When is a warship a cruiser?

[WatcherZero]

SSBN's are todays battleships, they perform similar deterrence and prestige duties and have a similar relative cost value.
SSN's/SSGN's are today the first half of the 20th centuries heavy cruisers to hunt for enemy shipping/naval assets while possessing formidable firepower second only to a battleship the latter of course specialised in shore bombardment.
Todays destroyers are the equivalent of early 20th century light cruisers or age of sail Frigates, able to protect themselves and destroy smaller warships but vulnerable to SSN's or other destroyers when alone, group together for self protection in flotillas, capable of performing significant duration detached operations.
Todays frigates are the equivalent of early 20th century destroyers and destroyer leaders, the workhorses of the fleet providing mass and geographic coverage, primary role is escorting the merchant fleet or forming larger taskforces.
Todays corvettes are the same as WW2 and age of sail corvettes, protecting supply lines, border protection, and the primary defence capability of less wealthy countries against similar rivals.
Fast Attack Craft and conventional submarines today perform the same duties previously performed by motor torpedo boats, monitors and other brown water ships.

Which leaves out what constitutes a cruiser today as it doesnt comfortably fit into any of these better defined roles. I would argue what constitutes a modern cruiser is an oversized air defence destroyer with significant land attack capability. In historical terms this may be similar to the German Pocket Battleships or Japanese Battle Cruisers, (oversized heavy cruisers but sacrificing so much armour they are not capable of engaging a true battleship).

 

[pathology_doc]

Today we have destroyers which carry area anti-aircraft systems and general purpose frigates which do not.

The Oliver Hazard Perry class frigates muddied those waters extensively!!!

Isn't it to do with the number of swimming pools, the size of the ballroom and the number of Michelin stars the restaurant holds?

In all seriousness, I always thought it was related to the presence of onboard engineering workshops that enabled them to do their own maintenance when deployed.

That was the feeling I got as well. I'll have to check my Friedman and my Brown, but IIRC there are also factors concerned with the standard to which the hull is built.

First, there is nothing either intrinsically right or intrinsically wrong about liberty or slavery, democracy or autocracy, freedom of action or complete regimentation.

Off topic - That's Mentor of Arisia talking, isn't it?

 

[Yellow Palace]

That was the feeling I got as well. I'll have to check my Friedman and my Brown, but IIRC there are also factors concerned with the standard to which the hull is built.

There's a NAVSEA report from 2005 which looked at what made a cruiser here:https://navalmarinearchive.com/research/docs/cruisers/cr_navsea.html

About half-way through, there's a breakdown of the difference between cruiser and destroyer practice in the Royal Navy in 1957. Their final conclusion is that a modern cruiser - as distinct from a carrier escort directly replacing the CG-47 class - would include the following features:

• Increased survivability, especially against ambush attacks, including a return to structural armor,
• Increased stores and fuel loads for independent operations,
• Increased self repair stores and shops to allow staying on station for an extended period while remaining fully capable,
• First responder capabilities (such as limited medical facilities, small arms for the crew and an extensive boat/helo outfit), and
• Crew sized not only to operate the ship but to put small detachments ashore or onto seized merchant ships.
• Provisions for carrying a small command staff and a senior officer (if assigned a role in the command structure).

 

[WatcherZero]

Since 1957 I would argue both Destroyers and Frigates have taken on many of that list of duties in the Royal Navy. The Type 45 had twice the displacement of the Type 42 (about 8,500 to 4,500 tons) while Frigates have gone from the 2,500 of the 1950's Leopard and Salisbury classes to 8,000 on the Type 26 and 5,700 on the Type 31 with the Type 32 expected to return to a 6-8,000 general purpose design.

 

[Dilandu]

Off topic - That's Mentor of Arisia talking, isn't it?

Yep)

 

[chimeric oncogene]

The Oliver Hazard Perry class frigates muddied those waters extensively!!!

You mean the patrol frigate, guided missiles, right?

 

[pathology_doc]

You mean the patrol frigate, guided missiles, right?

FFG-7 class. That which by any other name would carry a Mk13 launcher, a 76mm gun, a CIWS, torpedoes and a helicopter.

 

[Scott Kenny]

FFG-7 class. That which by any other name would carry a Mk13 launcher, a 76mm gun, a CIWS, torpedoes and a helicopter.

Which were originally proposed under the Patrol Frigate name...

