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PostPosted: Sun Feb 12, 2017 11:20 am 
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HMS Warspite wrote:
I hope it's not going too far off topic - but could you tell me in what ways Chevalier Paul was simplified with respect to CNGF (and T45?).


It's important to distinguish between the Type 45 and CNGF here. Essentially what happened was that the RN compromised on many of its requirements to accommodate the French and Italians and, when CNGF imploded, it reversed a lot of those concessions. Personally, I think that retaining any of the CNGF design art was a mistake and they should have simply abandoned the work and gone from scratch. It wouldn't have taken any longer and would have produced a much better ship. Type 45 is only a shadow of what she could have been and was supposed to be. However . . . .

Chevalier Paul went the other way. The French had (very grudgingly) accepted a more capable ship than they really wanted and one of their complaints was that she was too expensive to procure in the numbers they needed. So, they simplified the CNGF design. The big changes were in the machinery spaces. They abandoned the WR21 gas turbines in IFEP configuration and replaced them with LM2500s and diesels in simple CODOG. Oddly, that actually worked for them since the LM2500 is a much better gas turbine than the WR21 - really, seriously much better. WR21 has fundamental design issues and is essentially a failure. Note that nobody else bought it.

The French also deleted the medium caliber gun (something the RN insisted on including) and replaced them with OTO Melara 76mms. Here's the funny thing. In the Italian ships, they have three OTO Melaras positioned so they give 360 degree coverage. Those guns are linked to a CIWS command system and are pretty good at what they do. They're a gun-based CIWS that works. The French deleted the CIWS command system to save money (simplifying the electronics significantly) so the 76s don't have any anti-missile capability. They replaced one of the guns with a Sadral missile launcher. Essentially, they replaced a gun-based CIWS that does work with a missile-based CIWS that doesn't. Note that the two remaining 76mms forward are winged out and have limited arcs of fire. They're there for show.

They also cooled down the EW and command systems in general and replaced the original battle management system (which is one of the glories of the Type 45) with a system which is basically the one developed for the Lafayette class light frigates. EW system likewise. Essentially the French ships have no battle management system; their ships are self-defense and have only very limited area defense capability. The Type 45s can run a full-scale air battle pretty much to the level of an Arleigh Burke - as long as their engines work anyway. By the way, one place the Type 45s cheaped out and the French didn't was emergency power supplies. Both ships use diesels which is dumb bit the French have four, the British two. They should have used gas turbines for emergency power generation and had four each. That would have been better and cut down on noise.

To cut the post a bit short, what the French did was to go through the CNGF design and replace all the on-board systems with cheaper alternatives. A couple of times, they'd score by doing so but mostly they ended up with a less capable ship. Personally, if I had to be on a ship in a middle of a hi-class naval battle, my first choice would be a DDG-51 and secondly one of the Dutch De Zeven Provinciëns. Third would be an F-124 and then an F-100. The Type 45 would follow them, primarily because of the unreliability of their machinery. If the RN has any sense, they'll bite the bullet and re-engine them with MT-30s.

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PostPosted: Sun Feb 12, 2017 11:34 am 
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If the RN has any sense, they'll bite the bullet and re-engine them with MT-30s.


Might well be something they do when the ships come in for major refits. If they do re-engine them would that move the 45s up in your estimation?

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PostPosted: Sun Feb 12, 2017 12:12 pm 
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Bernard Woolley wrote:
Might well be something they do when the ships come in for major refits. If they do re-engine them would that move the 45s up in your estimation?

I hope so; the machinery plant is those ships biggest limitation. They're adding another generator right now which is too little, too late. They need to rip the diesel generators out and replace them was gas turbines - three Rolls Royce 4500 would do just fine. That's what the USN uses now. At the moment the Type 45 is a Rolls Royce with the engines out of a Triumph Stag.

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PostPosted: Sun Feb 12, 2017 12:24 pm 
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At the moment the Type 45 is a Rolls Royce with the engines out of a Triumph Stag.


