G3 Battle Cruiser and N3 Battleship


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8 March 2007
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'Shocked and stunned' that there is nothing on the site about these 2. The 2 best ships Britain never built. The G3 was a fast battle cruiser with 9 x 16 inch guns and the N3 was its more heavily armoured 9 x 18 inch gun battleship cousin (a British Yamato 20 years earlier). They were both scraped soon after the 1921 Washington treaty and all we got was the Nelson class scaled down versions instead (as I'm sure you must know) Below, the top picture is my impression of a G3 based on a Nelson class. Also I've attached 2 other renderings of a G3 and an N3 from the internet but I forget the source. If anyone knows please tell me as I remember it was a fantastic site with many other renderings of uncompleted designs. I fear though it may no longer exist. I'm sure gentlemen of your caliber must have heaps of information on these ships and perhaps even more impressive British designs?

Cheers, Woody


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Thanks JohnR
I had it bookmarked on my old computer, back in NZ, but could'nt find it again from here. The geocities link I did find just came up with errors. The guy's a gifted artist but pretty secretive, he's not you is he? :)

Cheers, Woody
Definitely not!! Wish it was though.

D K Brown's "The Grand Fleet" has a large section in the back which covers these ships and others. There was a series of designs from F right through to O for various battleships/cruisers mounting 15"/16"/16.5"/18" guns. I'll put together something that'll give more detail, including pictures.

The G3 design eventually laid down was one of the smallest designs, mostly chosen because of its smaller size leading to easier docking around the Empire. A comparison with the USS Iowa design(similar size) of 20 years later is quite telling. There is no appreciable advantage with Iowa save 1-2knts of speed. G3 has considerably superior armour.

More on the others in the series later...
I look forward to Red Admiral's post.
If you can find/afford them, the most complete references are
British Battleships of WWII by Raven and Roberts
Articles by NJM Campbell in Warship (numbers 1 to 4)
F Battlecruisers

The almost last ships in the series. Following the Washington Treaty limiting size to 35000 standard tons two series of designs were drawn up to match. They were the F series and the O series. O3 was eventually chosen for production as the two Nelson Class ships. The F designs, F2 and F3, were battlecruisers mounting 15"/50 guns. The armourscheme was similar in placement and thickness to that of the O3 battleship, the increase in speed to 30knts coming from decreasing the calibre of the main guns to 15". A new 50-cal weapon was tentatively planned but I personally feel that newbuild 42-cal weapons would have been used after the previous poor experience with the 12"/50. They would have been capable ships and extremely useful in WW2. Possible improvements would have been the replacement of the 6" battery with dual-purpose 4.5" or 5.25" in the late 1930s as the 6"/50 was found to have an extremely limited anti-aircraft ability. They compare quite well with the later designs from the 1930s.


A rough layout sketch by Crystaleye


Design details. Note displacement includes 1000tons oil. Standard displacement would be around 34000tons or less given the weight savings in Nelson/Rodney.
Here's a drawing of the 1921th battlecruiser design from Siegfried Breyers "Schlachtschiffe und
Schlachtkreuzer 1905 - 1970". Sorry for the distortion by the centerfold


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.. and when I just put back Breyers book into the bookshelf, I've found two
othre small drawings in an old paperback (Heyne-Bildpaperbacks "Schlachtschiffe
1919 - 1977"), showing the G3 and N3.


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In early Warship issues there was a series on the post-WW1 British battleships and battlecruisers: a couple of dozen designs.. I'll try and scan all, if you like.
Thanks guys, this is great stuff.

red admiral said:
There is no appreciable advantage with Iowa save 1-2knts of speed. G3 has considerably superior armour.

I thought the G3 was faster and less armoured than the N3, so if the G3 was more armoured than an Iowa what was N3 like? Though I thought they were of similar displacements. And it is my understanding that these 2 were actually laid down, is this right?

Jemiba said:
Here's a drawing of the 1921th battlecruiser design from Siegfried Breyers "Schlachtschiffe und
Schlachtkreuzer 1905 - 1970".

I take it this drawing shows the armour distribution but armour is often described as angled (over magazines). I know how this works on a tank but I've never seen it explained for a ship. Since, at long range, shells would be falling at 45 degrees I can't see how it would help.

