Jump to content
Sign in to follow this  
You need to play a total of 5 battles to post in this section.
DeliciousFart

US Navy 18"/48 gun turret design sketch from April 1938

31 comments in this topic

Recommended Posts

Members
1,296 posts
867 battles

Tony DiGiulian, owner of Navweaps, recently obtained sketch drawings of double and triple 18"/48 gun turrets for "slow" Escalator Clause battleship designs of 1938.

WNUS_18-48_mk1_twin_pic.jpg

WNUS_18-48_mk1_triple_pic.jpg

For a little bit of background, I'll copy and paste what I wrote for Wikipedia a few months back. 

Work on what would eventually become the Iowa-class battleship began on the first studies in early 1938 following the planned invocation of the "escalator clause" that would permit maximum standard capital ship displacement of 45,000 long tons. Using the additional 10,000 long tons over previous designs, the studies included schemes for 27-knot "slow" battleships that increased armament and protection as well as "fast" battleships capable of 33 knots or more. The "slow" designs carried either twelve 16"/45 cal Mark 6 guns or nine 18"/48 cal guns and with more armor and a power plant large enough to drive the larger ship through the water at the same 27-knot maximum speed as the South Dakotas. The April 1938 "slow" design's characteristics are below, from Friedman page 307.

Waterline length 800 ft
Beam 108 ft 3 in
Draft 35.96 ft
Max displacement 56,595 long tons
Battle displacement 54,495 long tons
Standard displacement 45,495 long tons
Speed 27.5 knots
SHP 130,000
Range (15 knots) 15,000 nmi
Main battery 9 x 18" (457mm)/48
Secondary battery 20 x 5" (127mm)/38
Belt (19 degrees on 30# STS) 14.75" (375mm)
Heavy deck 5.1" (130mm)
Bomb deck 1.5" (38mm)
Splinter deck 0.63" (16mm)
Barbette, conning tower 21" (533mm)
Turret face 20" (508mm)
Turret, CT roof 10" (254mm)
Traverse bulkheads 16.75" (425mm)
Splinter protection 2.5" (64mm)

Given the hull's outer dimensions, the belt armor would've almost certainly been arranged internally like on South Dakota and Iowa. The heavy deck would presumably be laminated on 1" STS for a combined thickness of some 6". Also, if the ships were completed, the additional AA and electronics alone would have added another 2-3000 tons, based on the displacement figures from the Iowas. While the "fast" studies would result in the Iowa class, the "slow" design studies would eventually settle on twelve 16" guns and evolve into the design for the 60,500-long-ton Montana class after all treaty restrictions were removed following the start of World War II.

Side note: The displacement figures for the April 1938 design does seem rather optimistic, so I would like to consult some naval historians on how feasible it would be to actually build this ship to its design displacement values.

As you can see, a double 18"/48 turret has a barbette diameter of 34 ft 6 in, while the triple turret has a barbette diameter of 41 ft 0 in. Their respective weights are 3,559,000 lbs and 4,850,000 lbs. For reference, the barbette diameter of a 16"/50 Mark 7 triple turret is 37 ft 3 in and the turret weight is 3,825,920 lbs. So it's perfectly possible to substitute a triple 16"/50 Mark 7 turret with a double 18"/48 turret, though whether that's actually a worthwhile tradeoff is another matter entirely. Link and drawings below.

Note that the spacing of the gun axes is 132 inches. This compares to the 16"/50 Mark 7 spacing of 122 inches.

If an 18"/48 caliber gun was developed, it would have fired a 3,850 lb (1,746 kg) Superheavy AP shell at a muzzle velocity of 2,500 ft/s (762 m/s), resulting in a muzzle energy of 507 MJ. This muzzle energy would dwarf even the 474 MJ of the Soviet 457 mm gun (1,410 kg at 820 m/s) and the 444 MJ of the Japanese 460 mm gun. Also keep in mind that the high mass, CRH, and moderate muzzle velocity means better energy retention downrange. The 18"/47 Mark A itself tested a 3,848 lb (1,745 kg) prototype SHS at a muzzle velocity of 2,508 ft/s (764 m/s) at a chamber pressure of 19.91 tons per square inch.