Now that's a whole different discussion. ;)
Some people replace the Triumph 3 litre V8 with the Rover 3.5. The fact that different parts of the same company were building two similar engines was a real sympton of how bad things were at BMC/British Leyland. In an ideal world the Stag would have had the Rover (Buick) engine.
However I have read that it is possible to fix the problems with the engine. Although that is a bit like how Microsoft seems to use its customers as Beta testers every time it updates Windows. :D

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PostPosted: Sun Feb 12, 2017 1:06 pm 
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I've got this notion developing in my head that I've been trying desperately to shake for the last month or so. But it just won't go away. It is this: the Ford Class isn't big enough to do everything a large-deck CVN will need to be doing in the time frame from about 2035 on forward.

A CVN fighting in a major conflict in the year 2035 and beyond will need more hangar space, more jet fuel capacity and ordnance stowage capacity, the capability to handle more and larger aircraft than a Ford Class CVN can now handle, and the ability to embark and support a full complement of F-35B's in addition to its planned F-35C's.

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PostPosted: Sun Feb 12, 2017 2:24 pm 
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Francis Urquhart wrote:
Bernard Woolley wrote:
Might well be something they do when the ships come in for major refits. If they do re-engine them would that move the 45s up in your estimation?

I hope so; the machinery plant is those ships biggest limitation. They're adding another generator right now which is too little, too late. They need to rip the diesel generators out and replace them was gas turbines - three Rolls Royce 4500 would do just fine. That's what the USN uses now. At the moment the Type 45 is a Rolls Royce with the engines out of a Triumph Stag.


So the biggest problem is with the generating plant, and not the hull, weapons systems, sensors and the ones and zeroes that tie them all together. That's really interesting. It suggests that the problems with the ships and the challenge in making them really world- class are fixable "just" by re- engining them. And as they're IFEP and so the GTs are gensets, that means just straight unitised replacement (via the uptakes I presume?)

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PostPosted: Sun Feb 12, 2017 2:36 pm 
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The Stag V8, in proper tune, sounds absolutely glorious. For a sports car, its worth it just for the noise and who cares how often it breakes down or overheats, or that the Rover engine is lighter, has more torque, and almost as much power even when held back by factory fitted asthma.

The Rover V8 was another kind of awsome. An american engine procured for the British industry almost by accident, and as a lightweight small to medium sized V8 almost ideal for medium and large cars in the British market, even when applied to saloons and sports cars in an agricultural, land rover tune.


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PostPosted: Sun Feb 12, 2017 2:40 pm 
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Craiglxviii wrote:
So the biggest problem is with the generating plant, and not the hull, weapons systems, sensors and the ones and zeroes that tie them all together. That's really interesting. It suggests that the problems with the ships and the challenge in making them really world- class are fixable "just" by re- engining them. And as they're IFEP and so the GTs are gensets, that means just straight unitised replacement (via the uptakes I presume?)


Assuming that the footprints of the WR21 and the MT30 are the same, then a unitized replacement should be possible. That should address the most pressing problem. The next one is replacing the diesel generators, either with much more powerful diesels or with gas turbines. I suspect the big problem at the design stage was the pressure to keep the hull size down and that caused most of the issues. The problem with using gas turbine generators is they need better ducting. To give you some idea of how bad the situation is, the Type 45 has 4 MW of generating power and has to use her main turbines to make up the difference. Chevalier Paul has 6.4 MW. An Arleigh Burke has 13.5 MW and can run on two of her three generators (in fact, usually does).

Just to make like difficult, it's turning out the Type 45s are unusually noisy. Quite why is a matter of debate abut its suspected a loss of institutional expertise in quiet running has something to do with it. Based on my experience with Type 22s, I'm looking suspiciously at those diesel generators. Its sad because a major reason for going to IFEP is that it makes the ships quieter.

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PostPosted: Sun Feb 12, 2017 2:53 pm 
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Unusually noisy in absolute terms or relative to modern top end DDGs?

