20 inchers when? (aka The March of Large Calibre Guns)

[oldpop2000]

I have enclosed for your comparison, the two Yamato class ships that I have prepared. The designs are not perfect, but I have used as much available data that I can find. I am still looking for a good drawing and I believe I know where it is.

The first is the Yamato as built. The full load displacement is about as accurate as I can actually make it. The second design is the Yamato with 20-inch guns and all modifications to make it a workable ship. To compensate for the blast effect, I have increased the length by 100 feet, 50 feet at the bow and the stern. As one can see it changes almost everything.

My purpose was to illustrate to the best of my ability, the results of increasing the caliber of the guns. You do not get something for nothing in the world of military technology, trust me.

Anyway, I hope this is useful. I am sorry for the excessive length, I believe in providing all the data that I have. 



Yamato, Japan battleship laid down 1937

Displacement:
53,855 t light; 57,448 t standard; 61,276 t normal; 64,339 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(881.65 ft / 863.00 ft) x 127.60 ft x (36.00 / 37.35 ft)
(268.73 m / 263.04 m) x 38.89 m x (10.97 / 11.38 m)

Armament:
9 - 18.10" / 460 mm 45.0 cal guns - 2,990.15lbs / 1,356.31kg shells, 150 per gun
Breech loading guns in turret on barbette mounts, 1937 Model
3 x Triple mounts on centreline ends, majority forward
12 - 6.10" / 155 mm 60.0 cal guns - 124.32lbs / 56.39kg shells, 150 per gun
Breech loading guns in turret on barbette mounts, 1937 Model
4 x Triple mounts on sides, evenly spread
12 - 0.98" / 25.0 mm 40.0 cal guns - 0.46lbs / 0.21kg shells, 150 per gun
Breech loading guns in turret on barbette mounts, 1937 Model
6 x Twin mounts on sides, evenly spread
Weight of broadside 28,409 lbs / 12,886 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 16.1" / 410 mm 560.95 ft / 170.98 m 20.00 ft / 6.10 m
Ends: 11.8" / 300 mm 302.03 ft / 92.06 m 8.00 ft / 2.44 m
Upper: 11.0" / 279 mm 560.95 ft / 170.98 m 8.00 ft / 2.44 m
Main Belt covers 100 % of normal length
Main Belt inclined 20.00 degrees (positive = in)

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 25.6" / 650 mm 10.0" / 254 mm 21.5" / 546 mm
2nd: 5.00" / 127 mm - 10.0" / 254 mm
3rd: 2.00" / 51 mm - 2.00" / 51 mm

- Box over machinery:
9.10" / 231 mm
Forecastle: 7.87" / 200 mm Quarter deck: 7.87" / 200 mm

- Conning towers: Forward 19.70" / 500 mm, Aft 19.70" / 500 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 116,032 shp / 86,560 Kw = 27.50 kts
Range 8,300nm at 16.00 kts
Bunker at max displacement = 6,891 tons

Complement:
1,946 - 2,531

Cost:
£27.443 million / $109.771 million

Distribution of weights at normal displacement:
Armament: 4,606 tons, 7.5 %
- Guns: 4,606 tons, 7.5 %
Armour: 23,067 tons, 37.6 %
- Belts: 11,016 tons, 18.0 %
- Armament: 5,949 tons, 9.7 %
- Armour Deck: 4,783 tons, 7.8 %
- Conning Towers: 1,319 tons, 2.2 %
Machinery: 3,216 tons, 5.2 %
Hull, fittings & equipment: 22,967 tons, 37.5 %
Fuel, ammunition & stores: 7,421 tons, 12.1 %
Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
97,361 lbs / 44,162 Kg = 32.8 x 18.1 " / 460 mm shells or 7.5 torpedoes
Stability (Unstable if below 1.00): 1.07
Metacentric height 8.3 ft / 2.5 m
Roll period: 18.6 seconds
Steadiness - As gun platform (Average = 50 %): 87 %
- Recoil effect (Restricted arc if above 1.00): 0.58
Seaboat quality (Average = 1.00): 1.32

Hull form characteristics:
Hull has a flush deck,
an extended bulbous bow and large transom stern
Block coefficient (normal/deep): 0.541 / 0.547
Length to Beam Ratio: 6.76 : 1
'Natural speed' for length: 34.47 kts
Power going to wave formation at top speed: 45 %
Trim (Max stability = 0, Max steadiness = 100): 66
Bow angle (Positive = bow angles forward): 30.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 32.31 ft / 9.85 m, 26.05 ft / 7.94 m
- Forward deck: 30.00 %, 26.05 ft / 7.94 m, 20.26 ft / 6.18 m
- Aft deck: 35.00 %, 20.26 ft / 6.18 m, 20.26 ft / 6.18 m
- Quarter deck: 15.00 %, 20.26 ft / 6.18 m, 20.26 ft / 6.18 m
- Average freeboard: 22.79 ft / 6.95 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 58.6 %
- Above water (accommodation/working, high = better): 167.7 %
Waterplane Area: 79,321 Square feet or 7,369 Square metres
Displacement factor (Displacement / loading): 111 %
Structure weight / hull surface area: 236 lbs/sq ft or 1,153 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.97
- Longitudinal: 1.28
- Overall: 1.00
Excellent machinery, storage, compartmentation space
Excellent accommodation and workspace room
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily



Yamato2, Japan battleship laid down 1937

Displacement:
64,409 t light; 69,058 t standard; 73,389 t normal; 76,854 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(982.71 ft / 963.00 ft) x 127.50 ft x (40.00 / 41.45 ft)
(299.53 m / 293.52 m) x 38.86 m x (12.19 / 12.63 m)

Armament:
9 - 20.10" / 511 mm 45.0 cal guns - 4,094.91lbs / 1,857.42kg shells, 150 per gun
Breech loading guns in turret on barbette mounts, 1937 Model
9 x Triple mounts on centreline ends, majority forward
12 - 6.00" / 152 mm 45.0 cal guns - 108.92lbs / 49.41kg shells, 150 per gun
Breech loading guns in turret on barbette mounts, 1937 Model
6 x Twin mounts on sides, evenly spread
24 - 0.98" / 25.0 mm 45.0 cal guns - 0.49lbs / 0.22kg shells, 150 per gun
Breech loading guns in turret on barbette mounts, 1937 Model
8 x Triple mounts on sides, evenly spread
Weight of broadside 38,173 lbs / 17,315 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 16.1" / 410 mm 625.95 ft / 190.79 m 13.55 ft / 4.13 m
Ends: 11.8" / 300 mm 337.03 ft / 102.73 m 13.55 ft / 4.13 m
Upper: 11.0" / 279 mm 625.95 ft / 190.79 m 8.00 ft / 2.44 m
Main Belt covers 100 % of normal length
Main Belt inclined 20.00 degrees (positive = in)

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 26.0" / 660 mm 10.0" / 254 mm 21.5" / 546 mm
2nd: 5.00" / 127 mm - 10.0" / 254 mm
3rd: 2.00" / 51 mm - 2.00" / 51 mm

- Box over machinery:
9.10" / 231 mm
Forecastle: 7.87" / 200 mm Quarter deck: 7.90" / 201 mm

- Conning towers: Forward 19.70" / 500 mm, Aft 19.70" / 500 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 141,127 shp / 105,281 Kw = 27.50 kts
Range 7,000nm at 18.00 kts
Bunker at max displacement = 7,796 tons

Complement:
2,229 - 2,898

Cost:
£34.693 million / $138.772 million

Distribution of weights at normal displacement:
Armament: 5,715 tons, 7.8 %
- Guns: 5,715 tons, 7.8 %
Armour: 27,724 tons, 37.8 %
- Belts: 10,140 tons, 13.8 %
- Armament: 10,890 tons, 14.8 %
- Armour Deck: 5,207 tons, 7.1 %
- Conning Towers: 1,488 tons, 2.0 %
Machinery: 3,912 tons, 5.3 %
Hull, fittings & equipment: 27,059 tons, 36.9 %
Fuel, ammunition & stores: 8,980 tons, 12.2 %
Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
107,735 lbs / 48,868 Kg = 26.5 x 20.1 " / 511 mm shells or 7.1 torpedoes
Stability (Unstable if below 1.00): 1.03
Metacentric height 7.6 ft / 2.3 m
Roll period: 19.4 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.81
Seaboat quality (Average = 1.00): 1.36

Hull form characteristics:
Hull has a flush deck,
an extended bulbous bow and a cruiser stern
Block coefficient (normal/deep): 0.523 / 0.529
Length to Beam Ratio: 7.55 : 1
'Natural speed' for length: 31.03 kts
Power going to wave formation at top speed: 41 %
Trim (Max stability = 0, Max steadiness = 100): 52
Bow angle (Positive = bow angles forward): 30.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 34.13 ft / 10.40 m, 26.00 ft / 7.92 m
- Forward deck: 30.00 %, 26.00 ft / 7.92 m, 26.00 ft / 7.92 m
- Aft deck: 35.00 %, 26.00 ft / 7.92 m, 26.00 ft / 7.92 m
- Quarter deck: 15.00 %, 26.00 ft / 7.92 m, 26.00 ft / 7.92 m
- Average freeboard: 26.65 ft / 8.12 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 63.1 %
- Above water (accommodation/working, high = better): 185.6 %
Waterplane Area: 83,556 Square feet or 7,763 Square metres
Displacement factor (Displacement / loading): 106 %
Structure weight / hull surface area: 242 lbs/sq ft or 1,180 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.97
- Longitudinal: 1.18
- Overall: 0.99
Caution: Hull subject to strain in open-sea
Excellent machinery, storage, compartmentation space
Excellent accommodation and workspace room
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily

[oldpop2000]

I've just found a side view and minor details on the Japanese super-yamato class battleships. Japanese estimates stated that they would have a speed of 27 knots to maintain weight of 80,000 tons. They were going to keep the Yamato length but I feel that D.K. Brown's estimates of having to increase the length to account for gun blast are accurate for any ship with increased gun caliber. My specification is close. I suspect its the lack of details for me, on armor length and height. But I am satisfied that what I have presented does illustrate what will happen when you move to a bigger gun. Is it worth it, well we will be entering the age of aircraft and carriers along with long range bombers, I am not certain the extra cost of building, maintaining are worth it.

