Quick mods to the Courageous class

[Admiral Beez]

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.

I was thinking back to this thread. Forget about updating the Courageous class carriers as built, but what about constructing them differently from the onset of their conversion from battlecruiser. Same tear down, budget, machinery, etc. If we want the widest and longest possible flight deck and hangar, what can be done? My thinking is the hangar (dual or single) is made a structural support for the hull, rather than a weight placed on top. I'm no naval engineer, but can we make the hangar take some of the strain on the hull?

 

[EwenS]

I was thinking back to this thread. Forget about updating the Courageous class carriers as built, but what about constructing them differently from the onset of their conversion from battlecruiser. Same tear down, budget, machinery, etc. If we want the widest and longest possible flight deck and hangar, what can be done? My thinking is the hangar is made a structural support for the hull, rather than a weight placed on top. I'm no naval engineer, but can we make the hangar take some of the strain on the hull?

Sorry AB but you are assuming the flight deck wasn't a strength deck. From Friedman "British Carrier Aviation" when discussing Furious' rebuild in 1921:-

"The upper flight deck functioned as a strength deck for the rebuilt ship, considerably reducing hull stresses."

In a note he then cites the improvements expected in both hogging and sagging stresses. If you look carefully at the flight deck you will note that there were no expansion joints that would have been necessary if the hangars and flight deck were pure superstructure (see the USN carriers from Ranger onwards that had to have these fitted). These would have been necessary to cope with the flexing of a pure superstructure deck.

The reconstruction of Furious began in 1921 with her being stripped down to main deck level. She was then transferred to Devonport to be rebuilt. There were some concerns about her strength for this transfer and she was put into a temporary steaming condition. These kind of comments help explain the necessity of increasing the hull strength by making the flight deck a strength deck.

Courageous and Glorious then followed the same pattern.

 

[ThomasP]

Possibly of interest. There were fairly detailed engineering studies of the Furious, Courageous, and Glorious before WWII, which included serious rebuilds. Somewhere on the internet there is (or was) a report on this. From memory, the rebuilds included:
Extending the flight deck froward and incorporating a hurricane bow.
Improved elevator arrangements.
More powerful catapults.
New bulges - for better protection and for buoyancy/stability. The new internal space forward of the hangars would be used for crew quarters and such.
Updated machinery similar to what was done to the 3x QE class and Renown.
Improved AA armament, etc

 

[EwenS]

Possibly of interest. There were fairly detailed engineering studies of the Furious, Courageous, and Glorious before WWII, which included serious rebuilds. Somewhere on the internet there is (or was) a report on this. From memory, the rebuilds included:
Extending the flight deck froward and incorporating a hurricane bow.
Improved elevator arrangements.
More powerful catapults.
New bulges - for better protection and for buoyancy/stability. The new internal space forward of the hangars would be used for crew quarters and such.
Updated machinery similar to what was done to the 3x QE class and Renown.
Improved AA armament, etc

Burt's "British Battleships 1919 - 1945" contains some details. According to that it was a 1938 proposal to convert C&G only (Moore in "Building for Victory" however indicates all 3 ships were to be included), to single hangar ships. Hangar had to be at least 62ft wide (increased from 50 feet) to allow stowage 3 abreast as in the Illustrious class, height had to be sufficient to allow 3 gallery decks of reasonable width for accomodation. Beam would have to increase by 14ft.

He provides a drawing of the midships section of the proposal. So although the beam was only to increase by 14ft it seems to have involved not just bigger bulges, but a complete reshaping of the external hull with vertical sides instead of outward sloping sides to generate the extra width. So at hangar deck level a lot more space is generated than an increase in beam of 14ft by bulging might suggest. Overall the ship would have had a lower profile. The extent of that level of reconstruction seems to me to far exceed anything with any of the capital ships of any navy and that carried out by the Japanese on Kaga & Akagi in the1930s.

Those are huge changes which would have been costly both in terms of time (years out of service) and money. Moore notes that the cost of these reconstructions, including incorporation of new machinery, would be almost the same as building a new carrier of the same displacement.

By then C&G were already 20+ years old, and, IIRC, could be replaced by new construction anyway under the terms of the various Treaties. So what is the advantage of rebuilding them? And while they are out of service RN carrier numbers are reduced.

