Quick mods to the Courageous class

[Admiral Beez]

Nothing indepth, but had HMS Courageous and Glorious survived intact to the end of 1940 after HMS Illustrious and Formidable have entered service, what quick mods or updates were possible? My thinking is a forward flight deck extension (with catapults deleted), keeping it light weight, with open bows just with vertical support columns like IJNS Kaga below - not ideal for the North Atlantic but should be fine for the MTO and Indo-Pacific. We'd need to build the extensions in advance so to limit the dockyard time.

But considering how little was done with HMS Furious, maybe that's out of the question.... or even unnecessary given the avgas and space restrictions to the CAG size. What mods do you think are both useful and feasible? Aft round down removal? Increased AA, communications or radar?

 

[SaparotRob]

How extensive a refit would it have been to enlarge the elevators/lifts? The flight deck extension seems the easiest improvement. Could the massive island structure be somehow reduced to improve sea keeping?

 

[Admiral Beez]

How extensive a refit would it have been to enlarge the elevators/lifts? The flight deck extension seems the easiest improvement. Could the massive island structure be somehow reduced to improve sea keeping?

I think lift enlargement is out of the question for a fast mod, but really isn't necessary. The Courageous class 46-by-48-foot lifts, shown below moving the ship's band were wide enough for every non-folding aircraft the FAA operated.

The island on the Courageous class is actually rather compact once you account for the necessary funnels.

I'd keep it, and add more AA on sponsons to its outer edge, like HMS Victorious below.

 

[SaparotRob]

More AA Drill Sergeant! More AA!

 

[Admiral Beez]

More AA Drill Sergeant! More AA!

Indeed, on that we wholly agree. When they were lost the Courageous class had sixteen single 4.7" QF DP guns. That's it, no 2-pounder pom-poms or even automatic 20mm singles. This isn't unusual for pre-war carriers, but if they survive into 1941 and beyond I'd like to see these ships absolutely bristling with 20mm and 40mm single and multi-barrel AA. That's my priority one mod, more AA, and plenty. But we'll need to find accommodations and rations for all these extra gun servers.

 

[EwenS]

Indeed, on that we wholly agree. When they were lost the Courageous class had sixteen single 4.7" QF DP guns. That's it, no 2-pounder pom-poms or even automatic 20mm singles. This isn't unusual for pre-war carriers, but if they survive into 1941 and beyond I'd like to see these ships absolutely bristling with 20mm and 40mm single and multi-barrel AA. That's my priority one mod, more AA, and plenty. But we'll need to find accommodations and rations for all these extra gun servers.

C&G had 3 octuple Pom poms and 2 quad 0.5" fitted from the mid 1930s. 1 Pom Pom Mount on flight deck abaft the island, with the other pair on the lower flying off deck, ahead of the 4.7" mounted there. I don't know where the 0.5" were fitted.

Look to Furious for expected armament upgrades. So maybe another octuple Pom Pom ahead of the island and 20mm (Furious ultimately had 22). Don't expect huge numbers, it was 1943 before the Illustrious class received more than 8-10. Possibly also an HACS, but where to fit it given the relatively small bridge structure ahead of the funnel, with the mast on top of it. If anything the island needs increased in size, not reduced.

The other change would be to add radars of different types as time went on. Start with probably Type 281 air warning in 1941/42, exact timing depending on the theatre they were being employed in. Quite how that would be fitted is open to question due to the Type 72 beacon fitted to these ships and Ark Royal at the masthead, which AIUI precluded any mast structure above (the Illustrious class had an entirely different mast layout to accommodate it, but Furious kept the original fit to the end). So maybe another mast at the aft end of the island.

Given the pressures of war I believe it is unlikely any other structural modifications would have been made just as happened with Furious. In particular I doubt that any weight to extend the flight deck forward would have been available. The explanation lies in the fine battlecruiser bow construction of these ships and how they rode heavy seas. Add more weight and their seakeeping gets worse. See these photos for what I mean.

