HMS Hermes (95), reasonable interwar rebuild

[Admiral Beez]

HMS Hermes (95) had IMO three flaws that I would like to address:

1) The huge destabilizing island and tripod mast
2) The inclusion of six 5.5" low angle guns (with FC directors on tripod mast)
3) The aft lift being exposed to the sea on three sides (was thus designed to enable aircraft to be moved from barge straight into hangar.

Here is Hermes at her launch.

You can see how high she was in the water before the island and other fittings were installed.

I suggest that reducing the island size, eliminating the tripod mast and anti-ship armament, along with enclosing the stern (if her keel and hull can take it) would make for a better ship. Hermes had wide elevators, and a good-sized rectangular hangar.

What other flaws would you like to address in the interwar period? And no you resident contrarians, scrapping and using the treaty tonnage to build a replacement carrier is not an option. Perhaps squaring off the bows, squaring the T-shape lifts, removing the aft rounddown, adding crash barriers and outriggers? We'll need to increase the avgas and magazine stores if we want a larger CAG.

 

[Admiral Beez]

No Hermes unfortunately, but I have to recommend this site Ship plans

 

[Shortround6]

And no you resident contrarians, scrapping and using the treaty tonnage to build a replacement carrier is not an option.

Well, if you take the best option off the table all you are left with is a bunch of minor tinkering of various cost for little overall result.
The 5.5 in guns weigh around 14-15 tons each without shield, Shield weighs about 4.5 tons if 1 1/2 in thick. So pulling the six guns gets you just over 100 tons on a 10,000ton ship (13,000tns full load) Reduced load in the magazines and reduced crew may be just as important.
The ship already trimmed by the bow so adding flight deck there may not be a good option. Granted adding a crap load of weight aft may help things out.

Ship is on the slow side, I don't believe she ever got new boilers? so book speed might be subject to question? Or at least hard steaming for long periods of time should be avoided.

Basically you already have 1.5 liters in a 1 liter bottle and no matter what you do you aren't going to get much more in.

 

[RCAFson]

HMS Hermes (95) had IMO three flaws that I would like to address:

1) The huge destabilizing island and tripod mast
2) The inclusion of six 5.5" low angle guns (with FC directors on tripod mast)
3) The aft lift being exposed to the sea on three sides (was thus designed to enable aircraft to be moved from barge straight into hangar.

Here is Hermes at her launch.



You can see how high she was in the water before the island and other fittings were installeI suggest that reducing the island size, eliminating the tripod mast and anti-ship armament, along with enclosing the stern (if her keel and hull can take it) would make for a better ship. Hermes had wide elevators, and a good-sized rectangular hangar.

What other flaws would you like to address in the interwar period? And no you resident contrarians, scrapping and using the treaty tonnage to build a replacement carrier is not an option. Perhaps squaring off the bows, squaring the T-shape lifts, removing the aft rounddown, adding crash barriers and outriggers? We'll need to increase the avgas and magazine stores if we want a larger CAG.

The RN could have completely rebuilt Hermes if they so desired and if the treasury would have parted with the funding.

As with Renown and Warspite, Hermes' elderly machinery could have been replaced with modern machinery of less weight, but more power and efficiency. Use the space saved to add a larger ~30,000IG avgas stowage system and larger magazines.

Remove the obsolete HA guns, LA guns and FC systems and replace them with a new DP HA armament and modern FC (say 8 x 4in DP guns), more short range AA weapons. New lifts to take larger aircraft.

So we get a 27-28 knot carrier, with capacity for maybe 20 Albacore sized aircraft in her hangars, greater cruising range and better AA.

 

[Admiral Beez]

The RN could have completely rebuilt Hermes if they so desired and if the treasury would have parted with the funding.

As with Renown and Warspite, Hermes' elderly machinery could have been replaced with modern machinery of less weight, but more power and efficiency. Use the space saved to add a larger ~30,000IG avgas stowage system and larger magazines.

Remove the obsolete HA guns, LA guns and FC systems and replace them with a new DP HA armament and modern FC (say 8 x 4in DP guns), more short range AA weapons. New lifts to take larger aircraft.

So we get a 27-28 knot carrier, with capacity for maybe 20 Albacore sized aircraft in her hangars, greater cruising range and better AA.

