mm interior bulkhead will be increased to a 25mm armored holding bulkhead, which is sufficiently strong to both withstand small torpedoes, and stop splinters created from parts of the bulge and hull in front of it. This will be the first true TDS in Italian service.
Depth of system : (8mm) 1.5m (hull) 1.5m. (25mm)

Step 4) The depth of the TDS system will be increased and liquid loading introduced. Two new bulkheads will be added, and all bulkheads made of a ductile high tensile armor steel. The blister will be retained, and still kept void on the flawed decoupling premise. The first 1.5m wing passage will be retained for damage control, but an 8mm bulkhead will be added to allow a 1m wide fuel-oil filled passage prior to the 25mm armored bulkhead. To respond to concerns about the elasticity of the armored bulkhead, a second 1.5m wing passage for damage control, backed by an 6mm bulkhead will be added.
Depth of system : (8mm) 1.5m (hull) 1.5m. (8mm) 1m (25mm) 1.5m. (6mm)

Step 5) A second 1m wide fuel filled  is added prior to the armored bulkhead. This would probably be similar in effectiveness to US or French preWWII systems.
Depth of system : (8mm) 1.5m (hull) 1.5m. (8mm) 1m (8mm) 1m (25mm) 1.5m. (6mm)

Step 6) The blister was now also loaded with styrofoam, and the armored bulkhead increased to 40mm, while the remaining bulkheads made of thinner 6mm ductile armor.  This should be extremely effective, in large part due to the great depth (6.5m), but also the bulge is now not a source of off-center flooding.
(8mm) 1.5m (hull) 1.5m. (6mm) 1m (6mm) 1m (40mm) 1.5m. (6mm)

[Kaiser Kirk]

incomplete

Naval Artillery

Naval Artillery has several considerations – Penetration, Effect, Effective Engagement range, Accuracy, Danger space, Barrel wear, Rate of fire, lethality over time, etc.

Mounts vs. hoists vs Turrets :

Mounts are generally unpowered, and so hand trained.

Mount & Hoists are useful for ammunition transfer, and fairly needed for heavier rounds. Hoists are not required for separate bag & shell designs, but failure to have a hoist means a drastic slowdown in ROF once the ammunition locker is depleted, and a far greater fire hazard due to the flammable bags.  These mounts power training AND power ramming. In limited cases, there may be a small auxiliary motor attached to the mount, which will be addressed in miscellaneous weight.

Turrets are fully powered with integral hoists and power ramming.

When to use which
Historically, you find negative comments about rates of train associated with several weapons. The Twin 6" 52 ton twin mounts on the Omaha class were cited as slow to train and cramped. The Royal Navy's twin 5.25" 77.5 tons semi-stalked mount & hoist design was cited as too slow to train in unpowered mode for it's role. Likewise the Hawkins 7.5" 46-ton mount had similar criticisms, though it did have power assist on training. The successful 5"/38 twin enclosed base ring mounts ranged from 37.5-85tons, but the last 4 designs were all 48-60tons...and all were powered so they make poor benchmarks. 

Result : The Italians will not field Mount or Mount & Hoist designs, when armored, that exceed 50 tons. Turrets will be used when in excess of that mark.

In several navies, the limit for the largest hand loaded & rammed shells were tried. Germany – 6.75" (141lbs), USA 7"(165lbs), UK 7.5" (200lbs), French 194mm (165-202lbs). It is said the Japanese, being of generally smaller stature,  wanted the treaty limit for a heavy cruiser to be 8" in order to force all powers to use turrets with power ramming and hoists
Result The Italians started with a copy of the 1887 French 194mm/165lb, and have introduced the 1901 180L45 with an 80kg round, but will place their upper handloaded limit (and so Mount & Hoist limit) at 187lbs (85kg) in the next generation of 180L55mm guns.

[Kaiser Kirk]

copied from my Italian ships thread :
So, I got a polite PM comment suggesting a 3T2 design would be better as a battleship.
Which has real merit, and I've got some 3T2 designs I've considered, and I appreciate the comment.
Plus - I look around and the 3T2 seems to be the "standard" folks are building.
While I am admittedly going to push to lay this down prior to any all-big gun Dreadnaughts being commissioned,
I'm not the UK, I can't afford to waste tonnage on a design that doesn't even meet the standards of it's day - which does seem to be the 3T2.

So, this time, it led to me really breaking down my mental presumptions and double checking things, which I've written up.

With this one I decided to go with a classic Pre-dread.  Both for looks, and definitely for what I find neat, but also period practicality.
But basically, the 16x180mm is taking the place of an amidships 2x305mm on this design. There a 1.03 comp hull difference.
10x180mm bear each broadside, fore or aft. The 10x180mm which can fire aft  will make a mess of the bow of anything chasing, destroy it's floatation, and it's speed.

