Shipbucket

The Mark 3 mounting didn't exist in 1938. In fact the 40mm Bofors didn't enter service with any of the major navies for another three years.

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Yes agreed, I need to make my own gun/mount for this AU .......

I want a good heavy AA gun and the Bofors 40 mm/60 (1.57") Model 1936 is the obvious choice (the other is an improved 2pdr ?)

From my looking at navweps, So with a bit of cash I think you could easily have them in production by 37/38 for my BB (who would get priority IMO)

How would you think a quad Bofors for the RN in 37 should look ? any comments help welcome !

Thanks JSB

Hi JSB,

Given the sheer volume of 2pdr ammunition that the UK had at that point, you might find that, particularly for a "we need it yesterday" design, some improvement to the 2pdr (or, depending on the rush, the one that they actually shipped. I'm not sure but I think that in 1938 nobody really knew quite how the pom-pom would compare to other AA of similar calibre in combat)

Regards,
Adam

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The thing with the 2 pdr is that,

1) I think most of it was built post 37ish (at least the multiple mounts, 4 and 8)

2) there are actually more than 1 type (Yay RN standardisation again ) LV and HV and the HV was introduced in 38

so Im not sure you get much benefit from keeping it as your gun ?

I think I may go with a Bofors barrel in the Pompom mount ? introduced in 38 instead of the OTL 2pdr HV (LV 2pdr still in 2nd echelon use)

would this work ?

JSB

now if only I could use layers with MS paint

No.The Bofors is fed from the top with 3rd, 4rd or 5rd clips. Stacking guns on top each other is not an option. They also require a fair amount of crew to keep them fed, at least one loader per barrel which is why all the Bofors mountings where open until the Italians came up with a 142 round magazine for it in the 1950ies IIRC.

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I did say sorry if I didn't spell out what breach and feed mechanism I would use

The options would be,
- Pompom style belts
or
- Bofors style clips from above

I was thinking belts would be faster and save men (as long as you can get them to work and not jam !) do you think this is the wrong way to go ? So a Pompom but with Bofors 40/60 ballistics ? (and hopefully more cash spent fixing any problems pre war)

Or should I ditch it and just go for plain Bofors guns ? (ie Mk3 with cosmetic changes ?)
JSB

[quote='Navweaps']The internal gun mechanisms were very complex and required much care and skilled maintenance to keep them in working condition. Jams and stoppages were frequent, although the linked ammunition proved to be more reliable in service than the older belt-fed guns.[/quote]
The Pompom had enough issues without burdening it with a shell that's 1.5 times as energetic. The thing that made the Bofors the best light AA gun of the war was its reliability, not its ballistics. Not that they were anything to sneeze at either.

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Krakatoa said: "So that's 6x15", 24x4" and 48x40mm. That's a lot of AA for 1938"
You might like to consider Design 16A, 1930
[The 1930 designs fell into two groups. 16A was what might have been built if a. money allowed; b. the 10 year BB 'holiday' after Washington had not been extended; c. no smaller BB size could be negotiated in the 1930 London Treaty discussions. The other designs were studies of what could be done with smaller BBs, in particular smaller guns, and ranged from 14B with 8x14in on 29,000tons down to 10C with 8x10in on 22,000tons.]
But back to 16A: quite a detailed spec exists, but in brief
35,000tons 4x2 16in (complying with Washington) Belt 13 - 11in; deck 6.25 - 4.25in; turrets 15in face, 6in roof; 45,000shp 23knots.
Secondary and AA:
6x2 6in (with 60 deg elevation as Nelson for AA barrage fire);
4x2 4.7in HA (recall Hood's request for details of the 4in twin trialled on Resolution. The drawings of the 1930 BBs indicate a similar style for the proposed twin 4.7)
6 Mark M pompoms with 500 rounds per barrel. The Mark M in 1930 was the 8-barrelled version.
That is quite a formidable AA fit 7 years earlier than but quite comparable to JSB's design, so that is not unrealistic.

Having done it by eye rather than spring sharp I now get to try and sim it....