It is worthwhile remembering that, at least for the RN, warship reconstructions were not a replacement for new construction. They were solely to extend their life (capital ships) or repurpose them (AA cruiser conversions) until new construction of better, more modern ships could be built and brought into service. By the end of 1938 the carrier build programme already had 5 ships building (Ark just entering service and 4 Illustrious) and one on order (Implacable) plus agreed plans to build 1 more per year in the 1939-41 programmes. Indefatigable (the 1939 ship) was certainly seen as a replacement for one of the early carriers, Argus or Eagle if not both. Consideration was being given 1938/39 to extending the carrier build programme 1942-44 specifically to build replacements for F,C&G.

I can understand the desire for a wider hangar. At 50ft you can only fit 2 Swordfish/Albacore/Barracuda abreast. And with an increase in length from 36ft in the Swordfish to 40ft in the Albacore/Barracuda, aircraft capacity would be falling. Capacity can begin to be restored at 62ft.

By May 1939 RN plans looking forward to 1942, with the first 6 Armoured carriers in service, would have seen all 3 ships in reserve in peacetime and reduced to trade protection roles (hunting raiders) in the Atlantic and/or Indian Oceans with a reduced complement of 24 aircraft. At least part of that reduction is due to those aircraft being larger.

 

[Admiral Beez]

Possibly of interest. There were fairly detailed engineering studies of the Furious, Courageous, and Glorious before WWII, which included serious rebuilds.

I've seen those, but I'm proposing addressing the fragile bows from the onset through making the hangar a more stress bearing structure.

 

[Admiral Beez]

According to that it was a 1938 proposal to convert C&G only to single hangar ships.

By then C&G were already 20+ years old

By 1938, they should be left alone to serve as best they can until replaced by the Illustrious class.

No, I'm now looking doing a different job from the onset of the 1920s reconstruction to better address the hull weakness. A single hangar, like on Argus, Hermes and Eagle might help offer some displacement to structural strengthening.

 

[don4331]

I've seen those, but I'm proposing addressing the fragile bows from the onset through making the hangar a more stress bearing structure.

I understand the request, but don't know how to engineer it. Part of problem is the original hull design was 80' beam. The carrier conversion has added over 10' to that (13%). Increasing another 14' for a wider hanger is asking for trouble.

The flight deck is already the stressed member, so option to change that.
Extending the flight deck/hurricane plating over the bow is going to cause ship to trim nose down. Which is going to increase the structural load on the bow - I doubt you are even breaking even. Any attempts to increase buoyance - e.g. bulbous bow, again just increases the structural strength issue.

Aside: Courageous class already had small tube boilers and geared turbines. QEs started with large tube boiler and direct drive turbines. So, QEs gained a lot with newer machinery; Courageous class would have benefited some from boiler with superheated steam, and decade newer turbines but it would be a small amount.

 

[Admiral Beez]

I can understand the desire for a wider hangar. At 50ft you can only fit 2 Swordfish/Albacore/Barracuda abreast. And with an increase in length from 36ft in the Swordfish to 40ft in the Albacore/Barracuda, aircraft capacity would be falling. Capacity can begin to be restored at 62ft.

I was thinking back to the Courageous class. Had the design of the 1924-1928 conversion wanted the widest possible hangar or hangars, starting with a clean sheet from the battlecruiser hull, how wide a hangar could they go? Minus the bulges, the max beam at waterline was only 81 feet.

The Japanese did their best to get the widest ship on the narrowest of waterline beams.

 

[GreenKnight121]

I understand the request, but don't know how to engineer it. Part of problem is the original hull design was 80' beam. The carrier conversion has added over 10' to that (13%). Increasing another 14' for a wider hanger is asking for trouble.

The flight deck is already the stressed member, so option to change that.
Extending the flight deck/hurricane plating over the bow is going to cause ship to trim nose down. Which is going to increase the structural load on the bow - I doubt you are even breaking even. Any attempts to increase buoyance - e.g. bulbous bow, again just increases the structural strength issue.

Aside: Courageous class already had small tube boilers and geared turbines. QEs started with large tube boiler and direct drive turbines. So, QEs gained a lot with newer machinery; Courageous class would have benefited some from boiler with superheated steam, and decade newer turbines but it would be a small amount.

Years ago I had worked up a modernization for the trio... and bow strength (and buoyancy) were a point I addressed.

Specifically, I added a bulbous bow AND bulges that ran all the way forward to become that bulb... thus adding significant strengthening to the bow (doubling the vertical plating of the below waterline bow).

