The Centaur carrier fleet - a better fate...

[A Tentative Fleet Plan]

I learned about the island thing here in February, and will repeat like a good schoolkid.

British carriers have big (or 2) islands because they didn't have a gallery deck between the flight deck and hangar roof. The British believed that a ship needed a 120' beam to have a gallery deck, otherwise the ship wouldn't be stable. So the big island makes perfect sense, its a simple design constraint/compromise.

Both the 1952 Fleet Carrier and CVA-01 had a gallery deck.

 

[EwenS]

But what does everyone mean by a "gallery deck", and what do you believe existed there?

And in part this brings us back to the differences in carrier construction between USN & RN.

In the Illustrious class and successive armoured carrier designs, the beams supporting the flight deck were sufficiently deep that there was space between them at the "upper gallery deck" level which was used in part at least for various purposes.

In the 'closed' hangar overhead area between those beams of the Illustrious class that included, in various places, store rooms, a parachute packing room and a compartment forward for the accelerator / catapult gear. Forward of the hangar and lift well were crew accommodation and recreation spaces, while aft of the after lift were more stores, squadron offices etc. Between the hangar walls and the ship's side the space at this level was put to other uses.

There was also a "lower gallery deck" at about half hangar height, with compartments fore and aft the hangar & along its sides.

When Victorious was reconstructed, the "Upper Gallery Deck No.2" was used almost entirely along its length for crew accommodation.

Looking at the deck plan of CV-11 Intrepid of the Essex class as completed, only part of the "Gallery Deck" was used. Virtually all of the space at that level aft of the after lift was unused and open to the hangar as was most of the area between the island and the forward lift. These were the areas which I assume would have been used to suspend the spare aircraft intended to be carried in the original design. The latter practice was discontinued in US carriers in late 1942, as it was found to be a fire hazard. Very little of the remaining space was taken up with crew acomodation (a bit forward of the forward lift and another for senior officers abreast the island). Most was squadron offices, stores, ready rooms and other compartments necessary for the air group.

 

[A Tentative Fleet Plan]

By "Gallery Deck" I mean a deck between the flight deck and hangar roof, running the full length of the ship.

 

[Rule of cool]

But what does everyone mean by a "gallery deck", and what do you believe existed there?

Obviously this was where the carrier displayed Art, people practiced pistol shooting and played pinball and other games. In addition to this cool stuff it's the interface between the flight deck and the iceberg of stuff that keeps it moving: aircrew ready and briefing rooms, the huge amount of admin before a plane is signed off as servicable, aircraft spotting etc etc etc. A full length gallery deck keeps all this under armour, without it at least some has to be moved into the island.

BTW the 120' beam thing is a stability requirement for both a full gallery deck AND deck edge lifts. Get rid of deck edge lifts and you can have a full sized gallery deck, or whatever other design comprises that best suit the requirements.

 

[BlackBat242]

Both the 1952 Fleet Carrier and CVA-01 had a gallery deck.

In addition to the comments between these two posts, it was also an issue of (in general):
two hangar decks = no full-length full-width gallery deck
one hangar deck = yes full-length full-width gallery deck

 

[GK Dundas]

When one examines the operating concepts of British Defence industries. One doesn't know whether to laugh or cry.
Almost every ship or aircraft seems to been a "one off " in particular their Carrier fleet
I'll bet finding spare parts even with a laid up sister ship must have been interesting.

 

[Rule of cool]

In addition to the comments between these two posts, it was also an issue of (in general):
two hangar decks = no full-length full-width gallery deck
one hangar deck = yes full-length full-width gallery deck

Apparently its all about freeboard and weight up high in the ship and its effects on stability. It appears that these ship designers aren't totally stupid.

 

[zen]

When one examines the operating concepts of British Defence industries. One doesn't know whether to laugh or cry.
Almost every ship or aircraft seems to been a "one off " in particular their Carrier fleet
I'll bet finding spare parts even with a laid up sister ship must have been interesting.