Sorry, when I mentioned re- engining I was referring to total installed power not just the main GTs. Surely in a hull of that size, there's enough room to put more turbines in? I mean it's not rocket science or anything, why the chap at Vospers can sell me a ship with the same number of gun mounts for half the price...

Being serious, as I understand it with GTs the issue is more of a packaging exercise. The hull stress loads on a ship of that size cannot be coming critical if we're talking a difference of five- ten tons per genset install...? I'm not familiar with GT gensets but I do know that a late model PT-6 weighs about 300kg dry and can output 1.3MW continuous, so distribution of enough of those around the ship taking into account intake and exhaust couldn't be tooooo challenging, surely?

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PostPosted: Sun Feb 12, 2017 3:11 pm 
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Francis Urquhart wrote:
Assuming that the footprints of the WR21 and the MT30 are the same, then a unitized replacement should be possible.

They aren't, the MT30 module is slightly wider and significantly longer, and Type 45 doesn't have the most spacious engine rooms known to man. It's always struck me as suspicious that they're exactly 500 feet long.... The acoustics issue is, I think, simply a case of the signature not being of major concern whilst most of the experts were working on ASTUTE. Not the first questionable trade-off and not the last either.

An uncompromised Type 45 (within limits - I keep reminding people that all design is compromise) would be a thing of beauty.

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PostPosted: Sun Feb 12, 2017 3:24 pm 
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Craiglxviii wrote:
Unusually noisy in absolute terms or relative to modern top end DDGs?

That's what I am trying to sort out now. If I was in charge of investigating the situation, the first thing I would be doing is checking the ships bow to stern for sound shorts. I suspect, again based on previous experience doing just that, there are a lot of them. To keep a ship quiet, the crew have to be trained to be noise-conscious all the time. If something rattles, they shouldn't have to be told to stop it rattling. Now. A screwdriver that bridges the gap between the hull structure and rafted machinery essentially negates the rafting.

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Being serious, as I understand it with GTs the issue is more of a packaging exercise. The hull stress loads on a ship of that size cannot be coming critical if we're talking a difference of five- ten tons per genset install...? I'm not familiar with GT gensets but I do know that a late model PT-6 weighs about 300kg dry and can output 1.3MW continuous, so distribution of enough of those around the ship taking into account intake and exhaust couldn't be tooooo challenging, surely?


Typically, an Arleigh Burke has three auxiliary generators. In the latest ships, they are Rolls-Royce RR-4500s that generate 4.5 MW each. They're basically a warmed-over Allison 501K and weigh about 23 tonnes each. One is in the bow, one amidships and one in the stern. Usually, two are run at any one time in rotation with the third down for routine maintenance. If everything has just dropped in the pot, all three are brought on line.

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PostPosted: Sun Feb 12, 2017 4:31 pm 
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Craiglxviii wrote:
Being serious, as I understand it with GTs the issue is more of a packaging exercise. The hull stress loads on a ship of that size cannot be coming critical if we're talking a difference of five- ten tons per genset install...? I'm not familiar with GT gensets but I do know that a late model PT-6 weighs about 300kg dry and can output 1.3MW continuous, so distribution of enough of those around the ship taking into account intake and exhaust couldn't be tooooo challenging, surely?

Problem is that turning mechanical power into electrical power is HEAVY. Keeping within the current state of the art but using some fairly exotic materials, 300kg gets you about 500kW of generator - going significantly more power dense is possible but the power quality goes to ratshit and you end up spending all the saved weight in power electronics to clean that up. That means a 1.5MW genset is about a ton and a half...

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PostPosted: Sun Feb 12, 2017 4:40 pm 
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pdf27 wrote:
Craiglxviii wrote:
Being serious, as I understand it with GTs the issue is more of a packaging exercise. The hull stress loads on a ship of that size cannot be coming critical if we're talking a difference of five- ten tons per genset install...? I'm not familiar with GT gensets but I do know that a late model PT-6 weighs about 300kg dry and can output 1.3MW continuous, so distribution of enough of those around the ship taking into account intake and exhaust couldn't be tooooo challenging, surely?