 

[owlscreech]

Not really the FIII Burkes have C&C spaces in them now from I’ve read and heard.

The cruiser designation is just dying out that’s all.

Personally I think large surface combatants should be cruisers, medium/small frigates, and modern corvettes and things like the ASuW LCSes should shoulder the title destroyer since it is just a shortening of torpedo boat destroyer, and modern destroyers do not fit that role at all any more.

I'm partial to the functional definition used by the Commonwealth navies i.e. destroyer = primarily AAW, frigate = primarily ASW/GP. However, I am a British-Australian dual national so I would say that lol

As for cruisers, I agree it's rather become a designation in search of something to designate.

Funny you point out that the LCS is closer to the historical TBD than modern DDs/DDGs, because I've long said that trying to build a PT boat the size of a Type 12 frigate was inevitably going to be a hell of a thing to make work.
As we all know now of course, it has indeed been hard to make the LCS work, but the LCS makes plenty of hard work for their crews!

 

[Scott Kenny]

There's a NAVSEA report from 2005 which looked at what made a cruiser here:https://navalmarinearchive.com/research/docs/cruisers/cr_navsea.html

About half-way through, there's a breakdown of the difference between cruiser and destroyer practice in the Royal Navy in 1957. Their final conclusion is that a modern cruiser - as distinct from a carrier escort directly replacing the CG-47 class - would include the following features:

• Increased survivability, especially against ambush attacks, including a return to structural armor,

I don't know how much structural armor will help against modern munitions. I mean, even the old and out-dated US AT4 antitank rocket could punch the main belt of an Iowa-class, and newer antitank missiles can punch over a meter of RHAe. That said, it may be easier to put thicker steel between compartments to contain damage better on surface ships.

Better damage control gear is easy to do, though it does take some careful designing so that it is very hard to leave a large area without a fire main or whatever.

• Increased stores and fuel loads for independent operations,

And increased crew habitability space.

• Increased self repair stores and shops to allow staying on station for an extended period while remaining fully capable,

This is a point where I think the USN has been working the opposite direction, less spare parts on board and less ability to fix anything onboard.

"Part X has gone bad, don't have one onboard"
"Pull and replace the higher assembly, then."
"We don't carry the higher assembly onboard, either."
"Seriously? (lots of expletives deleted)"

Example: one of the highly skilled Navy Enlisted Classifications (NEC) was one that had the name "Undocumented Troubleshooter", the guy who could look at the prints onboard and work through the different parts to see what exactly was broken. That school no longer exists, and neither does the NEC. It hasn't existed since the early 2000s. The only reason I know it exists is because a friend of mine was one.

Also, with how heavy even a 3mm steel sheet is when it's 4x8 or larger for simple hull plating, I'm not sure how much "patch the hole" can be done with onboard supplies if the ship doesn't have a crane rigged up to haul the sheets to the deck and hang them over the side to be welded in place.

• First responder capabilities (such as limited medical facilities, small arms for the crew and an extensive boat/helo outfit), and

A lot of this has happened in general post-9/11. The amount of guns and other supplies we got after 9/11 was unreal, and we were submarines!

• Crew sized not only to operate the ship but to put small detachments ashore or onto seized merchant ships.

That's a MARDET in the USN, and/or a Coastie LEDET, though having some bluejackets available again would be interesting.

• Provisions for carrying a small command staff and a senior officer (if assigned a role in the command structure)

This is arguable. The only time the USN needs flag officer space is for the Air Warfare boss in an escort group. I believe that most of these points should be added in general to newly designed/constructed ships of all classes.

 

[johnpjones1775]

I'm partial to the functional definition used by the Commonwealth navies i.e. destroyer = primarily AAW, frigate = primarily ASW/GP. However, I am a British-Australian dual national so I would say that lol

As for cruisers, I agree it's rather become a designation in search of something to designate.

Funny you point out that the LCS is closer to the historical TBD than modern DDs/DDGs, because I've long said that trying to build a PT boat the size of a Type 12 frigate was inevitably going to be a hell of a thing to make work.
As we all know now of course, it has indeed been hard to make the LCS work, but the LCS makes plenty of hard work for their crews!

The LCSes were poorly planned, that’s for sure but they’re becoming very important parts of our fleet.