No a great deal is standardised parts.
From catapult sections to seats to pipes. It all pretty much standard really.
For aircraft there was...is a need to fit in aerodynamic form and spread weight rationally. So things had to have alterations to fit.

 

[Temeraire]

British carriers have big (or 2) islands because they didn't have a gallery deck between the flight deck and hangar roof. The British believed that a ship needed a 120' beam to have a gallery deck, otherwise the ship wouldn't be stable. So the big island makes perfect sense, its a simple design constraint/compromise.

That is some complete and utter Bollocks. HMS Victorious had a gallery deck from her Rebuild (Hermes might of, I can’t remember and honestly i can’t be bothered to check this late at night) Eagle was supposed to get one however she only got a half-assed refit (i don’t think it even qualifies as a rebuild) and Ark Royals was even worse than that.

The reason for two islands, (or one long one) is because it allows the funnel uptakes (and thus the machinery spaces) to be spaced out which Improves Survivability. Conventional American super carriers didn’t do this, which reinforces my notion (as a proud Brit) that the Americans are dumb, and Nuclear carriers don’t need funnel uptakes, meaning their islands can be much smaller

 

[Temeraire]

When one examines the operating concepts of British Defence industries. One doesn't know whether to laugh or cry.
Almost every ship or aircraft seems to been a "one off " in particular their Carrier fleet
I'll bet finding spare parts even with a laid up sister ship must have been interesting.

Not our fault the yanks piled mountains of debt on us that meant we couldn’t afford jack shit.

 

[Temeraire]

BTW the 120' beam thing is a stability requirement for both a full gallery deck AND deck edge lifts. Get rid of deck edge lifts and you can have a full sized gallery deck, or whatever other design comprises that best suit the requirements.

Was that really a thing?
As far as I’m aware the only thing that prevented Victorious from getting a Deck edge lift was her low freeboard

 

[zen]

To get freeboard at hanger deck level over 24ft AND a full Gallery deck as per HMS Victorious's rebuild. The freeboard needed for deck edge lifts.
DNC stated the ship needed ideally 120ft waterline beam.

Victorious's Gallery deck was a little cramped and so new ships would have to have a greater height to fit all the piping, lagging and air ducting (for aircon)

The 1952 carrier started out at 115ft but got to 116ft prior to cancellation. The favoured design had a full Gallery deck and deck edge lifts. But how stable compared to the ideal is an interesting question and it may have forced compromises.

Later CVA-01 studies seem to imply some would either choose between deck edge lifts or full Gallery deck. Likely to examine trade off in capabilities.

The bigger island designs were to house the full two deck AIO arrangement. Victorious avoided this by citing the lower deck AIO in the Gallery deck beneath the island.

Twin island design was to increase capacity to operate with damage and provide greater separation of radar and radio aerials, of which there wouldbemany and avoiding them conflicting with each other isn't a trivial matter.
It also eased trunking of exhaust from the engines.

CVA-01 seems to start out with twin islands, but they then add a walkway between them to carry cables and things spiraled until there was just a tunnel through the island remaining.

 

[BlackBat242]

That is some complete and utter Bollocks. HMS Victorious had a gallery deck from her Rebuild (Hermes might of, I can’t remember and honestly i can’t be bothered to check this late at night) Eagle was supposed to get one however she only got a half-assed refit (i don’t think it even qualifies as a rebuild) and Ark Royals was even worse than that.

The reason for two islands, (or one long one) is because it allows the funnel uptakes (and thus the machinery spaces) to be spaced out which Improves Survivability. Conventional American super carriers didn’t do this, which reinforces my notion (as a proud Brit) that the Americans are dumb, and Nuclear carriers don’t need funnel uptakes, meaning their islands can be much smaller

So they planned to cut Eagle from 2 hangar decks to 1?