[oldpop2000]

I wanted to ask if anyone could check the length of our battleships, say from the Nevada to the Iowa’s. I sense as I have checked myself, that as the caliber increased from say 12 in. 45 to 12 in. 50 and so forth, the length of the ship got longer. Now, I know that the higher the length to beam ratio is, the faster the top end speed. However, it does make the ship heavier due to increases in armor length and height, engines have to be bigger and so forth. If I am reading this correctly, then this would confirm what I believe. A longer barrel gun does have a higher muzzle velocity and would have a high muzzle blast effect.

Anyway, a second opinion would be nice. Later I will go through my Friedman US battleship book

[elouda]

I don't think just caliber is enough to go by here, as actual pressure at the muzzle will vary a lot between guns depending on their specifics. In basic principle, the same charge/shell combination in a longer gun (say /50 vs /45 cal length) will result in a lower muzzle pressure and higher velocity.

I'd also speculate that gun positioning and spacing is going to matter more than straight up hull length. Obviously, a longer hull gives you more room to play with in this regard, but smart (and alternatively, not-so-smart) gun positioning can mitigate (or lead to) blast problems regardless of overall length.

As for length, the US standards went from a 14in/45 to 14in/50 to 16in/45 with basically very minor change in length (~185m on Pennsylvania to ~190m on Colorado). I do not know if the actual turret positioning was more widely spaced on the later classes, that would be an interesting insight. As far as I know none of these had series issues with blast damage in service.

As an interesting aside, Nelson and Rodney, which did have issues with blast overpressure, particularly on the bridge from what I recall reading, are some 25m longer than Colorado. I suspect here the placement was the issue, and highlights that being more of an issue than overall length. The British 16in/45 does also use a higher pressure charge, so this may also have been a factor to some degree.

As for trying to find an overall trend across multiple ships on length vs gun/length, while it might shed some light on the issue, the main problem is that there's also going to be length growth as a general trend due to increases in displacement and speed, so it might be a little tricky to narrow down. I also think particularly looking at the sub-14in category is not going to help much, as apart from blast issues when firing directly over another turret or across the deck early on, these probably weren't nearly as severe as once you step into the 14-16-18in range.

Some thoughts on solutions;
-Since ship length is not under our control in RTW (much as I wish it was, even as a general L/B factor), even if there is a direct connection from looking for trends, it might be hard to relay that to the player in the designer
-Perhaps some sort of restriction/penalty for firing large guns directly over the hull/across the deck or over another turret, dependant on firing gun caliber and deck/turret armour? Maybe even a tech to even allow superfiring directly over turrets or to reduce the required roof armour to allow it
-Additionally, to simulate the gun-spacing (as opposed to length issue), perhaps a similar penalty when you group enough large guns into close enough locations, depending on displacement perhaps? So at some displacement, twin 18in ABY might incur it for the front pair, and AXY for the rear pair, by AVY might not. Likewise triple 16in ABY might be fine, but triple 16in ABC/ABL might not.

-These penalties could probably be reductions in accuracy and rate of fire depending on the severity of the issue, along with a higher chance to knock out your own radar / mess with FCS in some other way

-A part of the the weight/reinforcement needed for larger calibers could be (or maybe even is) abstracted into the actual weapon weights in the ship designer

Edit: Few small corrections, added last point to summary

[oldpop2000]

Sept 30, 2018 15:08:25 GMT -6 elouda said:

I don't think just caliber is enough to go by here, as actual pressure at the muzzle will vary a lot between guns depending on their specifics. In basic principle, the same charge/shell combination in a longer gun (say /50 vs /45 cal length) will result in a lower muzzle pressure and higher velocity.

I'd also speculate that gun positioning and spacing is going to matter more than straight up hull length. Obviously, a longer hull gives you more room to play with in this regard, but smart (and alternatively, not-so-smart) gun positioning can mitigate (or lead to) blast problems regardless of overall length.

As for length, the US standards went from a 14in/45 to 14in/50 to 16in/45 with basically very minor change in length (~185m on Pennsylvania to ~190m on Colorado). I do not know if the actual turret positioning was more widely spaced on the later classes, that would be an interesting insight. As far as I know none of these had series issues with blast damage in service.

As an interesting aside, Nelson and Rodney, which did have issues with blast overpressure, particularly on the bridge from what I recall reading, are some 25m longer than Colorado. I suspect here the placement was the issue, and highlights that being more of an issue than overall length. The British 16in/45 does also use a higher pressure charge, so this may also have been a factor to some degree.

