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Danae Class AA Cruiser conversions
http://67.205.157.234/forums/viewtopic.php?f=15&t=5637		 Page 1 of 3
Author:  Krakatoa [ October 3rd, 2014, 11:09 pm ]
Post subject:  Danae Class AA Cruiser conversions
So far I have produced the D class variations for overseas buyers, real D class ship, and now a couple of D class Anti-aircraft conversions. All of the ships share the same hull and machinery. It is the fittings allocated to each version which denotes its useage.

Only two D class ships had AA conversions underway prior to the outbreak of war. Once war started no more conversions were contemplated as the ships needed to be at sea no matter what their condition. The conversion process had taken 18 months per ship and while the result was extremely useful the base ship was still a 20 year old cruiser. The money required for the conversion process outweighed the ships usefulness, and even if war had not broken out, further conversions would not have been proceeded with. It was more cost effective to build more Dido class cruisers.

[ img ]

The most expensive part of the conversions was stripping out all of the old 6" fittings (guns, shell handling, magazines) and replacing them with the new twin 4.5" turrets, barbettes, shell hoists and magazines. The control systems for the new guns also required both space and money to give the ships the necessary directors for the different weapon systems. All the new equipment required the removal of all the old weapons and torpedoes to ensure that added topweight was kept to a minimum.

The Daedalus shows the ships as they completed their original renovations, while the Dryad is after the refitting with the new 40mm weapons.
Author:  JSB [ October 4th, 2014, 6:39 am ]
Post subject:  Re: Danae Class AA Cruiser conversions
Nice ! :mrgreen:

-Turrets are nice but would open mounts not make more sense ?
Ie have the 4.5 off Scylla and Charybdis so you don't have to fit deep stalks into the ship not designed for them ?

-Not sure I would go without any torpedoes at all ? makes you very venerable to anything bigger than a destroyer.

- would swapping the 8x pompom for 2 more 4x not give you better arcs ? (especially if they are pushed out to the side as far as possible ? and give the front ones the same as well)

- would such old ships get rebuilt with new guns in 43 ? (and don't really like the arcs of the forward quads can you swap with directors behind them ?)

JSB
Author:  Krakatoa [ October 4th, 2014, 7:26 am ]
Post subject:  Re: Danae Class AA Cruiser conversions
JSB,

Open 4.5" would be ok if they were available in this timeline. In RL the open 4.5" is produced for the Ark Royal, which is a different ship in this 'now'.

Torpedoes were always the first things to go when fighting topweight, these two ships would always be around bigger ships acting as AA escorts, those ships would have the torpedoes or big guns necessary.

The heavy AA guns are replacing the 6" mountings, so a single octuple mounting replacing the mid-aft 6" where it can use the 6" handling rooms is fine. No expensive alterations required. Same with the forward quads/40's they are where they are without having to make structural changes to fit them. To move them one step back would require a lot of structural work to make the area strong enough to take the quads/40's.

In 1943 these would still be in use as frontline AA escorts as such ships were few and far between, upgrading the AA suite is not outlandish. (And would only be done if one or both of the ships still existed at that stage and had not been sunk by enemy action - yet to be determined.)
Author:  Hood [ October 4th, 2014, 8:38 am ]
Post subject:  Re: Danae Class AA Cruiser conversions
An interesting exercise.
I think it works well and the topweight would be reasonable, perhaps the later-war with all those Bofors more borderline. I think overall this is a practical layout and would have worked well. Fitting the turrets and hoists is going to be the biggest work here. Don't forget the internals too, all these extra pom-pom directors, radars and power hoists and powered turrets are going to need extra electrical power. You might have to sacrifice internal space or some boilers for additional generators. The drive to gain adequate electrics was a limiting factor in all these conversions. Also, would kind of capacity would the 4.5in magazines have for sustained fire? I'm wondering if 3x2 4.5in would allow you to carry more ammo to keep in action longer, important if crossing the Med for example.
Author:  Krakatoa [ October 4th, 2014, 10:13 am ]
Post subject:  Re: Danae Class AA Cruiser conversions
Thank you Hood,

The question of extra electrical power I had not given much thought to. My mistake if I want to add all the extra power operated weapons and electronics. With only 28-29 knots on their original machinery to remove boilers to supply electrical generation would adversely affect speed (down to 25 knots?). The only other way to alleviate the problem would be to do a machinery change as was done to the BB/BC conversions. A powerplant of the L-M class DD's (that were being built at the same time as these ships were being converted) could replace the original machinery. This would probably give a saving in space and weight as the later machinery package would be better. The L-M machinery gave 48,000shp compared to the D's 40,000shp which should give the extra power to generate the electrical power necessary without loss of speed. This of course would make the conversion even more expensive and longer (possibly) and would certainly limit the number converted to the first two only.