Cheers, Woody


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N3 only 23 knots, but 18" guns and armour to suit
G3 laid down, just, before cancelled by Washington Treaty.
N3 not laid down
Armour is sloped inboard from top to bottom, so plunging shells hit at a more oblique angle.
There is a huge amount of data and several good naval websites to tell you more.
Try www.navweaps.com for the real stuff, and www.phpbbplanet.com/warshipprojects/index.php?mforum=warshipprojects for the unbuilt.
Why in hell do they place a turret midship instead of on the stern??? This makes no apparent sense as it can only fire volleys from the broadside, and not aft.
Thanks Smurf,

smurf said:
Armour is sloped inboard from top to bottom, so plunging shells hit at a more oblique angle.
There is a huge amount of data and several good naval websites to tell you more.
Try www.navweaps.com for the real stuff, and www.phpbbplanet.com/warshipprojects/index.php?mforum=warshipprojects for the unbuilt.

Great links but I still couldn't find a diagram of the slope. Since the deck(s) armour is thinner than the vertical armour (?) that would make the thinner deck armoured area over the magazine larger so still not help. I think I'm missing the point so I'll have another look.

And Firefly, the turret placement is as much about armour coverage as fields of fire as there's only so much armour you can have and still move or float. So if you keep your turrets and magazines together you can have much thicker armour, all else being equal. Few commanders would choose to fight stern on with the use of only one turret. You'd have to if you're running away but the British believed they never did that ;D and if you've got a better ship you shouldn't need to. (Same reason most fighter plane have guns at the front).

Cheers, Woody
thinner deck armoured area over the magazine larger
no, speaking crudely, just turn the magazine round through 90 degrees. the area of the roof is the same.
Woody puts most of my reply to firefly, but it also made the ship shorter to fit existing docks. Later ships returned to fore and aft in part to allow AA guns to be better sited for all round fire away from the blast efects of the big guns.
Jens, Breyer's external profiles are incorrect. They show an external belt that is definitely not there.

Woody, N3 had thicker armour but a similar placement. The belt armour was increased to 15" angle inboard at 18°. The deck armour was increased to 8" all over IIRC with 9" on the slopes at the edges of the deck. The 4xG3s were just laid down in time for the Washington Conference. This was a good bargaining ploy by the Admiralty that cost them essentially nothing and meant that they didn't have wastage as with USS Washington or IJN Tosa(that were scrapped incomplete by treaty)

Firefly, the midships turret enabled the armoured length to be reduced, saving weight, which meant that thicker armour could be used. Room for engines and turbines on G3 was also a concern. In the 30s with advances in making boilers/turbines smaller they reverted to the conventional ABX arrangement.

Woody, Here is an armour diagram; I hope it makes things clearer. If you have any more questions I'm sure I can answer.

RA has beaten me to it! But here is another armour diagram showing what was behind the armour.
Another factor after the mid 1930's was arranging very numerous medium and light AA with good all round fire, but away from the blast effects of the big guns. (though G3 had very good AA for its day) Warship design involves a lot of compromises, some of them not at all obvious. For those interested, I highly recommend Norman Friedman's book Battleship design and development 1905-1945 ISBN: 0831707003 about $40 second hand see Abebooks.com.
As you can see, shortening the ship saves both belt and deck armour. Iowa was 887 ft long; G3 856ft. The extra knots were very costly: G3 needed 160000shp for 31.5knots. Iowa had 212000 for 33, not possible without great developments in turbine power/weight and volume.
Deck armour is more extensive than belt, and so costs more weight, and so has to be thinner.
Trading off one against the other involves decisions about tactics - at what range do you intend to fight?
Whether a shell strikes deck or belt depends on the "shadow" of the ship which the incoming shell "sees".
At short ranges (what that means depends on when you ask!) the shell sees only the belt, so 19th century battleships had little deck armour - to keep out splinters only.
An inclined belt has two advantages. Plunging shells hit it more obliquely. Flat trajectory shells "see" a greater thickness of armour because of the slope. The problems come in linking the belt to the anti torpedo defence system below, and the extra weight for a given height of belt.
At longer ranges (say over 15000 yards) the shells start to come in at steeper angles of descent, and will hit the deck. Bombs are even worse.
Another factor for Firefly to remember is the slowness of naval combat. A shell at WWI or II fighting ranges takes about 30 seconds to reach the target. In that time the ship has moved about 400 yards, or rather more than its length. You are then about ready to fire again - partly because it takes that long to reload the guns (though you might fire half of them at a time) but mainly because you have to wait to see the result. You can always change course a bit to bring guns to bear. Remember too, no radar in 1921 when the G3 was designed.
Sorry, I'm going on a bit. I first came to this site from the Warships Projects one, so I'm on my hobby horse! Here endeth the second lesson!