http://www.navweaps.com/Weapons/WNUS_18-48_mk1.php

https://www.navsea.navy.mil/Home/Warfare-Centers/NSWC-Dahlgren/Dahlgren_Centennial/Blog/18_Inch_Gun/

 

 

Edited by DeliciousFart
  • Cool 13

Share this post


Link to post
Share on other sites
169
[BLHK]
Members
555 posts
58 minutes ago, DeliciousFart said:

 

If an 18"/48 caliber gun was developed, it would have fired a 3,850 lb (1,746 kg) Superheavy AP shell at a muzzle velocity of 2,500 ft/s (762 m/s), resulting in a muzzle energy of 507 MJ. This muzzle energy would dwarf even the 474 MJ of the Soviet 457 mm gun (1,410 kg at 820 m/s) and the 444 MJ of the Japanese 460 mm gun. Also keep in mind that the high mass, CRH, and moderate muzzle velocity means better energy retention downrange.

And able to throw the average family car 25 miles, with an in flight time of over 45 seconds

  • Cool 1

Share this post


Link to post
Share on other sites
172
[FTH]
Members
999 posts
14,882 battles
On ‎12‎/‎31‎/‎2018 at 2:25 AM, Forgottensoldier117 said:

Anybody think we have any chance of seeing these awesome guns come into the game?

I wish, but I also doubt it...not trying to start a argument, but it would probably put us over the allowable US Broadside weight for the game, especially the triple mounts...and having run both 457 and 419 Conq...twin mounts vs triples doesn't really matter how much bigger the shell is, if there is a third less of them, unless you're going from a 8" round to a 12" or so, lol.

Share this post


Link to post
Share on other sites
7
[N2O]
Members
17 posts
7,317 battles

Good stuff.  I think Friedman's US series is due for a revision to bring them up to his newer British ship series level.

Share this post


Link to post
Share on other sites
573
[UFFA]
Members
1,899 posts
73 battles
On 12/31/2018 at 3:25 AM, Forgottensoldier117 said:

Anybody think we have any chance of seeing these awesome guns come into the game?

 

On 1/1/2019 at 6:43 AM, Purg473 said:

I wish, but I also doubt it...not trying to start a argument, but it would probably put us over the allowable US Broadside weight for the game, especially the triple mounts...and having run both 457 and 419 Conq...twin mounts vs triples doesn't really matter how much bigger the shell is, if there is a third less of them, unless you're going from a 8" round to a 12" or so, lol.

Given enough time yes. A lot of crazy things will appear in the latter half of the development cycle if WoT is a guide. 

Share this post


Link to post
Share on other sites
172
[FTH]
Members
999 posts
14,882 battles

I seem to recall them saying there were enough plans for 4 different U.S lines alone...Tillerman IV for me please, lol. 

Share this post


Link to post
Share on other sites
1,123
[LEGIO]
Members
3,349 posts
6,879 battles

Unfortunately the HMS Conqueror shows us that 18" guns, even these ones, are pretty much irrelevant in this game until WG puts 2 and 2 together and gives them the same overmatch capability as Yamato's 18.1" guns.

I know somebody is going to say "I do okay in the Conqueror with the 18" armament" but the truth is they'd always be doing better with the 16.5" selected.

Share this post


Link to post
Share on other sites
1,982
[XODUS]
Alpha Tester
4,691 posts
2,034 battles
On 12/31/2018 at 12:25 AM, Forgottensoldier117 said:

Anybody think we have any chance of seeing these awesome guns come into the game?

Wargaming suggested, back before Alpha started, they actually had enough data for up to five lines of US battleships. It is quite possible a second battleship line might cap with 18" guns.

Share this post


Link to post
Share on other sites
Members
909 posts
5,992 battles
3 hours ago, NGTM_1R said:

Wargaming suggested, back before Alpha started, they actually had enough data for up to five lines of US battleships. It is quite possible a second battleship line might cap with 18" guns.

I know I would love to see more of the us standards in the game. I love those slow old battle wagons. Really I love all the US BBs and would love to have 5 full lines! But I could settle for at least one more. :Smile_smile:

Share this post


Link to post
Share on other sites
276
[UN1]
Members
719 posts
2,705 battles
On 1/3/2019 at 5:32 PM, Lampshade_M1A2 said:

Unfortunately the HMS Conqueror shows us that 18" guns, even these ones, are pretty much irrelevant in this game until WG puts 2 and 2 together and gives them the same overmatch capability as Yamato's 18.1" guns.