 

[Rule of cool]

IIUC the 120' is the stability baseline for a single hangar, full length/width gallery deck AND deck edge lifts. I reiterate that this is a baseline, and everything is negotiable: want less stability with those 3 things you can have less beam. If you want a gallery deck and stability on less beam cut back on deck edge lifts or gallery deck size, if you want 2 hangar decks then other things must go, the combinations are endless.

 

[Temeraire]

So they planned to cut Eagle from 2 hangar decks to 1?

No they didn’t, it was late at night where I am so I couldn’t really remember correctly

 

[GK Dundas]

I think the biggest problem with the Gannet is the compact size of the airframe. That limits the amount of electronics that can be packed in when compared to a Grumman S-2 Tracker or Lockheed S-3 Viking.

Where do you put all the extra sonobuoys (Gannet carried less than a dozen IIRC), plus MAD gear, diesel sniffers etc.? And do you then need a third operator to man them? And unlike a helicopter it can’t stop and hover to dip a powerful active sonar into the water to prosecute underwater targets.

So the RN took the view in the mid-1950s to move to the helicopter for ASW equipped with that active dipping sonar as the best tool for the job. Only later in the 1980s do they add do they add sonobuoy and MAD gear to the Sea King.

I should have known the answer to this , one of the reasons the CP 121 trackers were retired in the 80's was you really couldn't cram any ASW systems aboard them. That would have provided enough of an advantage to be worth the costs of a refit.
A couple of years later and the boom in computer development it would been a genuine gamechanger.

 

[BlackBat242]

The S-2 carried plenty of sonobuoys...
The engine nacelles carried JEZEBEL sonobuoys in the rear (16 in early marks, 32 in the S-2E/G). Early Trackers also carried 60 explosive charges, dispensed ventrally from the rear of the fuselage and used to create sound pulses for semi-active sonar (JULIE) with the AN/AQA-3 and later AQA-4 detection sets, whereas the introduction of active sonobuoys (pingers) and AN/AQA-7 with the S-2G conversion saw these removed. Smoke dispensers were mounted on the port ventral surface of the nacelles in groups of three each.

It also carried other ASW systems... The Tracker had an internal torpedo bay capable of carrying two lightweight aerial torpedoes or one nuclear depth charge. There were six underwing hard points for rocket pods and conventional depth charges or up to four additional torpedoes. A ventrally-mounted retractable radome for AN/APS-38 radar and a Magnetic Anomaly Detector (MAD) AN/ASQ-8 mounted on an extendable rear mounted boom were also fitted. Early model Trackers had an Electronic Support Measures (ESM) pod mounted dorsally just aft of the front seat overhead hatches and were also fitted with a smoke particle detector or "sniffer" for detecting exhaust particles from diesel-electric submarines running on snorkel. Later S-2s had the sniffer removed and had the ESM antennae moved to four rounded extensions on the wingtips. A 70-million-candlepower searchlight was mounted on the starboard wing.

 

[GK Dundas]

Most of those dedicated ASW systems had been removed from the CP 121's .The government of the day was more interested in surface contacts then sub surface ones. Fisheries patrols ( Fish Pat) and Sovereignty Patrols. (Sov Pat )were the order of the day
At the same Soviet submarines were getting disturbingly quiet. A slightly larger aircraft then the Tracker dedicated to coastal ASW work might have been nice .
DeHavilland offered up both the Dash 7 and 8 as I recall.

 

[Rule of cool]

Early Trackers also carried 60 explosive charges, dispensed ventrally from the rear of the fuselage and used to create sound pulses for semi-active sonar (JULIE)

I read a novel when I was at school about a RAN Tracker sinking an Indonesian sub by accident with one of these explosive charges.

 

[H_K]

Here are Centaur's plans (from the Royal Museaum Greenwich)

Cleaned up as best I could.