 

[Antonio]

RID Rivista Italiana Difesa - Nuovi dettagli sugli incrociatori pesanti DDX

Nuovi dettagli sugli incrociatori pesanti DDX

www.rid.it

Note that In the article the ships are referred as "heavy cruisers" (Incrociatori pesanti). Interesting

 

[DWG]

Isn't it just RID christening them that based on displacement?

the displacement, which at the moment can be estimated at 14,000-14,500 t full load; a significant displacement, in fact, which has thus led us to “force” the title with the categorization “heavy cruiser”.

If they're purely considering displacement, by the historical measure anything over 7,100t can count as a CA based on the Furutaka class, or 8,500t based on the York class.

 

[NMaude]

14,000 - 14,500 tons displacement is typical of cruiser.

 

[WatcherZero]

The post WW2 US guided missile cruisers from 1960's to late 1990's ranged from 7,800 tons to 11,000 tons with most on the smaller side. Ticonderoga still in service 9,800 tons. The Soviet Cold War cruisers ranged from 4,800 to 5,600 tons standard displacement with the in-service Kara class being 8,200 tons.

 

[NMaude]

So a heavy-cruiser displacement then?

 

[Scott Kenny]

The post WW2 US guided missile cruisers from 1960's to late 1990's ranged from 7,800 tons to 11,000 tons with most on the smaller side. Ticonderoga still in service 9,800 tons. The Soviet Cold War cruisers ranged from 4,800 to 5,600 tons standard displacement with the in-service Kara class being 8,200 tons.

Bad comparison, due to the "cruiser panic" and mass reclassification in 1975. A whole bunch of large destroyers (DDGs and DLGs) got bumped up to being called cruisers (CGs). The Tico class are literally Spruance class DDs with a new superstructure on top. From the main deck down Ticos are identical to Sprucans.

USS Long Beach CGN-9 was the last cruiser hull built for the USN, and was 15,000 tons. The Baltimore-class CAs of WW2 were 17,000 tons, and the Des Moines class were 21,000 tons.

 

[WatcherZero]

They did design a 25,000 ton cruiser to follow the 60's cruisers but it was cancelled. I think its derogatory to just call them Destroyers though, they do displace far more than most WW2 light and even a few heavy cruisers. The Spruance destroyer would form the basis for the Ticonderoga cruiser but the Spruance came in the 70's, later than most of the 60's cruisers (which were built on enhanced Frigate hulls), in doctrine it wasn't the cruisers being up designated it was the concept of a destroyer being up designated with the addition of a helicopter deck however their armament was initially quite limited with no anti-ship capability beyond a 5" gun until Tomahawk was added later. The guided missile cruisers on the other hand were specifically designed for hunting other ships not being escorts (and the smaller ones kept the non-cruiser designation). You also had the four converted Baltimore class which served as guided missile cruisers which were also carrying Regulus missiles, you could refer to them as Heavy Cruisers. Its also worth pointing out that historically a Frigate was a larger and more powerful ship than a Torpedo Boat Destroyer which initially were very small.

 

[Scott Kenny]

They did design a 25,000 ton cruiser to follow the 60's cruisers but it was cancelled. I think its derogatory to just call them Destroyers though, they do displace far more than most WW2 light and even a few heavy cruisers. The Spruance destroyer would form the basis for the Ticonderoga cruiser but the Spruance came in the 70's, later than most of the 60's cruisers (which were built on enhanced Frigate hulls), in doctrine it wasn't the cruisers being up designated it was the concept of a destroyer being up designated with the addition of a helicopter deck however their armament was initially quite limited with no anti-ship capability beyond a 5" gun until Tomahawk was added later. The guided missile cruisers on the other hand were specifically designed for hunting other ships not being escorts (and the smaller ones kept the non-cruiser designation). You also had the four converted Baltimore class which served as guided missile cruisers which were also carrying Regulus missiles, you could refer to them as Heavy Cruisers.

The USN classed those heavy escort ships as Destroyer Leaders, built on destroyer-style unarmored hulls. Or at best on an unarmored light cruiser hull, in the case of USS Norfolk, DL-1.

Its also worth pointing out that historically a Frigate was a larger and more powerful ship than a Torpedo Boat Destroyer which initially were very small.

That definition of "Frigate" was out of use as soon as steam replaced sails. The "largest vessel not in the line of battle" was called a cruiser when powered by steam. When powered by sail, such a vessel needed to be fully square-rigged like a ship of the line (historical definition).

Between 1890 and 1910, Torpedo Boat Destroyers went from ~300 tons to over 1100 tons. By the end of WW2, the typical destroyer was 1800 tons and had effectively replaced the Torpedo Boat it was supposed to hunt.