Problem is that turning mechanical power into electrical power is HEAVY. Keeping within the current state of the art but using some fairly exotic materials, 300kg gets you about 500kW of generator - going significantly more power dense is possible but the power quality goes to ratshit and you end up spending all the saved weight in power electronics to clean that up. That means a 1.5MW genset is about a ton and a half...


A kilo per watt then... does that scale?

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PostPosted: Sun Feb 12, 2017 4:49 pm 
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Craiglxviii wrote:
A kilo per watt then... does that scale?

Current state of the art for a generator meeting aircraft standards is about 2.5 kW/kg, give or take a little and not including some necessary systems like a generator control unit, external oil cooler, etc. Problem is to do this we're already running at high frequency - minimum of 400Hz electrical - and systems start to get upset as you push the frequency up. There are some improvements to be made - I've just had a patent application filed for one which should improve power density by a few percent for instance - but it isn't easy.
Cost is a major issue - we use some fairly exotic iron alloys to get the power density this high, but they're seriously expensive (nearly $1,000/kg) and a bit of a pig to work with. A more conventional build for a shipborne generator would probably be about 1 kW/kg if they're working to keep the weight reasonably low.

Really high power densities are possible, but they're probably a really bad idea in this case - exotic materials and exceptionally high speeds in an environment where reliability and robustness are the key attributes wanted.

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PostPosted: Thu Feb 16, 2017 2:18 am 
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Type 23 benifited from 40 years of cold war experience and a good specification, and was by all accounts probably one of the quietest "small" escort ships ever built.

Re the Type 45 issues being reported,

What degree of noise reduction was actually specified in the design? It seems pretty clear that it was never intended they match, say T23 noise reduction measures at low speed.

Are they "noisy" only in comparison to previous "quiet" ships?

Or are they "noisier" than even than the original degree of noisiness specified?

Is the problem at low speed, high speed or at all ends of the operating profile?


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PostPosted: Thu Feb 16, 2017 3:05 am 
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pdf27 wrote:
Craiglxviii wrote:
A kilo per watt then... does that scale?

Current state of the art for a generator meeting aircraft standards is about 2.5 kW/kg, give or take a little and not including some necessary systems like a generator control unit, external oil cooler, etc. Problem is to do this we're already running at high frequency - minimum of 400Hz electrical - and systems start to get upset as you push the frequency up. There are some improvements to be made - I've just had a patent application filed for one which should improve power density by a few percent for instance - but it isn't easy.
Cost is a major issue - we use some fairly exotic iron alloys to get the power density this high, but they're seriously expensive (nearly $1,000/kg) and a bit of a pig to work with. A more conventional build for a shipborne generator would probably be about 1 kW/kg if they're working to keep the weight reasonably low.

Really high power densities are possible, but they're probably a really bad idea in this case - exotic materials and exceptionally high speeds in an environment where reliability and robustness are the key attributes wanted.


Thank you. 1kW/kg was what I was getting at, only an order of magnitude out by typo! OK, so that suggests that deleting the diesel gensets and adding in 15 ton of turbine gensets could be feasible weight-wise, the only problem would be trunking volume at a guess?

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PostPosted: Thu Feb 16, 2017 2:44 pm 
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Yes, with reservations about the different weight distributions causing grief.

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PostPosted: Thu Feb 16, 2017 2:58 pm 
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pdf27 wrote:
Yes, with reservations about the different weight distributions causing grief.

Pfff can't be that hard, it's only maths ;)

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PostPosted: Fri Feb 17, 2017 2:00 pm 
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HMS Warspite wrote:
The Roman army was quite decentralised, then quite centralised, then quite decentralised again. A decentralised navy beat the Armada but Parliament won the Civil War with the New Model Army which was as centralised as it gets.


That sounds exactly like the company I used to work for. Every few years there was a change from centralized to decentralized branches followed a few years later by a reversion to centralized branches. I guess that if nothing else it kept some of the paper pushers busy.


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