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Yasutomi
Post subject: Small DDG Concept KitbashPosted: July 29th, 2014, 4:44 pm
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Yes, it's a kitbash I'm afraid...but I was curious whether something like this might actually work:

[ img ]

The DDV design studies of the early 90s included an austere "frigate" variant with half the powerplant of a Burke destroyer (so presumably 2 LM2500-30s instead of 4); however, although I've seen its hull described as "shortened", the quoted length (466 feet PP) is that of a regular Flight I. Which got me thinking...what's the spare engine room being used for? It seems like rather a waste of space.

My concept (illustrated above) therefore involves a definitely shortened Burke hull, approximately 445 feet PP. Since each engine room is rather longer than the 21 foot reduction in hull length (at least according to the information I've seen), it seems perfectly reasonable to assume that it would be possible for the design to have a single, but slightly larger, engine room with a pair of the uprated LM2500+G4 turbines. Given that (again, from what I've read) the LM2500+G4 turbine assemblies are similar in size to the older LM2500 assemblies, albeit requiring larger inlets (57 sq feet as opposed to 48), I can't think of any reason why this isn't feasible, provided the funnel is extended to provide the extra inlet space required. With a combined output of 69,400 kw (compared to the Burke's 88,000), the design should have enough power to function, albeit at a more modest speed...perhaps somewhere in the region of 27 kts (i.e. comparable to a Nansen Class frigate).

But would there be sufficient space to fit auxiliary diesels for a CODAG arrangement...or even an IEP system similar, if smaller, to that installed on the Makin Island? I really don't know enough about the engineering requirements to judge and would be interested to hear the opinion of someone with greater knowledge of such things.

The forward VLS has been slightly enlarged to contain 48 missiles, so providing an equivalent capacity to a Bazan Class frigate, but other than that I've tried to remain as close to Rl designs as possible, in order to maximise the plausibility..I hope!

Whether such a concept is cost effective is an entirely different matter, of course...


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TimothyC
Post subject: Re: Small DDG Concept KitbashPosted: July 29th, 2014, 5:38 pm
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First, welcome aboard.
Second, Very nice looking. I'm not sure you've got the space to expand the forward VLS, but I'd have to dig deeper. She is certainly better than my first kitbashes!

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acelanceloet
Post subject: Re: Small DDG Concept KitbashPosted: July 29th, 2014, 5:59 pm
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agreed, nice work.
there are some things that might pose a problem though.
- shortening an existing hull might pose a problem. if there is not a straight midship section, it means reshaping the hull and this might mean an all new hull. if you want to keep the ship cheap, the best idea is to keep the hull.
- in this design, you remove weight from below (the hull, the engines) and keep most if not all the weight up top from the regular burke. this might result in stability problems
- the shorter hull might have more wave resistance, keeping the top speed indeed not any higher then 27 knots, even with the upgraded power from the DDV-1 design.
- as the engine rooms on the burke are completely separated, creating one larger one will not only reduce it's resistance to damage but also will require a rebuild of the internal structure.
- the intakes of the burke class are not actually on the funnel, but on the superstructure.

for these reasons, I would suggest the following:
- keeping the original hull, both for resistance and stability issues, which also limits development costs.
- fitting the LM2500+, possibly with generators instead of gearboxes, in the forward engine room
- fitting the aft engine room with the diesel generators and possibly electrical main propulsion engines.
- I doubt 48 cell VLS would fit forward, but what about having 16 or 32 aft, in the helicopter hangar?

this gives the ship upgrade capabilities (IEP), more reserve, and lower cost then the original burke class, without having much development cost.

of course, it is your design, so try to give me arguments back how you solved or are going to solve the problems mentioned above :P

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Hood
Post subject: Re: Small DDG Concept KitbashPosted: July 29th, 2014, 7:29 pm
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Welcome aboard!

This is an interesting concept and it looks good.
Ace has raised some good points. The only thing I would mention is perhaps the ASW torpedoes, they would be better under cover and they seems a bit high above the waterline.

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eswube
Post subject: Re: Small DDG Concept KitbashPosted: July 29th, 2014, 7:54 pm
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Welcome aboard. Nice work. :)


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erik_t
Post subject: Re: Small DDG Concept KitbashPosted: July 29th, 2014, 7:55 pm
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Hood, that's where the real-life IIA Burke carries her torpedoes.


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Hood
Post subject: Re: Small DDG Concept KitbashPosted: July 29th, 2014, 8:12 pm
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Fair enough Erik_t, just looks a little high to me but if it works out in real life then I have no objection.

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usna2k
Post subject: Re: Small DDG Concept KitbashPosted: July 30th, 2014, 11:51 am
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I messed around with something similar to this idea a couple years ago when I first joined. I never have much time to devote to these things, however...so this is where I finished out with it. It's got a lot of flaws like bad/old parts, etc.

This was a single screw variant.