Not bad ideas. The USN's 31 knot Independence class CVLs were about the same size of Hermes (11,000 tons standard displacement, approx 600 ft x 70ft), though at least three feet deeper in draught. At 25 knots Hermes is already faster than most of the RN battlefleet, though your engine improvement to over 30 knots does have merit for flight ops and running with KGV class battleships, other carriers, plus cruisers and fast escorts. A smaller engine does free up space and weight as well, as you suggest. I'd like to enclose the stern to allow for deeper draught. Let's cut the giant island down to size, keeping in mind that our plans for a larger CAG will require space for personnel. If we're keeping the big island, what about adding radar?

With greater speed, Hermes might have been further south when Nagumo's strike arrived and may have survived the day.

 

[Admiral Beez]

This model gives us an idea of Hermes' hangar layout.

I have to wonder what was stored forward of the hangar, as there's nearly half of the ship's length there. Perhaps aircraft parts stowage or accommodation space? I'd love to find some blueprints for Hermes.

 

[Shortround6]

The RN could have completely rebuilt Hermes if they so desired and if the treasury would have parted with the funding.

Use the space saved to add a larger ~30,000IG avgas stowage system and larger magazines.

Yep, if you stripped her right down to the keel and started over you might get a carrier that could support 30 aircraft for about a day and half.
Bit of an exaggeration but the Hermes used 6 boilers and 2 shafts to get 40,000hp. The Indiependence used 4 boilers and 4 shafts to get 110,000hp. Changes in boilers from 1917-18 to even the late 30s was huge but you are not going to turn the Hermes into a 30 knot ship with anything less than nuclear propulsion and/or a total rebuild of the boiler, turbines and shafts.
BTW the 1942 plans for the Independence class were for 12 fighters, 9 dive bombers and 9 torpedo bombers with a fuel storage of 120,000 US gallons.
You can't change the boilers without either ripping off the flight deck or cutting large holes in it. Trying to change the Turbines is just as bad, just in a different area.

The cost/effort is not worth the result. The Battleship rebuilds were justified in that the naval treaties allowed reconstruction but not replacement. The Hermes was exempt from that. The early carriers were allowed to be replaced at any time.

There was a plan to take out the 5.5 in guns and the 4in AA guns and replace them with four twin 4 in mounts and a few 2pdr pom poms but it was never implemented. During the late 30s the British had a shortage of the twin 4 in mount and a shortage of the 2pdr pom pom guns. They wanted to fit more of them than they did but production didn't allow it.

The picture just posted by Admiral Beez shows part of the problem with the Hermes, She had a very fine bow, which limited space.

On the Independence class carriers the forward lift was where it was due the hanger and the hull shape. The flight deck ended short of the bow because they figured the hull would not support a flight deck out to or overhanging the bow. The upper deck of the cruiser hull also curved up at bow which meant without redesign/rebuild=delay they couldn't use the added under flight deck space for hanger space anyway. The Independence class was about 10% heavier than the Hermes and 10% buys a lot of improvements when you figure in some of the differences in construction like welding over riveting.

 

[Freebird]

Well, if you take the best option off the table all you are left with is a bunch of minor tinkering of various cost for little overall result.
The 5.5 in guns weigh around 14-15 tons each without shield, Shield weighs about 4.5 tons if 1 1/2 in thick. So pulling the six guns gets you just over 100 tons on a 10,000ton ship (13,000tns full load) Reduced load in the magazines and reduced crew may be just as important.
The ship already trimmed by the bow so adding flight deck there may not be a good option. Granted adding a crap load of weight aft may help things out.

Ship is on the slow side, I don't believe she ever got new boilers? so book speed might be subject to question? Or at least hard steaming for long periods of time should be avoided.

Basically you already have 1.5 liters in a 1 liter bottle and no matter what you do you aren't going to get much more in.

Agreed.
One would have to balance the expected results with the costs, in both £ and shipyard time.
Also depends when you're contemplating this.
During the 1920s the Royal naval shipyards are busy, building HMS Eagle, Furious, Courageous and Glorious.
Following the Washington treaty, from 1930-1937 the British yards (& budget!) are full with the Leanders, Southampton's and laying down Ark Royal & Illustrious class, not to mention numerous refits.
Since the intent was to replace Hermes's tonnage with an Illustrious class carrier, it doesn't make much sense to cancel other critical navy needs for a major rebuild.
By 1937-38 after Japan has withdrawn from the treaty and Germany begins its march to war, they might come to the realization that they likely won't be scrapping warships, and now a minor Hermes refit makes sense.