As for trying to find an overall trend across multiple ships on length vs gun/length, while it might shed some light on the issue, the main problem is that there's also going to be length growth as a general trend due to increases in displacement and speed, so it might be a little tricky to narrow down. I also think particularly looking at the sub-14in category is not going to help much, as apart from blast issues when firing directly over another turret or across the deck early on, these probably weren't nearly as severe as once you step into the 14-16-18in range.

Some thoughts on solutions;
-Since ship length is not under our control in RTW (much as I wish it was, even as a general L/B factor), even if there is a direct connection from looking for trends, it might be hard to relay that to the player in the designer
-Perhaps some sort of restriction/penalty for firing large guns directly over the hull/across the deck or over another turret, dependant on firing gun caliber and deck/turret armour? Maybe even a tech to even allow superfiring directly over turrets or to reduce the required roof armour to allow it
-Additionally, to simulate the gun-spacing (as opposed to length issue), perhaps a similar penalty when you group enough large guns into close enough locations, depending on displacement perhaps? So at some displacement, twin 18in ABY might incur it for the front pair, and AXY for the rear pair, by AVY might not. Likewise triple 16in ABY might be fine, but triple 16in ABC/ABL might not.

-These penalties could probably be reductions in accuracy and rate of fire depending on the severity of the issue, along with a higher chance to knock out your own radar / mess with FCS in some other way

-A part of the the weight/reinforcement needed for larger calibers could be (or maybe even is) abstracted into the actual weapon weights in the ship designer

Edit: Few small corrections, added last point to summary

I appreciate your excellent comments. I went back to my books to remind myself that the larger caliber generally means a lower muzzle velocity. However, it does not preclude a bigger muzzle blast which according to D.K. Brown does in fact happen. On your point about increasing the distance between the guns, that could happen except that increase,  increases the barbette size and consequently the beam of the ship. If I don't increase the length, the LtoB will decrease and affect my top end speed. As we all know, you don't get something for nothing in this. I think your solutions might work but that is up to the team. I believe there should be some way to develop a cost for increased gun caliber to keep things correct.

[elouda]

Sept 30, 2018 16:35:17 GMT -6 oldpop2000 said:

Sept 30, 2018 15:08:25 GMT -6 elouda said:

...

I appreciate your excellent comments. I went back to my books to remind myself that the larger caliber generally means a lower muzzle velocity. However, it does not preclude a bigger muzzle blast which according to D.K. Brown does in fact happen. On your point about increasing the distance between the guns, that could happen except that increase,  increases the barbette size and consequently the beam of the ship. If I don't increase the length, the LtoB will decrease and affect my top end speed. As we all know, you don't get something for nothing in this. I think your solutions might work but that is up to the team. I believe there should be some way to develop a cost for increased gun caliber to keep things correct.

Apologies if I was unclear, with regards to distance between guns I intended to say distance between turrets, which is what I was talking about with the Nelson/Rodney case and regards to point #3 at the end regarding different arrangements.

Regardless, it will be interesting to see how it pans out. In any case, given how much love the developers gave RTW1 after its release and how a lot of things changed for the better, even if the inital implementation isn't perfect that doesn't rule out improvements later on.

I might see about trying to find any data on actual pressure at the muzzle for some of the larger guns, or barring that just run some rough numbers for them to see what things look like.

[oldpop2000]

Sept 30, 2018 17:05:55 GMT -6 elouda said:

Sept 30, 2018 16:35:17 GMT -6 oldpop2000 said:

I appreciate your excellent comments. I went back to my books to remind myself that the larger caliber generally means a lower muzzle velocity. However, it does not preclude a bigger muzzle blast which according to D.K. Brown does in fact happen. On your point about increasing the distance between the guns, that could happen except that increase,  increases the barbette size and consequently the beam of the ship. If I don't increase the length, the LtoB will decrease and affect my top end speed. As we all know, you don't get something for nothing in this. I think your solutions might work but that is up to the team. I believe there should be some way to develop a cost for increased gun caliber to keep things correct.

Apologies if I was unclear, with regards to distance between guns I intended to say distance between turrets, which is what I was talking about with the Nelson/Rodney case and regards to point #3 at the end regarding different arrangements.

Regardless, it will be interesting to see how it pans out. In any case, given how much love the developers gave RTW1 after its release and how a lot of things changed for the better, even if the inital implementation isn't perfect that doesn't rule out improvements later on.

I might see about trying to find any data on actual pressure at the muzzle for some of the larger guns, or barring that just run some rough numbers for them to see what things look like.

Thanks for clarification, I thought it was my old age again. Please do try to find more data, and I will also. I think it is important for all of us to understand what it takes to design a ship. I have some early 20th century naval architecture books, I will see if there is anything in there.