 

[H_K]

Also here's a hypothetical enlarged Centaur, with a 66ft hull plug (i.e. 2 standard hull sections). Could have been an interesting what-if scenario if the RN had wanted to improve the Centaurs while still building them in the late 40s.

This would bring the Centaurs to "almost Clemenceau" size, allowing for a larger air group of ~24 fast jets.

 

[kaiserbill]

H_K.. that is interesting.
One wonders the huge impact that extended hull could have had on British naval aviation over the following decades.
The class would have been fully as long as the Audacious class, albeit on a narrower hull.
You'd get 4 vessels in the HMS Victorious class, but without that ships issues.
With 4 modified (with 8 or 8.5 instead of 5 or 6 degree angled deck) and lengthened Centaur class entering service in the 50's, I would hazard a guess that these would serve well into the 1980's.

 

[H_K]

With 4 modified (with 8 or 8.5 instead of 5 or 6 degree angled deck) and lengthened Centaur class entering service in the 50's, I would hazard a guess that these would serve well into the 1980's.

Indeed. Here’s my lengthened Centaur in the 80s with 25x F/A-18s.

I added a long waist catapult (199ft BS5 as on Eagle/Ark Royal) for higher take off weights and a Hermes-like angle deck with a ~6.75 degree angle (wasn’t sure a large Victorious like sponson could be made to work on such a narrow hull)

 

[kaiserbill]

Indeed. Here’s my lengthened Centaur in the 80s with 25x F/A-18s.

I added a long waist catapult (199ft BS5 as on Eagle/Ark Royal) for higher take off weights and a Hermes-like angle deck with a ~6.75 degree angle (wasn’t sure a large Victorious like sponson could be made to work on such a narrow hull)

Nice work.
The Dutch managed to fit an 8.5 degree angled deck on the narrower hull of the 2 Colossus carriers they rebuilt.
In the Minas Gerais, they added an access way starboard of the island for balance reasons.
Hermes (the best of the Centaurs) only got a 6.5 degree angle.
I wonder whether there was scope to apply the Dutch treatment in this case.

 

[BlackBat242]

Minas Gerais also got her forward aircraft lift moved 9' to starboard, making the starboard edge of the lift line up with the starboard bulkhead of the hangar. This allowed a longer catapult to run beside the lift.

The Colossus-class hangar was 52' wide, and the lifts were 34' wide and centered in the hangar, making for a constriction 9' wide on each side of the lift - this is where the lift machinery was located.

Here are the layouts showing the modification:





MG hangar view looking aft - note the aft lift catered in the hangar:



MG hangar looking forward - note the starboard hangar side aligns with the starboard lift well side, and the greater space to port of the port lift well side:

 

[BlackBat242]

Now look at H_K's drawings - note that the same modification to the forward lift is possible for Centaur-class CVLs, allowing a longer and more-powerful port bow catapult to be fitted.

Extending the flight deck edge before and aft the island, and aft on the port side similar to Ark Royal's extension there, would provide mass to counterbalance a wider angled extension of the flight deck.

Not having moved the fore lift to the front of the angle allows a catapult to be installed on the fore half (or 1/3) of the angle, which also allows the starboard bow to be used for aircraft parking.

If the aft lift is moved to the starboard deck-edge during completion in the same manner Hermes' fore lift was moved to port while moving the fore lift 9' to starboard (62' wide hangar, 44' wide lifts), and the deck edges expanded, then a CVL even more-capable than Hermes is created, even without lengthening the ship any.

Note the light gray line of the hangar shape (I left the spaces used for the lift machinery etc to be converted to replace the spaces lost in extending the hangar to the outboard hull side for the deck-edge lift):

 

[BlackBat242]

I forgot that I forgot the reasoning which favors H_K's aft lift move to deck-edge over the historic move of Hermes' fore lift to deck-edge.

Not only does moving the aft lift de-conflict landing operations and aircraft moves between the hangar and flight deck, and NOT moving the fore lift means NOT adding conflict between such moves with it and landing operations - it also allows moving the starboard bow catapult to the angle deck.