Between 1955 and 1975, the USN called their big ships Frigates, trying to reflect back to the Original Six Frigates of the USN that were the biggest and most dangerous ships of their time. Nothing that could kill them could catch them, and nothing that could catch them could kill them. But that was when people were calling the old ASW Destroyer Escorts "frigates", which led to US congress getting their panties in a bunch over how the USSR Navy had all these cruisers and the USN had so few and they were all WW2 veterans. So in 1975, the USN redesignated all their DLGs as CGs, DLGNs as CGNs. And started calling the ASW "Ocean Escorts" frigates like how Europe was calling their ASW escorts frigates.

 

[DWG]

14,000 - 14,500 tons displacement is typical of cruiser.

The Washington Treaty disagreed:
​

Article XI

No vessel of war exceeding 10,000 tons (10,160 metric tons) standard displacement, other than a capital ship or aircraft-carrier, shall be acquired by, or constructed by, for, or within the jurisdiction of, any of the Contracting Powers.​

Heavy Cruiser (or incrociatori pesante) has a fairly precise definition under the London Treaty*, a) below:​

Cruisers​

Surface vessels of war, other than capital ships or aircraft carriers, the standard displacement of which exceeds 1,850 tons (1,880 metric tons), or with a gun above 5.1 inch (130 mm) calibre.
The cruiser category is divided into two sub-categories, as follows:​

(a) Cruisers carrying a gun above 6.1 inch (155 mm) calibre;
(b) Cruisers carrying a gun not above 6.1 inch (155 mm) calibre.​

The definitions fell through as the Japanese withdrew, but 14,000t cruisers were either the last gasp of the first class armoured cruisers, or a temporary aberration around WWII, they were never typical, always being grossly outnumbered by the smaller cruiser classes.

And we're getting grossly off topic.

* Though having looked at the text it doesn't actually use the word 'heavy'.

 

[MihoshiK]

The Washington Treaty disagreed:



Heavy Cruiser (or incrociatori pesante) has a fairly precise definition under the London Treaty*, a) below:​

The definitions fell through as the Japanese withdrew, but 14,000t cruisers were either the last gasp of the first class armoured cruisers, or a temporary aberration around WWII, they were never typical, always being grossly outnumbered by the smaller cruiser classes.

And we're getting grossly off topic.

* Though having looked at the text it doesn't actually use the word 'heavy'.

It's been eighty years since we've defined ship types by tonnage.

 

[Firefinder]

The Washington Treaty disagreed

The Washington Naval treaty and the London Naval treaties been render Null and Void since 1938.

No one but historians or story writers even look at it at anymore.

Also by that Definition the US Des Moines class Heavy Cruisers that clock in FLAT EMPTY at 17,000 tons is not z cruiser when it very much is.

Ditto for the 16k Worcester Baltimore amd Oregon City classes. Which compain are nearly 30 something ships, out doing both the RN and IJN classes combine.

Ship types as a whole general get heavier as time march on unless Artificially limited by the mention treaties. As seem by the modern Destroyers which average 9 to 10k tons, or right smack in the Treaty Cruiser range, which begs of the question of what does that make them?

Answer is destroyers still.

The treaty system is deader then battleships and have no bearing on modern designs.

So stop acting like it does.

 

[A Tentative Fleet Plan]

The guided missile cruisers on the other hand were specifically designed for hunting other ships not being escorts (and the smaller ones kept the non-cruiser designation).

US Guided Missile Cruisers (and I mean the actual cruisers, Long Beach and the conversions) were designed primarily as escorts, they carried the flag facilities, height finders and fighter control facilities to control the CAPS and assign sectors to the Frigates (DLG/DLGNs like the Coontz/Farraguts, Leahys, Belknaps, Californias, Virginias) to defend.

 

[DWG]

The Washington Naval treaty and the London Naval treaties been render Null and Void since 1938.

That was rather my point. Just like the term 'heavy cruiser'.

 

[johnpjones1775]

Someone liked one of my posts here so I decided to reread the thread.

It’s wild what the LCSes have been doing.
A single LCS, defeated 2 Burkes in exercises.
For most of the Red Sea conflict they’ve been the only USN asset regularly in the SoH and gulf.
They’ve also been busy intercepting weapons shipments from Iran to the Houthis, as well as ensuring OPBOXes are clear of USVs/FAC/FIACs for the CVN to operate in the area.
And more that’s not classified but not publicly published in regards to ‘exercises’ with the PLAN, but my source has asked me not mention it publicly.

