JFC Fuller said:
Actually it had been planned to perform much more substantial upgrades to Rodney and Nelson but the outbreak of war got in the way. The consensus was that the best approach was a one-for-one replacement of the 6" gun turrets with 5.25" weapons, new machinery for an extra 2 knots and some minor armour improvements.
A G3 would actually have quite a bit of scope for improvement in a 1940s rebuild, the 16x 6" could become 16x5.25" removing the need for the 4.7" and freeing up space for additional light weapons. Also, the design was at the limits of its hydrodynamic performance so more power was not necessary thus machinery improvements could be used solely to increase fuel efficiency (thus extending range) and saving weight for additional protection- beyond the substantial amount already fitted.
I have seen the dates for the reconstruction program somewhere which went on to the Hood in 1941-3 and I think it was the Malaya next in 1942.
Rodney probably would have followed around the time the last of the KGV class was in service and the R class would have been scrapped at the same time.
So that would be 1943-4 for Rodney (she was considered to be a dog in 1939!) so similarly the first of the G3s.
I doubt they would have tried to get any more speed out of them. To go from 32 knots (if they ever did make that!) to 34 knots requires a power increase of 20%, 160,000 to 192,000 shp.
In the case of the Renown they wanted a little extra speed to make sure she could keep up with the new aircraft carriers which she was intended to ride shotgun over, hence fitting the same 4.5” DP guns. I think it more likely they would have aimed for the same 160,000 shp output and figured anything extra would be a bonus.
I’m sure they would have concentrated on improved the subdivision and improve the ammunition stowage as in the original design space was tight for the this especially the 6" guns.
The ships covers indicate what a balancing act the whole design was.
I have always wished there was an N3 cover - I've spent hours trying to work out how to get 18" turrets into a shortened G3.
In fact it was so tight I think that the DNC might have finally won the battle to get rid of the torpedo tubes!
For the replacement of the engines/boilers look at what they did to Renown when when they reconstructed her. They left the bulkhead between the Boiler rooms and Engine rooms where it was.
Bearing in mind Renown had bulky large tube boilers originally - not the more compact small tube ones like Hood & the G3s.
They fitted the more compact boilers forward of this bulkhead so leaving more space at the forward end.
There would not be such a saving in length as Renown but it would have left enough room to fit magazines suitable for AA weapons like 4"guns? or pom-poms - later converted to 20mm/40mm stowage?
Due to the large engine rooms aft of this bulkhead - the new ones could have been around 20% smaller!
Vanguard had 130,000 shp - to get 160,000 I figure adding about 3-4 feet to the length of each of her engine rooms would be about right.
That moves the after end of the engine rooms forward roughly 14-15 feet adding about 20% to the volume of the after magazines.
Plus the new engine rooms could have been about 5 feet further inboard.
If the gun makers could have built enough guns then yes I'm sure they would have converted them to 16 x 5.25" maybe even 20 x 5.25".
They could easily have fitted 3 turrets each side aft and there would have been sufficient ammunition stowage with the enlarged magazines and change to single calbre DP guns.
They would not have done it forward as the (old) 6" magazines were too small anyway - see the G3 covers for the comments.
Getting rid of the 6" & 4.7" guns would have freed up deck space for at least a couple more pom-pom mounts, though by 1943 I'm sure the pom-pom would have been on the way out.
Instead they could have fitted a forrest of 20 & 40mm mounts.
It's had to know what the total weight saving would have been, but throwing out the old boilers/engines could have been as much as 2000 tons! The 6" & 4.7" guns maybe another 500 tons.
What would they have done with the weight? Easy! Exactly as Nelson - an armoured deck forward and extensions to the lower edge of the main belt.
Comments were often made about doing this in Nelson and Rodney prior to WW2.
Now with new fire control and the ammunition supply arrangements for the 16" turrets made to work properly the Bismark would have been toast!
I'm sure I saw a contemporary comment about turbo-electric propulsion for these ships. (Can't remember where at the moment but I think maybe it was in the Warship Vol. 1 article.) The upshot was that it would involve a larger volume, weight, greater cost and no particular advantage in reliability. Do some reading on the US Lexington and Saratoga especially re. action damage and you will see that this is a fair assessment in the 1920's.