This is more important than it might seem at first glance - the length (and thus capacity) of a catapult on the starboard bow is permanently constrained by the location of the island. Moving the fore lift to port similarly limits the length (and capacity) of a catapult placed on the angle, where it has to fit between the lowered location of the emergence landing arresting (crash) barrier and the aft end of the lift - not having the lift there adds at least 54' to the permissible catapult length (more if a "horn" is added to fit the water brake for the catapult piston and recovery of the launching bridles).

But there is another advantage to having an aft lift at the deck-edge instead of the fore one - the ship's hull aft of the island is more-stable in pitch and rise/fall caused by waves/swells, due to having significant lengths of hull both forward and aft of the lift at or near full-width, which reduces how deep in the water that part of the hull moves. The fore lift lacks this support forward, due to the narrow bow - which allows waves to adversely affect a lift where Hermes' was (see comments below).

We all have seen photos of carriers "burying" their bows in waves - but have you paid attention to how far aft on the hull those waves rise above the freeboard of the hangar?
The USN did, which is why, with their Essex class carriers, they did not move the fore lift to the deck-edge when they moved the aft lift.
Similarly. that is why the French kept their fore lift inboard even with the aft lift at deck-edge on the Clemenceaus - which were longer than the Centaurs.

This was a serious matter, as is shown by these comments from a sailor who served aboard Hermes:

(hermes82 on Navweaps):
Hermes fwd lift was a deck edge side lift.
It was pretty dangerous in choppy weather nearly got washed over the side on at least 2 occasions, really thought I was a goner.
My mate was the lift driver at flight deck level he got submerged by one wave whilst we stuck a cab on it, you can imagine how wet we were.
The lift acted like a knife blade through the water when it was at hangar level, damaged the cab as well.

There were maintenance issues due to water damage as well, as described in the attached report:

 

[zen]

I've been pointing out the issues of deck edge lifts and how exposed the RN felt it was for 20 years. Mostly to fall on deaf ears (or blind eyes).
Which is why CVA-01 had an inboard lift forward and only the stern lift was on the deck edge.

 

[H_K]

If the aft lift is moved to the starboard deck-edge during completion in the same manner Hermes' fore lift was moved to port while moving the fore lift 9' to starboard (62' wide hangar, 44' wide lifts), and the deck edges expanded, then a CVL even more-capable than Hermes is created, even without lengthening the ship any.

Yes, that said part of my rationale for the hull plug would be to also provide more internal volume for fuel & munitions for a larger air wing with more capable jet aircraft. Just optimizing the flight deck layout and increasing the deck park alone (with the impact on stability) may not help sortie generation... depending on where the constraints lie.

 

[bobtdwarf]

I've been pointing out the issues of deck edge lifts and how exposed the RN felt it was for 20 years. Mostly to fall on deaf ears (or blind eyes).
Which is why CVA-01 had an inboard lift forward and only the stern lift was on the deck edge.

Now it makes a lot more sense, I figured it might be something like that but left it a deck edge lift on one of my drawings because it was just easier than moving the elevator with what I was using.

 

[PMN1]

The 1952 Carrier A and B designs looked to have not realised the issues with forward deck edge lifts....unless the extra size of the ship reduces the issues.



Corrected partially in C and fully in D

 

[CV12Hornet]

The 1952 Carrier A and B designs looked to have not realised the issues with forward deck edge lifts....unless the extra size of the ship reduces the issues.

Given these predate the aforementioned issues on Hermes, the former. Size does matter - see USN supercarriers and the Midways getting away with such arrangements - but both those types are a lot bigger than the 1952 CVA.

 

[GK Dundas]

Now look at H_K's drawings - note that the same modification to the forward lift is possible for Centaur-class CVLs, allowing a longer and more-powerful port bow catapult to be fitted.