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HMS Furious taking heavy seas over her bow off Norway, 1940.[800x609] | Royal navy aircraft carriers, Royal navy ships, Royal navy

Apr 20, 2015 - Post with 48 views. HMS Furious taking heavy seas over her bow off Norway, 1940.[800x609]

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Just like Furious, their utility as fleet carriers falls off dramatically after 1942. No barriers were fitted in 1939 (nor to Furious although it was considered a good idea by at least one CO but never carried out). So no deck parks. Also a lack of petrol capacity (34,500 gallons in 1939 for a 48 plane air group). Furious had 20,800 gals in 1939 for 36 aircraft, Illustrious 50,650 gals for 33 aircraft, and Ark Royal 100,000 gals for 60 aircraft. Aircraft types coming into service after that were much thirstier. Finding space for more capacity to meet RN safety standards would have been difficult.

 

[Admiral Beez]

In particular I doubt that any weight to extend the flight deck forward would have been available. The explanation lies in the fine battlecruiser bow construction of these ships and how they rode heavy seas.

It's a good point. My thinking was the kinder waters of the MTO and Pacific, along with the removal of the twin cats might allow for a relatively light weight forward extension. Not that the Pacific wasn't capable of chewing up carriers.

 

[SaparotRob]

Awwww. It has a "frowny" face!

 

[Thumpalumpacus]

Extend the flight deck, plate up the lower forecastle, and shift stuff around to gain extra fuel stowage.

You'll never get a first-class carrier out of the hull, but you can certainly get better.

 

[Admiral Beez]

You'll never get a first-class carrier out of the hull, but you can certainly get better.

That's kinda where I'm going. Add crash barriers and outriggers to enable deck parking, keep it simple. These are two 30 knot carriers with relatively up to date machinery (better than Furious anyway). If they live to see 1941 they'll be very useful. For starters at Taranto in Nov 1940.

Is the bow forward of the hangar truly so daintily constructed that adding a 200 ft, open extension would cause the keel to snap? If so then we can still flatten the aft deck to increase useful space and fill the old flying off deck with AA.

 

[Thumpalumpacus]

Is the bow forward of the hangar truly so daintily constructed that adding a 200 ft, open extension would cause the keel to snap? If so then we can still flatten the aft deck to increase useful space and fill the old flying off deck with AA.

I hadn't heard that, but I can believe it. They were huge ships built to 1910s light cruiser standards.

 

[EwenS]

A number of points about the construction of C&G.

Firstly they were designed with a long, shallow and narrow hull. Draught was only 23-26ft, beam 81ft at main deck level, when completed as battlecruisers. Compare that with Renown and Repulse which were only 15 ft longer between the perpendiculars but had 9ft more beam and 4ft more draught as completed with that extra 15" turret forward needing support. A long narrow shallow hull girder is inherently more inclined to bend. Admittedly some extra strength was built in by adding the flight deck and the bulges.

Secondly, they had a very long narrow bow ahead of A turret. A turret would have sat where 4.7" mounts 5 & 6 were located, just ahead of the island. The fore end of the island approximates to the fore end of the battlecruiser superstructure. If you look at them from ahead there is considerable flare on the hull around the forward end of the hangar reflecting a narrow hull at the waterline. It is the same at the stern. The bulges do little for buoyancy in these areas as they don't start until roughly level with gun mounts 3 & 4 and end just aft of mounts 13 & 14.

On conversion they gained a lot of weight. From 19180 tons (22560 tons deep) to 24970 tons (27419 tons deep) for Glorious in 1935. Much of that weight is high up affecting stability. Extending the flight deck forward by up to 200ft just adds to that problem.

As for the aft flight deck extension in Glorious in 1936, Burt in his British Battleships book quotes a report that compared C with G while travelling in company after G had this modification.