Removing the island is probably too big a job, although definitely replacing the 5.5" guns with 4" AA or pom-pom mounts would be a good idea. The barge accessible rear lift is a useful feature
Realistically though, the Hermes is well enough suited for the missions that it would be used for, trade protection, hunting U-boats and surface raiders, and aircraft transport.

To be honest, in the late 30's I'd much, much rather see the British use their limited shipyard space to rebuild HMS Vindictive as a proper light carrier, rather than waste time on redesigning HMS Hermes which is already functional as an auxiliary carrier.

 

[Admiral Beez]

Agreed.
One would have to balance the expected results with the costs, in both £ and shipyard time.
Also depends when you're contemplating this.
During the 1920s the Royal naval shipyards are busy, building HMS Eagle, Furious, Courageous and Glorious.

This could be a good project for the overseas yards. In 1938 the Singapore naval base opens with a complete dry dock facility. Earlier, in 1924 the Esquimalt Graving Dock opened. Both are capable of taking Hermes' 600 ft size. By the 1930s the Canadians are already building civilian and naval ships on both coasts, but I imagine BC could use the work. Taking an active carrier out of service in 1938 when all three future Axis nations are rattling their sabres is not wise, so unfortunately Singapore is out (though I'd still like Hermes to use the base post-1938), so it's either Canadian or Australian yards. As for finances, why not sell the ship to the RAN?

Now, replacing the machinery is a big job, essentially tearing out the flight deck and hangar deck, unless one can access this from the side. So this presents a good time for other upgrades.

 

[Shortround6]

In reverse, the boilers are usually below the water line, at least the parts under pressure, Ducting for the hot gases obviously go much higher. Some large ships have 3 or more decks above the boiler rooms, Large American carriers may have 5 or more counting the hanger and the flight deck. The boiler rooms on ships bigger than destroyers don't reach the side the side of the ship. at least one bulk head/compartment separates the boiler room from the hull side, sometimes several depending on torpedo protection scheme.

Trying to use some overseas yards just runs up the cost and delays things. You need more than dock space, you need a source for all the "parts" you are going to need, and that is a lot more than just the guns or new boilers, it is all the fittings, the plate steel, the piping and so on. Shipping all that stuff (plus spares) half way round the world because you have an underutilized dock there may not be that good an idea.

 

[Admiral Beez]

In reverse, the boilers are usually below the water line, at least the parts under pressure, Ducting for the hot gases obviously go much higher. Some large ships have 3 or more decks above the boiler rooms, Large American carriers may have 5 or more counting the hanger and the flight deck. The boiler rooms on ships bigger than destroyers don't reach the side the side of the ship. at least one bulk head/compartment separates the boiler room from the hull side, sometimes several depending on torpedo protection scheme.

It took some digging through this excellent collection of ship plans, but here's HMS Hermes 95 blueprints. The boilers are positioned two bulkheads inward, but being directly below the hangar deck should make for "easy" access from above. The turbines may be deeper in the guts of the ship.

Note how the original 1918 plan was for a flat and more useful stern flight deck, not the later round down.

This plan gives an idea of how busy the large island is. Note these are the rectangular lifts before they were revised to their T-shape.

One challenge compared to a CVE or CVL is how slender Hermes is below the waterline.

 

[Glider]

In many ways the changes you are suggesting are similar to those made to HMS Furious. Mixed low angle and high angle guns replaced by 12 x 4in AA guns and a total of 4 octuple 2pd (pre war changes) plus about 20 x 20mm during the war. Her machinery was refurbished (not replaced) between the wars and her flight deck extended.

 

[RCAFson]

Yep, if you stripped her right down to the keel and started over you might get a carrier that could support 30 aircraft for about a day and half.
Bit of an exaggeration but the Hermes used 6 boilers and 2 shafts to get 40,000hp. The Indiependence used 4 boilers and 4 shafts to get 110,000hp. Changes in boilers from 1917-18 to even the late 30s was huge but you are not going to turn the Hermes into a 30 knot ship with anything less than nuclear propulsion and/or a total rebuild of the boiler, turbines and shafts.
BTW the 1942 plans for the Independence class were for 12 fighters, 9 dive bombers and 9 torpedo bombers with a fuel storage of 120,000 US gallons.
You can't change the boilers without either ripping off the flight deck or cutting large holes in it. Trying to change the Turbines is just as bad, just in a different area.