[oldpop2000]

I did find a statement in U.S. Battleships by Norman Friedman that "heavy twin turrets had to be spread along much of the length of the hull, stressing it. The closer the heavy weights to the ends of the ships i.e. the greater the number of turrets, the greater the stress. Worse, high speed required fine (and therefore not too buoyant) end and also that a great portion of the length amidships be devoted to machinery...." This would indicate to me not only muzzle blast was a problem but if you had larger turrets for bigger guns, they could not be extended too far toward the bow due to speed considerations. I guess that is what it means.


This statement in on Page 64 at the bottom left. Your opinion?

[alexbrunius]

Sept 30, 2018 11:04:53 GMT -6 oldpop2000 said:

Sept 30, 2018 10:40:18 GMT -6 Fredrik W said:

There will be 20 in guns in RTW2, and I feel reasonably confident the AI can handle them.

To Fredrik:

Will the games ship designer, take into account that a ship with 20 inch. guns will have to be longer, the armor belt and the citadel will have to be bigger which will add to the weight and this will require more engine power. All this will increase the cost dramatically. I have taken my Yamato battleship design in Springsharp and made the appropriate changes for a 20 inch guns. It does change everything. I am still working on the original design to get the weights correct so then my second design will be closer to reality.

Thanks for providing the information

Old pop

Couldn't Japan pretty easily just have changed the Yamato class design with Triple 18.1 inch gun turrets to Double 20 inch turrets instead?

This seems to have been basically their approach with the Design A-150:

en.wikipedia.org/wiki/Design_A-150_battleship

[director]

I'd like to broaden the discussion a bit if I may, to question the requirement.

As I understand it, Japan went to the 18" (18.1") caliber in order to achieve longer range, greater penetration ability and perhaps greater explosive power.

But if 'Montana' would have had a throw-weight of 324,000 pounds in 5 minutes (12 guns, 2 shells per minute, 2700-lb shell) and 'Yamato' comes in at 217,215 (9 guns, 1.5 shells per minute, 3218-lb shell) or 289620 (9 guns, 2 shells per minute, 3218-lb shell) then is the possible greater range and weight per shell actually worthwhile? ('Nelson' comes in at 184050 with 9 guns, 2 shells per minute and the light 2048-lb shell, 'Nagato' at 176400 with 8 guns, 2 shells per minute and a 2205-lb shell, 'North Carolina' at 243,000 with 9 guns, 2 shells per minute and the 2700-lb shell).

It seems to me that achieving hits at very great ranges depends on a lot of factors, most of which are uncontrollable (target range, manuevering, wind speed, etc). The one thing a gunner can reliably do to increase the number of hits is to increase the number of shells fired, usually by increasing the size of the battery. Raising the number from 9 to 12 would help; slowing down the rate of fire (handling time for larger projectiles) would hurt and dropping the battery to 6 even-slower-firing 20" would substantially reduce the already-slim mathematical odds of getting a hit at long range.

Given the greater cost developing and deploying a bigger gun, the increased wear, etc and so forth, is deploying an 18" or 20" weapon actually worth it? The reduced rate of fire and/or number of barrels seems to work against using them for long-range fire as the number of possible hits is sharply reduced. Secondly, since a standard or super-heavy 16" shell has good penetration stats at medium to close engagement ranges, does an 18" or 20" shell's greater individual weight offer advantages to offset its slower rate of fire?

So... would 'Yamato' actually have been a better investment with 12x16" guns? (264,600 for 12 guns, 2 shells per minute, 2205-lb shell)And would a super-'Yamato' with 6x20" guns be actually a better ship? I understand that using throw-weight can be deceptive since what we really want to measure is the effect of actual hits, but...

Is increasing the size of a ship (improving the chance of a hit on it) to carry fewer or slower-firing weapons (reducing the chance of a hit on the enemy) a better plan than more, smaller guns on a ship of equal or smaller size? Given the difficulty of increasing the rate of fire, I think the odds favor a larger battery, and, given the extreme difficulty of getting hits at long range and the penetrability of most ships at medium and close range, I just don't see that the 18" or 20" offers any significant advantage.

Your thoughts?

[rimbecano]

Well, at Surigao Strait, West Virginia hit Yamashiro at just short of 23000 yd on her first salvo. Now, granted, the Japanese did not have fire control radar, and the Japanese were unaware of the American force's presence, and thus not maneuvering, but in my view this indicates that there was still plenty of room for battle line engagements at long range before accuracy became unacceptable.

And in general, against an armored target, if you have acceptable accuracy, as few guns of as large a calibre as possible is optimal. Tanks, for instance, usually have just one big gun.

[oldpop2000]

Oct 4, 2018 7:58:07 GMT -6 director said:

I'd like to broaden the discussion a bit if I may, to question the requirement.

As I understand it, Japan went to the 18" (18.1") caliber in order to achieve longer range, greater penetration ability and perhaps greater explosive power.