So to explain my thought process to the disinterested, I decided to "reply" here. I'd like to say, while my reply is detailed, I'm not trying to be argumentative, just explain.
Anyhow, others can have different views, and still be right, because the values we place on design elements can differ.
Perhaps one player puts huge value on that belt penetrating critical, while I don't see it being easy to penetrate the belt + turtleback combos, or hit the relatively small target area of the belt.
As ships roll, or if they aren't 90degrees to each other, the distance to penetrate varies.

Setting
This is 1904 before effective armor piercing shells can even be researched. I have some belief that somewhere in this time frame the main guns fired nearly solid shot - no reliable bursting past a main belt.  There is no fire control so shell splash size is not a concern - plus 180mm is far from the 240mms where that was an issue.
Not to mention one could always just salvo fire the two sizes at seperate times once one *does* have central director fire control.
Battle ranges are 2-5000m, with torpedoes for close range, and extreme range being 8-10,000m. At this time, a large number of intermediate hits are thought to be important in wrecking a ship.

We're all used to the big gun dreadnaughts, but this is a different era. Heck, I'd like it if when a tech was available to research was a bit more random to cut down on preplanning.
And ships aren't all-or-nothing designs with a raft body, and in this period are still rather flammable, with lots of paint, wood, etc above the armor deck.  Even riddled stacks or bows both destroy speed.
Ships were turned to burning wrecks in the Sino-Japanese, Spanish-American, and the yet to be fought Russo-Japanese. Last I checked, they still aren't sure if Bismarck took a penetrating belt hit, but she
was wrecked and afire. Fire may have led to magazine loss and Hood's demise. Scharnhorst lost her directors to 8" fire.
While it was Warspite's main battery that hit Guilio Cesare, it was the blast wave that forced a boiler shutdown, not penetration.

Hit Rates
At those battle ranges, a 305mm gun firing 1-2 shots/minute will have a hit rate of no more than 10%. Or at least that's what they can manage against a moored target.
So every 5-10 minutes you score 1 hit with a shell that punches a hole, but doesn't burst for much. It's main advantage is it can score a waterline hit in a critical sector.
So trading a broadside of 2 x 305mm for 10x 180mm gives me 3 shells/min vs. 45 shells/min. About a 1:15 factor.

Comparison
A 3T2 configuration gives 3-6 rounds/minute, with a hit every 2-3 minutes.
My Regina Elena can fire 4  x 305mm on the broadside, and 10 x 180mm.
With my I'll manage 2-4 rounds/minute with the 4 x 305, for a hit every 3-5 min and 40-50 rounds/min with the 10x 180mm. For 4-5 hits/minute.

I used "BigGun" because it gave me a relative metric, not necessarily a "correct" one. Unfortunately I haven't got it to work on Win7, but I have a saved 180/45.
So as a proxy for what the Italians in 1900 knew, vs what Facehard can come up with, I'm happy with it.

According to that those 180mm will penetrate 150mm upper belt armor at 6200m or less, and lighter 250mm main belts at 2900m, while up to 380mm at point blank range.
Which means at the 2000-5000m battle ranges, they will punch through any cruiser or anything less than a battleship's main belt...and can defeat those at under 2000m.
Meanwhile at extreme ranges- should they get lucky, they can penetrate ~30mm of deck, which takes care of many cruisers.

Damage
Ahh, but a 400kg hit is more damaging than a 80kg hit !...
Yes and no.

For the sake of simplicity, let's say both hit armor they can penetrate, and both blow up, and both produce a lethal volume in m3 equal 10x  to the weight kg of the shell.
so 4/3r3 = vol of a sphere and so r3 = vol * 3/4
So all you need is the cube root
So on a 400kg shell, Volume would be 4000m, and radius would be 14.42m
While on an 80kg shell, volume would be just 800m, and radius would be 8.43m

So, 1 to 1 , the 400kg shell is *so* much better.
But... we're talking 1 x 400kg shell for 15x80kg shells.
Which is 400:1200 in throwweight.

Not only do the 80kg add up to more throw weight, but they potentially will wreck a much larger area of the ship (127m vs 15m).
Not to mention 15 shots have a better golden twinkie capacity.
The counter is of course that the 400kg shot may penetrate the main belt...but I'm pretty sure it won't detonate, or have a really tiny bursting charge, even if it hits that small % of the ship.
Plus I still have 4x305mm for that.

And high velocity, flat firing 180mm weapons in lighter turrets are more capable of engaging destroyers and light cruisers than larger 305mm guns.
Of course there's also the 90mm in casements for that, lower down and closer to the water for a flatter, higher hit % shot.
Which for the size limited Italian fleet that can't afford lots of screening vessels, is a bonus.

So,
I've really liked writing this up, as it allowed me to challenge my notions and double check my thought processes as a step by step.
I *thought* that the higher ROF would mean more hits and thus more area damaged...but I hadn't done the math.

When the all big gun ships roll out, this will change some, then will come all-or-nothing armor, and the final nail will
be about 1912 the equations will change as Fire Control moves the range stakes. But the Italian designers don't know that yet.

Again, folks with the ability of more screening vessels may want to rely on ACs for some of this, and use their 3T2 Battleships as the final hammer.
Or they just expect the belt hits to be more decisive than I do.