Extending the flight deck edge before and aft the island, and aft on the port side similar to Ark Royal's extension there, would provide mass to counterbalance a wider angled extension of the flight deck.

Not having moved the fore lift to the front of the angle allows a catapult to be installed on the fore half (or 1/3) of the angle, which also allows the starboard bow to be used for aircraft parking.

If the aft lift is moved to the starboard deck-edge during completion in the same manner Hermes' fore lift was moved to port while moving the fore lift 9' to starboard (62' wide hangar, 44' wide lifts), and the deck edges expanded, then a CVL even more-capable than Hermes is created, even without lengthening the ship any.

Note the light gray line of the hangar shape (I left the spaces used for the lift machinery etc to be converted to replace the spaces lost in extending the hangar to the outboard hull side for the deck-edge lift):


View attachment 744487

Can I get it in a greyish off-white color, if so I'll take two . Please don't bother to wrap them .

 

[SSgtC]

Given these predate the aforementioned issues on Hermes, the former. Size does matter - see USN supercarriers and the Midways getting away with such arrangements - but both those types are a lot bigger than the 1952 CVA.

Makes sense when you think about. I had always wondered why the Navy left the number 1 elevator on the centerline in the Essex class.

 

[BlackBat242]

Makes sense when you think about. I had always wondered why the Navy left the number 1 elevator on the centerline in the Essex class.

Just remember... always with the negative waves!


USS Midway, Oct 08 1988 typhoon near Philippines 26-degree roll:





Starboard forward lift (Elevator #1) with F/A-18:

 

[BlackBat242]

Even the large Midways had issues with waves aft as well... here is the story of how waves stole her aft deck-edge lift (this was during its "halfway modernized" phase before her 1966-70 overhaul when her lifts were completely re-arranged):

USS Midway Museum®

Live the adventure & honor the legend of the USS Midway with activities & fun for the whole family onboard! Voted #1 “Thing to Do” on Trip Advisor SD!

www.midway.org

Gone with the waves: Midway's aircraft elevator

Here are the 2 stages of Midway's modernization and her original configuration. The above incident was with the middle arrangement:



Note that the middle state left the aft deck-edge lift reliant on its roller track along the ship's side and one set of lifting cables less than half-way out for its support.

Compare that in the photo of Midway's #1 lift with the wave hitting it - you can see 2 sets of lifting cables, one near the hull and one almost to the outer edge of the lift... this change was as a result of the incident listed above, to retain the lift even if it came out of its tracks.

On my drawing of my modified Centaur you can see the pair of angled extensions of the flight deck along the starboard lift - this is to move the attachment point for the pulleys of the outer lift cables further out from the hull.

 

[BlackBat242]

Aircraft carrier and LHA/LHD hangar deck freeboards:
Centaur: 24'. Hermes might have been 23' 6", as I've seen that number sometimes and 24' other times.
Victorious: 14'
Indomitable: 23' 6" (upper hangar)
Ark Royal & Eagle: upper hangar 30', lower hangar ~10'
1952 carrier proposal: 24'

Clemenceau: 24'
de Gaulle: 23'

Cavour: 18' (light-moderate sea use only)

Essex: 25'
Midway 25'
CVNs: 28'-30'
Wasp class: 34'

 

[kaiserbill]

The more info posted, including those hangar freeboard numbers, the more interesting a lengthened and properly designed angled deck Centaur Class becomes.
I think the exorbitant cost of the Victorious rebuild would have been better directed toward the 4 Centaur vessels.

 

[Archibald]

Yes but... wasn't the Centaur machinery only 76 000 hp, much less than the 100 000 ++ of the other carriers ? and the speed lower, 27 kt or less ? if the ships are lenghtened, the additional weight will make them even slower.

 

[H_K]

less ? if the ships are lenghtened, the additional weight will make them even slower.

Lengthening would cause no speed loss, and might actually help a little due to reduced wave drag.