Furious also had her long aft horizontal funnel runs removed in favor of a funnel incorporated into a new island and a set of exhaust vents amidships on the port side below the flight deck. I had her torpedoed instead of Ark Royal, but surviving (as I had Courageous survive her torpedoing) by both being fully buttoned-up for possible combat.

 

[Admiral Beez]

Years ago I had worked up a modernization for the trio... and bow strength (and buoyancy) were a point I addressed.

Specifically, I added a bulbous bow AND bulges that ran all the way forward to become that bulb... thus adding significant strengthening to the bow (doubling the vertical plating of the below waterline bow).

Furious also had her long aft horizontal funnel runs removed in favor of a funnel incorporated into a new island and a set of exhaust vents amidships on the port side below the flight deck. I had her torpedoed instead of Ark Royal, but surviving (as I had Courageous survive her torpedoing) by both being fully buttoned-up for possible combat.


View attachment 731134View attachment 731135

Here's ex-HMS Furious cutdown at the scrapyard. I think this is where we'd need to start.

HMS Furious

 

[Shortround6]

I was thinking back to the Courageous class. Had the design of the 1924-1928 conversion wanted the widest possible hangar or hangars, starting with a clean sheet from the battlecruiser hull, how wide a hangar could they go? Minus the bulges, the max beam at waterline was only 81 feet.

View attachment 731051

The Japanese did their best to get the widest ship on the narrowest of waterline beams.

View attachment 731182

British carriers were designed for more "unfriendly" seas than the Japanese ships.

every once and while the Japanese got caught. The US got caught. Google "Halsey's Typhoon"

 

[Admiral Beez]

British carriers were designed for more "unfriendly" seas than the Japanese ships.

True, but the Courageous trio as well as Hermes were daintily built. There's a reason Hermes had to spend her days in the Indo-Pacific. Here's Furious taking it in the nose.

 

[ThomasP]

Actually, Hermes was quite sturdy and capable of handling heavy seas, at least according to DK Brown. The reason she was sent to the Far East was her design being that of a trade protection and scouting nature.

 

[Admiral Beez]

Actually, Hermes was quite sturdy and capable of handling heavy seas, at least according to DK Brown. The reason she was sent to the Far East was her design being that of a trade protection and scouting nature.

Interesting. I figured the open stern (intended for launching floatplanes) and low freeboard aft would have invited a following sea to crash into the rear and cause damage.

 

[Shortround6]

A lot depends on what it was designed for, like the actual strength in the areas where the seas are impacting.
Also even a few knots of speed can lessen the impact of the following waves vs the impact of head seas.
Even large ships had to go bow on to the waves in really bad conditions.
The British were usually pretty good about designing for sea conditions. The County class cruisers are often decried by many modern critics for their poor showing in a quick statics table. They were often 1 deck taller than many of the other 8in cruisers and handled bad seas a lot better, they didn't have visit the repair yards after being in a storm.
They paid for it in higher hull weight.

 

[EwenS]

Here's ex-HMS Furious cutdown at the scrapyard. I think this is where we'd need to start.

View attachment 731202

HMS Furious

See my post #82 above

 

[GreenKnight121]

Here is the historic concept for modernizing the Courageous class...

 

[Shortround6]

So basically take the old machinery (boiler and turbines) out,
build new hull,
install the 1916 machinery in the 1938 hull and have a world beater

I can see how they thought long and hard about that one.........................................not.

 

[Admiral Beez]

So basically take the old machinery (boiler and turbines) out, build new hull, install the 1916 machinery in the 1938 hull and have a world beater

At this stage I'm more interested in how without hindsight the original 1925-1928 conversion could have been improved upon, rather than redoing the ship in the 1930s. I think we've discussed the latter to its conclusion. IMO, 1925 when the design is tabled; scrap the aft rounddown and forward hangar level flying off deck. Maximize hangar width. Install a larger island like Hermes below, but without the tripod, to allow more space for flag and flight ops control.

 

[Admiral Beez]

As an aside, I was surprised to see how much of the aft space beneath the flight deck was taken up by the captain in Hermes. Below we see Captain's sleeping cabin, bathroom, day cabin and dining room. That's a lot of luxury on a carrier the size of a wartime CVE, but I suppose deemed necessary for a foreign station. I imagine this was a good place during the interwar China station tours. If I'm redesigning the 1925 rebuild of the Courageous trio the captain will be getting less space, with the focus being on whatever the ships need to maximize CAG size and overall capability.