"Extension to flying deck is a great improvement. The more gradual and extended slope has produced a surface which gives an uninterrupted air flow enabling pilots to land further aft without having to fly through the turbulence set up by the steeper and shorter round-down of Courageous type. There is no question of any down when coming in to land.

It was noticeable that when we were in company with Courageous, aircraft touched down further forward than us which indicated a higher approach taken by the pilots in order to avoid the eddies caused by the abrupt round-down. Although total extension amounts to 41ft, only 3ft 6in of this is level deck so that very little ranging area is gained.

Most aircraft touch down with their hook on the forward end of the after lift and wheels a little ahead. Maximum number of our striking force is 24 ie 18 ranged on deck, 1 behind each accelerator and 2 ready each side to take onto trolley."

The flight deck extension was planned for C in her 1939 refit, but with war looming, never implemented.

So what does this mean for your proposals?

Well the aircraft G operated in 1936 were a mixture of biplane torpedo bomber types including the Swordfish she carried in ww2. So flattening the flight deck aft is clearly not all good news. While it might help with the numbers of aircraft that can be ranged aft for launch, it doesn't appear to do much for landing them back on. Unless the FD can be extended forward there is no more room than historical for a deck park forward. Note the RN made extensive use if wind tunnel models to check on airflow over the flight deck of its carriers and the shape of islands before concluding that the large round downs were of benefit. As aircraft got heavier and landed faster, there was less of an influence. But that is not going to happen until mid-war.

And given that it was intended to catapult launch the first 6 of a range of 24, just how far can you increase numbers to be ranged, without modifying the aft end of the flight deck, if all then need to make free take offs?

Then if you have to talk about internal rearrangements to gain extra petrol storage then it looks to me like longer and longer periods in dock at a time when the ships will be badly needed.

And the whole purpose of your exercise is supposed to be quick and easy. That is why I can see little being done to them beyond what historically happened to Furious.

 

[don4331]

Is the bow forward of the hangar truly so daintily constructed that adding a 200 ft, open extension would cause the keel to snap? If so then we can still flatten the aft deck to increase useful space and fill the old flying off deck with AA.

Short answer - Yes, the bow (and stern) are so daintily constructed that adding flight deck would cause the keel to buckle in a seaway.

Longer version -during builder's trials, Courageous, as large light cruiser, buckled her bow running into a head sea. 130 tons of structural steel were added to strengthen the bow. Courageous class large light cruiser would be operating at just over 19k tons normal*. Post carrier conversion, Courageous was operating at well over 24k tons normal. >25% increase load on a bow that is already marginal on strength was asking for trouble.

Also note, the large light cruiser hull was rebuilt from 80' beam to 90' beam - the integrate bulge you can add when you have lots of time to work with. Yet the carrier conversion still sits 2' deeper in draft than the originally designed hull.

Add another 1k tons of flight deck and structure to hold it in place will cause the carrier to settle even deeper. In fact, you will have a trim issue that results in the bow being even deeper = under further strain. Reconstructing the bow with a bulbous forefoot to restore trim, does nothing to reduce the strain on the keel (in fact it probably increased it).

The Courageous class machinery was state of the art in '16 - doubling of the small tube boilers/geared turbines installed in the CL Champion. Far better than Repair and Refit, probably as good as the mighty Hood. Yes, the 3 drum boiler of '36 is better than the small tube boilers installed, but the possible improvement of the turbines is only a couple percent - properties of steam didn't change, and RN hadn't move to the high pressure/high temperature systems that other navies were experimenting with. Re-powering the hull to get the original speed back on a 20 year old hull is asking for something to fail.

The deck has a rise so the airplanes of the day can stop with their mediocre brakes. The FAA having found that arresting gear was a. very hard on wood and fabric air frames and b. slowed operations. FAA pilots could put their plane (landing/taxi) directly onto the lift. The lift could then be cycled fast enough that the 1st plane was struck below and lift restored to flight deck before the next plane landed.

If you want a hull with 50% more capacity, build a ship 50% bigger and put the old horse out to pasture.

