Shipbucket

The standard British destroyer weapon through the 1930's into the early 40's was the 4.7" open mounting. In only one class type did the Admiralty try to put this gone into a turret with the L & M. class. The biggest drawback with this weapon was the low elevation of the mountings. A high elevation 4.7" mounting was designed for the Nelson class but this was a large heavy mounting and with fixed ammunition it was not suitable for use on destroyers (or any other ship for that matter). The answer was to produce a dual purpose (DP) mounting of a size that could be used in all classes of ship from destroyers up to battleships and aircraft carriers. The Admiralty started work on DP weapons as early as 1931 and with a bit of thought could either have retained the 4.7" size or gone to the 4.5" gun size that we are familiar with today. The trials with the fixed ammunition on the Nelsons 4.7" should have put that option out of contention for any future weapons. Unfortunately the Admiralty tried the same fixed ammunition system for the 4.5" weapon developed in the late 1930's that became the BD/UD mountings on the Renown, Ark Royal etc with similar results. At that time the only way to go for light weapons of this size was the bag and shell separate arrangement.

I do not know how many zillions of 4.7" rounds the Admiralty must have had in stocks all over the world, but it must have been an awful lot. Keeping the 4.7" gun size for me is a no-brainer, all they needed to do was to produce a decent dual purpose mounting with 80-85 degree elevation that could be fitted to destroyers and other ships in single open mounts and twin light or armoured turrets for the capital ships. Starting development in 1930-31 the Admiralty could have had such weapons available in 1935-36 and these could have been fitted to the H (possibly) and I (definitely) class destroyers. Instead of the four single open mountings, two light weight twin mountings could have been mounted and the end result could have looked like the ship below.

The mounting I have used is big enough to take either a 4.5" or 4.7" high angle gun. Changes to an I class ship would be mainly in an increase of breadth to take the turret, a slightly longer hull to compensate for that and also to give room for the quad 2 pounder mounting between the funnels. From a 1500 ton ship, the alterations would probably have taken it to a 1600 ton ship and would have been a step between the A-G types and the following J design which I would expand to a 1750 ton design with 3 turrets.



With the drawing, removing the forward superfiring mount superstructure allows the turret to be mounted further aft to avoid having too much weight forward. The extra weight of the turret is somewhat compensated for by the removal of the mounting superstructure, which could have been removed entirely but as with the later HMS Savage I have retained enough of the superstructure to mount some light AA weapons.

Having had all the experience lately with drawings for the A-I series and the J, K, N, series of destroyers, finding an alternate was not difficult.

With the alternate J, I have kept with the 3 boiler arrangement to keep the Chief of Engineering happy, otherwise it is essentially a lengthened I to take the 3rd turret.


(Yes Kim I actually drew a real COA for Jupiter)


As an alternative to the turret mounted 4.5"-4.7" could be a more AA oriented 'H' class destroyer. But as noted elsewhere the Admiralty was worried about being outgunned by its foreign contemporaries. So the chances of a reduction in gun armament is unlikely especially as the Admiralty already had the 6x4" sloops in production.

My questions would be,
1)
Why that turret with widely split guns, rather than accept from the start a rotating trunk and save weight ?
2)
What 4.7 gun to use OTL the RN had 4+ in use, so not sure they can use each others shells to save costs & logistics.

JSB, please take the time to compare the turret I have drawn here to the one used on L/M type. They are quite a bit different.

With 30-40 A-G type DD's in service there would be a few shells for those guns floating round the armouries.

It might just be me but I still think it looks like the barrels are separated by a wide central 'bit' ?
I would go for a 4.5'BD mount (flat fronted) but with the mount taller (like yours) as it will be raised up rather than sunk and with split ammo for ease of handling.

Added HMS Jupiter to first post.

JSB, I will add the BD mount to that graphic for you to see them together.


Pictures of BD mounting showing "Below Deck" portion can be found here: http://www.dockmuseum.org.uk/archive/br ... &subtitle=

My only problem is that all the other RN turrets look flat at the front other than the L&M so I think your looks like it will have something big between the guns.

My try at what I'm trying to say with words (probably badly)

"that turret with widely split guns" was not a turret, but a weatherproof mounting.
Turrets have trunks below deck which rotate with the guns, so that ammunition is always supplied near to the gun breech.
Open mounts, as in the A-I, Tribal and JKN destroyers have the ammunition supplied behind the guns, and picked up and loaded through the wide open back of the mounting.
The L,M mounts were enclosed to protect the crew from the weather, but with no rotating trunk below deck, the ammunition was supplied at the centre of the mounting, hence the wide spacing of the guns to leave room for the crew to collect and load the ammunition.
The gun was L50, not L45, with a larger chamber volume, firing 62lb shells instead of 50lb shells of the earlier guns.
More details: http://www.navweaps.com/Weapons/WNBR_47-50_mk11.htm

The RN gave priority to surface fire in the late 1930s designs. The best available HA weapon was the 4in. Four of the L class destroyers had four 4inHA twin mounts, which served them quite adequately as DP weapons in the Mediterranean. The loss of individual gun power in surface actions was offset by eight guns instead of six and their higher rate of fire.

The Twin 4.5in Mks IV and VI on Battles and Darings etc, were turrets.

Yes, but I maybe mistaken but I was thinking that Krakatoa's ship has an AU turret rather than a OTL weatherproof mounting ?

I think that the OTL route was the wrong one due to the WP mounting not actually saving any weight but just a result of early cost saving (due to 30s cuts probably) but not gaining anything from it ? I think a full turret is the way to go (unless you go cheap/easy and open).

(PS feel free to come a ripe mine apart as well)

Glad to see I have stimulated some discussion with these drawings.

What I have drawn is a true 'turret' not a weatherproof cover as with the L&M's. The problem with having any 4.7" twin enclosed mounting, everyone jumps in to say "those were rubbish", and I am the first to agree. The 4.7" twins on the L&M's had so many drawbacks that the Admiralty rearmed four of them with twin 4" as related by Smurf. Put a true power operated turret in place (80+ degree elevation) with proper loading facilities of either 4.5" or 4.7" bag and shell guns and you have a slightly heavier but much more useful mounting. Which is why I increase the dimensions a bit to compensate.

I totally agree with the logic of your plan, I just think your drawing at the moment doesn't really make me think of a good turret but something like the L&M version.

(I also think looking at navweps pics that your topveiw of the 4.5' has the guns to far apart, I would have them 3pixels apart rather than 5 as they are quite close together ? )