The cost/effort is not worth the result. The Battleship rebuilds were justified in that the naval treaties allowed reconstruction but not replacement. The Hermes was exempt from that. The early carriers were allowed to be replaced at any time.

There was a plan to take out the 5.5 in guns and the 4in AA guns and replace them with four twin 4 in mounts and a few 2pdr pom poms but it was never implemented. During the late 30s the British had a shortage of the twin 4 in mount and a shortage of the 2pdr pom pom guns. They wanted to fit more of them than they did but production didn't allow it.

The picture just posted by Admiral Beez shows part of the problem with the Hermes, She had a very fine bow, which limited space.

On the Independence class carriers the forward lift was where it was due the hanger and the hull shape. The flight deck ended short of the bow because they figured the hull would not support a flight deck out to or overhanging the bow. The upper deck of the cruiser hull also curved up at bow which meant without redesign/rebuild=delay they couldn't use the added under flight deck space for hanger space anyway. The Independence class was about 10% heavier than the Hermes and 10% buys a lot of improvements when you figure in some of the differences in construction like welding over riveting.

I stated 27-28 knots in my OP which could be achieved on about 50k SHP; Hermes made 26.2 knots on trials with 42.9K shp. 30kIG of Avgas would support about 200 sorties, which with a ~20 aircraft complement seems sufficient. USS Enterprise flew less than 400 sorties at Midway.

 

[Admiral Beez]

I stated 27-28 knots in my OP which could be achieved on about 50k SHP; Hermes made 26.2 knots on trials with 42.9K shp. 30kIG of Avgas would support about 200 sorties, which with a ~20 aircraft complement seems sufficient. USS Enterprise flew less than 400 sorties at Midway.

I like the speed, but I don't know if ~20 aircraft are possible. I've created some to scale pics below, before I saw the model pic with the forward hangar width reduction.

12 Fulmars, stowed for ops with space for maintenance and hanger moves, rather than crammed in for ferry work. This requires square lifts.

Here's 19 Fulmars squeezed in. If we remove the stern round down and add a crash barrier and outriggers we could have the above 12 in the hangar and the others could be stowed on deck.

Here's 18 Brewster Buffaloes (plus one on the forward lift that I forgot to draw in.

Here's 22 Martlets, tightly packed with the original T-shaped lifts.

Okay, now we're getting silly, but 33 Martlets! Of course this is before saw the narrowing of the forward hangar. Note the Seafire, included to show that the T-shape will not accommodate an unfolded Seafire.

That was fun. So, if we flatten the stern round down, add a crash barrier and outriggers we should be able to deploy eight Swordfish/Albacores and at least twelve folded Martlets. So there's your 20 aircraft. We just need to find a space for fuel, munitions, spares, flight crew and maintenance personnel. It's going to be crowded in the berthing and mess areas - I imagine in warm weather some will opt to sleep on the flight deck or other open spaces. She's a small ship for certain.

WW2 British Aircraft Carriers

Some great pics of Hermes here, MaritimeQuest - Marine Ernest Walter Foster, R.M. Collection Page 1 including Charles Lindbergh and his wife flying in to visit on their round the world honey moon flight.

 

[RCAFson]

I was thinking of something like 8 Albacores and 12 Skuas. It might be possible to move, one or both, lifts to forward/aft of the hangar space, to increase the hangar stowage.

 

[Admiral Beez]

I was thinking of something like 8 Albacores and 12 Skuas. It might be possible to move, one or both, lifts to forward/aft of the hangar space, to increase the hangar stowage.

We may need to square off the lifts like I've done above for the Fulmars (Length: 40 ft 2 in), otherwise the Skuas may be too long to fit on Hermes' two 36 by 36.6 feet lifts.

EDIT - Skua is fine on the original T-shape lifts, though at 35ft 4ins long is very tight on length. Blackburn Skua II (L2490) Wingspan - 46ft 2ins (15ft 6ins folded). It's as if the Skua was custom made for Hermes, with barely an inch to spare.