I know somebody is going to say "I do okay in the Conqueror with the 18" armament" but the truth is they'd always be doing better with the 16.5" selected.

The 457mm guns on the Conqueror would be awesome if it had the Warspite/Hood/Vanguard dispersion tables, faster reload, and normalized AP (and normal HE performance).  That would give it a really cool alternative playstyle.

Share this post


Link to post
Share on other sites
Alpha Tester
4,003 posts
5,281 battles
On 1/3/2019 at 2:32 PM, Lampshade_M1A2 said:

Unfortunately the HMS Conqueror shows us that 18" guns, even these ones, are pretty much irrelevant in this game until WG puts 2 and 2 together and gives them the same overmatch capability as Yamato's 18.1" guns.

I know somebody is going to say "I do okay in the Conqueror with the 18" armament" but the truth is they'd always be doing better with the 16.5" selected.

Conq 457 has problems because it's the weakest of the guns above 420mm caliber and because the 419mm gun is the strongest gun at or below 420mm. It's hard to buy into the 457mm when it only has around 1km(or less at longer ranges) of effective range over the 419mm. Meanwhile the USN 18"/48 is one of the strongest guns likely to ever appear in the game due to generally good USN shell performance and the crazy kinetics involved. Only downside is that

On 12/28/2018 at 6:50 PM, DeliciousFart said:

 Also keep in mind that the high mass, CRH, and moderate muzzle velocity means better energy retention downrange. The 18"/47 Mark A itself tested a 3,848 lb (1,745 kg) prototype SHS at a muzzle velocity of 2,508 ft/s (764 m/s) at a chamber pressure of 19.91 tons per square inch.

this is likely not 100% true. The 18"/48 boasts incredible kinetics, but USN shells typically have awful drag profiles despite their long crh heads. The issue is that secant ogives are actually just sort of awful ogive profiles, and that USN shells are both heavier(which means a longer skin drag surface) and worse are not boat-tailed. That last one is a killer and probably in big part responsible for the worse drag profile on USN guns relative to stuff like Yamato and the guns of most of the continental powers.

  • Cool 1

Share this post


Link to post
Share on other sites
1,123
[LEGIO]
Members
3,349 posts
6,879 battles
6 hours ago, Aetreus said:

this is likely not 100% true. The 18"/48 boasts incredible kinetics, but USN shells typically have awful drag profiles despite their long crh heads. The issue is that secant ogives are actually just sort of awful ogive profiles, and that USN shells are both heavier(which means a longer skin drag surface) and worse are not boat-tailed. That last one is a killer and probably in big part responsible for the worse drag profile on USN guns relative to stuff like Yamato and the guns of most of the continental powers.

In game or in real life? In all I've read about naval gunnery I've never heard this claim that US WW2-era shells had a lot of drag. Some had a boat-tail like the shells for the 5"/54.

Share this post


Link to post
Share on other sites
Alpha Tester
4,003 posts
5,281 battles
9 hours ago, Lampshade_M1A2 said:

In game or in real life? In all I've read about naval gunnery I've never heard this claim that US WW2-era shells had a lot of drag. Some had a boat-tail like the shells for the 5"/54.

The game's drag model does a reasonable job of approximating reality. If you look at the ingame ranges at various elevations they match fairly closely to historical numbers, and USN shells need higher drag coefficients to make that happen. It's not talked about in naval gunnery because that discussion is usually about accuracy and fire control not the underlying ballistics of the guns. The 5"/54 was a very new weapon, and notably it entered service after the USN was exposed to modern French shell design which emphasized drag reduction. Hence its ballistics are much better than other USN shells.

Share this post


Link to post
Share on other sites
Members
1,296 posts
867 battles
On 1/10/2019 at 10:06 PM, Aetreus said:

Conq 457 has problems because it's the weakest of the guns above 420mm caliber and because the 419mm gun is the strongest gun at or below 420mm. It's hard to buy into the 457mm when it only has around 1km(or less at longer ranges) of effective range over the 419mm. Meanwhile the USN 18"/48 is one of the strongest guns likely to ever appear in the game due to generally good USN shell performance and the crazy kinetics involved. Only downside is that

this is likely not 100% true. The 18"/48 boasts incredible kinetics, but USN shells typically have awful drag profiles despite their long crh heads. The issue is that secant ogives are actually just sort of awful ogive profiles, and that USN shells are both heavier(which means a longer skin drag surface) and worse are not boat-tailed. That last one is a killer and probably in big part responsible for the worse drag profile on USN guns relative to stuff like Yamato and the guns of most of the continental powers.