Here is my best guess at a 35kt KVG , ALT RN bb ready in 38 laid down 1937

Displacement:
32,926 t light; 34,998 t standard; 37,690 t normal; 39,843 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(713.47 ft / 700.00 ft) x 100.00 ft x (35.00 / 36.50 ft)
(217.46 m / 213.36 m) x 30.48 m x (10.67 / 11.12 m)

Armament:
6 - 15.00" / 381 mm 42.0 cal guns - 1,938.00lbs / 879.06kg shells, 150 per gun
Breech loading guns in turret on barbette mounts, 1912 Model
3 x Twin mounts on centreline ends, majority forward
1 raised mount - superfiring
24 - 4.00" / 102 mm 45.0 cal guns - 36.00lbs / 16.33kg shells, 400 per gun
Quick firing guns in deck and hoist mounts, 1935 Model
12 x Twin mounts on sides, evenly spread
12 raised mounts
48 - 1.57" / 40.0 mm 45.0 cal guns - 1.96lbs / 0.89kg shells, 3,000 per gun
Anti-air guns in deck mounts, 1937 Model
6 x Quad mounts on centreline ends, evenly spread
6 raised mounts
6 x Quad mounts on side ends, majority forward
6 double raised mounts
Weight of broadside 12,586 lbs / 5,709 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 13.0" / 330 mm 405.00 ft / 123.44 m 22.00 ft / 6.71 m
Ends: 4.00" / 102 mm 260.00 ft / 79.25 m 8.00 ft / 2.44 m
35.00 ft / 10.67 m Unarmoured ends
Main Belt covers 89 % of normal length

- Torpedo Bulkhead - Additional damage containing bulkheads:
2.50" / 64 mm 665.00 ft / 202.69 m 35.00 ft / 10.67 m
Beam between torpedo bulkheads 64.00 ft / 19.51 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 13.0" / 330 mm 6.00" / 152 mm 13.0" / 330 mm
2nd: 1.00" / 25 mm - -
3rd: 0.50" / 13 mm - -

- Armoured deck - single deck:
For and Aft decks: 6.00" / 152 mm
Forecastle: 0.00" / 0 mm Quarter deck: 2.50" / 64 mm

- Conning towers: Forward 4.00" / 102 mm, Aft 1.00" / 25 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 125,066 shp / 93,299 Kw = 30.00 kts
Range 5,000nm at 20.00 kts
Bunker at max displacement = 4,845 tons

Complement:
1,352 - 1,758

Cost:
£10 ish million After using old 15' turrets

Distribution of weights at normal displacement:
Armament: 1,712 tons, 4.5 %
- Guns: 1,712 tons, 4.5 %
Armour: 14,437 tons, 38.3 %
- Belts: 5,423 tons, 14.4 %
- Torpedo bulkhead: 2,153 tons, 5.7 %
- Armament: 2,213 tons, 5.9 %
- Armour Deck: 4,527 tons, 12.0 %
- Conning Towers: 121 tons, 0.3 %
Machinery: 3,466 tons, 9.2 %
Hull, fittings & equipment: 13,010 tons, 34.5 %
Fuel, ammunition & stores: 4,764 tons, 12.6 %
Miscellaneous weights: 300 tons, 0.8 %
- On freeboard deck: 200 tons
- Above deck: 100 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
70,949 lbs / 32,182 Kg = 42.0 x 15.0 " / 381 mm shells or 13.7 torpedoes
Stability (Unstable if below 1.00): 1.17
Metacentric height 6.7 ft / 2.0 m
Roll period: 16.2 seconds
Steadiness - As gun platform (Average = 50 %): 60 %
- Recoil effect (Restricted arc if above 1.00): 0.59
Seaboat quality (Average = 1.00): 1.20

Hull form characteristics:
Hull has a flush deck,
an extended bulbous bow and large transom stern
Block coefficient (normal/deep): 0.538 / 0.546
Length to Beam Ratio: 7.00 : 1
'Natural speed' for length: 30.96 kts
Power going to wave formation at top speed: 56 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 27.00 %, 37.00 ft / 11.28 m, 25.00 ft / 7.62 m
- Forward deck: 30.00 %, 25.00 ft / 7.62 m, 24.00 ft / 7.32 m
- Aft deck: 28.00 %, 24.00 ft / 7.32 m, 24.00 ft / 7.32 m
- Quarter deck: 15.00 %, 24.00 ft / 7.32 m, 25.00 ft / 7.62 m
- Average freeboard: 25.79 ft / 7.86 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 86.4 %
- Above water (accommodation/working, high = better): 171.9 %
Waterplane Area: 50,299 Square feet or 4,673 Square metres
Displacement factor (Displacement / loading): 123 %
Structure weight / hull surface area: 184 lbs/sq ft or 898 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.93
- Longitudinal: 1.90
- Overall: 1.00
Adequate machinery, storage, compartmentation space
Excellent accommodation and workspace room
It doesn't match the above ship due to length to save weight and hull depth so will have to edit my drawing.

Feel free to take it apart ......

JSB

Edit - first post updated (for hull size) will redo with a new AA mount later.