*Standard displacement was a great equalizer for treaty purposes, but ships don't operate without oil. Normal displacement - fuel @ 50% - is a much better number to compare how ship is operating.

 

[SaparotRob]

Great posts, EwenS and don4331. Very informative. Good stuff!

 

[Admiral Beez]

Great posts, EwenS and don4331. Very informative. Good stuff!

I agree. It's too bad the Brits didn't negotiate a fresh start of two CVs rather than seeking conversions.

I doubt taking the Courageous conversion route saved any money. Per Wikipedia, converting Courageous into an aircraft carrier cost £2 million. Yes this is 1/3 less than the £3 million cost of Ark Royal, but she was significantly larger than Courageous or Glorious. I imagine for £2 million the RN could have got two advanced and new designed and built bespoke 30 knot CVs with a single three-aircraft-wide hangar to support 48 aircraft.

It does seem that the interwar the RN and Admiralty were often penny wise but pound foolish.

 

[don4331]

I agree. It's too bad the Brits didn't negotiate a fresh start of two CVs rather than seeking conversions.

I doubt taking the Courageous conversion route saved any money. Per Wikipedia, converting Courageous into an aircraft carrier cost £2 million. Yes this is 1/3 less than the £3 million cost of Ark Royal, but she was significantly larger than Courageous or Glorious. I imagine for £2 million the RN could have got two advanced and new designed and built bespoke 30 knot CVs with a single three-aircraft-wide hangar to support 48 aircraft.

It does seem that the interwar the RN and Admiralty were often penny wise but pound foolish.

You have to break a few eggs to make an omelette; when given lemons, make lemon aid.

No one knew what a carrier should look like in '19. What the RN knew:
a. The large light cruisers were a flop and they didn't want them counting against the RN WNT limits.
b. The large light cruiser had a state of the art power plant (small tube boilers/geared turbines), so to scrap the would be throwing away a million £ hull.
c. That separate landing on and take off platforms, separated by superstructure didn't work.
d. The Short Type 184 needs 30 gals/mission, the Sopwith Baby less than 1/3 that (RNAS planes aboard Hermes). No one's crystal ball showed that planes 20 years later would be needing >10 times that.

Yes, razing the superstructure, removing the turrets and then widening the hull/building hanger and flight deck cost more, but some of that was learning from Hermes/Argus/Vindictive and redoing things 2 and 3 times. And last time I checked, it's really difficult to get funds from the gov't for a new ship, the day after you have scrapped an old one. Much easier to asked for additional funds for a project that is 90% complete but can't be used until finished.

And if the RN hasn't built the Courageous class, Ark Royal would have been built from service from Argus/Hermes/Eagle. And RN/FAA would have been even worse off.

 

[Glider]

I agree. It's too bad the Brits didn't negotiate a fresh start of two CVs rather than seeking conversions.

I doubt taking the Courageous conversion route saved any money. Per Wikipedia, converting Courageous into an aircraft carrier cost £2 million. Yes this is 1/3 less than the £3 million cost of Ark Royal, but she was significantly larger than Courageous or Glorious. I imagine for £2 million the RN could have got two advanced and new designed and built bespoke 30 knot CVs with a single three-aircraft-wide hangar to support 48 aircraft.

It does seem that the interwar the RN and Admiralty were often penny wise but pound foolish.

I have always believed that not producing more Ark Royals with some modifications around the lift arrangements, would have been a much better idea that designing the Illustrious and following classes. The ships would have been available sooner and they carried more aircraft.
I hadn't thought about building them as replacements for C and G but I admit it makes sense. If the Ark Royal was approx £3m then a class would almost certainly have been cheaper per vessel. Brining it closer to the £2m to convert C and G

 

[SaparotRob]

Great post don4331. You connected a few dots for me that I should've connected already.
I do disagree on one point.
When life gives you lemons, make whiskey sours.

 

[EwenS]

Re the Washington Treaty and Furious, C & G.