The 4.5" magazines would be using the vacated 6" magazines which as you point out may not be big enough to supply/hold enough shells for sustained fire in the Med where I would expect these ships to spend most of their service, Norway was the other early area that took a toll on the AA ships. (Which is why I am not sure if they would survive to be upgraded later in the war.)
Author:  Hood [ October 4th, 2014, 1:06 pm ]
Post subject:  Re: Danae Class AA Cruiser conversions
Looking at Freidman now.
Real D Class conversion: 4x2 4.5in, 1x4 pom-pom, 2x4 0.5in HMG. 4.5in mounts ordered 1938 to keep production flowing, rebuild expected to take 12 months, 3x begin 1 January 1940 to complete Jan 1941, 1 to complete by May 41 and others rearmed beginning 1941. Mid-39 War Plan cancelled conversions and 4.5in mounts released for other purposes including rearming Scylla and Charybdis.
The four 4.5in mounts and two HACS would weigh 130 tons. For Delhi 5x1 5in and two Mk37 systems worked out at 113 tons. An alternative 5x2 4in with two HACS would weight 82 tons.
Delhi used the 6in magazines for her 5in mounts without changes. I note the 4in D Class conversions had 500pg for 5x2 4in so there should be ample room. I'm not sure of the rpg for the 5in.
There seems to be no extra generator spaces for Delhi so I'm assuming a simple replacement of the existing generators would suffice.
Author:  Novice [ October 4th, 2014, 7:09 pm ]
Post subject:  Re: Danae Class AA Cruiser conversions
Most AA cruiser conversions of the 'C' class cruisers used existing generators, but with more power. The usual generator was 25kw one and the modernization changed the generator in to a 40kw one (If I'm not mistaken with the generators output).
The larger generator was driven by the engines using steam from the boilers, and so occupied the same space. The auxiliary (usually Diesel driven), was added to ships only after war experience showed the need.
Author:  Krakatoa [ October 4th, 2014, 7:34 pm ]
Post subject:  Re: Danae Class AA Cruiser conversions
Interesting information Hood & Novice,

The 5" mounts used on Delhi did not have hoist loading so did not require extra electrical power for that whole system. The original 5x2-4.5" nominated by Friedman were the same as those fitted to Ark Royal (37) and were open mounts with an AA capability so would not have required the extra electrical power required for the turrets I have used. Your original comments on the requirement for extra electrical power to run everything was spot on. Unfortunately looking in Navweaps they do not seem to have an entry for Ark Royal (37)'s 4.5" mountings, they are lumped in with the BD mountings and not referred to specifically for a lot of the data. Does Friedmans give any layout data of where the 5 twin mountings would be placed? The extra mounting spot would have used the quad 2pd.

If I can get the placement data for the real D conversions I will do a separate entry for the Never Were Forum.
Author:  Hood [ October 5th, 2014, 10:50 am ]
Post subject:  Re: Danae Class AA Cruiser conversions
No, Freidman doesn't say where the mounts would be.
The only choices are A, B, X, Y or A, Q (aft of funnels), X, Y.
Since there was to be only one quad pom-pom, it would have been either in B or Q position. The C's had the pom-pom in B position, that might make more sense as having a 4.5in mount in Q position makes use of the midships 6in magazine and A mount can use A and B for more ammo/ split some for 2pdr. The HMGs would be either beside the bridge structure or where the forward midships 6in ahead of the funnels was.

The 4in version would have five mounts arranged like Delhi with her five 5in. There is no mention of the pom-pom fit, but I'm guessing like Delhi the 4in ships might have received two quad mounts abreast the former 6in position between bridge and funnel.
Author:  Krakatoa [ October 5th, 2014, 11:41 am ]
Post subject:  Re: Danae Class AA Cruiser conversions
Thank you Hood,

I'll try a couple of different outfits and post them, see which one makes more sense.

As I have done with these conversions would the real D conversions have removed the tripod to allow the HACS to be mounted at the back of the bridge.
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