As far as I know, only the Japanese had a boat tail for their shells. I'm not sure how the US Navy's heavier shells correlate with substantially larger surface area; the AP Mark 8 has a length/caliber of 4.5, which is comparable to the German's 380 mm shell with 4.4, the Italian 381 mm shell with 4.46, and the Japanese Type 1 with 4.47. Do you happen to have a source that lists the drag coefficients of these shells?

Edited by DeliciousFart

Share this post


Link to post
Share on other sites
573
[UFFA]
Members
1,899 posts
73 battles

Would a boat tail have even worked with the way the USN strengthened their shells? The French had bad experiences with the gas cavities and the USN would have had direct technology transfer from France with samples of said shells. 

I’m sure someone ran the numbers and decided it wasn’t optimal for US shells. The USN was very confident in their ballistics computers. I doubt NIMBY was an issue.  :Smile-_tongue:

Share this post


Link to post
Share on other sites
2,809
[HINON]
Privateers, In AlfaTesters
7,728 posts
2,122 battles
10 hours ago, DeliciousFart said:

As far as I know, only the Japanese had a boat tail for their shells. I'm not sure how the US Navy's heavier shells correlate with substantially larger surface area; the AP Mark 8 has a length/caliber of 4.5, which is comparable to the German's 380 mm shell with 4.4, the Italian 381 mm shell with 4.46, and the Japanese Type 1 with 4.47. Do you happen to have a source that lists the drag coefficients of these shells?

If I'm not mistaken, the French used boat-tails on almost everything except for maybe the battleship shells - they became quite heavily invested in ballistic performance following the shock of WWI when most other naval powers engaged at ranges impossible for French ships.

Aa far as drag goes, I can help insofar as what's used for in-game data;

Yamato (46cm/45 Type 94):

  • 46cm Type 91: 0.292
  • 46cm Type 0: 0.543

Nagato (41cm/45 3rd Year Type):

  • 41cm Type 91: 0.355
  • 41cm Type 0: 0.505

Iowa (16"/50 Mk.7):

  • 16" APC Mk.8: 0.352
  • 16" HC Mk.13: 0.346

Roma (381/50 Modello 1934):

  • 381mm Palla: 0.295
  • 381mm GP: 0.275

Richelieu (380mm/45 Mle 1935):

  • OPfK Mle 1943: 0.279
  • OEA Mle 1945: 0.279

Bismarck (38cm SK C/34):

  • Psgr. L/4,4: 0.276
  • Spr.gr. L/4,6: 0.276

Share this post


Link to post
Share on other sites
Members
770 posts
1,706 battles

The French designed an 18" gun too. Unfortunately I cannot find any sources but I have read before the Washington naval treaty they did design them. 

Share this post


Link to post
Share on other sites
1,877
Supertester, Members, Alpha Tester, In AlfaTesters, Beta Testers
11,331 posts
1,963 battles
18 hours ago, Schnitchelkid01_ said:

The French designed an 18" gun too. Unfortunately I cannot find any sources but I have read before the Washington naval treaty they did design them. 

They designed a 450mm gun, which comes out as something like 17.7". 

They went for this calibre because of the limitations of their gun foundries. It was designed in 1920 for the planned generation of post-war battleships. Of course, that was a pipe dream even before the Washington Naval Treaty (due to the state of French finances, and the need to rebuild in the formerly occupied zone). 

Share this post


Link to post
Share on other sites
Members
1,296 posts
867 battles
On 1/22/2019 at 9:39 AM, Phoenix_jz said:

If I'm not mistaken, the French used boat-tails on almost everything except for maybe the battleship shells - they became quite heavily invested in ballistic performance following the shock of WWI when most other naval powers engaged at ranges impossible for French ships.