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Thanks Smurf and Red Admiral,
Its great to get good explanations from real enthusiasts. I could read this stuff all night. But I must say that, even from your diagrams, the sloped side armour creates marginally more deck armour area, though I'm sure the designers must have considered it worth it some how. Sloping the deck armour baffles me as it would present a more perpendicular surface to any incoming shell ???. Great G3 drawings anyway.

Cheers, Woody
smurf said:
thinner deck armoured area over the magazine larger
no, speaking crudely, just turn the magazine round through 90 degrees. the area of the roof is the same.
Woody puts most of my reply to firefly, but it also made the ship shorter to fit existing docks. Later ships returned to fore and aft in part to allow AA guns to be better sited for all round fire away from the blast efects of the big guns.

Thanks Smurf and Woody.
Djeezes, I have a lot to learn.
sloped side armour creates marginally more deck armour area
The alternative to sloped internal armour is an external belt. (You can see these in photos as a sort of panel on the sides of most armoured ships in the 20th century.) In the cross-section it would go straight down from the outer edge of the deck armour, which stays the same size. You see what I mean about linking to the antitorpedo bulges at the bottom of the belt?
Sloping the deck I'm not too sure about, but the height of the belt is limited by weight considerations, while the level above the keel of the deck armour is set by what goes beneath it - magazines, engines etc. That satisfies me, but I'm not sure it is the whole story.


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That bulge looks pretty bulky. Did it interfere with the hydrodynamics of the hull?
The armour plate was 14in thick. The beam of the ship about 104ft. Bulge is negligible compared to underwater anti-torpedo bulges. Those were first applied (in a battleship) to HMS Ramillies in WWI and only cost about 0.5 knot at 22kn. They increased beam from 88' to 102', reduced draught by 1ft despite weighing 2500 tons. After that they went in at the design stage, as well as being added to earlier ships.

One point I forgot, for completeness: repairs to inboard (sloping) armour were difficult. Later RN battleships like King George V illustrated went back to vertical external plates, so getting more height to the belt and easier repairs, though they were thicker than sloping belts of US battleships of the same era.
My justification for inward, from top to bottom, sloping armour is as follows. (Tell me if I'm on the right track :)):-

It's easier to score hits with a flatter trajectory so it makes sense to armour against such hits (with sloping armour etc.).
Short range flat trajectory hits on the side armour would be at higher velocity.
Plunging hits on the decks would be at longer distances so at lower velocity.
Long range hits are less likely.
Long range plunging hits are more difficult to range anyway because of their falling trajectory.
Plunging shots could be fired at shorter ranges with less propellant power but this would be counterproductive as the penetration power would also be reduced.

Did battleships vary the propellant charges and how does the range effect shell velocity and penetration?

Here's the layout of the Bismark's armour from: http://www.kbismarck.com/proteccioni.html - some internal and some external with selected sloping here and there.

Cheers, Woody


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Working backwards:
Bismarck's scheme makes a good contrast with RN and USN schemes, but is generally regarded as essentially WWI, very like Baden.
Varied propellant charges I believe were not used, or at least very rarely - enough variables to worry about when finding the range. The older unreconstructed 15" gun RN battleships, whose guns had only 20 degree elevation, were issued with supercharges, but these were to the best of my book references never used.
For the rest, in general terms you are on the right lines; in detail you do have to put numbers in. Once you are over really 'short ranges' shell striking velocity is less affected by range than you might imagine, but terms like "short range" are a bit iffy. You need to specify distance. In 1900 3000 yards was long range; by 1905/6 6000; in WWI fire was opened at 15000; (essentially same gun designs). US battle practice in WWII went to 30000 yards, and the Italians opened fire for real at such ranges. The longest ranged hit in battleship combat was by Warspite against the Italians, at 26000 yards. RN design in WWII was based on fighting at around 15000 yards.
For this kind of detailed understanding see navweaps.com both for gun data and for the technical articles, particularly by Nathan Okun. http://www.navweaps.com/index_nathan/index_nathan.htm
There is also a two-part article in the just published and just about to appear issues of Warships International by Bill Jurens, another recognised authority.
Is it true that the 16"/45 guns designed for for the G3 and later mounted on the Nelson, Rodney and Duke of York were the only 16 inchers and the largest the British had in WWII? And were the only other 16" gun WWII ships were the classes of the Iowa, South Dakota and Nagato?

According to http://www.navweaps.com/Weapons/WNBR_18-40_mk1.htm the British did build 3 18"/40 in WWI but mounted 2 of them on the lightly armoured Furious to be able to scrape through the Baltic Narrows but they were never used. Am I right that the only other guns bigger than 16" and the largest ever mounted on a battleship were the 18"/45s of Yamato and Musashi?

smurf said:
The longest ranged hit in battleship combat was by Warspite against the Italians, at 26000 yards.