C&G were not at risk from the WNT. Despite being equipped with 15" guns they were not listed as either capital ships to be retained or scrapped. All parties therefore seem to have accepted that they were not capital ships probably by virtue of their "large light cruiser" description.

Unlike the US and Japan, Britain did not have any incomplete hulls at the time of the WNT. The G3 battlecruisers were ordered just before the Conference but the shipyards had been told not to proceed with construction. They became a negotiating point for Britain.

Back in July 1920, when the RN was looking at its post WW1 carrier plans, it decided it needed two fast carriers. These were to be reconstructions of Furious and either C OR G. Work on the design for reconstruction of Furious was begun immediately and she was stripped down to the main deck at Rosyth in 1921. That was all BEFORE the Washington Conference even began. She was transferred to Devonport for rebuilding between 1922, after the Conference had concluded, until Sept 1925. As she was considered either a carrier, or a carrier in the course of construction, at the commencement of the Conference, the RN considered her "experimental" along with Argus, Eagle and Hermes under the terms of the Treaty. That would have allowed their replacement at any time, regardless of age, during the period that the Treaty remained in force ie up until 31 Dec 1936.

(For the duration of the Washington Treaty Britain (and the USA) was limited to 135,000 tons of carriers. Each carrier was limited to a maximum of 27,000 tons. Under the 1936 London Treaty, there was no overall limit on tonnage but each carrier was limited to 23,000 tons. The RN had argued for 22,000 tons based around its experience with the Ark Royal design process.)

On 27 July 1921 G was chosen for conversion as she could be more easily replaced in the turret drill ship role she was then fulfilling. Then in 1922, after the Washington Conference, the decision was taken to convert BOTH C&G. Initially they were to be copies of Furious but work on a new design was undertaken and the eventual design approved in January 1925. By then work to strip Courageous had already begun and she finally completed in Feb 1928. Work on G also began in 1924 at Rosyth, before she was towed to Devonport, where her reconstruction continued until Feb 1930.

Even in 1926 there was no unanimity in the RN of what an aircraft carrier should look like. By then Argus and Furious were in service with flush flight decks while Eagle and Hermes had islands, with the C&G scheduled to be built with islands. But CinC Med wanted a reversion to flush decks while EinC argued for the island with a funnel as it saved weight which was important in times of limited Treaty tonnages.

The RN had planned a new carrier from 1923/24 but for various reasons kept getting postponed. It began again in 1931 using the experience gained with C&G. At that point the full length flight deck began to appear in the designs considered. That led to Ark Royal, ordered under the 1934 Programme, laid down in 1935 and completed at the end of 1938.

The switch to the Armoured Carrier arose from RN experience and thinking during the Abyssinian Crisis of 1935/36, when the level bomber began to be seen as a major threat to the fleet. The background to their development can be found here.

Armoured Aircraft Carriers in World War II

Action reports and battle damage for the armoured aircraft carriers HMS Illustrious, Formidable, Victorious, Indomitable, Indefatigable and Implacable in World War II, 1940-1942

www.armouredcarriers.com

 

[don4331]

I have always believed that not producing more Ark Royals with some modifications around the lift arrangements, would have been a much better idea that designing the Illustrious and following classes. The ships would have been available sooner and they carried more aircraft.
I hadn't thought about building them as replacements for C and G but I admit it makes sense. If the Ark Royal was approx £3m then a class would almost certainly have been cheaper per vessel. Bringing it closer to the £2m to convert C and G

Actually, the final cost of Ark Royal was £2,330,000! (The £3million was the original estimate). Shows that when you know what you are building from the start you can get it done at a much lower price (being in middle of depression doesn't hurt either).

The problem is you need hindsight to know the armoured sides of the Illustrious and following classes isn't worth adding - there's still no Radar when they are being designed and there aren't enough cruisers, to ensure your carrier group always has one. But yes, more Ark Royal with modifications to sub-divide the boiler rooms would have been better.