What about going the other way on lift dims, and resize them to the original 44 by 20 feet lift design, shown below? This will be fine for any folding aircraft in the FAA, including even the relatively huge Grumman Tarpons (40 ft x 19 ft folded) and Fairey Firefly (38 x 13 ft folded) . This would free up hangar space, if only for spares and work space beside the lift wells.

 

[Shortround6]

Carriers sometimes have trouble with the lifts. The Hull bends and twists in a seaway and throw the lift guides (rails?) out of alignment.
Also cutting large holes in decks affects the strength of the deck. Granted on a lot of carriers the "strength" deck was the hanger deck.
The elevators were fitted in wells and the machinery may have gone below the hanger deck.
The Hermes trimmed by the bow (bow was deeper than the stern) if left alone and there was a lot shifting of the fuel oil to keep her in trimand things were so tight that allowances had to be made for the different specific gravity of the fuel oil from different sources.

There is no doubt that the Hermes could have been "improved". What is in doubt is how much and more importantly, at what cost.
Would the Hermes have lived out her last years as an aircraft ferry and training carrier if the the British had not lost the Courageous and Glorious so quickly and to so little purpose?

How much time and effort should have been spent upgrading the smallest and possibly least capable aircraft carrier?
Perhaps more money should have been spent on the Eagle (which did get new boilers in 1931-32) as even with her greater size her hanger was the same length as the Hermes.

 

[Admiral Beez]

There is no doubt that the Hermes could have been "improved". What is in doubt is how much and more importantly, at what cost.

Start with the cheap and fast mods. Add crash barrier, outriggers, flush stem to stern flight deck, replace anti ship guns with AA, add radar when available. Hermes greatest improvement can be in the aircraft she is given, if Hermes lasts long enough, folding Martlets.

Would the Hermes have lived out her last years as an aircraft ferry and training carrier if the the British had not lost the Courageous and Glorious so quickly and to so little purpose?

IDK, but by the end of 1941 Courageous, Glorious and Ark Royal have been sunk and the new Illustrious and Formidable crippled and undergoing repairs in the USA. Until these latter two AFD carriers re-enter service in Feb 1942 HMS Hermes is one of only five RN fleet carriers (Indomitable, Victorious and Furious and Eagle). I think an updated Hermes could serve in front line roles into 1944.

If given sufficient mods and aircraft I could see Hermes leading the Allies in the Aleutians against the two light IJN carriers.

 

[southjn1982]

Very intresting discussion sorry if I necroed it as its a few months old by now, Personally If I was going to do anything to Hermes in the 1920s/early 30's I would be trying to shave 851 tons off its displacement even if that meant dropping down from 25knots to 23/24 knots as then it would be legally below 10,000 tons and thus not an aircraft carrier under the treaty system at that point I would give her at least 10 sister ships using up the cruiser tonnage as well as giving two each to the Aussies, Canadians and the New Zealander's these vessels would be used as trade defence cruisers. It would be a great export product for the UK not only for the Dominions but also traditional UK customers of the time like Chili, Portugal, The Netherlands etc as they would be intrested in a low cost budget vessel that gives them a lot of extra capabilities without breaking the bank (similar in principle to how many nations bought derivatives of the 1942 light fleet carrier post WW2) this would also secure other contracts as they will need planes one a semi regular basis to go with them. They would basically be filling in a role similar to the CVE's of WW2 although. This would also allow the UK to use these vessels on anti-submarine and other non-strike roles such as aircraft ferrying and in secondary theatres early in WW2 allowing a concentration of larger fleet carriers into an armoured fist and potentially preventing the loss of Courageous, Glorious and Ark Royal Courageous and Glorious especially were wasted but this could potentially have all three of them along with Furious still availiable in 1941/42 and have Fishers 3 sisters and Ark forming a centre of a strong Indo-Pacific fleet while the more heavily armoured carriers operated in the Med and in Home waters with Repulse and POW acting as heavy escort for the four carriers creating a super Force Z although not ideal would certainly make things intresting.

 

[Admiral Beez]

shave 851 tons off its displacement below 10,000 tons and thus not an aircraft carrier under the treaty system

At that point we might as well do a Langley and convert Hermes to a seaplane tender. Something like HMAS Albatross that entered service in 1929.