I thought that the Warspite held the record for the longest range hit against a target underway (is this the same?), whether that means the Warspite or the target or both I don't know. The Warspite also holds the record for the most tonnage sunk of any ship ever I believe. An awesome ship.

Cheers, Woody
Warspite: yes, the same. Both under way, battle of Calabria
the only other guns bigger than 16"
yes if you say built and mounted on a ship. Others were planned, and some trial guns built by Japan and USA
Furious only ever got one gun. 2 went to monitors, all three eventually for trials and relining.
NONE went to Singapore.
First question. Maryland class also had 16". Again, plans for others.
Nelson and Rodney the only RN 16" ships completed. Lion class laid down 1939 not completed.
Oops, the Duke of York was of course a KGV class and the Maryland launched in 1921!, it did well to escape the Washington treaty.
Cheers, Woody


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Smurf, Red Admiral or anyone else.

smurf said:
Lion class laid down 1939 not completed.

Do you fancy starting a thread on the Lion class. I think it would qualify. I would be very interested as I've got nothing.

Cheers, Woody
H Series Battlecruisers

Three designs, H3a H3b and H3c differing in main gun placement. These were the smallest and fastest ships considered. They mount 6x18"/45 guns, heavy armour and have a speed in excess of 33knts.

Dec 1920
Statistics apply to all three design, except as noted.

H3a: 825pp (860oa) x 105 x 32.5
H3b Beam: 825 x 106 x 32.5
H3c Beam: 825 x 104 x 32.5

H3a 44,500
H3b 45,000
H3c 43,750

SHP: 180,000
Speed 33.5 (H3a) 33.25 (H3b) 33.75 (H3c)

6 x 18” (2x3)
16 x 6” (8x2)
5 x 4.7” (5x1)
4 pom-poms (maybe ten-gun or 8-gun)
2 x TT (24.5")

Belt: 14” magazines 12” machinery
Bulkheads: 12” forward 10” aft
Barbettes: 14”
Turret Front: 18” Sides: 14” Roofs: 8”
Conning Tower: 12”, 6” roof CT tube: 8”
Director hood: 5” and 3”
Main deck: 1” burster
Upper Deck: 9” and 8” over mags, 5” and 4” over machinery
Lower deck: 7”, 5” and 4” forward, 7”, 6”, 5” and 4” aft

General Equip: 1,000
Armament: 6,150
Machinery: 6,430
Fuel: 1,200
Armor and Protective plating: 13,250 (H3a); 13,600 (H3b); 12,800 (H3c)
Hull: 16,250 (H3a); 16,400 (H3b); 15,950 (H3c)
Board Margin: 220


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Thanks Red Admiral,
Those twin turret H designs are possible even more interesting than Gs and Ns, taking the idea of keeping the magazines together even further. Do you have the plans of the bigger ones? As I was saying on The Bar page, Furashita's Fleet thread I've always liked the twin turret Richelieu and I've made a drawing in photoshop of how the configuration could have looked with 18" guns. I would be interested in yours and Smurf's opinion.


But now I've got your real H plans I might try mocking up one of them for this thread.

Cheers, Woody
K series Battlecruisers

These are some of the earlier designs and are more like progressed and larger versions of HMS Hood.

K2 and K3(differences shown in Italics)

Oct. 1921

LxWxB: 850 (885 oa) x 106 x 33 33.5ft
Disp: 53,100 tons 52,000 tons
SHP: 144,000
Speed: 30knts

8 x 18” (4x2) 9 x 18" (3x3)
16 x 6”
6 x 4.7”
4 pom-poms
2 x 24.5" TT

Protection: (same for K3 design)
Belt: 12”
Bulkheads; 11”
Barbettes: 10” and 12”
Turret Front: 15”Sides: 12” Roofs: 8”
Conning tower:10”, 12”, 15” 8” roof Tube: 11”
Director hood: 6” and 4”

Main Deck: 1” (over magazines)
Forecastle Deck: 1.25-1.5” Upper deck: 7” and 6”
Lower deck: 6”, 3” and 2” forward
6” and 3” aft

Weights at Legend Displacement(tons)
General equipment: 1,000
Armament: 8,770 8,670
Machinery: 5670
Fuel: 1,200
Armor and protective plating: 17,310 16,060
Hull: 18900 19,150
Board margin: 250


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red admiral said:
K series Battlecruisers

These are some of the earlier designs and are more like progressed and larger versions of HMS Hood.