But if 'Montana' would have had a throw-weight of 324,000 pounds in 5 minutes (12 guns, 2 shells per minute, 2700-lb shell) and 'Yamato' comes in at 217,215 (9 guns, 1.5 shells per minute, 3218-lb shell) or 289620 (9 guns, 2 shells per minute, 3218-lb shell) then is the possible greater range and weight per shell actually worthwhile? ('Nelson' comes in at 184050 with 9 guns, 2 shells per minute and the light 2048-lb shell, 'Nagato' at 176400 with 8 guns, 2 shells per minute and a 2205-lb shell, 'North Carolina' at 243,000 with 9 guns, 2 shells per minute and the 2700-lb shell).

It seems to me that achieving hits at very great ranges depends on a lot of factors, most of which are uncontrollable (target range, manuevering, wind speed, etc). The one thing a gunner can reliably do to increase the number of hits is to increase the number of shells fired, usually by increasing the size of the battery. Raising the number from 9 to 12 would help; slowing down the rate of fire (handling time for larger projectiles) would hurt and dropping the battery to 6 even-slower-firing 20" would substantially reduce the already-slim mathematical odds of getting a hit at long range.

Given the greater cost developing and deploying a bigger gun, the increased wear, etc and so forth, is deploying an 18" or 20" weapon actually worth it? The reduced rate of fire and/or number of barrels seems to work against using them for long-range fire as the number of possible hits is sharply reduced. Secondly, since a standard or super-heavy 16" shell has good penetration stats at medium to close engagement ranges, does an 18" or 20" shell's greater individual weight offer advantages to offset its slower rate of fire?

So... would 'Yamato' actually have been a better investment with 12x16" guns? (264,600 for 12 guns, 2 shells per minute, 2205-lb shell)And would a super-'Yamato' with 6x20" guns be actually a better ship? I understand that using throw-weight can be deceptive since what we really want to measure is the effect of actual hits, but...

Is increasing the size of a ship (improving the chance of a hit on it) to carry fewer or slower-firing weapons (reducing the chance of a hit on the enemy) a better plan than more, smaller guns on a ship of equal or smaller size? Given the difficulty of increasing the rate of fire, I think the odds favor a larger battery, and, given the extreme difficulty of getting hits at long range and the penetrability of most ships at medium and close range, I just don't see that the 18" or 20" offers any significant advantage.

Your thoughts?

I modified my Yamato Springsharp design to change the main armament to 12- 16-inch guns. The weight went down. I did not increase the length of the ship to include the fourth turret. But I suspect that might have to be done. The increased length would increase the weight and necessary engine power but that might be compensated a little by the increase in length to beam. Many changes including the length of the armored citadel would have had to be made to ensure that the magazines would be protected.


Personally, I believe that updated versions of the Nagato class battleships might have been a better choice. Three turrets with 16” 50 caliber guns might have been possibly on the length. That class could already do 27 knots and with engines of later technology, an extra two to three knots might have been possible. The original drawings were available, and the cost of these ships would have been less, and they could have built, possibly two for each Yamato. This is cost per performance. Later, I will put together two designs using Springsharp and verify what I believe.


For a nation with limited oil access and shipyards, I think personally building four more modified Nagato's makes far more sense. On the hand, in an era improved carriers and aircraft, building more battleships does seem a waste. However, if it must be done, keep costs to a minimum since you already are prepared in the area of maintenance and spares for the Nagato's. 

[alexbrunius]

Oct 4, 2018 7:58:07 GMT -6 director said:

I'd like to broaden the discussion a bit if I may, to question the requirement.

...

So... would 'Yamato' actually have been a better investment with 12x16" guns? (264,600 for 12 guns, 2 shells per minute, 2205-lb shell)And would a super-'Yamato' with 6x20" guns be actually a better ship? I understand that using throw-weight can be deceptive since what we really want to measure is the effect of actual hits, but...

Is increasing the size of a ship (improving the chance of a hit on it) to carry fewer or slower-firing weapons (reducing the chance of a hit on the enemy) a better plan than more, smaller guns on a ship of equal or smaller size? Given the difficulty of increasing the rate of fire, I think the odds favor a larger battery, and, given the extreme difficulty of getting hits at long range and the penetrability of most ships at medium and close range, I just don't see that the 18" or 20" offers any significant advantage.

Your thoughts?

Well that argument works both ways doesn't it?

Why would the say 9x16" on the Iowa be superior to a fictional Battleship of similar tonnage that carried 12x14" or 12x12" guns of modern make with faster firing speeds, heavy shells and sufficient penetration to get the job done?


It is also a bit unfair to only compare the Japanese 18.1" with the American 16" IMO and conclude that the step to 18" or above was not worth it. We should instead compare Japanese guns to other Japanese guns and US guns to other US guns ( and use equivalent ammunition types ).