The LCSes were poorly planned, that’s for sure but they’re becoming very important parts of our fleet.

 

[johnpjones1775]

This is really the key one. No ship classifications have been handed down on stone tablets from above.

FWIW, the classification I prefer is:

• Cruiser - full-spectrum surface warship capable of air, surface, subsurface and strike warfare, with task force command capability
• Destroyer - full-spectrum surface warship capable of air, surface, subsurface and strike warfare
• Frigate - specialised surface warship capable of fleet speed and self-sustainment
• Corvette - specialised surface warship capable of fleet speed but not self-sustaining
• Sloop or aviso - generally capable only of self protection, self-sustaining but not capable of fleet speed
• Patrol ship - can point something that goes 'bang' and radio for help

As far as I can tell, this system is unique to me.

I must have missed seeing this before.

But for me a blue water PC should be more capable than just a RWS for a gun and a radio.

The French have a new class of PCs coming with a 40mm RAPIDfire gun, some sort of new drone jammers mounted just below the bridge on 3(4?) sides, HMS, and a hangar w/ flight deck for medium helicopter.

This means it can operate as an ASW picket which is its intended primary role, clearing an area of enemy subs as their subs go out to sea, but also makes it a great counter drone unit.

And historically, PCs had pretty serious capabilities in WWII and early Cold War periods.
Examples PC-461 type boats, x1 3”, 3-5 20mm, ASW mortars, and depth charges, was fairly capable.

Even the old cyclones were originally pretty capable, with 2 mk38s, up to 4(?) griffin missiles, and launching rings for MANPADs.(which have proven a lot more threatening in Ukraine than I ever expected them to be.)
Compared to so many other modern classes of PCes that are much larger cough-River class-cough.

Anyway, it’s not hard to make a modern PC that’s got some potential in a high end conflict, nations just choose not to. It’s as simple as 2-8 ASMs and maybe an FC radar for said missiles,(but since datalink is a thing it’s not particularly necessary) and a DP 35-57mm gun

 

[Scott Kenny]

I still mark the difference between a modern Guided Missile Cruiser and a Guided Missile Destroyer as the presence of AAW Flag facilities for the cruiser, and the lack thereof for a DDG. So yes, by my definition Japan has 6x CGs as all their Aegis DDGs have flag facilities.

I'd like for the cruiser to be bigger so it has more space for spare parts to allow it to stay at sea longer, but that's not a requirement when the DDGs have stores for at least 90 days away from port as a standard fit. And in general the various navies are making warships bigger so they have more crew comforts as well. Gyms, bigger library, etc ad nauseam.

 

[johnpjones1775]

I still mark the difference between a modern Guided Missile Cruiser and a Guided Missile Destroyer as the presence of AAW Flag facilities for the cruiser, and the lack thereof for a DDG. So yes, by my definition Japan has 6x CGs as all their Aegis DDGs have flag facilities.

I'd like for the cruiser to be bigger so it has more space for spare parts to allow it to stay at sea longer, but that's not a requirement when the DDGs have stores for at least 90 days away from port as a standard fit. And in general the various navies are making warships bigger so they have more crew comforts as well. Gyms, bigger library, etc ad nauseam.

Iirc Greek MEKO-200 FFGs have flag facilities, being less than 4k tons, and extremely limited missile loadouts, I think we can all agree they’re not cruisers.

 

[Scott Kenny]

Iirc Greek MEKO-200 FFGs have flag facilities, being less than 4k tons, and extremely limited missile loadouts, I think we can all agree they’re not cruisers.

And those are frigates.

 

[johnpjones1775]

And those are frigates.

They have the flag facilities you said a cruiser have, so what keeps them from cruiser status?

 

[Scott Kenny]

They have the flag facilities you said a cruiser have, so what keeps them from cruiser status?

I said that the difference between a cruiser and a destroyer is the flag facilities.

What's the difference between a destroyer and a frigate?

 

[johnpjones1775]

I said that the difference between a cruiser and a destroyer is the flag facilities.

What's the difference between a destroyer and a frigate?

Nothing.

 

[Dilandu]

What's the difference between a destroyer and a frigate?

Destroyer is usually multi-purpose, frigate more specialized.