[ img ]


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Yasutomi
Post subject: Re: Small DDG Concept KitbashPosted: July 30th, 2014, 4:55 pm
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Many thanks for all the welcomes and positive comments! :)
TimothyC wrote:
I'm not sure you've got the space to expand the forward VLS, but I'd have to dig deeper.
I was sceptical too, but the drawing of DDV 7 does show a 48 round VLS in that exact location.
acelanceloet wrote:
I doubt 48 cell VLS would fit forward, but what about having 16 or 32 aft, in the helicopter hangar?
On balance, I agree that this is probably the way to go.
acelanceloet wrote:
- shortening an existing hull might pose a problem. if there is not a straight midship section, it means reshaping the hull and this might mean an all new hull. if you want to keep the ship cheap, the best idea is to keep the hull.
I do see your point. My concern is that a full-sized hull is neither efficient nor cost-effective, given that there will likely be at least some excess space. Therefore, some degree of reshaping is likely inevitable.
Quote:
- in this design, you remove weight from below (the hull, the engines) and keep most if not all the weight up top from the regular burke. this might result in stability problems
Good point. Without access to the weight allocations of a RL Burke, it's difficult to judge how serious an issue it is. However:

1. I have removed some topweight, in the form of the second funnel; I could probably cut down the superstructure in other places too (see below)

2. To my eye, it doesn't look any more top-heavy than say, a Bazan class...although that's hardly an authoritative judgement!
Quote:
- the shorter hull might have more wave resistance, keeping the top speed indeed not any higher then 27 knots, even with the upgraded power from the DDV-1 design.
Agreed. I always accepted that the shorter hull would restrict the vessel's speed; however, I consider 26/7 knots adequate.
Quote:
- as the engine rooms on the burke are completely separated, creating one larger one will not only reduce it's resistance to damage but also will require a rebuild of the internal structure.
Lower resistance to damage has to be accepted if you're trying to do things on the cheap! And as I said above, I can't see how you could get away without some reorganisation of the internal layout even if you use the regular hull.
acelanceloet wrote:
for these reasons, I would suggest the following:
- keeping the original hull, both for resistance and stability issues, which also limits development costs.
- fitting the LM2500+, possibly with generators instead of gearboxes, in the forward engine room
- fitting the aft engine room with the diesel generators and possibly electrical main propulsion engines.
- I doubt 48 cell VLS would fit forward, but what about having 16 or 32 aft, in the helicopter hangar?

this gives the ship upgrade capabilities (IEP), more reserve, and lower cost then the original burke class, without having much development cost.
I had some spare time earlier today, so I decided to draw up a couple of designs incorporating your recommendations:

[ img ]

This version keeps the enlarged forward funnel, but adds a small exhaust/intake for the diesel engines in the rear engine room.

[ img ]

This version reverts to a more conventional superstructure layout, albeit with a slightly enlarged forward section incorporating an extra set of intakes for the new turbines and a smaller aft funnel for the diesels. The aft VLS has also been expanded to the 64-slot version.

I have mixed feelings about these designs, to be honest. For a start...I'm not really clear just how large an exhaust/intake arrangement would be required for the diesels. Moreover, while I can see the advantages of the standard Burke hull, effectively the concept has shifted from a "minimum Burke" to a "re-engined Burke"...and artistically, that's something of a problem as most of the changes are internal! The key feature of my design is the distinctive, single-funnel arrangement and that really isn't feasible given the spacing of the engine rooms; take that away, and you're left with ship that looks pretty much like a standard Burke...not exactly ideal for a personal design! ;)

My other main concern- which I've hinted at already- is that the standard Burke hull still need to be redesigned and reorganised. Although the uprated LM2500+ or LM2500+G4a are substantially the same dimensions as the turbines they're replacing, they do have different airflow requirements and if the margins are tight, that could be a problem (without a personal insight into the construction of the Burke, I simply can't judge). Similarly, the real engine room would like have to be substantially modified to replace the turbines with diesels and electric motors.

With this in mind, I've also prepared an revised version of my original design, with cut-down superstructures and two 32-round VLS instead of a single 48-round mounting:

[ img ]

For reference, I've also adapted an image I found to give a very rough insight into the internal layout:

[ img ]

The electric motors would have to be juggled in there somewhere...aft of the diesels? Between the diesels and turbines?

***

Well...to be honest, I'm a little bit stumped now! Logically, I agree with most of acelanceloet's comments...I just can't come up with a design that is visually distinctive enough to really justify being called a personal design.
usna2k wrote:
I messed around with something similar to this idea a couple years ago when I first joined. I never have much time to devote to these things, however...so this is where I finished out with it. It's got a lot of flaws like bad/old parts, etc.

This was a single screw variant.
Interesting! I considered a single screw version of my design. Regarding your drawing...perhaps the SPY-F would fit better in a vessel that size?


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acelanceloet
Post subject: Re: Small DDG Concept KitbashPosted: July 30th, 2014, 5:23 pm
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I certainly like the way you are thinking. may I recommend taking a look here: http://www.shipbucket.com/forums/viewto ... =16&t=2755 so you can play with the internals of your drawing?

a few comments:
- the funnel for the diesels, if you keep diesels close to the original diesel generators, can be a lot smaller. the funnel for the ship service generators on the flight 1 burkes is between the helideck and the VLS, it's very small. on the F2A I think it is on this same position, the small structure on top of the hangar
- if you want to go for austerity, it might help to fit only 2 directors. this will also simplify your funnel arrangement
- experience learns me that development costs of a new hull are higher then the cost of keeping a hull a bit too large, as long as the ship is build in small numbers. when you go over 10 ships build, then it becomes interesting to develop a new hull, but then it might be no longer a good idea to use the burke as base at all.
- I have a file for a COGOGL burke somewhere, gonna look it up for you.

I will try to look into the questions you seemed to have above tonight or later, when I have a bit more time ;)

keep up the good work!

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