Using this as a baseline:
www.navweaps.com/index_nathan/Penetration_index.php

Let's compare the calculated armor penetration values at a distance of 20000 yards = 18288 meter, and use the value for EFF = Effective Limit ( Effective Limit - The projectile will usually retain intact its explosive filler cavity, a seated base plug, and a working fuze ). Let's also use "US Class A Armor (1935-1943)" for comparison ( the intended target for the largest caliber guns historically fielded )


Japanese:
18.1"/45 gun, Type 91 AP (1937-45) = 20.5" belt, 3.2" deck
16.1"/45 gun, Type 91 AP (1931-45) = 16.4" belt, 2.8" deck
14"/45 gun, Type 91 AP (1931-45) = 12.2" belt, 2.4" deck

American:
16"/50 gun, Mk 8 1-5 (1943-44) = 19.1" belt, 3.5" deck
16"/45 gun, Mk 8 1-5 (1939-44) = 16.9" belt, 3.6" deck
16"/45 gun, Mk 5 1-4 (1939-44) = 17.5" belt, 3.1" deck
14"/50 gun, Mk 16 1-6 (1937-44) = 14.1" belt, 2.6" deck
14"/45 gun, Mk 16 1-6 (1937-44) = 12.9" belt, 2.6" deck

Looking at the values above and comparing performance within the same nation only instead, we can see a clear increase in belt penetration of around 25-35% for each step of 2" increase in gun caliber. Such a large difference is enough to make most enemy ship armor designed to face the previous generation of ships obsolete, and constitutes the difference between a full penetration of an intact shell vs a shell bouncing off the armor doing nothing more than denting it at most without inflicting deep internal damage.

So there is a clear technical motivation behind the historical arms race for bigger naval guns and thicker armor.

[axe99]

Oct 4, 2018 7:58:07 GMT -6 director said:

I'd like to broaden the discussion a bit if I may, to question the requirement.

As I understand it, Japan went to the 18" (18.1") caliber in order to achieve longer range, greater penetration ability and perhaps greater explosive power.

But if 'Montana' would have had a throw-weight of 324,000 pounds in 5 minutes (12 guns, 2 shells per minute, 2700-lb shell) and 'Yamato' comes in at 217,215 (9 guns, 1.5 shells per minute, 3218-lb shell) or 289620 (9 guns, 2 shells per minute, 3218-lb shell) then is the possible greater range and weight per shell actually worthwhile? ('Nelson' comes in at 184050 with 9 guns, 2 shells per minute and the light 2048-lb shell, 'Nagato' at 176400 with 8 guns, 2 shells per minute and a 2205-lb shell, 'North Carolina' at 243,000 with 9 guns, 2 shells per minute and the 2700-lb shell).

It seems to me that achieving hits at very great ranges depends on a lot of factors, most of which are uncontrollable (target range, manuevering, wind speed, etc). The one thing a gunner can reliably do to increase the number of hits is to increase the number of shells fired, usually by increasing the size of the battery. Raising the number from 9 to 12 would help; slowing down the rate of fire (handling time for larger projectiles) would hurt and dropping the battery to 6 even-slower-firing 20" would substantially reduce the already-slim mathematical odds of getting a hit at long range.

Given the greater cost developing and deploying a bigger gun, the increased wear, etc and so forth, is deploying an 18" or 20" weapon actually worth it? The reduced rate of fire and/or number of barrels seems to work against using them for long-range fire as the number of possible hits is sharply reduced. Secondly, since a standard or super-heavy 16" shell has good penetration stats at medium to close engagement ranges, does an 18" or 20" shell's greater individual weight offer advantages to offset its slower rate of fire?

So... would 'Yamato' actually have been a better investment with 12x16" guns? (264,600 for 12 guns, 2 shells per minute, 2205-lb shell)And would a super-'Yamato' with 6x20" guns be actually a better ship? I understand that using throw-weight can be deceptive since what we really want to measure is the effect of actual hits, but...

Is increasing the size of a ship (improving the chance of a hit on it) to carry fewer or slower-firing weapons (reducing the chance of a hit on the enemy) a better plan than more, smaller guns on a ship of equal or smaller size? Given the difficulty of increasing the rate of fire, I think the odds favor a larger battery, and, given the extreme difficulty of getting hits at long range and the penetrability of most ships at medium and close range, I just don't see that the 18" or 20" offers any significant advantage.

Your thoughts?

Good thoughts Director .  Some other thoughts, probably of wildly varying quality:

Another important factor is penetration at range. Referencing the penetration Alex brought up, at 24,000 yards the Japanese EFF for British armour for their 46cm Type 94 is 16.2 inches - compared with a KGVs belt of 15" (or deck of 3.8 inches) - if we look at their 40cm gun (Nagato), then at 24,000 yards their EFF is 13.1 inches (or 3.4 inches deck), such that the Yamato at ranges where they could be expected to start scoring hits, is likely to prove significantly more effective against a modern BB if it hits than Nagato.  Given relatively similar rates of fire for both, the choice of the Yamato's guns here seems like it could provide a decent advantage in an engagement (although whether that advantage offsets the massive cost of the ships, and what else could be bought instead, is a far more complex question to which I wouldn't hazard to guess).

Iirc, though the Japanese 51cm was only expected to have a rate of fire of 1 round per minute per gun, rather than two, changing the 'number of expected hits per minute at range' considerably.  My guess would be that they expected bigger and better armoured enemy battleships, as beyond a certain point (decreasing chance of hit with longer range, regardless of quality of aiming, given the time of flight of the shell gives an enemy time to maneuver (salvo chasing, for example)) the extra penetration capability at a range where one would be expected to make enough hits would have diminishing marginal returns.