More fantastic designs. They were doing pretty well to get 9 x 18" guns and 30 knots out of a 53,000 ton ship. Were these ships killed by the Washington treaty or did they loose to the N3? The configurations are more conventional than the H3s though. To me the H3b's format is the most intriguing. It only has 2 turrets and ,though I understand the desire to space them closely for armor coverage, I don't see the point in having the rear turret able to fire neither forward or rearward, especially as the front turret is mounted high enough to fire forward over another. Any ideas why this might be? It's my favourite for a mock-up though.

Cheers, Woody

PS: Nobody's commented on my Super Richelieu. If it's infantile you can say so, I can take it. I realise I put too many AA guns around the forecastle, limiting the B turrets field of fire but at least tell me if you spotted which ship it was faked from.
Were these ships killed by the Washington treaty or did they loose to the N3?
Basically, the K's were just too big for their time, chiefly too few possible docks. The design series went through I3 (G3 speed and layout 18" guns; the H's 2x3 18" forward on about 45000 tons to G3 when they gave up on over 30knots with 18" and settled for 16".
Hi guys,
I've had a crack at the H3b but as it's my fictional interpretation I put it in the Models and Fan Art section:


It's still a work-in-progress. I couldn't find enough deck clutter source material pictured from the right angle. The secondaries are from HMS Vanguard and I could find any 'Pom poms' (at the right angle) to recreate. The whole image needs more work to look photo convincing but I wanted to post it anyway to get your comments. Please tell me what and where these and other details should be placed. It's still an interesting looking beast though and I thought it would be nice to see it in (sort of) 3D. I' can't think of any other ship quite like it.

Cheers, Woody
I'll carry on with the I-series and other soonish.


Artist's conception of M3 Battleship design (foreground) and H3b Battlecruiser design
Painting by Geoff W. Hunt from "British Battleships of World War Two"
Hi Guys,
After a small mishap, I've montaged up a G3 for your consideration.
Cheers, Woody

J3 Battlecruiser

A very similar design to K3 but smaller with 9x15" guns. This design is comparable to Hood.

Nov 1920

LxWxB: 810 (860oa) x 104 x 29
Disp: 43,100
SHP: 151,000
Speed: 32

9 x 15”
12 x 6”
6 x 4.7”
4 pom-poms
2 x TT
Belt: 12”
Bulkheads: 12”
Barbettes: 12”
Front: 15”
Sides: 12”
Roofs: 8”
Conning Tower
10”, 12”, 15”
CT tube: 11”

Director hood: 6” and 4”
Main Deck: 1.25”
Forecastle Deck: 2”, 1.5” and 1.25”
Upper deck: “
Lower deck
4”, 3”, and 2” forward
4”, 3”, and 2” aft

General Equip: 910
Armament: 6,740
Machinery: 5,670
Fuel: 1,200
Armor and protective plating: 12,780
Hull: 15,640
Board Margin: 160


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L series Battleships

Massive designs that are unmatched in armouring. Huge armament of 18"/45 guns coupled with 18" belt and 13"-8.75" deck armour that makes them unvulnerable to most shellfire.


Jun. 1920

LxWxB: 850 x 106 x 31 x30.5
Disp: 50,750 tons 49,100tons
Speed: 25 26

8 x 18” 9x18"
16 x 6”
4 x 4.7” 4x4"

Belt: 18”
Bulkheads; 15”
Barbettes: 18”
Front: 18”
Sides: 12”
Roofs: 9”

Conning tower:

Upper deck: 8.75” (flat) and 13” (slope)
Lower deck: 3.5”, 5.5” and 8.75” forward
8.75” aft

Weights (tons)

General equipment: 1,000
Armament: 8,850 8,000
Machinery: 3,350 3,560
Fuel: 1,200
Armor and protective plating: 17,600 17,000
Hull: 18,500 18,100
Board margin: 250


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In view of recent comments with regards to copyright etc. the images in this thread will be reduced in size to 320px. Source given in first page; Best source for these ships is The Grand Fleet by D K Brown.
Although the N3 ships were never officially named, it has been suggested that if they had been built they would have been named after the four patron saints of the countries of the United Kingdom: HMS St. Andrew (Scotland), HMS St. David (Wales), HMS St. George (England), and HMS St. Patrick (Ireland)

Officially the G3 class were never given names, however several ideas on possible naming schemes have been advanced. Among these names speculated for the four ships planned were HMS Invincible, HMS Indomitable, HMS Inflexible and HMS Indefatigable from the First World War battlecruisers. Another suggestion is that they were to be another "Admiral" class and carry the names HMS Nelson, HMS Rodney, HMS Anson, and HMS Howe.


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