Aa far as drag goes, I can help insofar as what's used for in-game data;

Yamato (46cm/45 Type 94):

  • 46cm Type 91: 0.292
  • 46cm Type 0: 0.543

Nagato (41cm/45 3rd Year Type):

  • 41cm Type 91: 0.355
  • 41cm Type 0: 0.505

Iowa (16"/50 Mk.7):

  • 16" APC Mk.8: 0.352
  • 16" HC Mk.13: 0.346

Roma (381/50 Modello 1934):

  • 381mm Palla: 0.295
  • 381mm GP: 0.275

Richelieu (380mm/45 Mle 1935):

  • OPfK Mle 1943: 0.279
  • OEA Mle 1945: 0.279

Bismarck (38cm SK C/34):

  • Psgr. L/4,4: 0.276
  • Spr.gr. L/4,6: 0.276

I know these are the in-game drag values (it's pretty ludicrous that the Mk.13 somehow has a lower drag coefficient than the Mk.8). I'm talking about real life; most APC projectiles of various navies had a L/D not much different from the Mark 8's L/D of 4.5.

As far as I know, for battleship shells, neither the British, German, Italian, or French shells had boat tails. I think that was something only the Japanese did. That said, most projectiles that the US produced in WW2 did lack a boat tail. Even the 30-06 M2 ball didn't have one, and snipers in fact preferred using older stocks of M1 ball, which did have a boat tail.

Edited by DeliciousFart

Share this post


Link to post
Share on other sites
Alpha Tester
4,003 posts
5,281 battles
On 1/21/2019 at 10:46 PM, DeliciousFart said:

As far as I know, only the Japanese had a boat tail for their shells. I'm not sure how the US Navy's heavier shells correlate with substantially larger surface area; the AP Mark 8 has a length/caliber of 4.5, which is comparable to the German's 380 mm shell with 4.4, the Italian 381 mm shell with 4.46, and the Japanese Type 1 with 4.47. Do you happen to have a source that lists the drag coefficients of these shells?

Heavier shells have larger surface area because the shell's cap is generally a similar shape across all shells(it does differ, but USN caps are blunt which works against them in this way). Hence a shell that is proportionately heavier must have a longer body, which has full diameter and therefore contributes more to skin area than the windscreen.

The game's drag model is fairly sophisticated- it essentially simulates drag through flight, including air pressure/temperature effects. More importantly, the drag values aren't arbitrary, they make the guns line up with historically published range values at various elevations and muzzle velocities. 

Share this post


Link to post
Share on other sites
Members
1,296 posts
867 battles
On 1/26/2019 at 3:47 PM, Aetreus said:

Heavier shells have larger surface area because the shell's cap is generally a similar shape across all shells(it does differ, but USN caps are blunt which works against them in this way). Hence a shell that is proportionately heavier must have a longer body, which has full diameter and therefore contributes more to skin area than the windscreen.

The game's drag model is fairly sophisticated- it essentially simulates drag through flight, including air pressure/temperature effects. More importantly, the drag values aren't arbitrary, they make the guns line up with historically published range values at various elevations and muzzle velocities. 

I don’t think cap shape and length are so uniform; do we have measurements of how long the windscreens are relative to the length for all the shells? I’m not sure what you mean by “blunt”. Even though a secant ogive would result in a shorter windscreen for a given Crh, I would actually be curious in some concrete numbers. Given that the US AP Mark 8 shell has similar L/D compared to the AP shells of other navies, while also having quite a high Crh (compared to Britain, at least), I find it rather improbable that the US shell would somehow have a much shorter windscreen.

I’m also not convinced that drag contribution from the additional skin friction would be that significant. Especially when supersonic, wave drag is much more dominant, and here is where a boattail would be beneficial, but aside from the Japanese and perhaps the French, no other nations had boattailed battleship shells.

Furthermore, the game's ballistics does NOT align with real-life performance. Here is the angle of fall and striking velocity of the AP Mark 8 in game compared to real life.

image.thumb.png.79f1cc8fad4d086740a5106834b2ef08.png

Furthermore, here is the angle of fall of the AP Mark 8 and the Japanese 46 cm gun compared using in-game and real life values. The real life differences doesn't seem particularly large, while the difference in-game is noticeably exaggerated in comparison.

image.thumb.png.50d6756e30c961808097f522293be1b3.png

Edited by DeliciousFart

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

×