Also, rimbecano - 23,000 yards (21km or so) wouldn't, imo, be considered particularly long-range for a battleship. It's not short range, but many interwar navies planned for longer initial engagement ranges than that iirc (and I'm fairly confident that this applies at least to the USN, RM and IJN).



That's the best I've got, back to the experts now .

[director]

rimbecano -

And in general, against an armored target, if you have acceptable accuracy, as few guns of as large a calibre as possible is optimal. Tanks, for instance, usually have just one big gun.

That's just the problem - acceptable accuracy. If the percentage chance of hitting a target at (say) 24,000 yards is 1-in-36 (to pick a number) then four broadsides from a 6-gun ship give .67 hits, from a 9-gun ship deliver 1 hit and four broadsides from a 12-gun ship will land 1.3 (I think I got that right, but I was doing fast and dirty calculations, so no promises). Let's assume the ships fire steadily for one hundred rounds per gun at that range. That's 16.5 hits for a 6-gun battery, 25 hits for a 9-gun battery and somewhere between 32 and 43 (I think) for a 12-gun ship. All other things being equal (and they never are), size of battery matters.

I don't agree: tanks from our 1900-1950 period tend to have one big gun, but it has an effective range of a few hundred meters. They don't fire at targets out to the extreme range of the gun because they can't hit anything out there in any reasonable length of time. A group of guns firing steadily at a target might hit it sooner or later, but with one gun at long range I think you're just hoping for a 'golden BB'.


oldpop2000 - I tend to agree with you. The American 'Montana' is in the same tonnage ballpark as a 'Yamato'. I also agree that Japan might have come out better building a series of improvements to the 'Nagato' class, but I think the lure of the super-ship overtook them. The promise of being able to deal out massive shells from beyond the enemy's range was powerfully attractive, but given the state of optical fire control I don't think it was achievable. Using the 'Yamato' class at medium to close range just doesn't make a lot of sense either - their armor is stout but (as I understand it) still vulnerable at closer ranges. And as 'Bismarck' taught us, you don't have to break the armor to mission-kill the ship.

Doesn't a lighter shell tend to be more affected by atmospheric conditions? Is that one of the reasons for favoring a bigger bullet?


alexbrunius -

Why would the say 9x16" on the Iowa be superior to a fictional Battleship of similar tonnage that carried 12x14" or 12x12" guns of modern make with faster firing speeds, heavy shells and sufficient penetration to get the job done?

Well, I have always thought the 'King George V' class were underappreciated... Part of what I'm asking is exactly what you say. The US 9-gun battleships of 'North Carolina' and 'South Dakota' class were undersized for their guns and overgunned for their size. I think the main reason is that the designers couldn't squeeze 12-14" on a 35,000-ton hull with acceptable speed and protection, wanted the increased power and range of the superheavy 16" shell, and a 9-gun battery was considered adequate for delivering an acceptable number of shells with expected accuracy. The 'Iowa' class were not intended to be heavily armed, just fast, so they're an outlier rather than an example, I think.

A 14" shell is going to weigh in at around 1400-lbs (British 1590) while a good 16" is more like 2200-lbs and the super-heavy is 2700-lbs. That means even the heavier British 14" is about .72 percent of a standard 16" and about .59 percent of the superheavy. By comparison those 16" shells are around .68 and .84 percent of a Japanese 18" shell.

Let's not consider the 12" - Germany wouldn't have used the 11" on the 'Scharnhorst' class if they'd had anything better at hand and the 'Alaska' was intended to fight cruisers, not capital ships. The US 12" super-heavy shell at is 1140-lbs is pretty light to penetrate reasonable capital-ship armor of the period. There is, I think, a 'sweet spot' between having enough guns to get hits and having a big enough shell to make those hits count, and the 12" (even the US version) is, in my opinion, too light.

I am not arguing that shell weight and penetrative ability don't matter - they clearly do, and a lot. I am asking where the overlap of the Venn diagrams is - how do you balance getting more hits from a larger battery against the admittedly greater individual impact of a smaller number of hits? Is going to a larger caliber always a better idea, if it means reducing the number of guns in the battery?


axe99 - Hi! I suspect 'Yamato' would not have been able to deliver repeated hits at extreme ranges except under ideal conditions. I think every major navy realized the tactical value of getting in hits early, especially against deck armor, and simply trained under the assumption that, since they wanted to do it, they could... I just doubt that. I do completely agree that there is a lot of value in hitting an enemy early and landing shots on his deck. But getting hits that way would require a high expenditure of ammunition.

In general, and in my opinion, Britain and Japan might have been better off developing either a new 16" (to replace the 'Nelson' 16" wirewound) or a new superheavy 16" shell if existing guns could take it, rather than moving up to a bigger caliber of gun with its larger machinery and likely slower loading times.