 

[johnpjones1775]

Destroyer is usually multi-purpose, frigate more specialized.

The horizon class are destroyers and frigates. Not to mention datalink and VLS mean any VLS ship is multipurpose.

Constellation class is just as multipurpose as a burke, just has less VLS. Outside of arbitrary tonnage ranges there’s really no difference between DDGs and FFGs designed post 2000.

 

[H_K]

Outside of arbitrary tonnage ranges there’s really no difference between DDGs and FFGs designed post 2000.

So how about a role-based classification?

DDG -> Primary AAW / BMD escort. Able to take on Air Defense Commander role for a task force.

FFG / FF -> Primary ASW / GP escort

 

[Scott Kenny]

Constellation class is just as multipurpose as a burke, just has less VLS. Outside of arbitrary tonnage ranges there’s really no difference between DDGs and FFGs designed post 2000.

Disagree.

An FFG is primarily ASW with enough AA capabilities to defend itself and maybe chase off an MPA looking for the convoy it's protecting.

A DDG is primarily AAW with enough ASW capabilities to defend itself and maybe chase off the sub looking for a carrier.

It's just that the definition of "enough AA capabilities to defend itself and maybe chase off an MPA" has greatly increased since 2000.

 

[johnpjones1775]

So how about a role-based classification?

DDG -> Primary AAW / BMD escort. Able to take on Air Defense Commander role for a task force.

FFG / FF -> Primary ASW / GP escort

Except for maybe the ADC role, a Connie fills every other facet of DDG listed.

Classifications are simply more or less obsolete beyond very generic classification (sub, carrier, surface combatant, etc.)

 

[johnpjones1775]

Disagree.

An FFG is primarily ASW with enough AA capabilities to defend itself and maybe chase off an MPA looking for the convoy it's protecting.

A DDG is primarily AAW with enough ASW capabilities to defend itself and maybe chase off the sub looking for a carrier.

It's just that the definition of "enough AA capabilities to defend itself and maybe chase off an MPA" has greatly increased since 2000.

A Connie has SPY radar, it has VLS capable of launching the same exact missiles as a burke. Beyond depth of magazine a Connie will be able to do anything AAW that a Burke can do.

You can disagree all you want, doesn’t change the facts.

There multiple depths of VLS, one of which is ‘self defense’ length, the only SAMs that fit in that size are ESSM, but the Connies don’t have that, they have the full length cells. I believe they also can carry ASROC in self defense length.

If the Connies’ VLS was only self defense length you’d be correct here, but since that’s not the case, the Connies don’t match your definition of what an FFG is.

 

[Scott Kenny]

A Connie has SPY radar, it has VLS capable of launching the same exact missiles as a burke. Beyond depth of magazine a Connie will be able to do anything AAW that a Burke can do.

That's exactly my point, though.

A modern frigate doing convoy escort work requires a hell of a lot of magazine depth due to the missile threat level of even the Houthis, nevermind Iran, China, Russia, India, etc. This escort work requires VLS long enough to hold SM2s at the very least, if not SM3s and SM6s. A minimum of Tactical Length cells, and possibly Strike length (not sure what SM3 and SM6 need).

I suppose we could make an argument based on speed of the craft, but merchant ships have gotten a lot faster these days compared to WW2 convoys struggling to maintain 10 knots speed of advance. FFG7s were limited to about 28 knots, after all.

 

[johnpjones1775]

That's exactly my point, though.

A modern frigate doing convoy escort work requires a hell of a lot of magazine depth due to the missile threat level of even the Houthis, nevermind Iran, China, Russia, India, etc. This escort work requires VLS long enough to hold SM2s at the very least, if not SM3s and SM6s. A minimum of Tactical Length cells, and possibly Strike length (not sure what SM3 and SM6 need).

I suppose we could make an argument based on speed of the craft, but merchant ships have gotten a lot faster these days compared to WW2 convoys struggling to maintain 10 knots speed of advance. FFG7s were limited to about 28 knots, after all.

These types of classifications are just simply obsolete.

The LCSes have VLS mods for their topside module spaces (4-8) for self defense length coming.
That doesn’t make them FFGs either.

Really there’s only about 2 ways to do it.

VLS&tonnage(maybe ASMs)

So 3000-7000tons 24-64 VLS is frigate
8000-12000tons 72+ VLS is destroyer
13000tons 72+ VLS is cruiser

Might still have some weird overlap/gaps but should be comprehensive enough